Growing Lettuce Year Round 90 mins 2024.pdf

Lettuce Year Round
©Pam Dawling 2024
Twin Oaks Community, Central Virginia
Author of Sustainable Market Farming and
The Year-Round Hoophouse
SustainableMarketFarming.com
facebook.com/SustainableMarketFarming

I live and farm at Twin Oaks Community, in
central Virginia. We’re in US Winter hardiness zone 7a,
with an average last frost of April 30 and average first frost
October 14.
Our goal is to feed
our intentional
community of 100
people with a wide
variety of organic
produce year round.
www.twinoaks.org

Land Acknowledgement
I live and work on the ancestral and traditional territory of the
Monacan Nation, who lived in what is now Louisa County and other
parts of Central Virginia before white settlers pushed most of them out
in the 1700s. I am making this Land Acknowledgement as a way to
counter obliteration of Indigenous history.

What’s in this presentation
1. Growing conditions for lettuce
2. Lettuce types – Romaine and bibb head lettuce, leaf
lettuce, Batavians, the newer multileaf types and baby
lettuce mix.
3. Lettuce varieties for every season
4. Pests and diseases
5. Extending the lettuce season to every
month of the year.
a. Cold weather season extension
b. Hot weather season extension
6. Scheduling for continuous harvests
7. Resources
Gardener with Bronze
Arrow lettuce.
Photo Wren Vile

Lettuce year round
• We grow lettuce from transplants
– outside from February to December,
– in a solar-heated greenhouse for leaf
harvest November to March
– in a hoophouse from October to late
April (harvesting by the leaf).
• We grow winter baby lettuce mix in
our hoophouse
• We have in the past overwintered
lettuce
– with hoops and rowcover outside, and
harvested leaves all winter.
– in coldframes planted in September for
heads in November and December, or
leaves through the winter until March.
Flat of Buttercrunch lettuce
seedlings.
Photo Pam Dawling

1. Growing conditions - germination
• Lettuce seed needs light to germinate - don’t sow too deep:
1/4"–1/2" (6–12 mm) is ideal.
• Minimum soil temperature for germination is 35°F (1.6°C).
• Optimum temperature range for germination is 68°F–80°F
(20°C–27°C).
• Germination takes 15 days at 41°F (5°C), 7 days at 50°F (10°C),
3 days at 68°F (20°C) and only 2 days at 77°F (25°C)
• Germination takes 3 days at 86°F (30°C), but will not occur
reliably at temperatures hotter than that.
• Even a few hours at high temperatures can induce dormancy -
don’t leave your seeds for even 1 hour in your hoophouse or
greenhouse, or on a sunny windowsill.
• New lettuce seed can be harder to germinate, as it has higher
levels of the hormone that inhibits germination.

• Free-draining soil, high organic matter, pH 6.0–7.0.
• Fertile soil with good tilth will help roots grow.
• Don’t overdo the nitrogen – encourages E. coli.
• Keep lettuce growing quickly for good flavor -
plenty of water throughout its growth.
• Ideal growing temperatures 60°F–65°F (15°C–18°C).
• Some growth whenever the temperature tops 40°F
(4.5°C).
• Cultivate regularly and shallowly to remove weeds.
Lettuce roots are near the surface.
Crop requirements

Bolting
Bolting and/or bitterness are more likely
with
– Under-watering (bitterness before
bolting),
– Long days,
– Mature plants,
– Poor soil,
– Crowding,
– High temperatures,
– Vernalization—once the stems are
thicker than 1/4" (6 mm), if plants suffer
2 weeks of temperatures below 50°F
(10°C), followed by a rapid warm-up.
Photo Alexis Yamashita

Direct sowing
• Lettuce for mature heads can be direct seeded
whenever the weather is suitable.
• Baby lettuce mix is direct seeded, not transplanted.
• For raw seed, sprinkle thinly in a shallow drill.
• Some growers like to use pelleted seed for direct
sowing as it is easier to space the seeds.
• Pelleted seed is "primed" ready to grow: it
deteriorates fast in storage, so only buy it close to
sowing time. Keep the soil damp until the seedlings
emerge - the seed coating needs to absorb water
and split apart before the seedling can grow.

Advantages of transplanting
• In early spring, get an earlier
harvest from transplants than
from a direct-sown crop, since
the transplants grow indoors
while it is still too cold to direct
seed.
• In summer, you can start lettuce
in a cool place.
• Get ahead of the weeds.
• Allow another crop to mature in
the space while transplants are
growing, increasing overall yield.
• Transplants are better than
seedlings in resisting some pests
and fungal diseases.
Bed of young transplanted lettuce.
Photo Wren Vile

Sowing for transplanting
• Can sow in cell-packs or plug flats, 3 seeds per cell, later
reducing to 1 seedling with scissors.
• Cells with diameters from 1"–2" (2.5–5 cm) can be used.
• If suitable germination space is limited, sow seed in a small
flat, then spot the tiny seedlings into bigger flats or 606-cell
packs (2" × 2", 5 × 5 cm) to grow on before planting out.
• Soil blocks are also possible, but take more time.
Lettuce
transplants in soil
blocks.
Photo Pam
Dawling

Bare-root transplanting
• Can use an outdoor nursery bed from
mid-April to October, rather than flats. For
us, this is less work.
• We sow 4 x 3’ (1 m) rows for each final
planting of 120 lettuce.
• Water, weed, then transplant the bare-
root plants directly from the seedbed.
• Because fall hoophouse conditions can be
warmer than ideal for lettuce
germination, we sow leaf and head lettuce
outdoors in September and transplant the
bare-root seedlings into the hoophouse at
4 weeks old.
• But in very hot weather, indoor sowings
might give more reliable germination.
Lettuce seedbed.
Photo Bridget Aleshire

