Casual Gardener: Strawberry yields forever
With the right conditions you can extend the strawberry season...
I CAN'T imagine I'll be courting too much controversy by saying that strawberries are easily among the best and easiest things you can grow in your garden. They're generally an unfussy, low maintenance plant that simply likes nutrients, light and water. They're a crop that can be produced in even the smallest space, producing fruit that'll taste as good as any. At risk of sounding like a 'Boomer', I regard strawberries as something of a luxury, and arguably their allure stems in part from a relatively short season at the height of summer. When at their best – fresh, sweet and just about to soften – they are unmatched; an indulgence indeed but one that doesn't leave behind the same sickly guilt as a sausage roll or chocolate éclair.
These days, strawberries are available all year round, with those on the shelves out of season mostly originating in Spain. I've adopted my own BDS approach to tasteless supermarket strawberries sourced in southern Europe, so therefore rely on those produced in Ireland from spring onwards, or the ones picked in my own garden – the latter being by far the nicest, if not the best looking. For me, producing enough strawberries to feed two-three every day for a month (eaten in salads, porridge, desserts, or neat) isn't a problem, but I'd like to stretch out this luxurious indulgence for a few more weeks every year.
"Commercially, it's possible to produce fruit throughout the winter but it requires control of the environment, including the amount of light and heat," says Berta Cunha, a horticulture development advisor at Cafre's Greenmount campus who specialises in soft fruit.
"But with the right varieties and conditions, such as a glasshouse or polytunnel, it's possible for gardeners to extend the harvest period over a couple of months from May onwards."
While strawberries like warmth when they're fruiting, says Berta, they have alpine characteristics and need to undergo vernalisation, whereby the plants must be exposed to prolonged cold over winter. This can create complications if you're growing under cover, in that the temperature never drops far enough. "We have found that strawberries generally need 800-1,000 hours below six degrees," says Berta. "It doesn't need to be continuous, and between November and March most years they'd accumulate that outside. However, if your glasshouse is in a sheltered position where they don't get cold enough they will be less productive."
Some varieties are better suited to early cropping, says Berta, citing 'Emily', 'Earliglow' and 'Honeoye', but they therefore carry a risk that the blossom or emerging fruit will be damaged by frosts, which is why it's safer under cover. Berta stresses that feeding and watering are important, the former best derived from seaweed. "A general tomato feed can be good but only at some stages, for example when the plant is actively flowering and fruiting because it does provide extra phosphorous and potassium which is needed for flowers and fruit and to make the fruit sweet, but too much nitrogren and nitrate and the fruit will be less sweet," she says.
"Seaweed is a bio stimulant and that helps the plant withstand bacterial and fungal infections, as well as actually providing nutrients."
She recommends replacing your plants, by division or propagating runners, every two-three years as they become less productive. If you want to extend the season at the other end, Berta suggests seeking out varieties such as 'Flanella' and 'Flamenco'. She says she's even heard of gardeners getting fruit as late as Christmas.