Prune plum trees once they have started growing Make sure pots and seed trays in the greenhouse don't dry out Cut off dead flower spikes from summer-flowering heathers Prune spring-flowering shrubs more than three years old as they finish flowering Sow sweet peas directly into their flowering position Sow seeds of tomatoes in a heated propagator or on a warm windowsill to grow on outdoors when all danger of frost is over Buy in supplies of pots and compost for early sowing and potting. Store compost bags in the greenhouse so the compost warms up for seed sowing Pick off dead flowerheads of winter and spring bedding plants Once potted bulbs grown in the home have finished flowering, plant them outside and give them a liquid feed Remove floating electric pond heaters once the risk of thick ice has passed Protect blooms on cherries, currants and early-flowering fruit from damaging frost.