Sowing and planting
Sweet peas can be sown outside this month. Place autumn-sown sweet peas in a sunny position, perhaps on a high shelf in the greenhouse that gets plenty of light. Sow summer bedding plants in a heated propagator or under glass.
Other hardy annuals can be sown in pots or modules to provide colour in the garden. In mild areas you can sow directly outside. Mark out areas in borders to sow drifts of different seed to give a more natural look. For cut flowers it’s often easiest to sow in rows.
Early spring is an ideal time to plant herbaceous perennials, including Geranium, Astrantia and Oriental poppies.
Plant summer-flowering bulbs. Most bulbs benefit from soil being improved with well-rotted garden compost. Anemone coronaria tubers need particularly well-drained soils.
Plan a continuous crop of cut flowers. Annuals will flower this summer, while perennials such as delphiniums can be grown to produce a useful and beautiful display once established.
When space becomes available in the greenhouse, pot up cuttings of tender perennials taken last summer and at the beginning of this year. Bulk up plant numbers by taking more cuttings from the largest of the new plants.
Indoor forced bulbs that were in the house for winter displays, but have finished flowering, can now be planted into the garden, taking care not to disturb the roots.
Cutting back, pruning and dividing
Cut off old leaves of hellebores that produce flowers from ground level (including Helleborus × hybridus, Rodney Davey Group and H. niger) to expose the flowers and reduce foliar diseases such as hellebore leaf spot.
Cut back ornamental grasses and other perennials left for winter interest, if you have not already done so. Even if they still look good, you need to make way for the new growth.
Divide and/or plant bulbs-in-the-green, such as snowdrops (Galanthus) and winter aconites (Eranthis hyemalis), if not done last month.
Divide clumps of herbaceous perennials that you want to propagate, those that have become too large for their allotted space, and those that are flowering poorly or have lost their shape.
Divide hostas before they come into leaf. Aim for clumps with at least 3-5 good shoots and replant in soil improved with garden compost.
Divide hellebores and primroses and polyanthus after flowering. Remove faded flowerheads and keep well watered until they start growing strongly.
Propagation
Propagate more dahlias from tubers. Pot them up in peat-free multi-purpose compost so that the old stalk is just above the surface. Water and place in a warm, light position or in a propagator. Once the fresh shoots have grown to 7.5-10cm (3-4in), cut them off carefully with a knife. Push them into a pot containing peat-free seed and cutting compost. Place back in a propagator or clear plastic bag until roots appear out of the bottom of the pot.
Perennials that are showing new shoots from the crown can be propagated via basal stem cuttings. Shoots 7.5-10cm (3-4in) high are cut from the parent plant with a sharp knife and pushed into peat-free cuttings compost, as for softwood cuttings. Sometimes a piece of root can be taken with the cutting, which speeds establishment.
General maintenance
Continue to deadhead winter-flowering pansies and other winter bedding. Pansies will carry on into the spring and even to early summer, if picked over frequently.
Deadhead the flowers of daffodils (Narcissus) as they fade, but allow the foliage to die down naturally.
Herbaceous perennials infested with couch grass and other perennial weeds should be lifted so the roots of the weeds can be removed. Improve the soil by digging in organic matter, preferably homemade compost, before replanting.
Clear up weedy beds before mulching. Lighter soils can be mulched now, but heavier soils are best left until later in March, when the soil is drier and warmer. Mulching with a deep layer of organic matter, preferably homemade compost, helps to condition the soil, suppress weed growth and conserve soil moisture during the summer.
Alpine bulbs coming up in rockeries or containers may benefit from overhead protection from the rain. A sheet of glass or re-used perspex placed on piles of bricks will do the job.
Top dress spring-flowering alpines with grit or gravel to show off the plants and help prevent stem rots. Mulch may need replacing after weed removal.
Improve the drainage of heavy soils by working in lots of homemade garden compost. This is one of the few situations where double digging is useful.
Perennials putting on plenty of growth may need support by the end of the month. Hazel twigs, or bamboo canes or wooden posts with string (either around the outside of the posts or criss-crossed between) can all be effective. It is best to get supports in early, so that the plants grow up through them, covering them discreetly.
Check whether containers need watering. Even at this time of year, they can dry out. Pots that are sheltered by eaves or balconies can miss out on any rainfall. If in doubt, check the compost at a hand’s depth to see if it feels dry. Aim to keep pots moist, not wet, and don’t let them dry out.
Pots and tubs benefit from topping up with fresh peat-free John Innes compost. Old compost can be removed and replaced with new if there is not much room for topping up.
In mild areas, you should remove winter coverings of re-used or biodegradable fleece, straw etc., to prevent new shoots being damaged. In cold areas, you are best waiting until the risk of frost has passed.
Planning ahead
Members can order seed from the RHS Seed Scheme between November and the end of March.
You may wish to get your sweet pea wigwam growing supports ready. In mild areas, you can transplant young plants to the feet of the wigwam, using twine to tie them in.
Problems
Continue to protect new growth on lilies, delphiniums, hostas and any other plants affected, from slugs and snails.
Check autumn-sown sweet peas growing in cold frames, and keep watch for mouse and slug or snail damage.
Hellebore leaf spot can be a problem on old foliage of hellebores. Cutting back the old leaves should control the problem.
Aphids can multiply rapidly during mild spells. Where needed, remove early infestations by hand to prevent the problem getting out of hand. Protect sweet pea plants in particular, as they can get sweet pea viruses, which are transmitted by aphids and other sap-sucking insects. Aphids are an essential food for young birds, so only remove where needed and don’t use any sprays.
Watch out for downy mildew and black leaf spot on winter pansies. Remove any infected leaves and destroy badly affected plants.
Remove dead leaves from around the basal rosettes of alpine plants to prevent rotting. Top dress spring-flowering alpines with grit or gravel to show off the plants and help prevent rotting around the neck.
