courgettes
Seed can be sown in pots from March to the end of May. Fill a 7.5cm (3in) pot with compost and firm gently. Sow a seed on its side 2.5cm (1in) deep and cover. Label, water and put in a propagator or on a windowsill. When roots begin to show through the bottom of the pot, put into a 12.5cm (5in) container. Plant out into growing bags, soil or a large pot in late spring or early summer. Seed can also be sown directly into the soil from late-May to early summer. Choose a sunny, sheltered spot and improve the soil by digging in some well-rotted manure or compost. Sow two seeds on their side 2.5cm (1in) deep and once the seedlings have germinated, take out the weakest one.
Plenty of water is essential, especially when the plants are in flower and then when the fruits have started to swell.

April is a busy month in the garden.
Tulipa 'Johann Strauss'
This beautiful dwarf variety is perfect for planting in containers or in the rockery. It produces currant-red flowers, edged with sulphur-yellow, with golden yellow bases in March and April. The leaves are also attractive, thanks to their purple markings. Tulips are best planted in November as this minimises the risk of attack from the fungal disease, tulip fire, which causes the foliage to become distorted and covered with fuzzy, grey fungal growth and the flowers to either fail to open or to be marked with bleached spots. Any bulbs that become infected with this disease are best thrown away and the ground they were planted in should not be used to grow any tulips for several years. Remove the flowers as they fade to prevent plants wasting energy setting seed.

Growing bag
Despite only measuring 35cm x 95cm (13in x 37in), growing bags have enough space for three vegetable plants that will provide you with enough food for several meals over the summer. Plant two to three plants in each bag during spring.
Bags were traditionally used under glass and were introduced as an alternative to planting directly into greenhouse soil. Not having permanent borders meant the space could be used more efficiently throughout the year and plants would not become infected by soil-borne diseases. Today, they are still ideal for growing plants in the greenhouse, but are also perfect in a sunny spot outdoors.
Growing bags are ideal for plants that don't have deep roots, such as tomatoes, cucumbers, sweet peppers, chilli peppers, aubergines and courgettes.

Various types of onion, including spring onions, pickling onion and shallots can be successfully grown from sets or from seed, some from both.
Onion sets are small, immature onions, planted in spring or late summer. The sets increase in size and each forms one full-sized bulb when ready to harvest. Where possible, choose onion sets that have been heat-treated. This means their flower embryos have been killed, so they are less likely to run to seed or bolt. Generally, growing onions from sets is easier and more reliable than from seed and in cooler, damper areas, the sets should give a better yield of larger bulbs than if grown from seed. However the range of varieties available is far greater if growing onions from seed.
Sow seed in modules in January or February at 10 - 15°C (50-59°F). Sow five or six seeds per module in damp seed compost - when planted out the clumps of bulbs will push themselves apart as they expand.

All kohlrabi crops grow best in partial-shade, in firm, fertile, free-draining soil. Start digging over your soil in autumn, removing any stones you find and working in plenty of well-rotted manure or compost. Tread on the soil to remove any air pockets and make the surface very firm. Nearly all kohlrabi should be planted in a fowerbed or in modules under glass and then transferred. Seeds should be sown thinly, as this reduces the amount of future thinning necessary and potential risk from pests. Sow seeds 1.25cm (1/2in) deep and rows should be spaced 15cm (6in) apart. Once the seeds have germinated, thin the seedlings to 7.5cm (3in) between each plant.
Cabbage and broccoli seedlings are ready for shifting when they are between 6 and 8cm high (2.5-3in). Brussels sprouts and kale should be 15cm (6in). Water the day before moving, and keep well-watered until established. Space the plants according to the instructions on the seed packet. It can vary from 30cm for small cabbages to 75cm for Brussels sprouts.