Gardening with Dave Allan: The joy of nurturing a plant from seed to plate. greenhouses

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Thanks to last year’s lockdown, grow your own has never been more popular and with restrictions set to continue for a while, prepare for a busy and rewarding time in the garden.

Many green-fingered recruits have also seen the value of greenhouses and protective grow tunnels. Last May, at the height of the lockdown, a leading greenhouse manufacturer, Hartley Botanic, reported a 35% increase in sales. Managing director Tony Barry said: “The current experience is clearly changing consumers’ thinking… for many people ‘growing their own’ is the right choice for their own health and wellbeing, allowing them to feel more secure.”

Greenhouses, polytunnels and differently-sized cloches add an extra dimension to gardening. They extend the growing season and let you grow crops that would be impossible in the open ground. It’s so satisfying nurturing a plant from seed to plate. There’s a much greater choice of seed varieties at a fraction of the price of young plants.

There are protective coverings to suit any pocket, from small cloches and gro-zones costing upwards of £20 to large well-appointed greenhouses.

If you plan to invest 3, 4 or 5 figure sums on a tunnel or greenhouse, decide whether the growing conditions suit the plants you want. Where will you site your structure for sun and shelter? Does it need foundations, electricity or a water supply?

For starters, when planning the layout, what space do you need for seed trays and young plants? Will you use beds or pots and gro-bags or a combination? Wherever possible, I always recommend a bed for most summer crops, including tomatoes and cucumbers. This helps with moisture retention, preventing roots from drying out and overheating in pots as well as allowing plants to grow freely.

Greenhouses must be constructed on absolutely level ground, as should tunnels if at all possible. My tunnel is on a very slight slope longways, so is perfectly secure, but there could be better distribution of water throughout the beds.

Polytunnel hoops are driven well into the ground and the structure sits safely on compacted ground. But heavier greenhouses do need a solid base. Small ones can be secured with anchor spikes, driven into soil well compacted by a roller.

But a greenhouse larger than 8ft x 6ft should be screwed down on a concrete, slabbed or a perimeter brick foundation. This protects against subsidence and strong gales.

Greenhouse frames are made from different materials: steel, aluminium or wood. An alternative to glass, polycarbonate, reduces the intensity of summer sunlight and possibly some heat loss in winter. One greenhouse in the Robinson range includes a workshed at the back, perfect when you don’t have space for both.

With hugely fluctuating summer temperatures, greenhouse shading and good ventilation are essential. Modern greenhouses have windows designed to open automatically, but in my experience, that may not be enough. I leave both doors open and hope the geese don’t drift in for a refreshing green salad. Tunnel fluctuations are equally bad and again, I leave open a door at each end.

You may need heating to protect any overwintering tender perennials. I use a thermostatically controlled heater. Without a power source, you may be able to find a battery or solar-powered heater, avoiding paraffin if possible.

As for watering, I’ve found a water supply has been invaluable, letting me run an undersoil irrigation system. A water butt helps but quickly empties during a dry spell or overflows in winter, so you’d need to run a hose from a standpipe and organise a soakaway for winter. Sadly there’s never room for the butt inside: it would absorb some surplus heat in summer and release a little warmth in winter.

Plant of the week

Galanthus ‘Modern Art’ is a single flowered snowdrop, the three outer tepals are splayed showing off the large, green mark on the inner ones. Some warm sun will bring out its honey scent. Divide and plant snowdrops “in the green” after the flowers fade.

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