Transplanting
• Harden off before transplanting outdoors in spring.
• Transplant lettuce seedlings at 4–6 true leaves, 3–6
weeks of age depending on the time of year and
how fast they are growing.
• Handle transplants only by their leaves or the root
ball—try not to touch the roots or stem.
• 8"–12" (20–30 cm) spacing for full-sized heads.
Close spacing lets foliage cover the bed completely,
creating a cooler microclimate in summer.
• Accurate spacing saves a lot of time when hoeing,
and ensures maximum yield. Use measuring sticks,
row-marker rakes, rolling dibbles or transplanting
wheels.
• Alternatively, run drip irrigation for 15-20 minutes
before planting, and plant into the wet spots.
• Transplant in the late afternoon or evening in hot
weather to minimize evaporation losses. Lettuce bed.
Photo Wren Vile

Watering
• Water new transplants daily for the first 3 days,
• Every 4-7 days after that.
• Lettuce needs a relatively large amount of water
throughout its growth.
• Deeper weekly waterings equivalent to 1” (25 mm)
of rain are better than frequent superficial
irrigation - roots will grow deeper, giving the plant
greater drought-resistance.
• In cooler weather, water late morning or early
afternoon, to give the leaves time to dry before
sunset. This reduces the chance of fungal diseases.

2. Lettuce Types
1. Iceberg (crisphead) lettuces have little nutritional value. They
have no frost tolerance, due to high water content.
2. Butterheads (bibbs) have very tender leaves, but have shorter
shelf-life than romaines and leaf varieties.
3. Romaine (cos) lettuces are upright, often very crisp and
flavorful.
4. Leaf lettuces include the familiar oak-leaf types, and frilly ones.
5. Batavian lettuces (summer crisp or French crisp) are tasty,
thick-leafed varieties that have great heat and cold tolerance.
Although sometimes classified with icebergs as crisphead
types, they are very different.
6. Multileaf lettuces - familiar Tango, Panisse, Oscarde varieties,
and the newer Salanova, Multileaf and Eazyleaf brands
7. Baby lettuce mix, aka Mesclun, salad mix, spring mix and
misticanza. Some mixes include other greens.

Butterheads (bibbs)
• Butterheads (bibbs)
have soft, sweet, tender
leaves
• Shorter shelf-life than
romaines and leaf
varieties
• Can get tipburn in
midwinter
• Can also be used at the
baby stage in mixes
Buttercrunch bibb lettuce.
Photo Kathleen Slattery

Romaines (cos) lettuces
• Romaines (cos) lettuces
are upright, usually
green, often very crisp
and flavorful.
• They have double the
vitamin A and vitamin C
of other kinds of
lettuce.
• Like bibbs, romaines
can suffer from tipburn
in the winter.
• Jericho and Kalura have
good heat tolerance.
Rouge d’Hiver red romaine hardy lettuce
Photo Kathryn Simmons

Leaf lettuces
• Leaf lettuces include the oak-
leaf types, as well as frilly ones
that add interesting texture
and important “loft” in mixes.
• Leaf lettuces are usually the
quickest to produce
harvestable sized leaves, and in
general they have more heat-
tolerance (but not bolt-
resistance) than romaines.
• Despite the name, leaf lettuce
can also be harvested as whole
"heads." Red Salad Bowl leaf lettuce.
Photo Pam Dawling

Batavian lettuces
• Batavian lettuces
(summer crisp or
French crisp) are
tasty, thick-leafed
varieties that have
excellent bolt-
resistance as well
as heat and cold
tolerance.
• Cherokee Batavian lettuce.
Photo Pam Dawling

Multileaf lettuces
• Familiar Tango, Panisse and
Oscarde varieties,
• Newer Salanova, Multileaf and
Eazyleaf brands
• Lobed oakleafs, incised frizzy ones.
• Bred for uniformly small leaves, with
more texture, loft and flavor than
baby mixes and faster harvesting.
• Transplanted 6"–8" (15-20 cm) apart
they produce 40% more than baby
leaf mixes, but take longer to
mature.
• Often only sold as pelleted seed.
Ezrilla Eazyleaf lettuce.
Photo Pam Dawling

Multileaf lettuce harvest
Multileaf lettuce Photo Osborne Seeds
• The full-size plant can be
harvested as a head
• Or harvested with a single
cut, as shown, providing a
collection of bite-sized
leaves.
• Or just one side (or the
outer leaves) of the plant
can be cut and the plant will
regrow for future harvests.
• Growing multileaf heads
takes 55 days, compared to
30 days for baby lettuce.

Baby lettuce mix
• A direct-sown cut-and-come-again crop, meaning the plants will
regrow and can be harvested more than once in cool seasons.
• Weed and thin to 1" (2.5 cm).
• When 3"–4" (7.5–10 cm) tall, cut 1” (2.5 cm) above the soil.
• Gather a small handful in one hand and cut with using large scissors.
• Immediately after harvesting, weed the just-cut area so the next cut
won't include weeds
• We generally buy the ready-
made baby lettuce mixes,
but for the later sowings,
which we will only cut 1-3
times, we sometimes make
our own mix.
Lettuce Mix. Photo Twin
Oaks Community

• Sow several varieties each time—for the attractive
harvests, and to spread your risks if one variety
bolts or suffers disease.
• I like to sow 4 varieties each time: at least one red,
one romaine, and one fast, one slow.
• We have 4 lettuce seasons, with different varieties:
– Spring (Jan 17– Apr 22), 8 sowings
– Summer (Apr 23– Aug 14), 20 sowings (lots of seed!)
– Fall (Aug 15 – Sept 7), 9 sowings
– Winter (Sept 8 – 27), 9 sowings
See the handout for our list of varieties for each
season.
3. Varieties for every time of year

