Spring into action: Now's the time to prepare the garden for the coming season

It's been a long winter. I've never been kept so long from doing jobs outside. All the small interventions that I normally make – clearing away rotting iris foliage, cutting back the leaves of oriental hellebores, liberating snowdrops from smothers of forget-me-not – have been impossible. There's a lot of catching up to do before March, when the garden cranks into full growing gear.

A few plants have been brave enough to stick to their agendas. I was surprised to find tiny jabs of magenta on the bank, from the snub-nosed flowers of Cyclamen coum. Snowdrops have been later to appear than usual. Last season, I picked the first bunch of 'Atkinsii' snowdrops on Boxing Day. This year, they didn't open up until the third week of January. The ordinary Galanthus nivalis came a couple of weeks later.

After an iced-up winter, when even a trip to the compost heap with the potato peelings was a major undertaking, it is good to be able to mooch again, to visit plants, check progress. No Algerian iris (Iris unguicularis) yet. Why? Perhaps they didn't get baked enough last summer. Though we've had some sunny days recently, the ground is still cold and wet, certainly too cold to sow any seed outside. But there are quick-fix alternatives: young plants, mostly annuals, that you can order through the post and grow on to put out in May. I've just put in for five young Lotus berthelotii (Mr Fothergill £5.95) to be delivered sometime in mid-April.

Lotus is a trailer. Last year I planted it in a manger fixed to a stone wall and, by the autumn, it was reaching the ground. It is tender, so like most bedding plants, you can't risk putting it outside until at least the middle of May. I pot up the plants when they arrive, each in a 5cm (3in) pot and grow them on under cover until the weather warms up. By then, the root ball will be even bigger and the plant will be well equipped to survive whatever the coming summer throws at it.

You can buy plants in several different sizes: miniplants (about 5cm high), easiplants (7cm), garden-ready plants (9cm) and pot-ready plants (13cm). The bigger and more expensive they are, the later they are sent out. Snapdragons, asters, busy lizzies, lobelias, petunias and geraniums are standard fare, but tucked among those are other more unusual flowers such as the brilliant gerbera (£9.95 for three pot-ready plants) that Dobies is offering for the first time this year.

New in Suttons' catalogue is a handsome oxalis called 'Black Velvet' with dark clover-like leaves and starry white flowers (£7.99 for three pot-ready plants to be delivered in late April). From Suttons, too, you could get a cascading fuchsia called 'Explosion' (£7.99 for five pot-ready plants) which they describe as "the most floriferous fuchsia in the world". That surely will depend on the summer ahead. Fuchsias take some time to work up to their full potential. An early frost is disastrous. The fuchsias will be delivered in late April, so you would need to nurse on the plants under cover for a couple of weeks before putting them outside.

Thompson & Morgan are introducing "the world's most amazing new petunia" (they run out of superlatives very quickly, these catalogue writers) with petals striped in pale yellow and a dark, almost black, purple. A rainy summer might make the contrast less startling. This paragon is called 'Phantom' (£9.99 for five jumbo plugs to be sent out late March or early April).

So, that's the easy bit. Jobs outside require a little more effort. First of all – hellebores. If you haven't yet cut away last year's tattered leaves from around this season's new flowers, do it NOW. The flowers will look very much better without a ruff of aged memento mori foliage around them. You will also cut down the risk of last year's leaf spot disease being transferred to this year's growth.

A couple of hours spent spring cleaning among borders will also do wonders for the garden's morale. At this time of the year you can pull the dead bleached leaves of iris such as I. ochroleuca cleanly away from clumps, where fresh leaves are already beginning to sprout.

This particular iris has tall handsome leaves, often to a metre (36in), with white beardless flowers blotched with yellow. But all iris will appreciate a little attention now. Clear away dead leaves and other debris from the tops of the rhizomes and cut withered, weathered tips from existing foliage. 'Gerald Darby' is one of my favourite iris, making, like I. ochroleuca, great sheaves of clean foliage, but in this case, they are stained purple at the base. The new shoots looked very much more appealing when I'd got rid of the sodden mats of dead leaf from around them. Unfortunately, it doesn't pull away. You have to cut it.

Another iris, 'Holden Clough' kept its leaves through all the frost and snow. But the new foliage is shooting strongly and the whole clump, planted under Magnolia wilsonii, will look much better when I've dealt with the old leaves. 'Holden Clough' does quite well in semi-shade and its flowers are intriguing, though you could never call them showy. They're yellow, and so heavily veined with purple that the overall effect is a rich, warm brown. Nicer than it sounds. Iris like this also appreciate food at this time of year. They don't need anything heavy, but a handful of bonemeal or hoof and horn will cheer them up no end.

For a swift catch-up service that will enable you to float through next month unencumbered by worries about what you have not done, read on. Sow seeds of sweet peas, seven to a 13cm (5in) pot. They germinate fast. In choosing seeds, remember that deep pink- and salmon-coloured flowers usually have less scent than blue or mauve ones. If you have already sown seed, remember to pinch out the tops of young plants to encourage new side shoots.

Growth is galloping away on herbaceous perennials such as day lilies, but clumps of polygonum, campanula, rudbeckia and helenium that you meant to split and move last autumn can still be tackled. Water the hole each is going into before you put in the plant. You'll lose less water by surface evaporation if you work this way round.

Snip dead blooms from camellias. They will not fall on their own. This is a grave fault on the camellia's part, making them at this stage in their lives look like last week's funeral offering. Camellias flourish spectacularly in cool conservatories, where their flowers, especially the white ones, do not get spoilt by rain. When flowering has finished for the season, repot potted camellias in fresh ericaceous compost to build up plants for next year's display. That's it. For the moment...

Dobies: 0844 701 7625, dobies.co.uk; Mr Fothergill's: 0845 371 0518, mr-fothergills.co.uk; Suttons: 0844 922 0606, suttons.co.uk; Thompson & Morgan: 0844 573 2020, thompson-morgan.com