SWCAA RESOURCE POLYTUNNELS AND GREENHOUSES ON ALLOTMENTS

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Clementine Washington
6 years ago
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SWCAA RESOURCE POLYTUNNELS AND GREENHOUSES ON ALLOTMENTS Do you need planning permission? In general, you do not need planning permission for sheds, greenhouses, summerhouses or polytunnels.

So the answer is generally "no", at least for domestic tunnels (not large commercial ventures). Limitations on size The ordinary allotment tunnel should not be more than 3m high (or more than 4.

1 SWCAA RESOURCE POLYTUNNELS AND GREENHOUSES ON ALLOTMENTS Do you need planning permission? In general, you do not need planning permission for sheds, greenhouses, summerhouses or polytunnels. There may be some restrictions if you are in a national park, conservation area or area of outstanding natural beauty. So the answer is generally "no", at least for domestic tunnels (not large commercial ventures). Limitations on size The ordinary allotment tunnel should not be more than 3m high (or more than 4.2m at the ridge) or more than about 18m long and about 4.5 m wide at base in order to avoid planning permission problems. Planning disputes Here is some ammunition if ever you need it (if not, skip to next section): - Discussion Development of land generally needs planning permission: but Section 55(e) of the Town & Country Planning Acts 1990 states that: "the use of land for the purpose of agriculture or forestry and the use of any building occupied together with the land so used" does not constitute "development" so does not need planning permission. Allotments of course are agricultural land; and converting land to agricultural use (e.g. by turning it into allotments) does not require planning permission either. The Royal Institute of Chartered Surveyors summed this up: "Structures may be placed on agricultural land for agricultural purposes without the necessity for obtaining planning permission. However, no building or engineering works must be involved." OK to place the polytunnels on the land but not to pour a cement floor unless you can remove it when you leave. See: - There was a court ruling that "Spanish Polytunnels" - large, walk-in, double-spanned plastic tunnels - are a development operation and so required planning permission (Hall Hunter case December 2006). Some Councils then imposed new charges and restrictions on small

2 polytunnels as well, until Paul Hudson, the Communities and Local Government Chief Planner, sent round a letter to stop this... Planning Permission The Hall Hunter court ruling did not mean that "all future polytunnels will necessarily need planning permission". It depends on the type, size, degree of permanence and physical attachment to the ground. Polytunnels like farm buildings are subject to the current limitations on size (set at 465 square meters at time of writing). Read Paul Hudson's letter to Chief Planning Officers With planning issues hopefully out of the way we can turn to more useful questions. First: what exactly do you plan to use the polytunnel for? Remember in season the tunnel needs visiting morning and evening too open and close the doors. Tunnels can be labour-intensive. For flowers and hanging baskets you will need a good water supply, and potting benches; perhaps also heating or extra bubble-insulation for early germination or half-hardy annuals. Permaculture enthusiasts suggest chickens or livestock can provide some warmth to greenhouses or polytunnels: then you need a netted run and plenty of ventilation; make sure livestock cannot contact the polythene cover. If you are keeping canaries or chickens or rabbits a polythene tunnel is not suitable in summer heat. For this use a shade house: cover the tunnel with shade netting, keeping part of it polythene for shelter from rain, to increase the air-flow and halve the sunlight. Shade houses can be used for hardening championship vegetables, and for shade-loving plants like orchids and chrysanths, as well as livestock. Wind Doorways are the most vulnerable, so arrange for the prevailing wind to hit the tunnel sidewise on. Though tunnels are very strong, use a sheltered area on an exposed site, or plant a windbreak. Polytunnels (unlike tents) are immensely strong. Ground sidebars could be used to keep the cover taut, or you can dig it well in (up to a meter). Direction Lay the ridge-pole east-west for most heat, or swing towards north-south to avoid overheating in the summer; or get shade from the north side of a deciduous tree (not too close or leaves falling clutter the sheeting). That said, if you orient north-south you have even growth on both sides of the plants (nice round lettuces).