Varieties for spring
8 sowings, Jan 17 – Apr 22
For spring, we look for
❑Fast growth, some cold tolerance, some
bolt-resistance
❑Diversity of color, texture, leaf shape,
days to maturity
❑Some spring varieties only work until
2/14 (Bronze Arrow, Buckley, Ezrilla,
Hampton, Merlot, Oscarde)
❑Some work only until 3/15 (Panisse,
Revolution)
❑Some other varieties we like include
Buttercrunch, De Morges Braun, Green
Forest, Pirat, Salad Bowls, Swordleaf.
❑ Swordleaf lettuce on the right. Photo Bridget Aleshire

Varieties for summer
20 sowings, Apr 23 – Aug 14
For summer we look for
❑ Extreme heat tolerance/bolt-resistance.
❑ Secondary factors: diversity of color,
texture, leaf shape, days to maturity.
❑ Jericho, Kalura are great romaines
❑ Batavians include Albachiara, Cardinale,
Cherokee, Concept, Magenta, Nevada,
Pablo, Sierra, and Loma, a smaller, frilly-
edged one.
❑ Anuenue is the only iceberg we grow.
Some growers like Ben Shemen and
Queensland.
❑ De Morges Braun and New Red Fire are
leaf lettuces for quite hot weather July lettuce bed, Anuenue and
Cherokee. Photo Pam Dawling

Hoophouse lettuce mix
for summer
❑ Although not an obvious use, hoophouses with shadecloths can be
good places to sow fast-growing baby lettuce mix, arugula and other
traditional cool weather crops during the spring and summer, if the
crops are grown fast and only harvested once.
❑ We forego baby lettuce mix in the warm weather and grow lettuce
heads outdoors.
Hoophouse covered
with shadecloth for the
summer. Photo
Kathryn Simmons

Lettuce varieties for fall
9 sowings, Aug 15 – Sept 7
For fall we look for
❑ Some warmth-tolerance, some cold
tolerance
❑ Diversity of color, texture, leaf
shape, days to maturity.
❑ Heat-tolerant varieties are also very
cold-hardy, but we are tired of
Batavians by fall!
❑ Many spring varieties can be used
again in the fall.
❑ Less hardy varieties until Aug 26
❑ Then hardy varieties – see winter
slide
New Red Fire lettuce. Photo Bridget
Aleshire

Lettuce varieties for winter
9 sowings, Sept 8 – 24
For winter we look for
❑Cold-tolerance above all else
❑Diversity of color, texture, leaf
shape, days to maturity
❑Some bibbs for early winter
harvest.
❑Mostly leaf lettuce to harvest
by the individual leaf and leave
to regrow.
❑Some varieties that do well are
listed on the next slide.
❑Baby lettuce mixes in late
winter and early spring in the
hoophouse Merlot red and Panisse green lettuce in
December. Photo Pam Dawling

Cold-hardy lettuce varieties
➢ Buckley
➢ Ezrilla
➢ Green Forest
➢ Hampton
➢ Merlot
➢ Oscarde
➢ Panisse
➢ Red Tinged Winter
➢ Revolution
➢ Rhone
➢ Rouge d’Hiver
➢ Tango
➢ Winter Wonderland
➢ The Salad Bowls are not so good
outdoors in cold weather but do
well in the hoophouse.
Buckley lettuce. Photo Pam Dawling
Rouge d’Hiver Lettuce
Credit Southern Exposure Seed Exchange

4. Pests
Minimize pests by making good growing conditions, protecting crops with
fencing, rowcover, or insect netting and planting flowers that attract
beneficial insects.
• Aphids: Try a blast of water—most aphids can't travel far. Insecticidal
soaps, 3 times at 5 day intervals. Ladybugs. Flowers to attract beneficials
• Cutworms: plants get chewed off at soil level.
• Grasshoppers and crickets: Bring in praying mantids, or set bait
containing the parasitic nosema locustae.
• Groundhogs, rabbits, deer: Fence or set traps.
• Slugs: hunt them at night, or trap in dishes of diluted beer set in the soil.
• Thrips: Rowcover and very fine mesh nets can keep them away.
Proteknet insect
netting.
Photo Wren Vile

• Damping off: affects young seedlings in cold wet grey conditions.
Minimize watering in chilly weather, provide good airflow, foliar feed
with seaweed spray or compost tea. In cold weather, water only at
mid-day.
• Tip burn: A physiological disorder, not a disease. It follows a sudden
change to warmer breezy weather. When the transpiration rate is
much higher than the rate of water uptake, the outer edges of the
inner leaves don't get enough water,
so they brown and die. Reduce
transpiration by shading, and/or
protecting from the wind. If tip
burn seems to be a frequent
problem, choose resistant
varieties, and avoid bibbs, which
are more prone to tip burn.
4. Diseases
Nancy bibb lettuce with slight tipburn.

4. More Diseases
• Bottom rot: soil-borne cool-season problem caused by Rhizoctinia
fungus. Shows initially as slightly sunken rust-colored spots, possibly
with amber ooze. The whole plant can dissolve into black slime.
Solarization works well.
Sclerotinia: Lettuce drop fungus.
Attacks lower leaves at soil level
and produces a cottony growth.
The whole plant then collapses into
a flat limp pancake. It can be a
serious problem in hoophouses
where lots of lettuce is grown.
Solarize for two summer months
every four years.
Hampton Eazileaf lettuce with Sclerotinia in
our hoophouse in January.
Photo Pam Dawling

5. Extending the lettuce season
Provide lettuce harvests all year.
❑Season extension
techniques for cold weather -
Growing earlier crops in spring, later
crops in the fall, crops in the winter
(cold-hardy varieties)
❑Season extension
options for hot weather – getting
lettuce seed germinated, growing
non-bitter lettuce, keeping pests off.
For details, see my slide
shows
• Year Round Vegetable
Production,
• Hoophouse in Spring and
Summer,
• Hoophouse in Fall and
Winter
• Fall Vegetable Production,
• Cold-Hardy Winter
Vegetables
on SlideShare.net

Economics of season extension
• Season extension requires putting in more time and/or money
than main season growing, to gain extra production.
• There comes a point beyond which the diminishing returns
aren’t worth the extra energy put in.
• You might do better to turn your attentions to some other crop
(spinach, kale?) and not chase after lettuce regardless of costs.
• Before investing a lot of money, talk with other growers.
• A large hoophouse provides more lettuce per $ invested than a
smaller heated greenhouse made of expensive materials.

