Trees and shrubs

1. RHS Level 2
Certificate
Week 26 – Ornamental trees and
shrubs

2. Quiz
 10 questions – 15 minutes
 Exam conditions please
 Put your name on the quiz sheet as I
will collect in and mark to return after
Easter.
 NB – no class for the next two weeks.
Next session is on 19th
April.

3. Learning objectives
3. Understand the choice of woody plants for display and their
establishment and maintenance.
3.1 Name TEN trees suitable for growing in a domestic garden
3.2 Name TEN shrubs suitable for growing in a domestic
garden.
3.3 Name FIVE trees grown for winter interest and FIVE
grown for autumn display.
3.4 Name FIVE shrubs grown for winter interest and FIVE
grown for autumn display.
3.8 Describe the soil preparation and planting for trees and
woody shrubs.
3.9 Describe the routine maintenance for trees and woody
shrubs, to include pruning and the control of weeds and
common pests and diseases (aphids, powdery mildew,
black spot of roses, canker, coral spot, honey fungus).

4. Selecting Trees and Shrubs
 Be aware of final size and spread – allow
for the mature size when planning
planting.
 Forest trees do not belong in small
gardens!
 What season of interest?
 Bare root, container-grown or
containerised?

5. Bare root, containerised or
container grown?
 Bare root – plant in Autumn/Winter. A narrow window
for planting and only small plants available. However
cheapest and small plants often establish better than
large ones.
 Containerised – can be planted at any time of year and
you can see what you are getting in growth.
Disadvantages – possible limited root system, may
become pot bound.
 Container grown – most expensive, plant at any time
of year (provided you water them). May become pot
bound before sale. Large specimens may not
establish well.

6. Buying a healthy plant
 Check for dead, diseased or distorted growth
and any signs of pest infestation or fungal
problems. Signs of nutrient deficiency suggest it
has been in its pot too long.
 If the compost is very dry this suggests lack of
care.
 Avoid pot bound woody plants. Look for large
amounts of root growing through the base of the
pot and algae or moss on the surface.
 Look for a good shape and balanced growth –
an ‘ugly’ tree will be very hard to correct.

7. How to plant trees and
shrubs – changing practice
 Old approach was to enrich the soil in the
planting hole with compost and fertilizer.
 However this can encourage the roots to
remain in the hole.
 Poor soil should be improved in a wide area
around the site before planting instead.
 Previous advice was to dig a deep hole – twice
the depth of the root ball. Danger is that this
slumps, taking the tree too deep. Current
thinking is – wide but not deep.

8. How to plant (1)
 If soil is poor improve the whole area.
 Hole - 2-3 times the width of the root ball but
only slightly deeper. Square holes – encourage
root penetration.
 Fork over the bottom and sides of the hole. Add
mycorrhizal fungi if using- do not mix. Remove
plant from container and tease out roots.
 If planting bare root plant - untangle the roots,
trim any broken ones. Spread out the roots in
the hole. Take care not to plant deep.

9. How to plant (2)
 Position the plant centrally and use a cane to
ensure it is planted at the same level as the
nursery mark/crown. Add the stake if needed –
before filling so you can see the rootball to avoid it.
 Attach the tree to the stake using a tree tie with a
rubber stop.
 Then backfill in stages firming the soil with hands or
(very carefully) with your boot toe.
 Water in well – two cans of water at least.
 Mulch with organic matter drawing it well away from the
stem or crown to avoid rotting.

10. Stakes for trees
 Trees need to flex in the wind in order to grow
a strong trunk and a good root system.
 A stake is only needed until the roots take hold
firmly – exceptions for some dwarf apple trees.
 Stake must not go through the root ball – this
may kill the tree.
 Ideally, stake at 45° angle and secure the tree
low down.
 Any tree less than 1.5m in height should not
need staking unless very exposed.

11. Maintenance for trees and
shrubs
 Watering – keep well watered whilst establishing.
For trees this is 2-3 years.
 Feeding – feed spring flowering shrubs after
pruning; summer flowering shrubs as they begin
to grow in spring. Trees should not need feeding.
 Weeds – keep under control by handweeding;
remember that turf will compete with tree roots.
 Mulch – keep mulched to suppress weeds and
retain moisture.

12. Basic pruning techniques
 Tools – sharp bypass secateurs, pruning
saw, pruning knife and small steel for
sharpening.
 Shoots and small branches – look at how the
buds are formed. Alternate – cut 5mm above
an outward facing bud, sloping away from it.
Opposite – a straight cut 5mm above a pair of
buds.
 Branches – reduce the weight first, then
make an undercut at the branch collar and a
top cut down to meet the undercut. Do not

13. Pruning Trees
 In autumn for most trees, in summer for Prunus
and winter for trees that ‘bleed’ e.g. Betula sp.
 The four ‘Ds’ – remove dead, diseased,
damaged or ‘dysfunctional’ shoots and
branches.
 Remove suckers and ‘water shoots’
 Remove any reversion from variegated plants.
 Prune to shape and train young trees – keeping
the stem clear.

14. Pruning shrubs
 Spring flowering shrubs flower on last years
wood. Prune these immediately after flowering.
 Summer flowering shrubs flower on this years
wood. Prune these in the early spring, as soon
as the danger of hard frost is past.
 Shrubs grown for winter bark colour are pruned
to maximise new growth. E.g. Cornus alba is
coppiced to a low stool in early spring.
 Four ‘Ds’ apply to shrubs too; remove reversion
and any suckers in the same way.

15. Diseases
 Coral spot – normally on
dead or dying wood, but
can infest living wood.
Usually a sign of other
problems.
 Control – hygiene (burn or
bin prunings etc); do not
leave snags or cut flush to
the trunk; prune out
infected wood. Improve
growing conditions.

16. Diseases
 Canker – fungal or
bacterial in origin.
Often starts at pruning
wounds or damage.
 Slowly girdles the
shoot, causing death.
 Prune out to clean
wood, clean tools
between cuts. No
chemical control.

17. Learning outcomes
3. Understand the choice of woody plants for display and their
establishment and maintenance.
3.1 Name TEN trees suitable for growing in a domestic garden
3.2 Name TEN shrubs suitable for growing in a domestic garden.
3.3 Name FIVE trees grown for winter interest and FIVE grown for
autumn display.
3.4 Name FIVE shrubs grown for winter interest and FIVE grown
for autumn display.
3.8 Describe the soil preparation and planting for trees and woody
shrubs.
3.9 Describe the routine maintenance for trees and woody shrubs,
to include pruning and the control of weeds and common pests
and diseases (aphids, powdery mildew, black spot of roses,
canker, coral spot, honey fungus).