The benefits of temporary cover gardening

Fiann Ó Nualláin insists we don’t confuse the title of a movie with the beauty of the day — the cloche.

Last week I took a little inspiration from Kubrick and this week the title at least echoes another great film maker, Luis Buñuel. While in colloquial French Belle du Jour can mean a sex worker or indeed the Hemerocallis species, daylilies, (which is not a mistake you want to make ordering online), for me the “beauty of the day” is the cloche.

If you own some, now is the weekend to clean up the glass and think of where they can be employed in the coming weeks. If you don’t possess any, you might consider investing. They are ever useful and not at all as outdated as you might think.

While they are not all bell shaped — once their original shape and hence their representation by the French word for belle — they are all beautiful. Beauty is more than form. Beauty can be function. 

And cloches are perfect devices to protect plants from cold temperatures and wind scorch. We have had a soft winter so far — at least temperature-wise — but that can turn on a sixpence, as recent drops have shown.

This is where cloches come in — they can warm up a spot as much as shield a plant, so if you want to prompt some bulb action or break dormancy on an item underground, they are ideal. Put them in place now to warm up a spot or dry out some ground in advance of planting herbs or edibles as early as next week or early February.

Cloches are all about creating a microclimate — to cheat what’s going on in the real climate. When we think of them as mini glass houses we might just think “sure what would I fit under it?” — but it’s the portable, targeted nature of warming or protecting a dedicated spot that makes them so effective.

You can use them to advance asparagus when spears begin to protrude again, or you can cover some rocket seeds sown direct today to speed germination, facilitate healthy growth and ultimately commence your salad harvests early. 

That was the original purpose of bell jars back in 19th century France and they were a revolution in their time, helping to supply otherwise out-of-season vegetables to Parisian restaurants and delicatessens.

The bell remained popular over the next decades but square and case cloches developed too and the versatility of the cloche soon moved it into mainstream gardens as a protector and support to ornamental plants and general gardening.

The newer versions come with built-in vents, requiring less exertion to lift and slide a block under or out, to regulate microclimate and to stop the bell building up too much heat or too much condensation. 

So if you have a vintage cloche — do remember that it will need to be vented on warmer days and it may be worth the occasional lift and wipe to stop condensation becoming a detriment to seedlings, or any mildew-prone plants that it encompasses. If you have a modern square or case cloche, a swipe of the thumb sorts the built-in vent easily.

Cloches have an aesthetic I appreciate — and they have a low tech dimension I love. But also with the latest research into smart plastic, they will one day be part of sustainable pest management. I currently use cloches for quarantine — if I get an infestation or outbreak on a plant, I can apply my homemade garlic spray and other remedy and then cover with a cloche to contain the problem until treatment is successful.

Cloches are also great to isolate and limit the contagion potential of a plant with botrytis on a windy day — to come under a calmer more controlled situation. But these smart plastics filter sunlight to remove near-UV radiation which is involved in the lifecycle of aphids and other insect pests. 

Its absence halts the population expansion of any invasion beneath, and if those plastics are made into cloches or a film becomes available to adhere to existing cloches, then we will have portable treatment devices in our season extenders too. That would be a beaut on any day.

As it stands, cloches can be utilised as a line of defence. Those pea and bean seedlings beneath a cloche are safely housed away from their prime predators — field mice and pigeons, while leafy veg germinations are kept beyond the reach of slugs and snails. Cloches can be expensive, but the idea is easily replicated. Utilizing old water cooler bottles, skip diving for a window panel or even purchasing some strips of Perspex, you can construct your own shelter devices.

The clear polythene bag that covers your garment from the dry cleaners is ideal to make a mini hoop tunnel — the metal hanger supplying a hoop to start you off. I use such devices on larger sections or rows of crops. Plastic hoop tunnels are great to keep onions in place from marauding birds, but in a wet season they also help to sturdy up the edible bulbs. 

You can purchase commercial mini tunnels and also sheets of polytunnel plastic if you like to get diy when you giy. Recycling plastic containers is less aesthetic but no less effective. Any shelter device that you make or any cloche that you purchase

will function to pre-warm your soil. Keeping the rain off is part of it, as dry soil warms faster than wet soil, but the gentle solarisation amplifies heat during the day and slows its loss at night. 

The standard rule is to put it in place about a week to ten days before you commence sowing.

The extra warmth of the ground beneath it and the ambient raise in temperature, will efficiently encourage a quick and earlier germination — often known technically as ‘forwarding’ — starting plants a few weeks ahead of what it may say on the packet instructions and harvesting them earlier too). The extra warmth also extends the length of the cropping season.

When it comes to over-extending the season or wintering crops, cloches protect leafy veg from battering rain and mud splatter. And while parsnips and carrots will be sweeter this week after the touch of recent cold, that dip can bitter up salad and leafy crops so cloche cover keeps things sweet. 

Another sweet note is that this effect of forwarding can be used to improve our strawberries. Strawberries like cold over winter to set their fruiting potential — so applying a cloche over their underground crowns in December or January is not best practice, but waiting until February and then cloching sees a stronger root development and thus quicker formation of flowers. 

Those protected flowers will increase fruiting success and the heat will also amplify flavour. These little tricks make all the difference. Commercial growers in Wexford and elsewhere can have acres under glass or plastic but for the home grower — where space is limited, you want the best from the space you have.

Cloches also allow us to try plants that traditionally would only be chanced under cover or which require a longer season of sun and warmth than the Irish climate allows. 

Starting tomatoes or sweetcorn under a cloche and using a homemade larger device later in the season, makes it possible to supply that plant with all it needs to really ripen and be delicious. That’s worth ringing the bells.

No film references next week, for the year that’s in it I want to profile a horticultural hero in each month — some historic or current individuals or collectives who have put Ireland on the map in the sphere of horticulture.

There will even be a 1916 hero with roots in botany. Watch this space.


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