Cold-hardiness of lettuce
• Lettuce is a lot more cold-hardy than most people realize.
• Immature plants are more cold-tolerant than mature plants
• Baby leaf lettuce is more cold tolerant than full-sized heads
• Outdoors with good rowcover, lettuce may survive a dip to 10°F (-12°C)
—but not 8°F (-13°C).
• Our double plastic hoophouse keeps night temperatures 7–10F (4–6C)
degrees warmer than outdoors.
• Plants tolerate lower temperatures in a hoophouse than outside.
• Inside, plants can survive (without any inner rowcovers) 14F (8C) degrees
colder than they can outside.
• With the addition of thick 1.25 oz (42 gm) rowcover, hoophouse crops
can survive 21F (12C) degrees colder than they can outside.
• When outdoor temperatures were 14°F (-10°C) our lettuce survived a
hoophouse temperature of 10.4°F (-12°C) without any rowcover.
• When it dropped to -12°F (-24°C) outdoors, rowcovered hoophouse
lettuce survived a hoophouse temperature of -2.2°F (-19°C).

The role of water in saving
lettuces in cold weather
• Freshly watered plants seem less resistant to freezing damage, so
choose days with forecast mild overnight lows for watering.
• If cold weather is expected, spray with seaweed a few days
beforehand to help protect against frost.
• It is sometimes possible to save a frozen crop by spraying with water
by hand early in the morning and continuing until sunlight reaches
the plants.
Tango lettuce in
our hoophouse
in January.
Photo Pam
Dawling

Season extension
techniques for cold weather
o Fast-maturing hardy varieties
o Warm microclimates
(protection from prevailing
winds)
o In early spring, use transplants
o In spring, warm the soil with
black plastic mulch
o In fall, use light-colored
mulches to conserve soil
warmth by reducing radiation
losses
o Crop protection – see next
slides
Revolution and Green Forest lettuce in our
hoophouse in January.
Photo Pam Dawling

Cold Weather Crop Protection
Six basic levels of protection:
1. Rowcover
2. Quick Hoops
3. Caterpillar Tunnels
4. Coldframes and unheated
greenhouses
5. Hoophouses (High Tunnels)
6. Heated greenhouses
Photo Kathryn Simmons

1. Rowcover
• Keep crops alive and productive beyond their normal winter-kill
temperatures.
• Protect young crops in early spring.
• Better quality produce – reduced weather and pest damage
• Lightweight, easy to use and store.
• Hold down edges with bags of rocks or sand, jugs of water, or metal
or wooden stakes lying on the edges. Photo Wren Vile

Avoiding Pitfalls of Rowcover
➢ If you are growing on bare soil
rather than plastic, weeds
grow very secretly.
➢ Rowcover reduces light levels.
➢ Ventilate covered crops in mild
weather, so they don’t lose
their cold tolerance.
➢ Hoops keep rowcover from
sticking to frozen leaves and
reduce abrasion. 9- or 10-
gauge wire. In winter we use
double wire hoops — the 22
gauge wire outer hoops trap
the rowcover so it doesn’t
blow away. The microclimate
under hooped rowcovers is
very nice in chilly weather.
➢ There are also spring steel hoops,
for setting by machine or by
hand. Easy to store - they return
to a relaxed bow shape when
removed from the soil, don’t get
tangled. Seem to come in just
one length, 64" (1.63 m), which
is fine for a single row of plants,
but less good for our 48" (1.2 m)
beds with multiple rows.

2. Quickhoops
• Cover more than one bed,
close to the ground.
• Popularized by Eliot Coleman
in Maine.
• Can be covered with
rowcover topped by
hoophouse plastic for the
winter.
• Best for areas with reliably
cold winters, not back-and-
forth winters that include
spells too mild to keep crops
under polyethylene.
• Best for storing crops till
spring, rather than
harvesting during winter.
Photo Johnnys Seeds

3. Caterpillar Tunnels
Photo MOFGA
• Usually tall enough to walk in
• Sometimes narrower than Quickhoops. 2 beds + 1 path
• Plastic or rowcover held down by ropes at each hoop.
• Can be used for summer or winter.
• No sandbags.

4. Coldframes and unheated
greenhouses
• Coldframes are traditionally made
from blocks, boards or straw bales,
with discarded windows over the top.
• They are very useful on a small scale, but
but labor-intensive.
• Solar Gardening by Leandre and
Gretchen Poisson – good book on making small structures.
• For large-scale production, the construction costs of a
hoophouse are lower than for the same area of coldframes.
• Single-layer hoophouses are sometimes called coldframes.
• Unheated greenhouses with a masonry north wall will also
grow lettuces all winter (in central Virginia at least).
• Coldframe and greenhouse. Photo Kathryn Simmons

5. Hoophouses (High Tunnels)
For more details, see my slideshows
• Hoophouse Production of Cool Season
Crops
• Sequential Planting of Cool Season Crops in
a High Tunnel
• Hoophouse in Spring and Summer
• Hoophouse in Fall and Winter
• Many Crops, Many Plantings, to Maximize
High Tunnel Production Efficiency
on SlideShare.net
➢ Hoophouses are incredibly productive, crops grow faster
➢ Crop quality, especially leafy greens, is superb.
➢ Crops grow in the ground, often with drip irrigation
➢ Working in winter inside a hoophouse is much more pleasant
than dealing with frozen rowcover and hoops outdoors.
➢ One or two layers of plastic, I recommend two.
➢ Double-layer houses use a small electric blower to inflate the
gap. Solawrap is an option if you don’t have electricity.

