Grower’s Corner – strawberries
Assuming you don’t have strawberry allergies, there can be few more productive and popular crops than strawberries. They are relatively easy to grow if you put in the work to prepare the site in advance. Strawberries do not like wet roots, preferring a well-drained site and, if possible, a slightly acid, medium loamy soil – as you can see, that’s a fairly specific requirement which is why many people grow them in raised beds with ‘imported’ soil and lots of well rotted manure.
It surprises many people to learn that strawberries will tolerate partial shade but thrive in sunshine. It is vital to avoid frost and if even the lightest air frost is predicted protect the early flowers overnight with horticultural fleece. Many people grow them in greenhouses which deals with the bird problem at least, but can leave the plants more prone to botrytis.
Strawberries should be planted in early autumn or in the spring. If you put out your plants in spring, de-blossom them in the first season to allow the roots to establish. Crowns should be at soil level, about sixteen to eighteen inches apart in the row and with a good yard between the rows.
Diseases Generally there are three main enemies to deal with: botrytis, redcore and virus. Botrytis, which shows up as mouldy berries, is caused by soil and/or wind borne spores getting into the flower as it ripens. The only affective solution is to clean the strawberry bed plus the surrounding area during the winter with a strong fungicide to eradicate the infestation or at least get is under control. As and when mouldy berries appear, spray the flowers with a systemic fungicide and dispose of mouldy berries without spreading more spores.
Redcore is a fungal disease of the roots, which have red centres when infected. The symptoms are listless and dying plants: the prognosis is by cutting or breaking root members and looking for ‘red core’. The treatment is to remove and burn all plants whether sick or healthy. The cure is again a drenching of the bed to a depth of six to eight inches with a strong fungicide, followed by replanting with certified virus free stock.
There are several forms of virus: Strawberry crinkle virus, Strawberry mild yellow-edge virus, Strawberry mild yellow-edge associated virus, Strawberry pseudo-mild yellow edge virus, Strawberry mottle virus, and Strawberry vein banding virus, Strawberry lethal decline phytoplasma, and the causal agents of Strawberry feather-leaf, Strawberry pallidosis, Strawberry latent C and Strawberry leafroll - if virus is suspected all plants should be removed and burnt before clean replacement stock is planted. To avoid virus problems, buy certified virus free stock! Planting runners from friends or neighbours or ‘nicking’ them from pick your own sites is a risky business.
Propagation is normally carried out by pegging down runners at the end of the season. Peg them at the first node, so it forms a baby plant by thrusting roots down into the soil. After a few weeks when it is firmly rooted, the runner may be cut free from the parent and relocated to a new growing position. This process should be carried out so that the plants are replaced every three years, but remember that if the parent plants are carrying any virus disorders these disorders will be passed to the rooted runners. It is important when setting out runners in their final places, to maintain spacing between the rows for ease of cultivation. When you have set runners, remember to trim back the foliage on parent plants and old stock to around four inches to allow the new leaves to come through.
- Many gardeners grow strawberries through black polythene to suppress weeds, conserve water and stop soil splashing. Otherwise, tuck straw under the developing trusses for the same effect
- Slugs will travel miles for a ripe strawberry, closely followed by blackbirds and starlings! Netting and slug pellets or some other barrier method will be necessary if you are to get any of your crop
- To minimise the risk of pests and disease, make sure you clear away and burn both the cut foliage and any straw or other debris from around the plants
- Those annoying birds can be useful in the end - leave netting off the plants once the crop is done, to encourage birds to tidy up any pests that may be left behind
- To avoid disease build-up, grow strawberries in a different plot every three years.
Strawberry photographs by Per Ola Winberg and squeaky marmot, used under a creative commons attribution licence