A description of how to grow orchids either using water culture or semi-hydroponically.

1. Throw Out the Bark and
Grow Your Orchids
in Only Water or Wet Rocks
Harvey Brenneise,
with credit to Joff Morgan (Seattle),
Jennifer Pell (British Columbia)
Marin County Orchid Society
September 22, 2020

2. The root of great orchid
growing is growing healthy
roots

3. Yin-Tun Wang, then of
Matsui Orchids, wrote:
“The long-held widespread
belief of letting an orchid
medium become dry before
being watered is obsolete.”

4. Variations on “water growing”
 Full Water Culture (FWC)
 Semi Water Culture (SWC)
 Semi-hydroponic (SH or S/H, Ray
Barkalow and others)
 There is lots of experimentation
happening and few “established rules.”
Have fun, but seek principles more than
following “rules.” Varying conditions will
affect outcomes, with adjustments
necessary.

5. Water Culture
Only water or mostly water (many variations)
• No medium, only water, although in some cases, when water
is left in the bottom of the container (FWC), some rocks are
placed there to keep the crown out of the water.
• Some growers using FWC place a drainage hole or holes on
the side of the pot near its bottom (as in semi-hydro) and
leave water there between waterings with roots dangling in
the water.
• In SWC growers drain the pot entirely after a period of time
and leave the plant in the empty container until the next
watering (although some growers will mist)
• Some growers are obsessively clean (they don’t have many
plants!), others let nature take her course.
• Some have elaborate “rules,” others go with the flow.

12. Collections of water-grown
plants

16. Cattleyas

17. A little “root porn”

18. Held up by a sponge!

19. Cymbidium

20. Dendrobium

21. Epidendrum

22. Oncidiinae
Brassia
Miltoniopsis

25. Paphiopedilum

27. Phalaenopsis (of course!)
Phal in a mug, anyone?
Phal roots, adapted
to wander

30. Phal “on the rocks”
Phal rehab

32. Psychopsis

33. Vanda
Roots also like to wander

34. Zygopetalum

35. How does one stake when
there is no medium?

36. Fresh fish fertilizer?

37. More “root porn”:
Lotsa roots

39. Roots, roots, and more roots

40. Keep roots that have lost
their velamen?

41. Semi-Hydroponic
 Semi-Hydro or just S/H
 Popularized by Ray Barkalow of
www.firstrays.com
 A technique that provides the best conditions
for the plant
With minimum labor for the grower
(infrequent repotting)
Without the expense of a full hydroponic
system (circulating water with pumps) or
constant buying of bark
Reduced pathogens from a shared nutrient
bath (as in a full hydroponic system)

42. Semi-Hydro
 What is it?
 A passive hydroponic (lithophytic) culture
technique
 Using an inert (often rock) potting medium
 And a constant water supply

43. Advantages
 Medium is inert, reusable
(does not degrade, though
salts can build up)
 Similar initial cost to other
media (can be re-used,
however)
 No annual repotting; repot
only when plant outgrows
container
 Little root disturbance
 Consistent nutrient supply
 Moisture evenly distributed
 Once established, you can’t
overwater (as long as there is
sufficient air to the roots)

44. Semi-Hydro Containers
 Closed bottom
 Drill or burn two or more
¼” holes about one-inch
from the bottom to create
a reservoir (air AND
water at the roots)
 Plastic food storage or
deli containers, drinking
cups, decorative pots,
dairy containers, pop
bottles, trash cans, even
glass jars and vases

46. Preparing containers
 Choose the color of the container. Clear may promote
root growth and even photosynthesis, but it will also
allow algae to grow. This will not harm the plant but will
bother the fastidious, and they may engage in methods
to reduce or eliminate this growth. Use of hydrogen
peroxide is one of those methods.
 One can drill holes in container or vase, and will be
necessary if the container is glass or terracotta. Can
usea power drill or soldering iron for this.
 One can burn holds in plastic pots with a number of
tools including hot nails and wood burning tools
available at a hobby store.

47. Adding air to the container

48. Net pot inside SH pot

49. Semi-Hydro Media
 Often some form of rock, often
LECA (Light-weight Expanded
Clay Aggregate) or calcined
montmorillonite (monto) clay.
Around $30 for a large bag.
 Inert
 Lightweight
 Fairly uniform size
 Good capillary action (upward
wicking, though top layer can dry
out too fast)

50.  Provides plenty of air movement & gas exchange
 Very little salt build-up (needs regular flushing,
recommend at every watering
 Readily available at garden and hydroponic (i.e. “pot”)
supply stores, and online
 Rock tends to stay “cool” so can be too cold for some
genera in winter, though this can be helpful for others,
particularly in summer.

