What to do in hot weather to protect your plants

The days, for some of us at least, have cooled somewhat and we’re enjoying more tolerable temperatures and hoping for some gentle, soaking rain. I hardly ventured out in the heat as I can’t tolerate it like I used to so retreated to the house to try and find a cooling breeze, some shade and a cool drink.

For many plants their needs are no different to ours in the excessive heat - shade, a cooling breeze and being well watered. This applies to many vegetables especially when they are flowering, setting fruit and developing that fruit. Knowing your plants will help you to know what to do with them and where to put them for optimal growth in the more stressful conditions.

Mediterranean plants such as rosemary, marjoram, thyme and sage enjoy the heat and can cope with the dry weather. Even in pots they are more tolerant of drying out. These types of plants can often be identified by their waxy, leathery or tough, shiny leaves (rosemary and sage); by a grey or glaucous colour (sages); and by being hairy (Stachys byzantina or Lambs ear).

Pots and containers

it started as an experiment to see how much water I ran off before the warm water came through. It was 3-4 litres going down the drain. I now use this to water my pots at the front of the house.

Pots and containers need watering regularly as roots are not able to access water outside the pot whereas those planted in the ground can draw on deeper moisture. If possible, in hot weather, move container grown plants to a shaded area or one that gets morning sun and is shaded during the rest of the day. Water in the cooler parts of the day such as early morning or late evening. Grouping pots together also reduces evaporation.

If the pots cannot be moved then mulch with compost, leaving a small space round the stems of the plants. It may also help to increase the humidity to reduce the loss of water through evaporation tfrom the leaves.

Vegetables 

Vary in requirements for moisture depending on their stage of growth and the type of vegetable. You may need to prioritise watering for different vegetables giveing some a good soaking more regularly at certain times depending on where they are growin.

Salad leaves wilt easily without enough moisture and need a shady place with regular watering.

Peas, beans and sweetcorn need regular watering as they flower, set seed and mature.

Shallow rooted vegetables such as onions also need watering regularly

Deep rooted vegetables such as carrots and parsnips can be left longer but will still need a good soak once a week or when the soil dries out. Check beneath the surface as to how moist the compost is.

Greenhouses and conservatories

Temperatures in smaller greenhouses can fluctuate dramatically throughout the day. I recorded on Saturday at 13:45 a max of 35.5C in the greenhouse, overnight it had been 17.5C. At times recently it has peaked at over 40C.

Important keys for the greenhouse or conservatory are these:

Ventilation - to change the air and allow movement of air to reduce the temperature build up. Do this by opening the vents in the roof - mine are automatic, using the louvred side vents and keeping the door open. this not only allows a through flow of air but access for pollinating insects.

Humidity - Increase humidity by either misting the air, having a tray of water or, as I do, by watering the concrete base of the greenhouse. Higher humidity can reduce transpiration so the plant does not lose as much water from it’s leaves.

Shading - shade reduces the temperature and the risk of the plants being scorched by the sun. Shade netting or shade paint can be helpful at providing adaptable shade for the lightest months of the year but does reduce the amount of light for plant growth. On more overcast days this may need adjusting to give better light levels.

Watering - a good soak is better than a light watering as it allows the plant to access moisture throughout the compost and stops the growing medium drying out beneath the surface. Depending on the temperatures, watering may need to be done daily and misting, if possible 2-3 times a day. When watering check for moisture levels beneath the surface as an indication of whether you need to water or not. I am finding the peat free composts quicker to dry out. Once the compost is dry then watering may need to be done in small increments to allow water uptake or if a pot is moveable then use a trough and soak from the bottom. A similar effect also happens if you have a heavy rain after a period of dry weather. The water tends to run off the surface rather than soak in.

Observation of how your plants are looking and responding to the weather can give an indication of watering and shading requirements so enjoy a regular wander in your garden and keep an eye on the weather forecast.