Winter hoophouses
➢ A double-layer house provides about 8F (4.5C) degrees of night-time
temperature difference
➢ Solar heating is sufficient to grow a wide range of cold-tolerant crops.
➢ Cold-weather crops grow much faster inside
➢ Crops continue to grow throughout the winter whenever
temperatures are warm enough.
➢ Rowcovers can be used inside for extra cold protection
Hoophouse
December view.
Photo Kathleen
Slattery
For details, see
my slide show
Hoophouse in
Fall and Winter
on
SlideShare.net

Hoophouses for winter lettuce
• Growing winter salads is easy and
efficient.
• Salad greens in a hoophouse can
survive nights with outdoor lows of
14°F (–10°C) without rowcover.
• They can freeze every night and thaw
every morning without damage.
• Lettuces can tolerate cold nights
when they have the relief of warm
80°F–85°F (27°C–29°C) days.
• For harvest from November to April
we grow both leaf lettuce and baby
lettuce mix in our hoophouse.
• We transplant leaf lettuce in October
and sow baby lettuce mix between
October 24 and Feb 15
Red Tinged Winter and Tango lettuce in
December. Photo Wren Vile

6. Heated Greenhouses
• Greenhouses are great places to start your own transplants –
especially with a heated area for germinating seedlings
• But the cost of heating for growing crops to maturity may not be
worthwhile. You can buy several hoophouses for the price of one
greenhouse and heating
• Heat is only one aspect of growing plants – daylength and sunlight
intensity are also important.
• Aphids and whiteflies can quickly become problems in heated
spaces.

Season extension
options for hot weather
❑ Use only the most heat-tolerant varieties - others may not germinate
at high temperatures and the plants will bolt and taste bitter.
❑ Store seeds in a very cool dry and dark place
❑ Use tricks to germinate the seeds
❑ Use younger and smaller transplants than in spring.
❑ Transplant in the evening.
❑ Use closer spacings
❑ Plant to the north of tall
plants
❑ Use netting to keep bugs off
❑ Use shadecloth
Photo Alexis Yamashita

Various tricks:
➢ Store seeds in a tightly closed container in a freezer.
➢ Or freeze the seed for 4 days before sowing.
➢ After freezing, always bring the container to ambient
temperature before opening, to avoid dampening the seed with
condensation from the relatively warm air.
➢ An easier compromise is to store
seed in the fridge.
Shaded flats of lettuce seedlings. Photo
Bridget Aleshire
Storing lettuce seed in hot weather

Soak the seed in cool water for an hour, then drain before sowing.
Optional - store the drained seed in a jar in the fridge for 2 days
before sowing.
Small soaked seeds tend to clump together - drain off as much water
as possible, mix them with a dry material like uncooked corn grits,
oatmeal or bran, or coffee grounds or sand.
To use soaked seeds in a seeder, spread them on a tray to dry the
surfaces. Experiment on a small scale ahead of a big planting, to
make sure your seeder doesn’t just mush the seeds.
Soaking seeds

Starting seeds in hot weather
• Put the seeded flats in a plastic bag in the fridge, or
set the flat on a cool basement floor for 2 days to
break the dormancy
• Use plug flats such as Winstrip trays, or soil blocks
rather than open flats, to reduce transplant shock.
Lettuce transplants in soil
blocks.
Photo Pam Dawling

Sowing outdoors when it’s hot
➢ Soil temperature must be lower than 80°F (27°C) - use a
soil thermometer.
➢ Use a soil thermometer, and consult charts of days to
germination at various temperatures
➢ Find them in my book, The Year-Round Hoophouse
➢ If soil temperatures are too high for good germination, prepare
a small nursery bed for your seedlings and transplant later.
➢ Cool the soil for several days ahead,
by watering and covering with thick
mulch, shadecloth, boards or burlap.
➢ Sow in sunken furrows, as you don’t
want the seeds to dry out.

Start seeds outdoors
• Sow in the evening.
• After sowing (thickly), put ice on top of the
soil covering the seeds
• Cover with shadecloth (50 percent shade is
ideal), or tent screen windows, nylon
window screen or nylon net curtains. Use
something air can flow through, to prevent
overheating.
• Water with freshly drawn cool water at
midday (possibly more than once a day)
until the seed germinates.
Shaded nursery bed. Photo
Bridget Aleshire

One tray of ice cubes for 4 feet

Transplanting in hot weather
❑ Use younger and smaller transplants (3 weeks old) than you would in
spring—they will recover more quickly than larger ones.
❑ Transplant in the evening. Develop a fast technique so that you can get
your crop planted and watered in the last hour before sunset.
❑ Closer spacings such as 10"–12" (25–30 cm) will enable foliage to grow
to completely cover the bed and keep a cooler microclimate.
❑ Plant to the north of tall plants such as corn, tomatoes or pole beans.
❑ Use shadecloth for at least the first two
weeks after transplanting.
Anuenue and a red
Batavian lettuce under
shadecloth.
For more, see my
slide show
Season Extension
on SlideShare.net

Growing lettuce
in hot weather
• Water much more in hot weather — bitterness
before bolting is almost always a sign of water
stress. Just one day of insufficient soil moisture can
trigger bitterness in lettuce.
• If you have mature heads that you want to hold for
a couple more days, use overhead watering early in
the morning.
• For some crops, organic mulches can help cool the
soil. But they do not work well for lettuce, as stray
wisps of mulch mix with the harvested crop.
• Use white and silver reflective plastic mulches.

