C & D have asked do strawberries need direct sunlight in order to produce flowers – consequently, fruit? They refer to a segment on ABC’s Gardening Australia program that demonstrated a “strawberry table” where strawberries are planted directly into slashes made in a premium bag of potting medium. C & D are concerned that direct sunlight would cook all the good nutrients out of it the soil in the bag, and ask if dappled shade would be more appropriate.
The answer is this question is that a lot depends on the climate where the strawberries are grown. Some warming of the potting mix could be helpful in areas with a short growing season, such as Tasmania. Or, where strawberries are grown in winter to avoid fungal diseases encouraged by high humidity in summer. However, dappled shade would be more suitable in areas where days can be quite hot while strawberries are growing, flowering and forming fruit, in order to prevent not only cooking the mix, but also the plant roots.
In warm conditions, it is not necessary for strawberries to be in direct sunlight to form ripe fruit. If you observe how strawberries form, each flower cluster sits above the foliage. After pollination, the weight of the developing fruit pulls the cluster downwards until, quite often, the fruit is completely hidden by the foliage, and it reaches full ripeness.
In fact, as soon as our strawberry plants start forming flowers in mid spring, we place a 50% shade cloth canopy over them, positioned high enough to allow good air circulation. Otherwise, fruit not hidden by foliage becomes sunburned and inedible. The canopy also deters birds from eating the fruit. We have also had potted-up spare plants produce sweet, red fruit when grown in our shade house where they only received 50 % light through their entire growth period.
I can see a couple of problems with growing strawberries in a “table”. First, strawberry roots should be fanned out at planting, and this could be difficult to do if you have restricted access to the medium. Secondly, the bag would need holes punched along the underside to prevent the mix becoming waterlogged. Poor drainage will weaken the plants. Also, you would have to slash the bag open when runners start to form if you wanted to increase the number of plants. Strawberry plants should be replaced every two or three years.
If you would like to try this form of strawberry cultivation, avoid using a potting mix that contains a lot of mushroom compost as this is usually heavily limed and strawberries prefer a slightly acid medium. Debco make a certified-organic potting mix that would be suitable for this type of project. It is available from Bunnings stores. Unless conditions are cool, position the “table” where it gets any direct sun early in the day, rather than afternoon, and pack straw around the plants and the bag, if you feel the mix is getting too warm. However, I think growing strawberries in hanging baskets would be easier in warm conditions if lack of space were a problem – and the fruit would be safe from snails and slugs.