What to do in the garden in March
March is the month to sow seeds, plant and divide perennials, coppice dogwoods and willows, and get the garden growing again. Spring is properly on its way, soil is warming and every day brings something new. Here are the jobs that will make the biggest difference this month.
Plant and divide perennials
As soil warms, it is a brilliant time to plant new perennials. Their roots grow away quickly and they settle in with spring rain. It is also the ideal moment to lift and divide late-summer flowering perennials, such as asters, heleniums, rudbeckias and late grasses, which tend to prefer spring division to autumn. Dig up the clump, split it with a spade or two forks back to back, and replant the healthiest outer pieces with a little compost.
Planting in groups and combinations, rather than single plants dotted about, gives a border real impact. My post on plant combinations with geum, salvia and nepeta has an easy, long-flowering trio to try. Form Plants grows a wide range of perennials peat-free, if you are looking to fill some gaps.
Sow seeds
Under cover
Sow tomatoes, peppers, aubergines and celeriac in a heated propagator or on a warm windowsill. Half-hardy annuals such as cosmos and tithonia can be started under cover towards the end of the month, ready to plant out once frosts have passed. Use a peat-free seed compost and give seedlings as much light as you can.
Outdoors
Towards the end of March, once soil feels warm to the touch and is not too wet, you can start sowing hardy annuals direct, along with broad beans, peas, radishes and salad leaves. In colder areas, or after a chilly spell, wait a week or two longer. Cloches or fleece warm the soil and give early sowings a helping hand.
Prune for colour and flowers
Dogwoods (Cornus) and willows grown for their bright winter stems can be coppiced now, cutting all the stems back to a few centimetres above the ground. They regrow with vivid new stems for next winter. If you would rather keep a little height, take out one stem in three instead.
Cut buddleja back hard, to a low framework, to keep it compact and flowering well. Finish pruning bush and shrub roses early in the month if you have not already done so.
Look after spring bulbs
Snip off the faded flowers of daffodils so the plants put their energy into the bulb rather than seed, but leave the foliage to die back naturally for around six weeks. That green leaf is feeding next year's flowers. Make a note of any gaps where more bulbs would look wonderful, ready for planting in autumn. Late-flowering Narcissus 'Pheasant's Eye' (Narcissus poeticus var. recurvus), one of my favourites, is still to come, with its scented white petals and tiny red-rimmed cups.
Start dahlias and summer bulbs
Pot up dahlia tubers in peat-free compost and keep them somewhere bright and frost-free, such as a greenhouse or porch. Water sparingly until shoots appear. Lilies can be planted in pots now too, and summer bulbs such as gladioli can go in towards the end of the month or into April.
Lawns, weeds and new shoots
Give the lawn its first cut once the grass is growing and the ground is dry enough to walk on, with the mower blades set high. Hoe weeds on a dry day while they are tiny, and they will wither on the surface. Keep an eye on fresh hosta and delphinium shoots, which slugs and snails find delicious. Wildlife-friendly options include copper tape on pots, beer traps and evening torchlit patrols.
First early potatoes can be planted from late March in milder areas, about 10 to 15cm deep.
March checklist
Plant new perennials and divide late-flowering clumps.
Sow tomatoes, peppers and half-hardy annuals under cover.
Sow hardy annuals and early vegetables outdoors when soil is warm.
Coppice dogwoods and willows grown for winter stems.
Cut buddleja back hard.
Deadhead daffodils and leave the foliage to die back.
Pot up dahlia tubers under cover.
Give the lawn its first, high cut.
Hoe weeds while they are small.
If you are catching up, my February garden jobs cover cutting back and mulching, and next month's April garden jobs look at staking, hardening off and planting out.
Quick answers
Can I divide perennials in March?
Yes. March is ideal for dividing late-summer flowering perennials such as asters and heleniums, and for most grasses. Replant the healthiest outer pieces and water them in well.
When can I sow seeds outside in the UK?
Hardy annuals and early vegetables can be sown outdoors from late March or April, once the soil feels warm and has dried out a little. Half-hardy plants should wait until after the last frost.
When should I cut back daffodil leaves?
Leave daffodil foliage for around six weeks after flowering, or until it turns yellow. The leaves feed the bulb for next year's flowers.