Interplanting lettuce and tomatoes
• Interplanting lettuce and tomatoes is
39% more efficient than growing
each crop individually.
(Statistic and photos thanks to Alison and Paul Wiediger)
• Interplanting of transplanted
lettuces and tomatoes does not
delay the date of first tomato
harvest, or reduce lettuce yields.
• But lettuce sown just before
tomatoes are transplanted will have
a significantly lower yield - the tiny
lettuce seedlings cannot compete
with the fast-growing tomatoes.

Shadecloth
• Cover new transplants with shadecloth for at least two weeks,
preferably until harvest (may be only 3 weeks from transplanting),
to reduce water losses while the transplants are making new roots
• Shadecloth on hoops (wire, fiberglass or plastic piping) allows
better airflow than shadecloth lying on the plants. For maximum
airflow, fasten the shadecloth to the hoops with clips or
clothespins to hold the bottom about 12”(30 cm) above the soil.
Photos: Bridget Aleshire, Bridget Aleshire, Alexis Yamashita

Insect netting
We use ProtekNet insect netting
on wire hoops. It offers better
light, air and rain transmission
than rowcover.
Overly thick rowcover or rowcover
resting directly on the plants can
make the seedlings more likely to
die of fungal diseases in hot
weather — good airflow is vital.
Dubois, Purple Mountain and
Johnnys sell in 100 m or 250 m
rolls
Photos Dubois Engineering (upper),
Bridget Aleshire (lower)

6. Scheduling for continuous harvests
• Lettuce grows faster at some times of year than others, and the time
between one sowing and the next needs to vary to balance this.
• To harvest a new planting every week you need to have sowing gaps
of more than 7 days in the spring, 6-7 days in the summer, less in fall.
• In warm spring weather, baby heads of lettuce or individual leaves
can be ready to harvest 4 weeks after transplanting, and full-sized
heads 6 weeks after transplanting.
• In summer, full size heads can be ready in as little as 3 weeks from
transplanting.
• In the fall, as temperatures and day-length decrease, the time to
maturity lengthens, and a single day's difference in sowing date can
lead to almost a week's difference in harvest date.
• Lettuce for February harvest will take 2-3 times as long from planting
as that for September harvest.
• December and January sowings grow very slowly, and early February
sowings will almost catch up.

• January:
• Sow every 14 days indoors in flats in late January for
outdoor transplants
• If you have a greenhouse or hoophouse, trans-
plant there until mid-February
• Harvest indoor leaf lettuce and baby lettuce mix
• February:
• Same as January
• March:
• Sow indoors in flats every 13 days
• From late March or early April, you could switch to outdoor direct sowing.
(We transplant all our lettuce.)
• Transplant the first 3 sowings outdoors with rowcover
• Harvest leaf lettuce, baby lettuce mix from a hoophouse; starting late
March, harvest leaves from the first outdoor planting
See later for hoophouse lettuce scheduling January- April
Scheduling lettuce January to March
Freckles lettuce.
Photo Kathryn
Simmons

Scheduling lettuce April to June
• April:
• Sow every 9 days
• Transplant the March sowings
• Harvest whole heads from late April
• May:
• Sow every 8 days
• Transplant 1 week’s needs each week
• Harvest outdoor heads
• June:
• Sow every 6 or 5 days, under shade
• Transplant one week’s needs every 6
days, using shadecloth for the first
2 weeks
Bronze Arrow lettuce.
Photo Wren Vile

• July:
• Sow very heat-resistant varieties, every 5 days, in the evening, under
shadecloth
• Transplant one week’s needs every 5 days, covering with shadecloth
for the first 2 weeks
• August:
• Sow every 5 days early in the month;
every 3 days later in the month
• Mid-August is our last date for out-
door direct seeding (80 days before
first hard freeze)
• Transplant one week’s needs every 5
days outdoors, with shadecloth
• In late August/early Sept, could trans- -
plant into coldframes
Scheduling lettuce in July and August
Pablo lettuce under shadecloth. Photo Nina Gentle

• September:
• If you have somewhere to plant them,
sow cold-hardy varieties every 2 days
until Sept 21, then every 3 days
• September sowings will be only for
coldframes, hoophouses,
greenhouses, or –
• Or to overwinter lettuce outdoors with
hoops and rowcover. Aim to have
plants half-grown by the time the very
cold weather hits. Try a few different
sowing dates, as the weather isn’t very
predictable. For us, Sept 10–18 are the
best dates
• Transplant one week’s needs outdoors
every 4 days until Sept 22 (August 29
sowings)
Scheduling lettuce in September
Cold-hardy (not heat-tolerant) Tango
lettuce Photo Kathryn Simmons

• October:
• For a greenhouse or hoophouse, maybe sow every 3–7 days until Oct
15, then every 7 days until Oct 31. Sow hoophouse gap fillers 10/23
• In late October, direct-sow the first baby lettuce mix in a hoophouse
• Transplant September sowings into a hoophouse at 4 weeks old for
leaves from mid-November to early April, then heads until late April
• November:
• Sow filler lettuce 11/9. Maybe sow
once Nov 1–15 in a hoop-house or
greenhouse for January transplants
• Harvest the last outdoor heads, &
leaves of indoor lettuce.
Scheduling lettuce October to November
Lettuce in our unheated greenhouse
in November. Photo Wren Vile