51. Media Brands
 LECA—Hydroton, Plant!t,
Hydro Crunch (Home
Depot) and Grow It
(Hydrofarm), Odla (Ikea)
brands of horticultural
clay pellets
 Seramis (OrchiTop
Germany)
 Rocks (Sunleaves)
(superheated shale)
 Monto Clay (American
Bonsai or Bonsai Jack), is
a larger size of Turface

52. Other media which have been tried
with varying degrees of success
 #4 perlite (unstable?)
 Diatomacious earth (DE, Dynarok)
 Growstone (recycled glass, a type of
manmade pumice, possibly too alkaline
for many genera)
 Lava rock
 “Bean bag” styrofoam beads
 Pumice
 Glass marbles
 Akadama (Japanese bonsai clay)
 Mixed media

53. Hydroton LECA DE

54. Monto clay (small and large)

55. Monto clay in burlap sack from American Bonsai

56. Growstone

57. “Rocks”

58. Coarse perlite

59. Pumice

60. Bean bag styrofoam, used experimentally as a way to put
more air into fine media such as fine monto clay.

61. Aquarium gravel as top dressing

62. Did someone lose their
marbles?

63. Semi-Hydro Watering
 Frequency varies -
depending on growth, plant
type, conditions
 ¼ strength fertilizer
solution every watering
(200 to 400 ppm)
 Quickly fill to top of pot,
allow to drain to level of
holes
 Helps wash out any
decayed matter and plant
wastes
 Try to water before
reservoir goes dry, about
once/week (may need
more during hotter months)
Phrag roots

64. A Word About Roots
 Orchid roots tend to adapt to the
environment they are in
 Once grown, they do not change type
 When a drastic root zone or environmental
change occurs, the orchid will often grow
NEW roots that are “adapted” for the new
conditions
 The old roots will be less efficient and
eventually decay.
 If the media are similar, the roots may adapt
and just continue growing
 May be able to “pot on” or “pot up” without
removing old medium if already in S/H.

65. Repotting to SH
 Add a root hormone
solution like KLN
(DynaGro), SuperThrive,
or an auxin-based kelp
additive like KelpMax
(www.firstrays.com)Timi
ng is important
 Rinse and soak the
medium several times to
remove clay dust and
particles (may take days
or even weeks for the
TDS to decline and stable
pH to be obtained)

66.  Choose the plant to be
repotted, making sure
plant and its roots are
healthy and strong
 Set aside its tag
 Make sure plant is in
active root growth and
forming new roots
(varies by orchid genus
or group and time of
year)

67.  Remove the pot,
exposing the root
ball and old medium

68.  Remove all of the
old medium
 Trim away any dead
or damaged roots

69.  Add medium to your
pot
 Fill container about
one-third full

70.  Position the plant in
the pot
 Spread the roots
over the medium, if
needed

71.  Add medium a little bit at a time
 Gently shake the pot or tap the sides to
work the medium into the root ball

72.  Continue filling the pot with medium to the
appropriate plant depth. Use a fine
medium such as aquarium stones on top
 Reinsert the tag
 Water with the rooting hormone solution
 Reduce stress as the new roots adapt to
their new conditions, about 6 weeks
 Shaded spot
 Very humid conditions
 Warm area
 Bottom heat from a mat helps
tremendously!

73. Stages of adaptation. Fine layer on top not
present here is often helpful as roots will
sometimes resist a medium that is too dry.

