Timothy Walker
The Subtle Art and Precise Science of PRUNING – Timothy Walker.
Pruning problems are now a thing of the past since we have had the pleasure of listening to Timothy Walker and his talk entitled “The Subtle Art and exact Science of Pruning”.
Timothy was Director of the Oxford University Botanic Garden for 28 years and during his tenure the Garden was awarded 4 Gold medals at Chelsea Flower Show.
Timothy’s talk put all plants into groups for pruning purposes: Whether it is necessary and when, and when not to prune. His entertaining anecdotes and lively delivery make these rules easier to remember too.
His introductory message was that although pruning can cause fear and panic, one should not worry unduly - most plants do not need to be pruned and if they are healthy, flowering, fruiting well and the correct size and shape, they can be left alone. This is the “first Rule” - the full 10 rules are shown further below.
Pruning is a technique which can: increase flowering, improve fruiting, control the size of the plant, control the size and colour of the leaves and help to rejuvenate a plant - but it may not be the answer if something is wrong. Good horticulture is what is needed to keep a plant healthy, and vigorous. For instance, the case of a Magnolia siboldii sinensis that didn’t flower because it was underplanted with a Bergenia.
Wisteria is a special case: it is usually pruned twice a year, but Tim suggests pruning once, when the flower buds are showing - just prune all growth from there.
Timothy’s rules for pruning are thus:
Rule 1. No pruning is best, eg Acacia.
Rule 2. Pruning cannot work miracles. In the example of Kalmia latifolia where although it was correctly planted in an acid soil, it also needed more moisture to flower well.
Rule 3. Before starting to prune, look it up in the bible of pruning: The Pruning of Trees, Shrubs and conifers by G. Brown and Tony Kirkham.
Rule 4. Pruning is best carried out when the plant is either dormant or growing fast. Tim gave us the example of the Clematis Armandii that he cut to the ground which unfortunately did not recover.
Rule 5. Use the right tools and keep them sharp.
Rule 6. Tree surgery should be left to qualified arborists, but one should do formative pruning to shape.
Rule 7. When pruning a tree, keep the wounds to a minimum and as small as possible. Cut to the branch collar, not flush with the stem and do not use wound paint.
Rule 8. The plant should be left in a natural shape. Unless it is a hedge, eg Yew that can be cut right back to the main stem (one side at a time).
Rule 9. Sometimes the plant will die despite your best efforts – eg Cotinus “Grace” Some plants have a short life span and some just die unexpectedly.
Rule 10. Most plants fall into one of eight groups when it comes to pruning.
1. None except for hygiene, eg hamamelis molis, Chimonanthus praecox.
2. None except for deadheading and moderate size restriction, (Generally evergreen plants) eg Ceanothos thyrisiflorus var. repens. Bupleurum fruticosum.
3. None unless too big, eg Euphorbia mellifera, Mahonia undulata var punctata
4. Flowering before July on last year’s growth, eg Ribes sanguineum “King Edward VII”, Garrya elliptica “James Roof”. Straight after flowering remove 20% of old wood preferably to the ground.
5. Flowering after July on this year’s growth, eg Lavertera “Barnsley”, Nandina domestica (female plant). Annual running is when the plant is dormant in winter – remove 20% of old growth to make a healthy frame of branches.
6. Flowering on spurs from mature wood, eg Buddleja globosa, Campsis radicans.
7. Stooling for stem colour or large foliage. Prune in early spring when the frosts have finished, eg Cornus alba, Cotinus “Grace”, Palownia tomentosa.
8. Flowering on biennial shoots. Remove shoots to the base after flower, eg Euphorbia characias “Portuguese Velvet”, Musa.
The accompanying notes that Timothy kindly circulated provided lots more examples of the plants which fall into these categories. However, the message that applies to the hesitant gardener is to prune when you have time to make a good job - most plants do recover from pruning if they have, either mistakenly or intentionally, been pruned at the wrong time. If they die, it is a planting opportunity!
Reviewed by Philippa Dodgeson EAGG Member