Early in the Month
Sow annual climbers e.g. Asarina, Eccremocarpus, Cobaea, Ipomoea, Tropaeolum and Rhodochiton. Dead head daffodils and narcissi – feed them but DO NOT cut off the foliage. Keep an eye out for slugs and take steps to control them. Prune out any frost damaged shoots on less hardy shrubs such as Pittosporum. Plant summer flowering bulbs outdoors e.g. Gladioli and Nerine bowdenii, if you already have overcrowded clumps of Nerines in your garden lift and divide them now. For trouble free roses, spray with one of the safer rose combined pest and disease treatments or Uncle Tom’s Plant Tonic for an organic solution to rose diseases. Prune Forsythias and winter Jasmine after flowering. Finish dividing overcrowded herbaceous perennial plants. Plant summer flowering bulbs eg. Gladioli, Dahlias etc. Straggly silver foliage plants can be cut back now e.g. Saintolina. (but not down into old wood - that is risky). Lift and divide pond plants. This is also a good time to introduce new plants too. Plant Asparagus crowns and Jerusalem artichokes. Divide overcrowded clumps of Nerines and Siberian Iris. Treat potted ornamental plants with Bug Clear Vine Weevil Killer, as it acts as both a control measure and an insurance policy .One treatment lasts three months. Organically, place a half inch layer of horticultural grit on top of the compost to prevent successful egg laying. Cover some established strawberry plants with cloches to get an early crop. Plant new conifer hedges and trim established ones.
Tackle pernicious weeds, like bindweed, with a systemic weed killer containing glyphosate, it is best to use an “extra strong” version. Hardy annuals can still be sown in situ outdoors. Plant dormant dahlia tubers 10cm (4in) deep outdoors at the foot of support stakes. Undertake lawn renovations by repairing damaged edges and removing bumps and hollows. Watch out for whitefly appearing in your greenhouse, hang up some yellow sticky traps to monitor them. Plant some French marigolds or Coleus cannina near your tomatoes to deter the pests. Take conifer cuttings. Pull off 7.5 – 10 cm (3-4in) side shoots. Trim up the base. Dip in hormone and insert in free draining compost. Watch out for attacks of gooseberry mildew and gooseberry sawfly, these devastate bushes. Plant out cabbage, cauliflower, Brussels sprout and celery plants. Finish planting sprouted maincrop potatoes. Sow tomato seeds now for outdoor planting in June. Begin planting up hanging baskets, keep them inside until frost risk is minimal. Check your greenhouse regularly, as watering, shading and ventilation are important. Sow Basil indoors, but do not plant outside until there is no risk of frost. Start successional sowings of salad crops eg. Lettuce, carrots and radishes.
Sow tender veg. indoors for planting out next month e.g. courgettes, French and Runner beans. Sow marrow, courgette and squash seed on its side and soak Sweet Corn seed in water for 4 hours before sowing. Prune early flowered Clematis after blooming e.g. C. alpina and C. macropetala. This is only necessary where space is limited. This is a good time to re-pot any houseplants that are pot bound Store unused seeds left in open packets in an airtight container in the refrigerator. Treat your lawn to an application of lawn food. Miracle Gro Thick and Green is my favourite as its food is release according to the weather conditions.