If you have a heavy clay soil, finish any deep digging as soon as possible, so that late frosts can break it down into a workable tilth in readiness for sowing and planting. There is no need to dig now if your soil is light and sandy. Once the ground has dried out enough for it to be cultivated, lightly fork it over and cover it with cloches or polythene, to keep it dry and warm-it-up ready for the main sowings next month.
Only the hardiest and large seeded vegetables should be sown this month and protected with cloches or polythene tunnels. Autumn-sown seedlings in frames and cloches will benefit from a little ventilation on mild days.
Early sowings of carrots, lettuces, radishes, salad onions and summer cabbages may be made under cloches or tunnels, at the end of the month, once the weather shows signs of warming up. Space rows at 23 cm (9 in).
Make additional sowings of broad beans and peas at the end of the month for successional crops
Broad beans can be sown in the open when conditions are right. The 'Longpod' and 'Green Windsor' types are the best for sowing now. Place the seeds in rows 5 cm (2 in) deep, with 11~12 cm (4.5 in) between seeds, and 45 cm (18 in) between rows. If space is limited, grow one of the dwarf varieties, such as 'The Sutton' or the slightly taller 'Feligreen'. Space the seeds at 23 cm (9 in) each way.
Shallots can be planted now with the tops just showing above the ground, 15 cm (6 in) apart, with 30 cm (12 in) between rows. Plant them quite deeply to prevent birds pulling them out of the ground before they have rooted.
If conditions allow, parsnips can be also sown outdoors now to get a head start. Sow sparingly, as they will need thinning to at least 20cm (8 in) apart once germinated.
Chit seed potatoes if you did no do so in January.
Jerusalem artichoke is also a good vegetable to plant now. It is a relative of the sunflower and is very tough, surviving in even the poorest of soils. Plant tubers at 37 cm (15 in) apart, about 10 cm (4 in) deep. Remember that these plants grow enormously tall and may overshadow other vegetables. On the other hand, they make good windbreaks for the edge of a vegetable patch, and can always be planted in any rough bit of ground in an unwanted corner. Plant at least 1 m (3 ft) away from the nearest row of other vegetables.
Many vegetables will still be available for use from the garden and in storage. Spinach beet, probably some Brussels sprouts, cabbages and savoys, and weather permitting, celery, leeks and parsnips. Those being stored could include carrots, onions, shallots, swedes and turnips, potatoes and any Dutch white cabbages still hanging up.
Runner beans should be grown full sun, although they can tolerate some shade. Choose a sheltered spot away from high winds that can knock down the tall plants and their supports. Runner beans are usually grown in a double row, with 60 cm (2 ft) between the two rows and 15 cm (6 in) between plants. 180 cm (6 ft) canes or supports can be added at planting time.
Start now by prepare a deeply dug trench, approximately 60 cm (2 ft) deep, by 1 m (3 ft) wide, filling it with a good mix of soil and bulky organic matter (compost or manure) you can also use shredded cardboard and newspaper. Also add lime if your soil is acidic as acid conditions are undesirable. This can be done now in readiness for sowing or planting the beans later on in April.
Runner beans are very susceptible to frost, therefore seed should be sown indoors or under cloches from April onwards.
Celery, celeriac, cucumber (outdoor variety), aubergines, peppers and tomatoes can be sown now in containers filled with moist seed, compost. Scatter the seed evenly on the surface and just cover with the merest dusting of finely sieve, compost. Aubergines can take up to three weeks to germinate, tomatoes and peppers are quicker and the seedlings should be visible at the end of a fortnight.
Start off these vegetable on a warm windowsill or in a greenhouse, providing a constant temperature of at least 16°C (60°F). Heated propagators make economical sense if you don't want to heat your greenhouse to this temperature. But you will need to think about where to keep the young seedlings once they are too big for the propagator. One way is to gradually harden them off indoors before transferring them to the cooler greenhouse conditions. Their growth rate will slow down temporarily, but will quickly pick up again once the outside temperature rises.