Weather and the Gardener
Once spring has really arrived to stay and summer is not far away, the essential ingredients for good growth are energy from the sun, plant food from soil nutrients and, most of all, soil moisture available to the roots, without the rest are useless. Although rainfall is usually well distributed throughout the year, there often are dry spells, especially during the summer half-year, when evaporation from the soil and transpiration from the trees and plants exceed the rainfall replacement so that the soil moisture reserves decrease. To make good this deficit, gardens need watering or irrigation.
If we could only see the water used by gardens, it would be easier to realise how much soil moisture is lost to the atmosphere. At this time of year a garden will use 2.5cm (1in) of water - 24 litres per sq metre (4 1/2 gallons per sq yard) - every 10 days on average.
For maximum growth this loss should be replaced by rainfall plus watering, to maintain soil moisture at the optimum level. It is the vegetable garden which profits most from skilful maintenance of soil moisture regimes; heavy crops cannot be grown on a dry soil.
Trees and Shrubs
Those in flower in the month of May include crategus (hawthorn, may), laburnum (golden rain), malus (crabs), prunus (almonds, apricots, cherries, peaches etc.), pyrus (ornamental pear), sorbus (mountain ash), camellia, ceanothus, chaenomeles, Choisya ternata, cotoneaster, cytisus (broom), daphne, enkianthus, erica (heaths and heathers), genista (broom), helianthemum (rock rose), kerria (Jew's mallow), lonicera (honeysuckle), magnolia, paeonia (tree paeony), potentilla (cinquefoil), pyracantha (firethorn), rhododendrons (including azaleas), rosa (rose), clematis, lonicera (honeysuckle) and wisteria.
Pruning
Remove weak, straggly, diseased or old shoots from plants which have flowered in earlier months.
Cut, or pinch out with finger and thumb, dead flower heads of rhododendrons, azaleas and ericas (heaths and heathers).
Remove about two thirds of the length of the stems of recently planted evergreens such as cotoneaster.
Planting
Shrubs that need the protection of a sheltered position to survive cold winters are planted now; these include Cytisus scoparius (broom), choisya, and some fuschias, magnolias and hydrangeas. Water in thoroughly after planting.
Flowers
Thin out congested new shoots of clump-forming plants such as delphiniums, Michaelmas daisies, phlox, solidaga and lupins, to about 2.5cm (1in) apart, to encourage strong flowering stems.
Keep down weeds. How them out with a Dutch or swan-necked draw hoe, when they are so small you can hardly see them. Leave them to dry on the soil surface. Deep rooting perennial weeds such as bindweed, nettles, docks and thistles are best forked out, to remove as much of the root as possible.
Alpines
Plant summer-flowering species such as achillea, anthemis, epilobium, erigeron, penstemon, thymus, veronica and zauschneria, in gritty soil enriched with bine meal.
Top dress every part of the rock garden with a gritty mix of equal parts loam, peat, sharp sand, adding a arge handful of bone meal (sterilized) to each bucketful of the mixture. Spread this over the soil to a depth of 2.5cm (1in).
Bulbs
Plant acidantheras, Anemone coronaria, dormant begonias, gladioli, ranunculi, tigridias, and other summer flowering bulbs and corms. Set them to a depth of about three times their average diameter in well prepared soil.
Lift spring flowering bulbs such as daffodils, tulips and hyacinths, whose blooms have already faded and where the ground is needed for summer bedding, and replant them in good soil in a spare part of the garden in full light. Lift and dry off the bulbs when the leaves have turned brown and withered.