Managing Trees and Shrubs in June
Continue trimming hedges to keep the growth dense, right down to the base. Check for weeds along the bottom of your hedges and remove brambles, nettles and ground elder before they get a foothold. The quick growing types, such as privet and Lonicera nitida, will need clipping two or three times a year if they are to stay within bounds and form a dense hedge.
Keep the ground around trees and shrubs free of grass, so they do not have to compete for water and food.
Water shrubs and climbers, especially all plants growing against walls, if the weather is warm and dry. Also continue to water newly planted trees, shrubs and climbers generously at this time of year, as a severe dry spell can kill them.
If you have a laburnum, remove all pods within a child's reach and sweep up any that fall, as they are very poisonous and children can be fascinated by them.
Pruning Shrubs in June
Prune wall-grown shrubs which have finished flowering to keep them in-check and prune any early flowering shrubs to encourage the growth of new shoots to provide next year's flowers. Early flowering ceanothus (such as c. dentatus, C.'Delight' and C. thrysiflorus) and japonicas (Chaenomeles) should both be cut back to within 10 cm (2-4 in) of the old wood.
The main exception to the prune after flowering rule is for shrubs that provide winter berries, such as firethorn (Pyracantha). So if you prune hard after flowering, you will have virtually no berries in the following autumn and winter.
Take special care when pruning clematis, and if in doubt check the name of the variety to beforehand. June is the time to prune the early flowering clematis the evergreen C. armandii, C. montana, C. alpina and C. macropetala, and their named forms. These wont necessarily need pruning every year, but only when they start to overcrowd their neighbours. This is most likely to be the case with C. montana, which can be totally dominating, and C. armandii, if grown in a particularly favourable spot. Start by cutting out all the old and weak growth, and shorten the remaining growth by about half. By pruning now, you give the plant the whole summer to form new shoots, which will carry masses of blossom next spring.
Continue to deadhead lilacs, rhododendrons and azaleas as they finish, to keep the garden tidy and to conserve the plants' strength.
Many grey-leaved shrubs, notably Senecio x 'Sunshine' (S. laxifolius, S. greyi of gardens), artemisia (A. asborescens) and cotton lavender (Santolina chamaecyparissus) should have their flower buds removed as they form towards the end of June. Once these shrubs flower, the leaves lose their fresh, silvery sheen and the growth generally becomes lax and floppy.
The main display of deutzias, weigelas and bridal wreath (Spiraea x arguta) should be over by the end of the June. When flowering has faded cut out any old, dead or crowded wood and remove some of the flowered shoots at ground level to make way for new growth.
How to get Blue Hydrangeas
If your soil is alkaline and you want blue hydrangeas, then now is the time to apply aluminium sulphate, sequestrene or a proprietary blueing compound to the soil now (in accordance with the manufacturer's instructions). Else the flowers will come out a muddy pink, no matter how blue they were when you bought the plant.
Taking Care of Roses
To create top-quality large flowered rose blooms on Hybrid Teas, for exhibition or just for cut flowers, start to dis-bud them now. Simply restricting the number of flowers to the central or crown bud on a stem, will encourage larger, but fewer, blooms.
The opposite method can be used for cluster flowered Floribunda roses, by removing the crown bud, so the remaining buds get more nourishment and flower better.
Keep deadheading roses to encourage the production of more flowers. Leave the heads though, if you are saving seed for propagation or if you are growing roses that have pretty hips, such as Rosa moyesii and R. glauca (rubrifolia) which add colour to the garden in autumn. When deadheading, cut back the whole section that has flowered back to a strong bud that is pointing in the direction you want the new shoot to grow.
Continue to spray against blackfly, greenfly, mildew and blackspot. Also remove any suckers that have grown up from the roots, as for May.
Shrubs for June
Deciduous trees and shrubs in flower:
Kolkwitzia (beauty bush)
Philadelphus (mock orange)
Robinia pseudoacacia (locust tree)
Spiraea x vanhouttei
Viburnum opulus & plicatum
Evergreen trees and shrubs in flower:
Cistus (rock rose)
Hypericum (Rose of Sharon)
Phlomis fruticosa (Jerusalem sage)