Slopes Level ground is best; though a gentle slope down the length or the tunnel is OK and provides for run-of; put the doors at the bottom unless you want to dig in to the hill side (hard work!).

3 Slopes Level ground is best; though a gentle slope down the length or the tunnel is OK and provides for run-of; put the doors at the bottom unless you want to dig in to the hill side (hard work!). Slopes across the tunnel are difficult, because the side anchor-tubes must be as level as possible. Avoid damp hollows because the run-off in a downpour might swamp the tunnel. Site Clear about 1 metre (yard) around the tunnel base: this is a work-space for putting the cover on, and a barrier against tall weed growth shading the sides. Water You must have a plentiful water supply on hand - a stand-pipe, water storage, or a pipe line (dig it in deep enough to avoid frost and forks, and when trenching try not to cut tree roots). You might use mains water (expensive?), rain water from storage tanks (filter through an old stocking? add Citrox or a few grains of potassium permanganate to keep tanks clear? add a few drops of oil to film-over the surface and kill mosquito larvae? Flexible adhesive tunnel-gutter will fill water barrels quickly. Try digging a well (safely lined!) Or drawing water from a stream (watch out for water-rights: always test streams and wells for pollutants. If water-cress grows it is probably OK. Beware of used water (laundry, baths etc.) as this causes chemical build-up; and never use sewer water of course. Application: it is best to water in the evenings, especially for shallow-rooted plants. Using cans alone is very time-consuming in summer, except for the smaller tunnels. Hoses, over-head sprinklers (these may drip and cause soil-splash fungal growth - though you can tie string to dangle for the final droplets to run down - but sprinklers still water different plants indiscriminately), lightly buried soaker-hoses, and capillary beds can all help - but at a cost. Mulching (layer several inches deep) using straw, bark, peat or unbleached paper conserves moisture. Over-crowding the plants and continual watering encourages fungus and disease. Let the surface occasionally dry out, except for seedlings. Appearance An inconspicuous tunnel avoids unwelcome attention and pleases the neighbours. Flat-ended tunnels with sliding doors are dearer and no real gain. Straight sided tunnels may cost more have a larger planting area. Coloured coverings These are not for decorative appearance.

4 Green Absorbs infra-red light and was developed to provide a cool environment for shade-loving plants Blue Developed for commercial growers, is good for growing small, bushy bedding plants with good leaf colour; cooler in summer it gives a longer growing and selling time not to be recommended for allotments in general. Thermal Heat Block (THB) Polythene Reflects infra-red and so traps the warmth in the tunnel if you are heating it. So it reduces energy costs and is useful for overwintering vegetables and starting off seeds. When it is also treated against misting it reduces condensation and fungus risk. Clear Polythene In fact partly opaque, to scatter light and so reduce leaf-scorching if you water in full sun, and cut down shading from nearby plants. Most of the light gets through, so it is ideal for normal nine-month spring to autumn growing; no good by itself if you are heating the tunnel in the winter. UVA and UVB Filtered Polythene This cuts down the risk of fungus disease and the activity of flying insects, and aphid damage (they tend to cluster in small colonies only), because they rely on ultra-violet light to see. Insect pollination may be reduced, but by amounts insignificant for allotment growers. Tape Covers typically last five to seven years, and are cheap to replace compared with the original tunnel construction. Hot-spot tape (or anti-hotspot tape) cushions the cover where it contacts the frame and lengthens its life by about a year - so is essential and a good buy if you need extra. Polythene repair tape will be needed to patch the tears that even the most careful gardener will be faced with! Act quickly and apply the tape both inside and out or a tiny hole becomes a large split. The tunnel cover will need cleaning at least every spring (green algae) and can be washed with a mild detergent and a soft mop (no pressure especially as the cover gets brittle after three years). Use Citrox, a natural safe disinfectant and pot cleaner based on citrus, widely available on-line. Heating the Tunnel Heating is uneconomic for a whole tunnel under normal circumstances, not just because of the costs of laying cables or putting in burners but the price of the energy and rate of heat loss. Stopping up draughts around the door (and closing down any ventilation or second door) helps. Bring in anything that traps heat during the day and releases it by cooling at night also

