Fill your watering cans with water and allow them to stand in the greenhouse for at least 24 hours to warm before watering your plants. You may need to water two or three times while the weather is hot, especially if you are behind on your potting on and large plants are in small pots. Water seedlings with tap water. If there is a shortage of rainwater, (It’s happening again!) save it for plants that need soft water like citrus fruits.
Pay close attention to crops in growing bags, because they dry out really quickly and keep the compost moist. If you haven’t yet planted your growing bags, try this. Stand them on end, knock the compost to the base before laying them horizontally and only planting two tomato plants in each one, (rather than three). Two plants will form a larger root system in the deeper compost and have more water to draw on and you are less likely to have watering and feeding problems. One symptom of erratic watering is calcium deficiency in tomatoes (less so aubergines and peppers) which appears as ‘Blossom End Rot’, when the end of the fruit furthest from the stem, collapses and turns black. It looks rather unpleasant but you can slice the end off and still eat the tomato.
Now your tomatoes are growing well, remove the side shoots of ‘cordon’ varieties, when they are about 2.5cm long, with your finger and thumb to form a single productive stem. Don’t compost the side shoots, root them in water on a bright windowsill then plant them out later in summer to extend the cropping season or pass the plants to friends. Pinch out the tops of tomatoes when the main stem reaches the top of the green house or seven trusses have been formed.
Peppers and Chilli’s will need transplanting several times until they reach their final 23cm pot size. Pinching out the growing tip when they are about 15cm high encourages branching and heavier cropping.
‘Harden off’ and transplant outdoor crops as soon as you can to create space for these long-term greenhouse crops.
If you missed out on tomatoes, aubergines, peppers and chillies, it is still not too late to buy them from the garden centre, they will ripen later but you will still have a harvest and the garden centre will be really pleased to see you. (It is totally brilliant to have our nurseries and garden centres open once again).
Keep your greenhouse tidy and check daily for pests, using biological controls or organic insecticides if necessary. Checking regularly is important; it is easier to control a smaller infestation than an epidemic. (As we now know.)
Ventilate the greenhouse early while the weather is hot but avoid chilling drafts. While the wind is cold, open the ventilation on the lee ward side of the greenhouse. Damp down the floor of the greenhouse regularly on hot days, to increase humidity levels. This not only benefits plant growth but also reduces the risk of pests like glasshouse red spider mite.
Happy gardening. Matt