It’s time to sow Fennel, oriental vegetables like mizuna greens and Pak Choi, rocket, coriander dill, spinach, claytonia and land cress in modules as soon as you can. These will germinate quickly and can be planted out by mid-August for cropping in autumn.
Continue sowing ‘cut and come again’ crops like mixed herbs, in pots, greenhouse borders or growing bags. Mixed salads can be started in shade under greenhouse benching then moved outdoors. In late August sow spinach, spring onions, lettuce and spring cabbage for transplanting outdoors. If hot conditions persist then make sure you move them outdoors soon after germination, protect them with horticultural fleece from scorching sunshine and cold winds on overcast days.
Take cuttings from non-flowering shoots of salvias and penstemons and pelargoniums. Cuttings should be 10-15cm long, making a cut just below a leaf joint. Trim off the lowest leaves and pinch out the growing tip, then dip the cut end in hormone rooting powder knock off the excess then plant 3-4 around the edge of a 9cm pot, in multipurpose compost mixed with a little grit for drainage. Keep the cuttings shaded in a greenhouse propagator. Once rooted move them into 3” pots and keep them in the greenhouse for planting out the following year.
Fruiting crops like cucumbers, aubergines and tomatoes need a constant supply of water. Feed weekly, with high potash tomato fertiliser, and ‘damp down’ the floor to increase humidity or use a hand sprayer to mist among cucumber leaves. A constant supply of moisture is essential to avoid ‘blossom end Rot’ in tomatoes, peppers and aubergines. It is much better to water twice or even three times a day than once with twice the volume.
Removing tomato leaves which shade trusses of fruit, helps to speed up ripening. Removing some below the trusses improves air circulation and reduces the chances of tomato blight, but don’t remove too many. It enables you to see the base of the plans so you can apply water around roots. Avoid wetting the leaves.
Ventilate the greenhouse before temperatures rise on hot days and keep the vents open if overnight temperatures remain high.
Harvest cucumbers when they are green and firm, cutting the stem cleanly with knife or secateurs. Aubergines and sweet peppers should be glossy – if they lose that lovely gloss and start turning matt then they are going over. Cup your hand underneath to support the fruit then detach from the plant with knife or secateurs and carry carefully to avoid bruising.
If you are going on holiday, enlist someone to check your greenhouse daily, they can be ‘paid’ by letting them harvest your crops. If ripened fruits stay on the plant, they will deteriorate and attract disease and will also stop producing, so they are also doing you a favour. Fill up the watering cans and put them under the greenhouse bench to warm the water, before leaving and give your neighbour written bullet point instructions, rather than expecting them to rely on memory. Unless your helper is an experienced gardener, accept any fatalities or damage with equanimity.
Happy gardening. Matt