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Sally Nex

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Sally Nex

Tag Archives: frost protection

Life in the greenhouse: January

20 Friday Jan 2017

Posted by sallynex in greenhouse

≈ 1 Comment

Tags

citrus, frost, frost protection, greenhouse, lemon verbena, lemons, tender plants, winter

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Half-finished insulation to the left, not-quite cleared cucamelons to the right: I have, it is fair to say, totally failed to sort out the greenhouse this winter.

Blimey it’s chilly. Inside and out: life got a bit hectic last autumn and I didn’t get around to my usual bubblewrap-insulation-and-greenhouse-heater routine. So my greenhouse – usually a cosy refuge at this time of year – is distinctly less than welcoming at the moment.

However: the decision not to heat the greenhouse this winter, if a little unintentional, has been enlightening. Normally I would have the heater on 24/7 when the weather is like this: I don’t heat my greenhouse to tropical temperatures but I do like to keep it somewhere around the 5°C mark. When it’s -5°C outside, as it was last night, that would mean having to lift the temperature by a whole 10°C above ambient – loading my electricity bill to groaning point and playing who knows what havoc with the environment.

I’ve always felt mildly guilty about heating the greenhouse. As well as being positively profligate with resources I normally shepherd carefully – that is, electricity and warmth – it is very expensive and makes something of a mockery of my pretensions to thriftiness. After all, when your overwintered chillies cost you at least £50 to keep alive in a frosty winter you could probably buy gold-plated ones for less.

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But – avert your eyes from the weeds, please – I can’t be going far wrong when I’ve got lemons like these

Failing to heat my greenhouse, though, has been an eye-opener. Just look at my lemons! (No smutty jokes at the back, please). The scented-leaf geraniums have fared well too, and the lemon verbena.

Most of the tender herbs and edibles which I move into the greenhouse over winter to protect them from frost can survive down to a few degrees below. Lemons, for example, can tolerate -5°C; geraniums (pelargoniums), lemon verbena and French tarragon to about -1°C. The secret is to keep them dry. Soggy compost freezes at anything below zero, wrecking delicate root systems, while dry compost, though cold, will not freeze so does no damage.

So I haven’t watered my lemon tree, or the geraniums, since I brought them indoors in early November. They’re fine. So is the grapefruit, and the lemon verbena, and even the Nerine sarniensis which is the only thing in here which isn’t edible but I can’t bear to evict it as it’s so lovely when it flowers. The overwintering chilli (an Aji type, one of the more hardy) has succumbed, so I’d guess that very heat-loving Mexican types with fleshy, tender stems freeze at zero.

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I brought my three-pot salad system in here this autumn too: the extra shelter has kept them growing and I’ve had salads to pick since October.

But for most, just bringing them into a greenhouse without heating it has been enough. The glass alone raises temperatures by about 5°C, after all (and much more on a sunny day, though that heat is lost by nightfall). So if you take last night, the coldest here for several years at about -5°C, inside the greenhouse it will still have been only just at freezing. Not enough to do any damage. Line the greenhouse with bubblewrap or – I’m told but haven’t tried myself – cardboard, or wrap plants individually in horticultural fleece, hessian with straw tucked underneath, or more bubblewrap – and you can raise that by a few degrees further, potentially keeping even quite tender plants frost-free without the need for heating.

Other little tricks to try include keeping a pond in the greenhouse to act as a heat sink, absorbing the sun’s heat by day and releasing it by night; and of course hotbeds, which is too big a subject to tackle here but the most natural greenhouse heater you’ll ever have.

But I think my days of artificially heating a greenhouse are over. I’m sure the environment will thank me one day. My bank account certainly will.

All tucked up

23 Monday Nov 2015

Posted by sallynex in chicken garden, cutting garden

≈ Leave a comment

Tags

cut flowers, dahlias, frost, frost protection, overwintering, winter

dahlias_overwinter1

Tuck dahlias up for their winter hibernation as soon as the stems are blackened by frost

I arrived at the Chicken Garden this morning to find the big, handsome dahlias hanging their heads, their lush leaves turned slatey black and drooping disconsolately.

Abbie – garden owner – grows dahlias by the armful to cut for guests at the B&B, and very gorgeous they’ve been for the last few months. So there are two whole rows of them in the cutting garden as well as a dozen or so in various spots around the main flower beds.

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If you’re leaving them in the ground, cut stems right back (if lifting, leave 15cm of stalk intact)

You can leave dahlias as they are till the blackened-leaf stage (and they’ll keep flowering, too, if you dead-head) but once the first frost has struck it’s time to leap into action.

dahlias_overwinter3

Mulch thickly – at least 15cm deep. Autumn leaves are ideal for this as they don’t hold on to moisture as much as compost.

I always prefer to leave a plant in the ground if at all possible, and in the balmy south-west we’re in just the sort of place where you can get away with it with dahlias most years. But you never know quite what the weather has in store: if it’s a really wet one, or possibly even a really snowy one, you could still end up losing the lot.

I decided to cut my losses: so I’ve left the bigger (and therefore, I reason, more hardy) border varieties in the ground and lifted any smaller plants and also those in pots and containers where the roots are more exposed.

dahlias_overwinter4

And finally: cover the whole thing with a layer of hessian (as here), insect-proof mesh, weed-suppressing fabric, old t-shirts… in fact anything that’s breathable. Two purposes: 1) it holds the leaves in place and stops them blowing off, and 2) it gives one extra layer of frost protection to the tubers. Pin down securely with bits of sturdy wire. And that’s it till spring (I hope…)

In the cutting garden, I have covered one whole row and lifted the other. They’re currently trimmed back to about 15cm and turned upside down to dry and drain, the shortened stalks poked through the slats of the greenhouse staging to hold them in place.

Next week, once they’re fully dry, I’ll pack them into boxes of damp-ish sand or spent compost and move them to the shed (drier than the greenhouse). After that I shall be going round with fingers permanently crossed till the spring warms up next year and I can pull back the covers to see if my luck has held. Here’s hoping…

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