Pruning Australian Native Plants
In natural conditions plants are constantly subject to pruning – animals eat the foliage and break branches as they trample through the bush. Unless the damage is severe the plants survive these set-backs and vigorous, healthy new growth follows.
Why Prune?
♦ Appearance and flower production
Garden design, personal preferences and the function of a particular plant determine the type and degree of pruning for appearance each plant should be given. For example a screening plant might be regularly pruned to make it bushy, or a plant in a natural bushland setting might only be occasionally lightly pruned to blend in with the rest of the garden while maintaining a “natural” appearance.
Use these methods to achieve your desired appearance:
♦ Pruning for shape
Heavy pruning is used to remove unwanted growth so a plant remains in proportion with the rest of the garden. Pruning to ground level is used on plants with a lignotuber, and suckering plants, to encourage the growth of multiple stems leading to a better shape, more foliage and more flowers. Lignotuber is a woody swelling at or below ground level containing buds from which new growth forms if the top of the plant is cut or burnt.
♦ Tip pruning
Carried out by pinching out the growing shoots forcing the plant to make new growth further back along the branch. This increases the number of flowers, makes the plant bushy and prevents it from becoming straggly. Tip pruning can be started when the plant is young.
♦ Flower picking
Picking flowers for indoor use and removal of old flowers immediately flowering finishes, stops the plant putting energy into seed production thereby increasing flower production next season.
♦ Regular light pruning
Used to promote and maintain dense growth of hedge and screening plants right down to ground level.
♦ Maintenance of plant health
Remove diseased and damaged wood as soon as possible. Clean out unwanted foliage in the centre of the plant to promote air movement and allow light to penetrate, thereby discouraging pests and disease.
♦ Rejuvenation of old plants
Severe pruning rejuvenates and extends the life of many types of plants such as callistemons, grevilleas and others with a short life span.
Plants with a lignotuber should be pruned to near ground level just above the lignotuber. Lignotuber is a woody swelling at or below ground level containing buds from which new growth forms if the top of the plant is cut or burnt.
Pruning Rules
♦ Keep pruning tools sharp and clean
Ensure your pruning tools are sharp, and kept clean by regular washing in disinfectant. Blunt, dirty tools damage plant tissue and introduce disease organisms. Keep the cutting blades of secateurs and shears free of build-ups which might wedge between the blades springing them apart leading to bruising of plant tissue and ragged cuts.
♦ Use the plant’s natural habit of growth as a guide to its pruning requirements
Plants which grow slowly should only require light pruning to keep them tidy and well shaped. Fast growing plants may require frequent tip pruning and general pruning.
♦ Prune shrubs back by about one third of the new growth and always ensure some green leaves remain
This rule applies except in extreme circumstances such as rejuvenating an old plant, or where specific knowledge of a particular plant’s response to pruning suggests a different approach. Hard pruning into old wood may kill some plants or cause the loss of next season’s flower crop in species such as leptospermums, melaleucas and hakeas.
♦ Pruning cuts
Make pruning cuts at an angle so water will run off and not collect in growing shoots where it will encourage fungal growth. Undercut branches before making the top cut to remove them. This ensures a clean cut by preventing bark underneath the branch being torn from the plant or wood splintering as the branch falls away. If the branch is very heavy, cut it off a few centimetres further out from the trunk than your final cut so that most of the weight has been removed. Then make your final cut to remove the remaining short stub of the branch from the plant. Disguise cuts by making them inside the plant’s foliage envelope so that the cuts are hidden by the remaining foliage.
♦ Old and over-size plants
If a plant has got to the stage where you have nothing to lose, prune hard and see what happens. Plants requiring constant heavy pruning to constrain their size are too big for the location. Consider replacing them with a smaller plant.
When to Prune
Depending on your local climate and current weather patterns, late winter to early summer and late summer to early winter are generally the the best times to prune in Victoria.
♦ Established plants
Remove old dead flowers immediately after flowering. General pruning as needed whenever weather conditions are suitable.
♦ New plantings
Tip prune from an early stage if a bushy, compact plant is desired. On planting, establish the future shape of the plant by removing unwanted branches.
♦ Warning:
Never prune when there is the likelihood of damage to new shoots from extremely cold, hot or wet weather conditions. Do not prune flowering plants while flower buds are forming, if flowers are desired next season.
Pruning Notes for Specific Species
These notes supplement the pruning rules and should be read in conjunction with them. They are based on the experience of people living in southern Victoria.
♦ Acacia species
Trim to shape when planted. Thereafter remove dead wood, and, if required, straggly branches. If a bushy plant with heavier flowering is desired, prune immediately flowering has finished as far down the branch as the green wood or the last leaf buds nearest the trunk (typically about one third of the branch).
♦ Alyogyne species
Pruning is desirable to prevent them becoming straggly. A. hakeifolia – Straggly plants can be rejuvenated by cutting back to near ground level during spring. They will rapidly reshoot.
♦ Anigozanthos species (Kangaroo Paws)
Should be cut back to 25mm above the ground after flowering.
♦ Banksia species
Must not be pruned below the lowest green foliage as they will not reshoot from a leafless stem. For many species a savage pruning will rejuvenate them. Some species from fire-prone areas have a lignotuber and can be reinvigorated by pruning to near ground level above the lignotuber.
♦ Brachyscome species
Brachyscomes are generally annual or perennial herbs bearing typical daisy-type flowers. Removal of spent flower heads often produces a new flush of blooms. They should be pruned and fed a little fertiliser when they have finished flowering or begin to look a bit untidy. B. multifida – Wait until they start sending up new growth in early spring, then cut off the old growth.
♦ Correa species
All species should be pruned immediately after the main flowering as soon as the new shoots come in spring, then regularly tip pruned to keep the flowers coming.
♦ Callistemon species
Most callistemons can be heavily pruned after flowering. An exception is Callistemon viminalis and its cultivars, which have a weeping habit of growth and can be damaged by pruning. For all species remove the seed cases along the plant’s stems by pruning to promote more flower stems. Old plants can be rejuvenated by cutting them back almost to ground level.
♦ Chorizema species
Tip prune lightly after flowering if desired.
♦ Epacris species
Prune the shoots after flowering – erect types to within 2-3cm of the base, and pendulous types to half way along the new growth.
♦ Eremophila species
Prune early in their life to make them bushy and then to prevent them becoming straggly. E. glabra – Can be savagely pruned.
♦ Eucalypt species
E. caesia – Can be coppiced and will reshoot from the lignotuber at the base of its trunk. Eucalypts with blue-grey juvenile foliage – can be kept as bushy shrubs with juvenile foliage by cutting periodically to 20-30cm from the base.
♦ Goodenia species
Respond well to cutting back to ground level.
♦ Grevillea species
Cut on an angle just above a leaf node because this is where new growth shoots form. Rejuvenate straggly plants by cutting them back to near ground level during spring. Some cultivars such as G. ‘Robyn Gordon’ and G. ‘Superb’ respond well to this treatment.
>> Further information on pruning Grevilleas
♦ Hakea species
Cut on an angle just above a leaf node as this is where new growth shoots form. Straggly plants can be cut back to near ground level during spring and will rapidly reshoot. Some species can be pruned down to bare wood.
♦ Indigofera species
I. australis – Must either be lightly tip pruned after flowering or cut back to ground level and left to reshoot. Other types of pruning are not tolerated.
♦ Melaleuca species
All respond well to pruning, and some species can be pruned down to bare wood. Melaleuca ‘Green Globe’ – Can be heavily pruned almost back to bare wood.