Hoophouse filler lettuce transplants
• On 10/23 and 11/9 we sow some short rows of filler
lettuce to fill any gaps that occur in the beds of full-
size lettuce.
• We use plants from the first date to replace casualties
until December 31.
• We use the second planting from January 1–25.
• Lettuces don't make good growth before bolting if
transplanted after January 25. (Fill gaps with spinach
instead.)
Lettuce filler transplants in our
hoophouse.
Photo Kathleen Slattery

Scheduling lettuce in December
if you have a greenhouse or hoophouse
• December:
• At the end of December, sow a second
round of baby lettuce mix, for harvest
from late February to the end of March
• Perhaps make a sowing between Dec
1–15 to transplant in a greenhouse in
January
• Transplant at the end of December for
heads in February (or leaves in January
and February)
• Harvest leaves from the indoor lettuce
and start cutting the first baby lettuce
mix Panisse and Merlot in winter.
Photo Pam Dawling

Hoophouse lettuce
• Avoid the need for new sowings at the slow-
growing time of year – transplant lettuce in the fall
to remain in the hoophouse until spring and simply
harvest individual leaves from the plants all winter.
• If you want baby lettuce mix reliably every week,
use the graph-making method coming up.
Baby lettuce
mix in
December
Photo Pam
Dawling

Hoophouse lettuce Jan-Feb
• January: Harvest leaves from the transplanted lettuce; cut the 1st
baby lettuce mix whenever it reaches 4" (10cm); Fill gaps with filler#2
February: Sow the 3rd baby lettuce mix February 1, for up to 3 cuts
from mid-March to late April. In mid-February, consider a 4th sowing
of baby lettuce mix, especially if outdoor conditions look likely to
delay outdoor harvests. Harvest leaves from the transplanted lettuce,
as well as the 1st baby lettuce mix, clearing it at the end of February
before it gets bitter. Cut the 2nd baby lettuce mix when it sizes up.
Red Tinged
Winter and
Merlot
lettuce in
January.
Photo Pam
Dawling

Hoophouse lettuce Mar-April
• March: Harvest leaves from the transplanted lettuce. Cut the
2nd and 3rd baby lettuce mix whenever they reach 4" (10cm)
• April: Harvest the last of the transplanted lettuce as heads in
the first half of the month. Clear the 2nd baby lettuce mix and
continue to cut the 3rd and 4th mixes until they get bitter. Our
outdoor lettuce heads are usually ready to take over crop
production in late April.
Hyper Red Rumpled Waved and Ezrilla
lettuce. Photo Wren Vile

Lettuce logbook – see handout
• Record planned and actual dates of sowing,
transplanting, starting and finishing harvest of each
planting, for head lettuce from transplants.
• These exact dates probably won’t be right for your
farm, but you can see the general themes.
• Improve the sequence every year and get closer to
your goal of a continuous supply.
• The gap between one sowing and the next gets smaller
as the year progresses; the gap between one
transplanting and the next does likewise;
• The number of days to reach transplant size dips to 21
days in the summer, then lengthens as the weather
cools and the days get shorter.

#
Sow
Date
Sow
ing
Gap
formula
Sow
n
Days
to T/pl
form
ula T/plant
T/pl
gap
formul
a
Trans-
planted
Harvest
Start
Harvest
Finish Varieties
Success
/Failure
1 17-Jan 51 9-Mar 4/15 5/8
2 31-Jan 14 46 19-Mar 10 5/6 5/12
3 14-Feb 14 41 28-Mar 9 5/12 5/18
4 28-Feb 14 36 6-Apr 9 5/18 5/31
5 13-Mar 13 32 15-Apr 9 5/30 6/4
6 26-Mar 13 27 23-Apr 8 6/6 6/9
7 5-Apr 10 26 1-May 8 6/11 6/18
8 14-Apr 9 24 10-May 8 6/18 6/21
9 23-Apr 9 22 18-May 8 6/20 6/25
10 1-May 8 21 26-May 7 7/8 7/13
11 9-May 8 20 2-Jun 7 7/13 7/17
12 17-May 8 19 8-Jun 6 7/17 7/26
13 24-May 7 19 14-Jun 6 7/27 7/29
14 31-May 7 19 20-Jun 6 7/29 8/3
15 7-Jun 7 19 26-Jun 6 8/3 8/10
16 13-Jun 6 19 2-Jul 6 8/10 8/17
17 18-Jun 5 20 8-Jul 6 8/17 8/20
18 23-Jun 5 21 14-Jul 6 8/20 8/23
19 28-Jun 5 22 20-Jul 6 8/24 8/30
20 3-Jul 5 22 25-Jul 5 8/31 9/4
21 8-Jul 5 22 30-Jul 5 9/5 9/10
22 13-Jul 5 22 4-Aug 5 9/11 9/17
23 18-Jul 5 22 9-Aug 5 9/17 9/24
24 23-Jul 5 22 14-Aug 5 9/24 9/30
Log-
book
page –
see
hand-
out
for the
whole
thing

• A sequence of planting dates to provide an unbroken
regular supply.
• We recorded sowing and harvest dates for several years,
then plotted our data on a graph.
• We used the graph to determine a sequence of sowing
dates likely to
provide a regular
weekly harvest.
For details of this method
see
Succession Planting
on SlideShare.net
Succession planting
Young Sierra lettuce on 4
July.
Photo Pam Dawling

Make a Graph - 6 Steps
1. Gather sowing and harvest start and end
dates for each planting of lettuce
2. Make a graph: sowing date along the
horizontal (x) axis; harvest start date
along the vertical (y) axis. Mark in all
your data. Join with a line. Smooth the
line.
3. Mark the first possible sowing date and
the harvest start date for that.
4. Decide the last worthwhile harvest start
date, mark that.
5. Use the harvest end dates to see how
long a planting lasts (how often to have
a new patch starting). Divide the harvest
period into a whole number of equal
segments of that length. Mark the dates
6. See the sowing dates that match
Young Salad Bowl lettuce.
your harvest start dates.

