Summer Gardens – Top tips for Greenhouse gardeners

Summertime – when the English garden comes alive. Many of our most beautiful plants are in full bloom during the summer months, and our gardens are bursting with life, colour and vigour. But summer can also present a unique set of challenges for the gardener – especially at a time when temperatures start to rise. We spoke to the experts at Hartley Botanic, to get some useful advice for greenhouse gardeners this summer, and ideas on what to grow in your greenhouse.

Watering 101

During the peak of summer, it is important to keep an eye on watering and the condition of your plants. Maintain a regular regime of feeding and watering with tepid water. Find out if your containerised plants need watering by sticking your finger into the surface of the compost, if your finger is free of compost particles when you pull it out then the plant needs watering. It’s also helpful to learn how to judge this by the weight of the pot with wet and dry compost. When watering, give plants a thorough soak; a light sprinkle will only encourage roots to the surface where they are more susceptible to drought.

Water plants in the evening, poured around the roots not over the leaves and check your containers at least once a day and water even if it has rained. Water according to the type of plant – lavenders, from a Mediterranean climate have a low demand for water but bananas are watered copiously as they lose water through their massive leaves. Putting the ‘right plant in the right place’ helps, too, lavender, cistus, cotton lavender and plants from Mediterranean climates thrive on sandy soils and will only need watering until, established.

Creating a circular ridge of soil around the base of plants allows the water to pool, rather than run off, and adding plenty of well-rotted organic matter to the soil before planting, ensures that water is retained like a sponge. Don’t water established plants unless they are showing signs of stress and if possible, recycle grey water from the bath but not on edible crops and don’t use too much bubble bath, either! Mulching pots with mini bark or gravel will keep weeds down and conserve moisture, too. There are lots of practical ways you can save water. You can also help maintain humidity in your Greenhouse by damping down the floor.

 All about Greenhouse shade

When it comes to summer, it is not only lack of water which will cause plants to fail. When it is extremely hot, there is a potent combination of plants not being able to suck water up fast enough (triggering truss-wrecking blossom end rot) and the fierce intensity of the sun magnified by glass. It is often too much for plants, and too much for the gardener themselves! There are a variety of ways to shade your Greenhouse, whether you choose convenient roller blinds or a completely natural DIY solution.

One method is to paint on white shading. A tub to cover a Greenhouse of around 8 x 12 foot will cost just over £8. A downside of doing this, however, is that you need to wipe it off at the end of the season. A canopy of polypropylene shade netting can also be erected locally for specific plants or to cover the house by attaching it to the framework. Keeping netting on the outside means the inside is kept clear for tall crops like cucumbers and melons. In most cases running the netting along one side is sufficient (if your Greenhouse runs East/West for example, you can shade the south side). And when purchasing a Greenhouse it is sensible to consider including internal blinds as an extra accessory to have installed if you do have the budget.

For a completely eco-conscious DIY solution, which can also be fed back into your garden as mulch or compost, is to create shading yourself using plants such as bracken, rosebay willowherb (Chamaenerion angustifolium) or other tall-stemmed flattish branches of willow or hazel. Simply lie them over your Greenhouse glass and you have instant, natural shade. You can even use plants with huge leaves, such as Giant rhubarb (Gunnera manicata,) which has leaves up to 2m across, or if you have a Greenhouse with a low pitch, grass mowings. Once you have finished with ‘nature’s shading,’ you can then set it to work as mulch, compost material or food for your soil.

Essential jobs for the summer months

Check plants regularly for signs of whitefly, leafhopper, Glasshouse red spider mite, mealybugs and scale insects and treat them with biological controls or environmentally friendly sprays. Keep the Glasshouse free of fallen leaves, flowers and other plant debris to prevent the spread of diseases. Remove the side shoots from tomatoes as early as possible. Tie in and pinch out the main stems of tomato plants once they reach the top of the support, so all of the energies are channelled into ripening of existing tomatoes. Harvest crops regularly and train cucumbers and melons onto nets and frames; repot chillies, bell peppers and aubergines until they are in 23cm pots of peat substitute compost. Tie sweet peppers and aubergines to supporting canes if needed.

The following can be sown in July: Basil, Calabrese, Chinese cabbage, Winter purslane, (Claytonia), Chervil, Coriander and Dill, French beans (climbing and dwarf,) Lettuce, Florence fennel, Oriental greens like Pak Choi, Parsley, chard, endive, chicory, beetroot.

Feed citrus with specialist food and continue training climbing plants like Gloriosa superba ‘Rothschildiana’ in a spiral around a tripod of canes, tying in as needed. Keep the pot at the back of the Greenhouse away from the doorway where humidity is higher. If temperatures are unseasonally low, ventilate using the windows rather than opening the door which causes a draught.

From mid-July you can take semi-ripe cuttings from shrubs like ‘Star Jasmine’, Camellia, Ceanothus, Choisya, Cistus, Convolvulus cneorum, Fatsia, Mahonia and Viburnum. Cuttings taken in summer, rarely need a heated propagator. Keep the compost moist until they are well rooted and shade them from sunshine in hot weather.  Remove any dead or diseased cuttings and leaves that fall. Once the cuttings have rooted, they will need ‘hardening off’ for two to three weeks before potting on or planting out.

All Hartley Botanic’s Glasshouses and Greenhouses are handmade, bespoke and made to order.

To find out more, visit hartley-botanic.co.uk or call 01457 819 155 to speak to an expert.

Images: courtesy of Hartley Botanic

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