5 helps - for example dark-coloured water-butts: refill them inside and drain them out come the spring to move them back. Composting enthusiasts can run a hot heap in wooden or bale frame. Most of us make do with half-rotted straw and manure under a tarpaulin cover. Heating a small cloche inside the tunnel is more practical; if you can attach it to a hen coop four birds are about the same as a 60w light bulb, but get them out when it turns warm. Bubble Film This may come with fixings and can be used to line the interior for additional winter insulation. It is sold in 3m x 0.75m rolls (9ft 8in x 2ft 4in) for greenhouses etc. (Avoid the bubble sheets used for ground cover as they may be biodegradable and so don't last long.) Bubble film can also be used to make small bubble-wrap cloches in the tunnel. Fleece Use horticultural fleece to protect plants (especially seedlings) from the cold, and also to shade them from excessive sun. The fleece allows air and water through but unfortunately has little value for heating the soil. Use fleece to protect vegetables from pests if you wish, and remove it on hot days to dry out. Used outside fleece when wet may freeze onto the leaves and this does them no good. Clamps You can buy extra ones - use them to give more fixing points for the cover (but fit them before the polythene is put on). Side Rails, Doors and Ventilation: extra problems for long tunnels Steady air-flow is essential during the summer; one way is to have a door at each end, certainly if the tunnel is more than 3 or 4 m. (10 or 12 feet) long. It is not a good idea to throw shade netting over a polytunnel! Such netting is designed only for building a shade or airflow house. If you have a long tunnel then you have ventilation problems, so it pays to think about what you could do apart from installing expensive fan systems. The simplest is to use netting. To do that you fix the polythene cover to side-rails, instead of down to the base-rails (or instead of digging it into the soil); so only the roof and the top of the wall are under polythene on that part. You then cover the gap with netting, which will give more of a breeze, and this is essential for tunnels longer then 10m (30 feet plus). Netting used like that is also useful if you cannot get along very often to open and close the doors. But using netting means your polytunnel is open to gales and winter cold. So it may be better advice to use a removable polythene skirt instead. You might make it by edging some polythene with a batten which you then screw to the side rail, and use a second batten that you can then peg to the ground at night. This would be cheaper than buying wind-up skirts. Additional clamps will give extra fixing points for the cover (fit them before the polythene is put on).

6 Side Rails, Doors and Ventilation: a problem for long tunnels Air-flow is essential in summer; best to have a door at each end if the tunnel is more than 3 or 4 m. (10 or 12 feet) long. Do not throw shade netting over a polytunnel! It is intended for building a shade or airflow house. If you have a longer tunnel - not usual on allotments- then consider the following: - The polythene cover can be fixed to side-rails, for part of the tunnel length, instead of to base-rails (or instead of being dug into the soil); this leaves only the roof and the top on that side covered for part of its length. Use some netting to replace the cover there and allow air movement. This step is essential for tunnels longer then 10m (30 feet plus); or if frequent visits too open and close the doors are not possible. Since using netting means your polytunnel is open to gales and winter cold, it may be better to use a removable polythene skirt instead, for these very long tunnels. Edge some polythene with a batten which you screw to the side rail, and to a second batten which you peg to the ground at night (or you can buy wind-up skirts from some manufacturers). Storm braces If your tunnel has a base rail for fixing the bottom of the cover to, storm braces will bind the upper and lower part of the hoop firmly together, which stops the join from moving in high winds. Flexible Guttering This is just a plastic trough with adhesive backing, which is pliable enough to fit around the tunnel's shape at the hoops. You can fix it to the tunnel wall and stand a barrel under the open end for a supply of rain water. Staging A bench or small table at a convenient height for pots and trays is an absolute must! You could use a homemade one. Why not smear the legs with Vaseline (or wrap them with sticky tape) to discourage slugs and pests? Some gardeners hang wire trays by the corners from the hoops or crop bars and use those as a bench. If you are thinking of buying benching, then first check the height and size, low shelving will make your back ache. Otherwise work on the staging in your greenhouse or shed and bring the trays in to your tunnel afterwards.