Lettuce successions Graph – see handout

https://www.sustainablemarketfarming.com/

Resources – Lettuce
(Updated Dec 2023)
❑ North Carolina State Extension, Lettuce:
https://content.ces.ncsu.edu/lettuce
❑ Colorado State Specialty Crops Program, Lettuce Bolting
Resistance Project,
http://specialtycrops.agsci.colostate.edu/lettuce-bolting-
resistance/ Compared 50 varieties. 2003
❑ Janet Bachmann, Season Extension Techniques for Market
Gardeners, ATTRA, 2005. attra.ncat.org/attra-
pub/summaries/summary.php?pub=366
❑ George Kuepper et al, Specialty Lettuce and Greens: Organic
Production, ATTRA, 2002, https://attra.ncat.org/attra-
pub/viewhtml.php?id=375

Resources– General (Updated 12/28/23)
❑ ATTRA https://attra.ncat.org/ Market Farming: A Start-up Guide; Plugs
and Transplant Production for Organic Systems; Scheduling Vegetable
Plantings for a Continuous Harvest; Intercropping Principles and
Production Practices (mostly field crops, but the same principles apply
to vegetable crops); Season Extension Techniques for Market Farmers,
❑ SARE https://www.sare.org/ A searchable database of research
findings. See Season Extension Topic Room
❑ https://eorganic.info/ The organic agriculture community with
eXtension. Publications, webinars, videos, trainings, support.
❑ Growing Small Farms: growingsmallfarms.ces.ncsu.edu/ Farmer
Resources.
❑ https://www.roxburyfarm.com/roxbury-agriculture-institute-at-philia-
farm Jean-Paul Courtens, Roxbury Farm
❑ https://weatherspark.com/ Weather records for your area. Fun!
❑ Soil temperatures at your location
www.greencastonline.com/tools/soil-temperature

Resources – books (Updated Dec 2023)
❑ The Market Gardener, Jean-Martin Fortier, New Society Pubs
❑ The Winter Market Gardener, Jean-Martin Fortier and Catherine
Sylvestre, New Society Publishers
❑ The Complete Know and Grow Vegetables, J K A Bleasdale, P J Salter et
al.
❑ Knott’s Handbook for Vegetable Growers, Maynard and Hochmuth, 2006
edition
https://onlinelibrary.wiley.com/doi/book/10.1002/9780470121474
❑ The New Seed Starter’s Handbook, Nancy Bubel, Rodale Books
❑ The Organic Farmer’s Business Handbook, Richard Wiswall, Chelsea
Green
❑ Sustainable Vegetable Production from Start-up to Market, Vern
Grubinger, NRAES
❑ The Four Season Harvest, The New Organic Grower and The Winter
Harvest Manual, Eliot Coleman
❑ Crop Planning for Organic Vegetable Growers, Daniel Brisebois and
Frédéric Thériault (Canadian Organic Growers www.cog.ca)

Resources: more books (Updated 12/23)
❑ The Lean Farm, How to Minimize Waste, Increase Efficiency, and
Maximize Value and Profits with Less Work and The Lean Farm Guide,
Ben Hartman
❑ The Bio-Integrated Farm, Shawn Jadrnicek.
❑ Grow More Food, Colin McCrate and Brad Halm, Storey
❑ Market Farming Success, Lynn Byczynski.
https://www.growingformarket.com/store/products/155
❑ John Jeavons How to Grow More Vegetables 8th edition 2012, Ten
Speed Press has charts: Pounds Consumed per Year by the Average
Person in the US & Average US Yield in Pounds per 100 Square Feet
❑ Gardening When it Counts, Steve Solomon, New Society
❑ Wholesale Success, Atina Diffley, Jim Slama
https://static1.squarespace.com/static/5a6b36f28fd4d259ba4fae16/t/5
a7e00cc71c10b2ebf7df534/1518207192816/Wholesale-Success-
Manual.pdf
❑ Nature and Properties of Soils, 14th edition, Nyle Brady & Ray Weil
❑ Garden Insects of North America, Whitney Cranshaw

Resources – Season Extension
❑ The Hoophouse Handbook Revised and Expanded, by Growing for
Market: https://www.growingformarket.com/store/products/169
❑ Extending the Season: Six Strategies for Improving Cash Flow Year-
Round on the Market Farm, Second edition. A free e-book from
Growing for Market magazine
https://www.growingformarket.com/articles/Extending-the-Season-2
❑ Fall and Winter Gardening Quick Reference, Southern Exposure Seed
Exchange, https://www.southernexposure.com/fall-winter-quick-
reference/
❑ Johnny’s Growers’ Library, Winter growing guide.
https://www.johnnyseeds.com/content-
search/?q=Winter%20growing%20guide
❑ Solar Gardening: Growing Vegetables Year-Round the American
Intensive Way, Leandre Poisson, Gretchen Poisson and Robin
Wimbiscus, 1994, Chelsea Green. Small-scale structures for winter.

Web Resources (Updated Dec 2023)
❑ Soil Solarization for Gardens and Landscapes, University of California:
https://ipm.ucanr.edu/PMG/PESTNOTES/pn74145.html
❑ AgSquared online planning software: https://www.agsquared.com/
❑ COG-Pro record-keeping software for Organic Farms: https://cog-
pro.com/
❑ Using shadecloth to exclude pests. Ayanava Majumdar and Will
Mastin, High Tunnel Pest Exclusion System: A Novel Strategy for
Organic Crop Production in the South, Alabama Cooperative
Extension, 2015: https://www.aces.edu/wp-
content/uploads/2019/11/HTPE-System.pdf
❑ My Slideshows: www.slideshare.net/ Search for Pam Dawling

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