Spring Gardening Calendar
Bulbs make an important impact on the garden scene this month, as the winter-flowering crocuses flower in profusion and the blue, mauve, and purple cultivars of Iris reticulata come into full bloom, together with chionodoxas, Scilla sibirica, Anemone blanda, and the first(Narcissus). Later-flowering cultivars of the winter-flowering heathers (Erica) break into bloom this month, taking over from those that started in December and January. Forsythias open their yellow bells and the yellow Oregon grape (Mahonia aquifolium) and bright red and pink flowering quinces (Chaenomeles) begin blooming. Lungworts (Pulmonaria) produce of red, pink, and blue to start off a new season, while the earliest leopard’s bane (Doronicum) opens the first yellow daisies.
Finish putting in border plants and lifted trees and shrubs as soon as possible. Shear off the dead flower-heads from those winter-flowering heathers that have finished blooming, in order to keep them compact. Take cuttings of delphiniums and lupins as soon as the shoots are about 100 mm (4 in) high. Make sure each has a solid base, and set them in pots of rooting compost in a frame. Scatter general fertiliser around hardy border plants and and mix it into the surface. Towards the end of the month prune and hypericums; also deal with hybrid tea and and davidii before the month is out. Layer shoots of deciduous shrubs to make new plants, before their leaves get in your way. Plant a batch of gladioli for early flowers.
Daffodils and narcissi make a brave show this month, together with the early tulips, blue grape hyacinths, and the majestic crown imperials (Fritillaria). Yellow leopard’s bane flowers make a sunny display and are joined by Omphalodes cappadocica, epimediums, bergenias, and the earliest-flowering ajugas. Perennial yellow alyssum, purple to red au-brieta, and white arabis make masses of colour wherever grown as ground cover. The periwinkles (Vinca) start flowering in earnest this month, as do evergreen barberries () and Jew’s mallow ( ), while the flowering crab-apples (Malus) and snowy mespilus ( ) cover themselves in blossom and the early-flowering brooms ( ) burst into colour.
Sow seeds of hardy annuals to flower in summer. Also, sow seeds of perennial border plants, such as oriental poppies (Papaver), lupins, and coral flower (Heuchera) in a prepared seedbed out of doors if a lot of plants are needed cheaply. They are rarely up to the quality of named varieties, but help stock a new garden until better plants can be afforded. Plant gladioli for the main summer display. Start staking quick-growing border plants, such as delphiniums. Late April is a good time to put in evergreen trees and shrubs, including conifers. Make sure they do not dry out after planting, and syringe them with water in the evenings of dry days. Prune forsythias and other spring-flowering shrubs, if necessary, when their display has finished. From now until autumn trees, shrubs, and plants that have been raised in containers can be successfully established, but they will need to be watered whenever the soil around their roots begins to dry out. Keep down weeds by hoeing or treating the soil with a paraquat weedkiller.
Late narcissi are joined by regiments of colourful tulips and the bluebell Endymion hispanicus (syn. Scilla campanulata). The pretty cultivars of the dead-nettle (Lamium maculatum) produce their pink spikes, which go well with the variegated leaves. By now all the plants grown for their foliage – silver artemisias and lamb’s tongue (Stachys lanata), the hostas in wide array, the brilliant ajugas, the variegated and yellow- and purple-leaved shrubs – are contributing colour to the scene. Masses of blossom are provided by Japanese cherries (Prunus), the flowering thorns (), wisterias, and Clematis montana.
Thin out and weed hardy annuals sown earlier and support the taller ones; continue staking and tying border plants as they grow. Prune the early, small-flowered clematis, flowering quinces (Chaenomeles), and other shrubs when they have finished blooming. Watch out for attacks of greenfly and other pests from now on and spray with insecticide to control them as soon as they appear. About the middle of May dormanttubers can be planted in the garden. If you want to divide them use a knife and split the clumps so that each has a small section of the old stem attached; it is from the area close to the stem that the new shoots arise. Towards the end of the month half-hardy bedding plants can be set out in mild areas where danger of further frost is unlikely. Check regularly to make sure newly planted evergreens and container-grown plants are not suffering from drought.