RHS Level 2 Certificate

Week 25 – Ornamental trees and shrubs

Quiz

10 questions – 15 minutesExam conditions pleasePut your name on the quiz

sheet as I will collect in and mark to return next week

Learning objectives3. Understand the choice of woody plants for display and their

establishment and maintenance.3.1 Name TEN trees suitable for growing in a domestic garden3.2 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).

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?

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.

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.

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.

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.

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 heel.

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.

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.

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.

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 leave snags, tidy up carefully with a pruning knife.

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.

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.

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.

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. Copper fungicide on cut surface.

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 garden3.2 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).