July pruning of trees, shrubs and climbers
Early-summer- flowering shrubs can be pruned this month to keep them vigorous and flowering well. It is also the ideal time to prune several trees that are prone to bleeding if pruned at other times, and it’s not too late to complete the pruning jobs for June if you haven’t got round to them yet. I’ve given practical advice for pruning Abutilon vitifolium, Buxus, Carpenteria, Ceanothus, Cytisus battandieri, Escallonia, Euphorbia, Fremontodendron, Hebe , Helianthemum, Juglans, Kolkwitzia, Laurus, Lonicera, Paeonia, Philadelphus , Prunus, Rubus, Robinia pseudoacacia, Rosa, Sophora, Tamarix , Tilia, Viburnum, Weigela and Wisteria.
SHRUBS
Abutilon vitifolium
Although frost hardy, this abutilon can suffer from winter damage which should be pruned out after flowering. Deadheading spent flowers is also worthwhile.
Buxus (box)
All new box plants should be trimmed back by about half after planting to encourage bushy growth from low down on the plant. Thereafter, formal hedges and topiary should be trimmed this month once the initial spurt of growth is over. Pruning will then produce a sharp and neat outline that will last most of the summer. But if you grow it as an informal shrub, box does not require any routine pruning other than the removal of dead, diseased or damaged growth. If the shrub becomes lop-sided, over-long stems can be cut back to balance the outline. Old and neglected plants respond well to severe pruning and can be cut back to within 15-30cm (6-12in) of the ground.
Carpenteria
This early-summer-flowering shrub bears its blooms on wood produced in the previous season. No routine pruning is necessary, other than the removal of dead or damaged stems as well as any rubbing branches. However if you do need to prune do so immediately after flowering so that new wood has time to mature and ripen before the onset of winter. Mature branches that no longer flower can be rejuvenated by cutting back one-in-three stems to a younger shoot lower down or near ground level.
Ceanothus (Californian lilac)
Lightly trim ceanothus after planting to encourage a neat habit and bushy growth. Evergreen types such as Ceanothus arboreus ‘Trewithen Blue’, C. ‘Concha’, C. impressus, C. thyrsiflorus do not need routine pruning, but can be kept neat by trimming after flowering each year. Any lop-sided growth can be balanced, by cutting back long shoots by about one-third to a sideshoot lower down. However, evergreen ceanothus is reluctant to produce new shoots from woody stems so avoid pruning back into old wood. Old and neglected shrubs that are well clothed in foliage near the base can have all stems cut back by about half to sideshoots lower down on each stem, otherwise they do not respond to severe pruning and so are best replaced.
Cytisus battandieri (pineapple broom)
Little or no pruning is usually required, other than the removal of dead or damaged stems. Wall-trained specimens will need wayward stems cut back to the main framework and older plants can be rejuvenated by cutting out one of the older stems to a younger sideshoot low down that can be trained up the support to replace it. This is best carried out after flowering.
Escallonia
In the first spring after planting tip back the main branches to encourage bushy growth. Thereafter, little or no routine pruning is required unless you want to restrict growth. In this case prune after flowering. Wall- trained specimens should have flowered shoots cut back to a sideshoot near the main framework of branches that will grow and produce most of the flowers the following year. Escallonia grown as informal hedges can be trimmed now that flowering is over. Bear in mind that the harder you trim the less flowers you’ll get the following year. Old and neglected plants can be cut back hard, but you will loose the flowering display for a few years. If flowering finishes very late you could leave pruning until the following spring.
Euphorbia (spurge)
Popular varieties of euphorbia including E. characias ‘Wulfenii’ and E. myrsinites can have stems that have finished flowering cut back to the first sideshoot that hasn’t flowered lower down on the stem. Take care when pruning and wear long sleeves and gloves to prevent the irritant sap getting in contact with your skin. Old and neglected plants can be rejuvenated by pruning back hard to a stubby framework, but you will miss out on flowers the following season.
Fremontodendron
Little or no pruning is usually required, other than the removal of dead or damaged stems. Wall-trained specimens will need wayward stems cut back to the main framework after flowering. Old and neglected plants do not respond to severe pruning and are best replaced.
Hebe
Dwarf forms of hebe, such as H. pinguifolia, H. albicans, H. brachysiphon and H. rakaiensis, require little or no regular pruning, apart from the removal of winter-damaged stems and any that have died back. Otherwise, simply deadhead the plants by trimming off fading flowers using shears to keep the plants neat and dense. Hedges should be trimmed in the same way.
Helianthemum (rock rose)
Lightly trim rock roses after planting to encourage a neat habit and bushy growth. If they get too leggy and straggly you can cut the whole plant back lightly after flowering using a pair of secateurs. Feed and water well to encourage new shoots and, with luck, a second flush of flowers towards the end of the season. Old and neglected shrubs are best replaced.
Kolkwitzia (beauty bush)
Maintain the flowering performance of the beauty bush by pruning each year immediately after flowering. Cut back flowered stems to a sideshoot that hasn’t produced flowers or to a plump bud. Congested plants can have one-in-three stems removed, starting with the oldest. Old and neglected plants can be rejuvenated in the same way. Established plants tend to sucker and these may need to be removed.
