Sowing, pruning & dressing - what to do this week in your Hertfordshire garden

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BEST OF THE BUNCH

Spring-flowering heather is a real winner in tubs, troughs, beds and borders, even in windy gardens. There are lots of different named varieties in white, pink, red, mauve or purple and they look wonderful planted in front of conifers and evergreens, as they grow to around 8in (20cm) high and 18in (45cm) wide. They are generally lime-haters and do well planted in ericaceous compost in full sun. If you want something slightly taller, go for E. darleyensis, which grows to around 60cm (2ft) and blooms between November and April. They are also wonderful planted in containers with dwarf conifers, pansies, ivy and red-berried Skimmia reevesiana, to make a really colourful scene on the patio or by the front door. Once flowers have faded, the plants should be trimmed back lightly, but make sure you don’t cut back into old wood.

WHAT TO DO THIS WEEK

PA Photo/thinkstockphotos (Image: Archant)

:: Prune plum trees once they have started growing.

:: Make sure pots and seed trays in the greenhouse do not dry out.

:: Cut off dead flower spikes from summer-flowering heathers and prune young tree heathers.

PA Photo/thinkstockphotos (Image: Archant)

:: Make the first outdoor sowings of culinary and salad herbs.

:: Apply a spring fertiliser to established lawns once they are actively growing and cut grass when it is about 8cm (3in) high.

:: Transplant autumn-sown onions to their final quarters, spacing them alternately at 12in (30cm).

Wild flowers in the garden (Image: Archant)

:: Thin early sowings of lettuce.

:: Give roses a top dressing of rose fertiliser.

:: Sow campanulas under glass.

:: Clear remaining crops of leeks and celery so the ground can be prepared for new crops.

GOOD ENOUGH TO EAT

You should be able to make the first outdoor sowings of carrots now, but try to warm the soil up first to aid germination. Your soil needs to be free of stones or you’ll get funny-shaped carrots, but alternatively you could grow some in deep pots of compost. For a continuous supply of baby carrots, sow a short row and keep sowing at regular intervals through the summer, drawing out a 1.5cm seed drill, spacing the drills 15cm apart. Water the area with a fine rose watering can to minimise seed disturbance and keep the soil moist until germination. Once seedlings are large enough to handle, thin them out, leaving one seedling every 2-4cm. Further thin them a month later to a final spacing of 10cm. The first baby carrots should be ready for pulling in June. Good varieties include ‘Early French Frame’, which are small and round and won’t fork if they hit a stone, or ‘Early Nantes’, which grow well in light, sandy soil.