Claire Ratinon, our resident organic gardener, shares what to do in the garden in August, from sowing for a winter harvest to making sure your tomatoes are on track.

Claire: August is generally considered to be the hottest month of the year, so much of what we gardeners will be doing is harvesting and watering. 

It’s been a slightly odd summer so far where I live in the south of England with sunny, hot and tomato-friendly weather one day, changing to hefty grey clouds and cooling downpours the next. So, as always, keep a close eye on the weather as it will determine what gardening jobs need the most attention.

What To Sow in August
It might feel a little odd to be thinking about winter while you are harvesting courgettes or picking climbing beans in the sun but now is the time to start making decisions about what you want to eat when the warm months are over. After a couple of months without sowing seeds, I’m always glad when August comes around and I can get my box of seeds and compost out again.

This month is a great time to sow the faster-growing brassicas in time for planting out in autumn. Mustard greens, such as Purple Frills, Green in Snow and Mizuna, are easy to grow and offer an unexpected punch of heat at a time when the veg patch can be a little bland. Plus, their leaves, which vary from deep purple and delicately frilly to vibrant green and curled, look beautifully ornamental. Multi-sow four to five seeds per module as these plants grow well in a little group and are most delicious harvested when the leaves are on the small side before they grow larger and gather more heat.

Also in the brassica family, pak choi can be sown now and although some prefer to be directly sowed into vegetable beds, I have far too many slugs to trust the emerging seedlings to fate. I sow pak choi into seed trays (two seeds per module) and keep the emerging seedlings well-watered. They grow rapidly and are ready to transplant into the ground (or a pot) when they’ve grown at least four true leaves and can be ready to harvest in a month if you pick the young outer leaves. Alternatively, leave to grow on for a few more weeks and cut the whole head at the base.

It’s also a good time to sow endives and chicories for winter salads. These leaves, like mustards, can be really quite beautiful and their flavour far more intense than summer lettuces. The taste has a bitter edge which I adore but it might not suit those with a sensitive palette.

Plant Maintenance
Just as in July, August is a month of rampant growth, flowering and fruiting so keeping on top of plant care is key.

In very hot weather, your edible plants, especially those in containers, may need watering as often as every other day. Water early in the day and concentrate your efforts directly on the soil as many of your plants will prefer their leaves to stay dry as, if dampened, the moisture can promote the spread of certain diseases. For plants that bear fruit close to the soil, like winter squash, it can be worth the effort to prop up the fruit on a bed of dry straw or hay, or on a tile or piece of wood to save their skin from becoming damaged from being left to sit on moist soil.

Squash and courgette plants often suffer from powdery mildew which is a fungal disease that covers the surface of the plants and can affect the plant’s health and growth. It might sound odd but regularly spraying leaves showing signs of powdery mildew with a solution of milk and water on a sunny day stops the fungus from spreading.

Since this summer has included a handful of very wet days already, it’s important to keep an eye out for signs of blight on your tomato and potato plants. This is also a fungal disease, but it spreads far more rapidly and is far more devastating than mildew if it finds its way to your plants. Blight causes the leaves of tomatoes and potatoes to shrivel and turn brown and, once the disease has taken hold, can cause plant death within weeks. Removing infected leaves can slow the spread but an infected plant should be cut down at soil level and destroyed.

Most of my brassica bed is covered by insect-proof mesh but some of the plants have grown too big to fit under the protection so I’m regularly checking under the leaves for lemon-yellow eggs of the cabbage white butterfly as their caterpillars will decimate the leaves of most cruciferous vegetables including kale and purple sprouting broccoli. Rub the eggs off gently to avoid damaging the leaves. It’s labour intensive, but it works.