74. Angraecum
Don’t like to be repotted,
but seem to adapt readily

75. Bulbophyllum. Bulbos love water, so it’s an
easy transition.

76. Catasetinae
• Pot to S/H when new
growth and new roots
appear (April/May)
• Plants drain the reservoir
quickly in the Summer,
may need to water daily
and fertilize heavily in that
season.
• During dormancy
(December to spring),
either no water or just
plain water (no fertilizer)

77. Cattleya
• Quick to adapt to the
S/H conditions
• Can be converted anytime of
the year with good results as
long as there is active root
growth (best with new
growths)
• Mature Cattleyas can go
longer between waterings;
coarse lava bark an option, or
in a clay pot in a saucer

79. Catt grown in pumice in a clay pot
with clay saucer of water

80. Dendrobium
• Thrive in S/H, very quick to adapt, but must repot
when in active growth or they will keiki
• Bloom best when they are root bound, so don’t be
quick to move to a larger container

81. Cymbidium

82. Oncidium
• Best time is when
new growths are
“just” forming their
own roots
• Once acclimated,
rate of growth is
substantially faster
• Larger specimens
can deplete the
reservoir in less than
a day

83. Oncidiinae in Hydroton
Brassia Oncidium

84. Miltoniopsis love SH

85. Phalaenopsis and Vandaceous Genera
• May require a higher
percentage of air in the
water/air ratio

86. Renanthera in “Rocks”

87. Phalaenopsis
In lava rock Phal root in LECA

88. Paphiopedilum
• May stall root growth if there is not enough air
available to roots.

90. Paph in Hydroton that is too
wet (did not have enough air)

91. • Phragmipedium
• Phrag roots do not like to
dry out, so water container
when reservoir approaches
empty
• Can be converted to S/H
anytime they are in active
growth, but ..
• Phrag besseae crosses
take a bit longer to adapt to
S/H

93. Masdevallias &
Other Pleuros
• Plants enjoy the cooling
effect of the LECA and
the constant moisture
• Adapt readily to growing
this way

94. Evaporation Reducing Barrier
(Ray Barkalow)
Orchids grown in a very dry environment often have issues
with extremely fast evaporation of water from the top-most
parts of the LECA growing medium, and the resultant
relatively fast buildup of mineral and waste products.
While frequent watering and flushing may be one way
to remedy that, many find that an evaporation reducing
barrier, placed on top of the pot, may be a big help. A sheet
of clear, flexible plastic film, and a pair of scissors is all you
need.
Another option is a finer top layer such as acquarium stone.

95.  Cut a circular disk of the plastic that is approximately one
inch smaller in diameter than the interior of the pot.
Choose a plastic that has more rigidity than food wrap –
such as plastic page sleeves purchased at an office
supplies store.
 Cut a slit from the perimeter to the center of the disk.
 Cut out another hole in the center that will accommodate
the base of the plant, again making it about one inch
larger in diameter.
 Separate the cut ends of the plastic disk and carefully
place it around the base of the plant, and you’re all done!

96.  As the water evaporates from the pot, a good deal of it
will condense on the lid and drip back into the pot,
keeping it more uniformly moist, top-to-bottom.
 There is no need to remove it for watering, just flood
the pot, filling it rapidly to the top as you should always
do, with the water entering around the plant base, and
the perimeter of the pot.

97. Pests to watch for (slugs
love water)

98. Potential Problems and
Issues
 Water quality
 Algae growth on container
 Rolling stones of Hydroton on floor!
 Transportation (to shows, etc.)
 Fungus gnats (use insectivorous plants
to catch them)

99. Genera probably not suited for S/H
Dracula
Stanhopea
Tolumnia
Species and genera that prefer to be mounted

100. More Information
 www.FirstRays.com - Extensive information on SH; sells
KelpMax root solution
 www.OrchidBoard.com - Semi-Hydroponic-Culture section
 Do an internet search for Semi-Hydroponic or Semi-Hydro
orchids for all kinds of websites, YouTube videos, etc.
Alternatively search for orchid water culture.
 Facebook has several pages devoted to orchid water culture
(Orchid Water Culture, Orchids in Water Culture, and Water
Culture Orchids & General Orchid Care) with thousands of
members. Facebook pages for SH are Growing Orchids in
Semi-Hydroponics and Semi-Hydroponic Orchid Growing.

101. More
 Orchid Room (YouTube). Annabel Minton (UK) has a number
of useful videos.
 What is Semi Hydro? | Semi Hydro Orchid Setup Explained
for Beginners. Anna Maria of Miracle Orchids gives advice.
 How to prepare LECA (hydroton) for semi hydro orchid
culture - clean and stabilize the pH. Miracle Orchids also has
How to water orchids in semi hydro - the correct and easy
way to do it!

102. Thank you.
Questions?
Harvey Brenneise (Harvey.Brenneise@gmail.com)
https://www.slideshare.net/Sky7Bear/growing-orchids-in-water