Top ten jobs for May – RHS
Summer’s on its way
As bulbs fade and herbaceous borders grow in leaps and bounds, it is now clear that summer is approaching. Sowing and planting out bedding can begin, depending on regional weather variations, and you can take softwood cuttings. It’s also time to get back into the lawn mowing regime, as the lawn will be loving the warmer temperatures this month brings
Trees and Shrubs
Cut back tender shrubs and sub-shrubs such as Penstemon, Caryopteris and Fuchsia after the danger of frost has passed.
Clip evergreen hedges. If not too woody, shredded clippings can be added to the compost heap, ideally in combination with soft material such as grass clippings.
Prune spring-flowering shrubs such as japonica or Japanese quince (Chaenomeles), Choisya and Ribes after flowering. Remove one stem in three from Kerria and Spiraea ‘Arguta’, and shorten the other flowered stems to a suitable sideshoot. Evergreens such as Viburnum tinus can also still be trimmed this month.
Prune overcrowded, dead or diseased stems of Clematis montana once it has finished flowering. Untangling the stems can be fiddly, but once you can see where you are cutting, you need not worry about pruning this plant – it will take even hard cutting back very well.
Late spring is a good time to coppice or pollard Eucalyptus.
Prune out frost damage from affected evergreen shrubs.
Young mimosa trees (Acacia dealbata) can also be cut back now. Mature trees respond less well to pruning.
Remove any reverted green shoots on hardy variegated evergreens, to prevent reversion taking over.
Prune wall-trained pyracanthas, removing any shoots coming out from the wall, and shortening other new growth to about 8cm (3in). This encourages spur formation, and increased flowering relative to green growth.
Tie in climbing and rambling roses as near to horizontal as possible. This will restrict sap flow causing more side-shoots to grow along the length of stem. Therefore more flowers will be produced.
Twining climbers (such as honeysuckle and Clematis) need regular tying in and twining around their supports.
Ensure newly planted trees and shrubs do not dry out. Water with rainwater or recycled water wherever possible.
Loosen any tree ties that are digging into the bark, or could do so soon as the trunk girth expands.
Take softwood cuttings of deciduous shrubs, including Forsythia, Fuchsia, Hydrangea macrophylla, Philadelphus and Spiraea.
Layering is a good way to propagate climbers and lax-stemmed shrubs. Layers should root by next spring, especially if attention to watering is given during dry weather. Examples to try include Philadelphus, Forsythia, Hydrangea and Lonicera.