Gardening: Begonias

Tuberous begonias (S)
Tuberous begonias (S)

Tips this week on ripening tomatoes in greenhouses, planting bulbs, managing lawns and growing onions by Martin Fish - Show director, Harrogate Flower Shows

One group of plants that have grown very well this summer are the many different types of begonia. The small bedding types planted in borders and containers have flowered and flowered all through the summer and trailing begonias in baskets have also produced a wonderful display. I’ve also seen quite a few of the large flowered tuberous begonias this year in container and bedding displays. The small, fleshy leaved Begonia semperflorens is a perennial but tends to be grown as an annual and is discarded in autumn, although plants can be kept growing on a windowsill through the winter months. The tuberous types, however, naturally die back in autumn to the fleshy tuber. At this time of the year flowering will gradually slow down and the leaves will start to yellow as they plant diverts energy back to the tuber. Eventually, the stems will detach from the tuber and these can be added to the compost heap. The tuber can then be removed from the soil or container and stored over winter in dry, frost-free conditions. Paper bags are perfect as they allow the tuber to breath and a cool drawer in a shed or garage is perfect. If the tubers are kept too warm in the house they can dehydrate and may not re-grow next spring. With a little care it is possible to keep begonia tubers for many years and each year the tuber will grow a little larger and the plants will get bigger .

Readers’ Questions

I’ve had a couple of enquiries over the past week or so asking for any tips on how to ripen green tomatoes growing in a cold greenhouse?

This summer tomatoes have grown very well and on the whole have ripened without too many problems, although some people, including myself have had problems with fruits splitting. Later planted tomatoes, however, are still ripening and all being well will turn from green to red over the next couple of weeks before the weather really cools down. To help green tomatoes ripen there are several things you can do. First thing is to remove some of the foliage, especially if it has started to turn yellow. This helps to increase the flow of air around the fruits which is essential for the ripen process. Also try to keep the atmosphere as warm as possible and dry to prevent moulds developing in the plants. In a greenhouse or polytunnel ventilate during the day, but close the vents in the afternoon to try and trap a little heat. You should cut down the amount of water given to the plants, but don’t let them dry out. Although we are coming to the end of September, as long as the plants are kept ticking over and we get a few warmish days, green fruits should ripen. In the past I’ve had tomatoes ripening as late as the end of October, so don’t reach for the green tomato chutney recipe just yet!

Jobs for the Week

Plant spring flowering bulbs such as crocus, snowdrops and daffodils as soon as you can, making sure you plant at least twice the depth of the bulb.

Lawns can be given an autumn feed that is low in nitrogen, but high in phosphates and potash. This encourages a good root system and induced winter hardiness and resistance to diseases.

For an early crop of onions next June, over-wintering onion sets can be planted directly into the garden to give them time to establish before winter.