Anna Pavord's guide to the bulbs to pick for a spectacular window-ledge display

No garden? That’s no excuse for not putting on a show this spring says our gardening correspondent

'Lachenalia pustulata' is tender, but easy to grow inside or in a greenhouse (Alamy)

There's a window ledge on the left, just as you come in the door of our house, and it's where we have a kind of horticultural equivalent of the eternal flame. All through the dark months from November to just about now, I try to keep on the window sill a succession of plants in pots, preferably scented, to keep my gardening spirits up. The window itself faces south, so there's no shortage of light, and we don't use the central heating, so the air is not too dry. Both those things help to keep plants in pots happy and flowering over a long period.

If I didn't have a garden, I'd still grow things. And this is how I'd grow them – in pots on window ledges, though the process is easier to manage if you have a small space outside where pots can stand while the plants themselves drift into dormancy. The shady corner of a small balcony would be ideal. The draining board would be my potting-up place and the cupboard under the sink would be stacked with compost and spare pots, as well as washing-up liquid.

Cut flowers are a treat, but flowers that are growing last longer. You also have the added pleasure of watching them develop, combined with a ridiculous sense of delight in having helped to bring about the display. Leaving aside hard-working orchids such as the cymbidiums and the ubiquitous Phalaenopsis (moth orchid), the easiest seasonal displays come from bulbs, which leap up, do their thing and then sensibly put themselves away until they are ready to come back into flower.

Paper-white narcissus (blooming through November and December) and specially-forced hyacinths (in flower January-February) are perhaps the best known of the bulbs used for indoor displays. Both are easy, and the narcissus has the great advantage of being quick. You plant it, and six to eight weeks later it is in bloom. You don't need to keep it in the dark, or give it any other special treatment.

But there are plenty of other bulbs, too tender in most cases to grow happily outside, that will perform well on a window ledge and keep the flame burning through the whole year. Freesias, though they produce rather a lot of leaf compared with the amount of flower, are easy and superbly scented. They are blooming now in our greenhouse, but would be equally happy on the window ledge. The hippeastrums I've kept from previous years are coming into flower now too, though the ones you buy fresh in garden centres in early winter flower through January and February.

Blood-red sprekelia is just as easy to grow as hippeastrum, and is a show-stopper. Unfortunately, it does not last as long as you hope, but you can > replace it with pots of South African babiana or calochortus from California. Add sparaxis and ixia and you will have plenty to look at until the end of June.

The tuberose (Polianthes tuberosa), the blood lily (Scadoxus multiflorus) and the Scarborough lily (Cyrtanthus elatus) will fill any gaps through the rest of the summer, until it's time to bring in the Guernsey lilies (Nerine sarniensis) and start planting up the paper-white narcissus again. The bulbs of the paper-whites are not worth keeping from year to year. You need to buy fresh each season.

At the moment, the most riveting display comes from the so-called leopard lilies, different species of Lachenalia, which are much less well-known than they should be. They are tender, but many are easy to grow inside or in a greenhouse. The complexity of their colours is astonishing and you have plenty of time to admire them since, once out, they last about six weeks.

No lachenalia is content with producing flowers of just one shade. Their beauty lies in the flecking, the shading, the drifting of a purplish-pink into a yellowish-green. Flowers can hang down, as in the bells of the aloe-like kinds, they can stand upwards on the spike, as in L. pallida, or they can be held stiffly horizontal. Stems may be plain green, or mottled mysteriously with dark purples and browns. Sometimes the foliage, too, is splashed with purple, or striped with white bands, as in L. anguinea. L. pustulata has thick, fleshy leaves covered with bumpy lumps, like frogspawn.

When planting, use a loam-based compost (John Innes No 3) mixed with grit or gravel, and water only moderately until the bulbs start into growth (they like to be crowded, so you can set six bulbs into a pot 15-25cm across). The leaves emerge long before the flowers. Reduce watering as the foliage fades and keep the bulbs dry until fresh growth starts in autumn. Feed every two weeks while the plants are in active growth.

Graham Duncan of the botanic garden at Kirstenbosch (author of The Genus Lachenalia, Kew Publishing 2012) recognises 133 different species of this South African native. More than 80 are listed as available in The Plant Finder and of those, a dozen have been given an Award of Garden Merit for growing in a cool (frost-free) greenhouse. If you've never grown a leopard lily before, these are the ones that you might start with:

L. aloides var. aurea: A tall, strong-growing plant with golden-yellow flowers springing from a deep maroon stem. Height 45cm.

L. aloides var. vanzyliae: Gorgeous tubular flowers of aquamarine and lime-green spring from stems speckled in deep maroon. The foliage has the same snake-like markings. Height 50cm.

L. contaminata: Has grassy foliage like a grape hyacinth and fringed white flowers flecked with maroon. Height 20cm.

L. pustulata: Once common in the wild throughout the south-western Cape, has tight buds which open to intricately marked flowers of white and pale blue, which darken towards the base of each bloom. Height 17cm.

L. 'Rupert': One of the few hybrid lachenalias, with pinkish-purple flowers that stand out horizontally up the stout, maroon-flushed stems. Height 25cm.

Lachenalia bulbs are available from late summer onwards. A large selection (priced from £3-£7.50 each) is available from Jill Agg at Choice Landscapes, Priory Farm, 101 Salts Rd, West Walton, Wisbech, Cambs PE14 7EF, 01945 585051, by appointment only

WEEKEND WORK

WHAT TO DO

* If you still have bare-rooted trees to plant, soak them in a bucket for an hour before putting them in the ground. Plants in pots can soak in a tray overnight. This will keep them ticking over for a short while until you remember to water them again.

* When daffodil clumps become congested, the bulbs tend to flower less freely. Mark any particularly barren clumps now with a cane to remind you to lift, separate and replant the bulbs sometime between July and September.

* Weeds are growing fast. Keep on top of bittercress and groundsel. Both are in flower already. Both are dedicated procreators.

WHAT TO SEE

* Gardens open this weekend include 23 Canonbury Place, London N1 2NY, with award-winning front and back plots with fruit trees and a small wildlife pond, open today (2-5pm), admission £2.50. Tomorrow, the Metson family have their first open day of the season (11am-5pm) at Coverwood Lakes, Peaslake Rd, Ewhurst, Surrey GU6 7NT, a 14-acre landscape high in the Surrey Hills with early rhododendrons and a farm trail with Hereford cattle and lambs. Admission £5, children free.