Laurus (bay laurel)
Little or no pruning is usually required, other than the removal of dead or damaged stems. However, you can keep shrubs neat and rounded by pruning new growth back using a pair of secateurs. Bay laurel trained as standards will need any new shoots cut from the main stem. Hedges can also be trimmed at this time of year.
Lonicera (shrubby honeysuckles)
Shrubby honeysuckles, such as the popular evergreen L. nitida ‘Baggesen’s Gold’ and the flowering deciduous L. tatarica can both be pruned now. Evergreen hedges should be cut back by removing about half the new growth each year until they reach the desired height. Thereafter, trim the hedge during May and again in September. Flowering shrubby honeysuckles need no routine pruning, but can be kept neat and flowering well by cutting out one-in-three stems, starting with the oldest, after flowering is over.
Paeonia (tree peony)
No routine pruning is usually necessary, other than the removal of dead flowers or damaged stems. Leggy plants can be reshaped by pruning out one-in-three stems, starting with the oldest, after flowering is over. Avoid drastic pruning on grafted plants.
Philadelphus
Maintain the flowering performance of Philadelphus microphyllus by pruning each year immediately after flowering. After planting lightly trim to encourage bushy growth. In subsequent years cut back flowered stems to a sideshoot that hasn’t produced flowers or to a plump bud. Congested plants can have one-in-three stems removed, starting with the oldest. Old and neglected plants can be rejuvenated in the same way.
Rubus (ornamental bramble)
Ornamental brambles, such as Rubus cockburnianus, flower on wood produced the previous year, but are grown mainly for their attractive white winter stems. To get the best flowering and stem displays, remove stems that have flowered at this time of year by cutting them right back to ground level. The young stems left behind will have the best winter colour and will flower the following summer.
Rosa
Now in full bloom, all types of roses will benefit from regular deadheading as flowers fade throughout the month. Concentrate your efforts on repeat-flowering varieties.
Sophora
No routine pruning is usually necessary, other than the removal of dead flowers or damaged stems. This is best carried out during midsummer when the cuts are less likely to bleed. Wall-trained specimens need tying into their support and any wayward stems cut back or removed completely. Old and neglected plants are best replaced.
Tamarix
Prune early-summer-flowering tamarix, such as T. tetrandra and T. parvifolia, after the blooms start to fade - cutting all stems back by about half of the previous season’s growth.
Viburnum
The deciduous Japanese snowball tree (Viburnum plicatum) and the popular winter-flowering, evergreen V. tinus, can be pruned now. Prune the Japanese snowball tree carefully to preserve the natural tiered appearance. Viburnum tinus does not any need routine pruning other than the removal of dead or damaged stems and the reduction of over-long shoots. Hedges can also be trimmed at this time of year, but use secateurs to avoid leaving cut leaves on the shrub. Viburnum tinus also make excellent standards.
Weigela
After planting lightly trim to encourage bushy growth. In subsequent years, immediately after flowering, cut back flowered stems to a sideshoot that hasn’t produced flowers or to a plump bud – this will help maintain the flowering performance. Remove completely, any all-green shoots on variegated varieties. Congested plants can have one-in-three stems removed, starting with the oldest. Old and neglected plants can be rejuvenated in the same way.
TREES
Juglans (walnut)
English walnuts and black walnuts are prone to winter damage when they are young, so if the main leader is damaged, cut it back into healthy wood and train up another leader to take its place. Do not prune older trees unless absolutely necessary. They are prone to cavities after severe pruning if the collar at the base of the branch is damaged or stumps are left behind. For this reason it is worth raising the canopy when the tree is still young and keeping the stem clear as it grows.
Prunus
All prunus trees are prone to serious disease infection, such as silver leaf, through cuts made while pruning. It is, therefore, a good idea to keep any pruning to a mimimum and to prune only during midsummer when infection is much less likely. Prune out dead or damaged growth and remove suckers. Prune Prunus cerasifera hedges at this time of year too.
Robinia pseudoacacia (false acacia)
False acacia has brittle branches that’s prone to storm damage and in exposed gardens are prone to frost damage. They are best pruned in midsummer because the cuts are slow to heal. No routine pruning is necessary, but remove any suckers as soon as they are noticed. Old and neglected trees are best replaced.
Tilia (lime)
Limes are best pruned in midsummer because they are prone to bleeding if pruned in spring and slow to heal at other times. Most lime trees will form an attractive, well-balanced canopy without intervention and so require no pruning other than the removal of crossing or wind-damaged branches. Young trees should also be encouraged to produce a clear trunk, so remove lower side branches to gradually raise the canopy as the tree grows.
CLIMBERS
Wisteria
Wisteria is extremely versatile and can be trained against walls to form curtains of foliage and flowers or grown through pergolas where its pendant blooms can cascade overhead. It can even be trained to form impressive standards. No matter how you grow them, if you want to get a really spectacular flush of flowers you will need to prune them properly. This should be done twice a year, in summer and again in winter. By July, about two months after flowering, your wisteria will have produced masses of long wiry tendrils and if they are not required to extend the plant’s territory these should be roughly chopped back to within six leaves from where they join the main stem (this can just be done with a pair of shears if you like).
Next month: Buddleja alternifolia, Callistemon, Elaeagnus, Genista, Hydrangea, Laburnum, Philadelphus, Pyracantha, Rhus, Thymus and many more.
