Undercover: July 2012

Extending the harvest

It is easy to be lulled by the warmth and abundance of summer, but to keep your
tunnel fully productive in autumn and winter, you’ll soon have to plan more crops and sow the first seeds.

Start now and you can both extend the season of tender summer vegetables such as French beans, and also grow hardier crops such as chard, chicories and Chinese leaves to supplement staple outdoor vegetables right through the winter. I look forward to the vibrant mix of spicy winter salads from my polytunnel just as much as I relish the first home-grown summer tomatoes.

Growing in autumn and winter can have extra advantages too. Crops such as Chinese cabbage, pak choi and Florence fennel, which often fail to make good heads in summer, are much less prone to bolting in cool shortening days. The colours of red chicories and brassicas intensify and look stunning in salads, and nuisance summer pests such as cabbage caterpillars become less of a threat.

Preparing beds

July sown crops fit in well after early summer crops such as courgettes and sweetcorn have been cleared. Unless the beds have been well manured for the previous crop, fork compost into the soil surface before sowing or planting, particularly for veg such as fennel and Chinese cabbage that appreciate extra moisture.

Good ventilation

The ideal atmosphere in a greenhouse or tunnel is often described as ‘buoyant’, and you can feel what this means – a good circulation of air without raging draughts, which keeps the air cool and helps prevent fungal diseases.

Open all doors and vents on hot days. Netting screens will filter the wind and prevent birds and pets getting in.

Keep up with training and pruning plants – remove side shoots from tomatoes and pinch back cucumber laterals, for example. Excess foliage creates humid pockets where disease can take hold.

Remove dead and diseased leaves and be ruthless in clearing crops that are no longer giving worthwhile harvests.

To feed or not to feed?

Tomatoes, peppers and other fruiting plants grown in containers and growing bags will need regular feeding from now on. Use a proprietary tomato feed or home-made comfrey liquid. Top dressing with a nutrient-rich compost can also help.

Plants grown in beds well prepared with manure or compost don’t necessarily need extra feeding, but vigorous fruiting plants can benefit, particularly from extra potassium. Signs of a deficiency in tomatoes are yellow/brown margins to the upper/middle leaves and unevenly ripe fruit with areas of white tissue. Some varieties seem to be more susceptible than others. I don’t usually use liquid feeds on plants grown in the soil, but instead mulch them two or three times in July and August with chopped comfrey leaves.

Tastes of summer

Many tender crops will produce their first harvests this month – and once you have tasted your first sweet, juicy homegrown tomatoes, it feels like summer has really come.

❯    Tomatoes – the variety you grow can make a noticeable difference to the cropping time, so take note of harvesting dates for the future. The earliest are often small-fruited bush types such as ‘Losetto’ and ‘Red Alert’ – Don’t be impatient to pick them, leaving them on the plant in the sun to get really ripe gives them the best flavour (shop-bought tomatoes don’t get this chance!) and encourages fruits further down the trusses to ripen too.

❯    Cucumbers need regular picking otherwise the plant can become over laden causing embryo fruitlets to drop off. The length of the fruit gives some indication of maturity, but you can harvest them at any size. Left too long, the flesh will start to get soft and ridge types will start to form seeds. I prefer my cucumbers small, firm and crisp.

❯    French beans will grow quickly in the heat – harvest them as soon as they have reached their full length, before the beans start to swell inside. How long they get depends partly on variety – I grow ‘Fortex’ for very long slim beans.

❯    Peppers are generally slower to ripen, but you can use fruit when green; picking some of these now should help encourage more fruits to form.

❯    Other crops that could be ready for harvest: basil, coriander, courgettes, beetroot, carrots, potatoes, onions and peaches.

Sowing tips

At this time of year, sowing in modules of multi-purpose compost has several advantages:

❯    It buys you extra time to clear early summer crops and prepare beds.
❯    The modules can be moved into a cool shady place until they germinate to avoid excess heat; (too high a temperature can inhibit germination, particularly of lettuce and onions, for example).
❯    It is easier to keep seedlings in modules moist – in hot dry conditions, they can be covered with fleece or moved into the shade.

• Read the full article in Kitchen Garden magazine, July 2012!