Forcing fruit and vegetables in winter is fun way to ensure you have a steady supply of fresh greens for your family. It involves producing crops out of season through replicating the environmental conditions necessary for plant growth. This quirky custom dates back to at least the 1600s, but achieved peak popularity with the Victorians, when the better off sought to impress their friends with spring salads.
Forcing rhubarb is an easy way to start experimenting with forcing plants, and can be done throughout the winter, although it works best in January and February. Simply start by removing weeds and leaves around the rhubarb crown, and place some fresh mulch. Then use large cylinder (preferably a pot) to cover the crowns, plugging any holes in the process. This exclusion of light will start frenzied growth, and the stems should be ready in only eight weeks, provided the soil is kept moist! You can harvest when the stems hit the roof of the pot, although 20-30cm of growth is to be expected.
It is recommended that you use established plants as the young ones may not have sufficient energy reserves, and that you do not force again for 2 years as the process leaves the plant susceptible to disease. If you are in colder climate, or are expecting a harsh winter, insulating the pot will be necessary. The warmer it is, the faster the plant will grow, and 18-20°C is the optimum temperature. Unsurprisingly, as the rhubarb is deprived of the light, it will be unable to photosynthesise, and will appear paler than usual. Also noticeable, is how the resultant stem is decidedly less bitter, supposedly due to less sugar.
Forcing strawberries can be a little more difficult, but the key is to expose the plant to the cold until at least February, before moving it to a warm environment. This extended cooling is necessary to convince the plant that an extended period of warmth is about to begin, thus signalling the changing of the seasons. When choosing which strawberry plants to force, you can try older plants that perhaps performed poorly in the year, but if you are really keen, you can plant runners up to a year and a half early, and cultivate the plant’s root system through picking off its flowers.
Now, what kind of warmth are we talking about? An unheated greenhouse can produce a small crop, but instead it is better to use a either a propagation mat or a greenhouse heater to raise the temperature a small amount. Now, if you wish to keep your strawberry plants outside, you can use a cloche that can be removed on the milder days to attract bees.
Once you decide to move to the plant into the warmth, it is now time to apply some TLC. First remove dead leaves, runners and weeds and give them a dressing with mulch. Then as it is cold outside and there are no bees, you’ll have to do the pollinating. Grab yourself a paintbrush or cotton swab and rub it over each of the flowers as often as possible. (Some gardeners do this daily!) Finally it’s time to start the watering regimen, that is until the fruits finally ripen, when you should let the earth dry out. (This helps concentrate sugars in the fruit.)
Forcing doesn’t just have to be used in winter and other vegetables that are historically forced include Chinese Beansprouts, Chicory, Dandelion and Seakale. For fruits, gardeners have reported success with tomatoes and even pineapples. Do you have any experience with forcing fruit? If so we would love hear from you. Post in the comments below!
Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!
His ideal afternoon would involve a long walk, before settling down for scones.
Jorge is a journeyman gardener with experience in growing crops.