As the weather in March becomes warmer, more use can be made of the greenhouse; seeds can be sown, bulbs planted and cuttings taken. Unless the spring is cold, you can now remove the winter insulation from the glass. Controlling pests and diseases Higher temperatures bring an increase in insect activity, so watch out for aphids, red spider mites and whitefly. Watering and feeding Increase watering; do not let pots or seed trays dry out. Apply liquid feed to plants in pots on a regular basis as they start into growth. Sowing seeds The seeds of many plants can be sown this month. Sow everything listed in February. Also, sow dahlias, lilies, annual carnations, herbs, hardy annuals and any flowering plants that you plan to grow in pots. Prick out seedlings as soon as they are large enough to handle. Potting on Annuals such as schizanthus and nemesias that have been overwintered in 8 cm (3 in) pots grow rapidly at this time of year. Pot them on into 15 cm (6 in) pots containing John Innes No.2 potting compost. Insert supporting stakes for the taller plants and tie them in as it becomes necessary. Move these plants into the house or conservatory when they start flowering. At the end of the month, pot on gloxinias and begonias into 9 cm (3 1/2 in) pots containing John Innes potting compost No.2 with peat added at the rate of one part peat to nine parts compost. Pot on fuschias and chrysanthemums as required. Cuttings Take cuttings of dahlias , fuschias, pelargoniums, chrysanthemums, some shrubs, and indoor plants, such as abutilons, inserting them in a free-draining compost, preferably in a heated propagator. Peppers and aubergines Sow peppers two seeds to a pot at a temperature of 18-20°C (65-70°F) and remove the weaker of the two seedlings when they germinate. Sow aubergines at the same temperature, 5 mm (1/4 in) deep in pots. Tomatoes Indoor tomato plants sown in February will now need extra space to prevent them becoming drawn and spindly. Where practicable, stand the pots on the greenhouse border where they will be planted. Otherwise, space them out on the staging. If you wish to plant tomatoes in an unheated greenhouse in May, or outdoors, and have a heated propagator or a warm windowsill, sow the seeds this month at a temperature of 15-20°C (60-70°F), covering them with a thin layer of sifted compost. Pot the seedlings individually into 8 cm (3 in) pots of John Innes No. 2 potting compost as soon as the seed leaves are fully developed. If you have a cool greenhouse, prepare the border for planting tomatoes next month. Dig in plenty of well-rotted manure or compost and apply a balanced fertiliser. Alternatively, you can buy growing bags or use the ring culture method. To prepare the border for ring culture dig out a trench at least 20 cm (8 in) deep and line it with plastic sheeting. Fill the trench with a layer of pea gravel 15 cm (6 in) deep. Tomato plants are then grown in purpose designed bottomless pots which can be sunk into the gravel. The plants are watered via the gravel but fed via the pot. Vines Once growth begins ensure the vines get as much light and heat as possible.