7 Weed Control Membrane The toughest (though not the cheapest) seems to be Plantex Pro. You can trim it to size with a Stanley knife, and peg the edges down with wire hoops (though DuPont do supply pegs to go with it if you want). Overlap any joins by 30 cms. This ground-cover will allow water and nutriment through, and stop weeds from coming up. You could also plant through it by cutting an X shaped hole. To make it more durable cover it on paths with a mulch of chopped bark, or gravel, though Plantex Gold is said not to require mulching even for paths. Soil Quality You want to get off to a good start, so trench plenty of compost and manure into your beds to begin with. As plants grow they will use this up, which sadly means the soil level will sink down. So you need to replenish it with three or four inches of well- rotted manure every three or four years; and also bring up the level with the same amount of good seed-free compost in the years between. You will probably find that it is best to do this when your summer plants are finished. Where any winter planting is planned lightly fork the compost in, otherwise leave it to the earthworms, which will do it for you if the soil is not allowed to dry out. But you will still need fertilisers. Add mineral supplements until the soil is in perfect condition - so keep a look out for any signs of soil deficiency, like yellow lower leaves and green veins that show a lack of magnesium You should take the same care with raised beds (which are best edged with timber) as well as with your plants in pots and containers - and pots also offer good hiding places for pests and diseases. If you are growing your plants in containers many will thrive all their lives - but they do need more TLC - so pay extra attention to watering, fertilising, and pest or disease control. You can fight off mildew with 2 teaspoonfuls of sodium bicarbonate from the kitchen wellstirred in a quart of water, add a few drops of washing-up liquid, and spray it on. Make friends with toads and frogs! Polytunnels as part of your allotment You can just as well grow anything in your tunnel that you do on your plot, and you will then be able to grow earlier and later. A tunnel protects against three or four degrees of frost, perhaps enough by itself in the south and west, though you will need more protection elsewhere. For winter growing you should select the hardier winter varieties and those that are less affected by day length, like some long-season strawberries. If you are in the colder north or east put fleece over them when frosts appear, and perhaps you can supply heat in small cloches. You must get winter crops planted by late August, even if that means taking out some summer crops to make room. Perennials like globe artichokes would be left to keep growing and producing.

8 Many gardeners plant cauliflowers, small carrots, chard, beetroots, lettuces, celery, parsley, radishes, spinach, broad beans (Aquadulce Claudia) and winter peas, so that the tunnel carries on growing things in the winter. Also you can start your annual bedding flowers early. Other gardeners try extending their plot to different plants all together, such as growing melons, chillies, aubergines, and those beef tomatoes which don't do so well in the open; and some go on to try grapes, olives, pomegranates, the tenderer fig varieties, even guavas. A polytunnel influences the microclimate around it: providing shelter and a warmer patch on one side ready for putting out annuals and bringing plants on early. With the water run-off land cress and watercress (on manure in a shallow trench) might do well? Once it is working, even a small tunnel extends what you were doing and takes you in new directions. And that's its value. All content SWCAA

ALLOTMENT CORNER. March. In the vegetable garden

ALLOTMENT CORNER. March. In the vegetable garden ALLOTMENT CORNER THIS time of year is very exciting, as spring is near and we want to get growing, but you do not get something for nothing, not even in Piddinghoe, the more hard work you put in now getting