Undercover: September 2012

Tender harvests

❯    Tomatoes will still ripen well in warm weather. Remove dying and diseased leaves and rotting fruit to help keep plants healthy.
❯    Cucumbers often suffer from powdery mildew and root rots at this time of year, but I have found grafted plants with their extra vigour continue to crop for several weeks longer than their ungrafted counterparts. With slow autumn growth, the fruits tend to go watery and tasteless before they lengthen fully, so pick them while still small and crisp.
❯    Peppers and chillies stand up well to autumn damp and chill; leave fruits on the plants to ripen well into October.
❯    Some crops can be cleared to make way for winter plantings. Winter squash such as butternut should now be mature enough to harvest – leave them on a greenhouse bench or on slats off the ground in a polytunnel for the skin to harden fully. Pull up the plants of beans grown for drying, or herbs such as cumin and coriander grown for their seeds, and hang them up until they are rustling dry.
❯    Harvest now: Tomatoes, peppers, chillies, cucumbers, aubergines, melons, sweetcorn, basil, grapes, butternut squash, beans for drying.

Watering and ventilation

As growth slows, mature plants will need watering less frequently. To minimise problems with condensation and disease, avoid evening watering and open doors and vents as much as possible during the day when conditions allow.

​Pest control

Don’t relax on pest control, even though it is the end of the season for many plants. The more pests left to overwinter in your greenhouse or tunnel, the greater the problems next year. Pull up weeds that are thriving in all the hard-to-reach places – under a greenhouse bench or against the polythene cover – they can often be infested with whitefly. Remove old pots, trays, compost and canes as these can provide nooks and crannies for hibernating red spider mites.

Ordinary garden pests can also take advantage of the extra warmth undercover to carry on causing damage. I have found cabbage root flies tunnel into roots of late turnips and radish, spoiling their crisp white flesh, the best remedy being to cover them with pest proof net after sowing.

Dessert grapes are fickle to ripen when grown outdoors in all but the warmest areas of the UK, but the protection of a cold greenhouse or polytunnel tunnel can make all the difference. Choose the right varieties, and you can get reliable harvests of sweet fruits.

Go garden visiting this month and you’ll have a chance to see for yourself. The Victorian vineries in restored walled gardens are an inspiration – from Heligan and West Dean in the south up north to Chatsworth in Derbyshire and Normanby Hall in North Lincolnshire – they produce sumptuous bunches of grapes on gnarled, neatly trained vines. However, your own planting plans need not be as grand.

​Planting

Pot grown vines can be planted at any time of year; bare-rooted ones from November to March. Traditionally they are planted outside a greenhouse and the stem trained in through a gap created near the base by removing brick or replacing a pane of glass – this allows the roots to take advantage of the rain. A reinforced gap could similarly be made in the side vent of a polytunnel (one where the cover is attached to a rail rather than buried in the ground). Alternatively you can plant inside, but more attention to watering will be necessary.

It might not survive 200 years, but a vine will be a long-term addition to your garden, so prepare the soil well when planting. Although vines can be thirsty plants, they don’t like waterlogging. Make sure drainage is good – by adding rubble to the bottom of a large planting hole if necessary – and channel away excess water from a polytunnel or greenhouse roof. Add compost or well-rotted manure. Put up horizontal wires about 23cm (9in) apart to support the main stem and side shoots, keeping them a few inches away from the glass or polythene to help airflow and prevent scorching.

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