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Pruning Proteas
Blue
Mountain Nursery has a pamphlet in its "The facts" series on pruning proteas.
Essentially it makes the following points:
If you want a tidy and productive plant you will need to prune properly. Different species require different treatments, especially the genus Protea.
For Pr cynaroides and Pr speciosa that grow from a lignotuber or root sock (sic) that are "cut back" to ground level by fire, frost or mowers (!), you do not need to prune. Rather cut flower or seedhead stems to 100 mm from the ground to encourage basal growth.
Most other proteas need tip pruning when young. This should be done just before the new growth starts (from September to March). Cut back to leave about 100 mm every year if the plants produce longer stems without branching. After the third year allow flowers to form. No further tip budding is required, but cut fresh flowers or remove seedheads by cutting back to leave 100 mm of current-year’s stem (i.e. with leaves!). Leaving seedheads on the plants will encourage a scraggly plant. They also recommend that you disbud the buds that develop below the flowerheads to give a clean, unobscured blossom.
Pr grandiceps and Pr magnifica "do their own branching". Here a tidy plant will need to have the shoots that run at ground-level removed "to keep the plant off the ground."
All Pincushions and Conebushes can be treated the same, except for the Silver Tree. If
pruned/tipped you can grow "multistems" to 3m tall in this species. For the
others:
If young plants reach 300 mm without branching, tip them to 100 mm. Tip prune
all stems in October to 100 mm of current-year’s stem. Let flower in year three,
and then cut off old flowers, leaving 100 mm of current-year’s stem. Cutting
long stems for the vase will encourage strong growth. Heavier pruning may be required in
the 4th/5th year to thin the bush. Also remove branches tending to
sprawl or creep. Blue Mountains recommends that you mulch your plants after flowering with
compost and "Hoof and Hornmeal".
While the above are adequate for most gardeners, protea enthusiasts growing a wider selection of natural species are bound to encounter problems. For instance, all genera have resprouters that need to be treated like Pr cynaroides. Can we make some generalizations?
The major factor to be considered in pruning proteas is the mode of fire survival used by the species. (More details on this can be found in PAN 7:8-10). Note though, that when dealing with natural plants there is considerable variation between individuals and some caution is required – err on the conservative side before getting too drastic. By contrast, most cultivars and commercially available plants can be treated as identical clones - individual consideration will not be necessary – and horticultural advice can be stringently followed.
If you do wish to experiment with feeding your plants with bone- or hoof-meal as suggested, please expect to have to replace your plants shortly. The high phosphorous levels in these will usually kill your plants.
There are seven major growth habits in proteas with regard to pruning:
- Those with underground stems cannot really be pruned. The flowers are borne at ground level, or on very short stalks, and the stems are not evident for pruning. Very few of these species are grown. These are all Protea in the Dwarf-tufted, Snow and Western-Ground groups.
- Some are generally arborescent with buds beneath the mature stems. These can generally be pruned as you wish, and will even take severe pollarding or lopping. New branches will appear along the stems, and you can disbud these to create the plant shape you desire. Young plants will need training – you can choose between a tree form or a multi-stemmed shrub (see next group). Examples include Pr nitida and Pr caffra, but not Ls conocarpodendron, Mi fimbriifolius or Pr roupelliae, which, although they have a similar growth habit, escape fire rather than surviving it, and must be treated like species that are killed by fire.
- Those with underground rootstocks can be severely pruned back to near ground level or shaped as you wish. Examples include Pr cynaroides, Mi cucullatus, Ls cuneiforme and Ld salignum.
- Species that typically are killed by fire, cannot be heavily pruned. All pruning must be confined to stems with healthy leaves. Pruning into leafless stems will kill those stems. Careful training must therefore be initiated in young plants, as outlined in the Blue Mountain Facts. However, if this year’s growth has lost its leaves at the base, retain some leaves otherwise the stem will die.
- The exception among the fire-killed species are those with axillary branches. These species can be treated as hedge plants – provided that they are pruned from an early age – and cut back heavily into older, but not very old, wood. Examples include Ld coniferum, Ld meridianum, Ld salicifolium and Ld eucalyptifolium. These are all fast-growing and suitable as screens and hedges. With caution this can be applied to the White Proteas (e.g. Pr mundii) as well.
- Species with "corymbose" growth habits are interesting in that they produce vegetative growth at the base from which erect reproductive growth emerges. As a rule the reproductive growth can be severely pruned and new stems will grow from within the vegetative growth. Do not prune the vegetative growth beyond what is required for cosmetic purposes. Examples of these plants are some of the Delta-seed Conebushes (e.g. Ld uliginosum, Ld rourkei), Ld ericifolium, corymbosum and our new Conebush.
- Species that creep along the ground tend to be better able to handle severe pruning than sprawling and erect plants. Thus Ls heterophyllum or Ld pedunculatum could be heavily pruned, whereas the similar Ls calligerum would not tolerate heavy pruning. Note that some species resprout (e.g. Ls prostratum, Pr tenax) and even though prostrate, could be treated as resprouters should you wish to prune them. This would only normally be done to rejuvenate the plants when they start becoming moribund.
If you have any tips, or know of additional advice – please tell us!
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