ALLOTMENT MANUAL 2020
Where to start
Starting an allotment can be very daunting. You find yourself faced with a no-man's land of waist-high grass, thistles, brambles or nettles, with no indication of where it ends. You turn up on the first day and your heart sinks. But don't panic. It is not going to be easy to deal with, but it is do-able with some patience and persistence. First ask yourself a very important question: do you want to grow vegetables and fruit which are free from pesticides and herbicides, i.e. organic, or are you happy to use chemicals? How you deal with the plot depends very much on your answer!
Weeds and the Overgrown Plot
Firstly, identify what the main weed is. Everyone knows what grass looks like, but do you have any of these?
Thistles, Brambles, Dandelions, Nettles, Bind Weed, Ground Elder
As with many things, how you deal with them depends on what you have.
To rotavate or not to rotavate?
Rotavators are often seen by new allotment holders as a marvellous way of clearing the plot. They do have their advantages but not as many as you might think. To use one, you have to pull and push it backwards and forwards, which is very painful on the shoulders, even if it saves backache from normal digging. It will not dig as deep as traditional spade digging (especially if you double-dig: see box on digging) and more annoyingly, will chop up the roots of any plant it meets. For normal grass this is probably fine, but for couch grass, anything that can regenerate from tiny root sections like thistles, bindweed, dandelions, docks and ground elder, it simply makes the problem many times worse. So unless you are sure you don't have any of the above or are willing to go through the ground after rotavation to hand-remove all roots, beware!
Do you spray?
Glyphosate - This is an herbicide often called Round-up or Tumbleweed. It acts by penetrating the leaves of actively growing plants, and then working its way down to the roots (systemic action). This kills the whole plant and not just the top growth like most herbicides. Because it takes time, the effects are often not seen for 2-3 weeks after spraying. But beware: it is very powerful and you must NOT use it if there is even a slight breeze. If you do, you may well accidentally destroy neighbouring crops, and your fellow plot holders will not be pleased! It drifts a lot further than you think! It does become inactivated once it hits the soil, so ground can be planted up as soon as the weeds die back.
You might be able to borrow a decent strimmer from another plotholder, though if you don't know anyone, the local hire shop will probably be delighted to rent you one for a day. If you do this, make sure they give you (or you buy) a face mask or goggles, and earplugs/defenders. And wear stout shoes, gloves and full-length clothing. Flying débris can include slugs, snails, animal excrement, nails, stones or pieces of glass, so you want to make sure you are well protected. Fire up the strimmer and then gradually work your way across the patch, cutting it down to a height of a few inches. Do the strimming gradually - too much at once leaves you with vibrating fingers which can take hours to calm down.
The best way to deal with grass organically is to start by strimming it. Pile the grass up at one side: this pile will become your compost heap, so site it somewhere convenient. Assuming you manage to strim the whole plot in one go, you now have to dissuade the grass from growing again before you can dig it all over. The best method is to use a mulch of either old, hessian-backed wool carpet (don't use synthetics because of the chemicals), weed-suppressing thick black plastic or special weed-suppressing woven fabric, or cardboard. The first can easily be obtained by going to the local carpet shop and asking them if they have any old carpet in their skip. Carpets that have been taken out by their fitters is disposed of, which they have to pay for, and so they are usually delighted to have someone take it. The others can be obtained from most garden centres or DIY stores with garden sections. This can be an expensive solution. Cardboard is another cheap and cheerful one, and green too. Most supermarkets have huge amounts of corrugated cardboard from delivery boxes, and often will give it away. Once you've acquired a few dozen boxes (as big as possible), flatten them, remove all the big staples so they don't end up in the soil, and then overlap them across the plot. You can even pile the cut grass on top to exclude even more light. The other you just unroll across the plot.
These should keep the grass from getting out of control. Don't underestimate how fast it can regrow if you don't mulch!
Non-organic grass clearance simply consists of spraying the plot with an appropriate herbicide. There are several things to bear in mind first. Spraying very tall grass is very difficult, so you will still probably have to strim first (in which case, see above). Instead of mulching, spray. But then you will still have to mulch anyway, as new weed seed blows in all the time, so you might as well save the money if all you have is grass.
Creeping thistle is tricky to get rid of organically: the HDRA describes it as a pernicious perennial, meaning it's a pain to get rid of and doesn't die each winter. They recommend digging it out as deeply as possible, mulching the ground to weaken any new growth. Creeping thistles have very deep complex root systems. It has to draw on reserves of food in order to get back to the surface, and if it can't get light, it cannot replenish them. There is a finite number of times it can therefore regrow if it can't get light. You dig out, cover, wait a week or two, uncover, dig out the new sprouts as far down as you can get the fork, repeat… eventually it dies. But it's very persistent and so you can expect to be digging it out for months.
Non-organic approach: glyphosate. See box! With a very heavy thistle population, it is probably better to dig up as many as possible and then glyphosate the new growth (which will permit the herbicide to penetrate easier).
These are also a pest to remove, but it's not impossible to do it organically. The roots are relatively shallow, so can be dug out with a fork. Strimming the tops off first is however a great help. In this circumstance, you can't use a line strimmer. You need a specialist brushcutter which has a blade rather than plastic line. It will make short work of a patch of brambles. You also need very thick gloves, preferably leather, to pick up the pieces! Then you can go in with a fork (spades tend to sever roots, which can then regrow) and start levering out the roots. Some do go very deep: in this case if you get regrowth you go after them again.
Non-organic methods: again strimming might be a good initial option, but you need to spray with a brushwood killer such as SBK, which is powerful enough to kill woody stemmed plants such as brambles. The disadvantage is that it takes some months to disperse before you can plant crops. And you still end up having to dig in order to get the roots out.
These come under the same heading as brambles, i.e. strim and start digging. They generally have deep roots, but these are more fibrous than other perennial weeds. They die back each winter and then regrow in spring, so can be easier to deal with during dormancy. Again, you need to make sure you dig out all the root pieces, both the fibrous ones and the longer creeping sections which is how they spread. Inorganically, spray with either glyphosate or brushwood killer and wait. Glyphosate is probably better because it doesn't linger in the soil but may take several goes to kill all the plant.
This is another nasty weed. It doesn't grow very high but does smother everything in sight. The Romans introduced it as they believed it cured gout (along with introducing snails and rabbits, so they aren't usually popular with gardeners!). It forms a dense mat of roots a few inches below the surface which takes a lot of digging out as it's literally woven together. In this case, putting a light-excluding mulch on first is probably the best approach, which after a few months will have weakened the plants enough to make them easier to dig out. You'll need patience, a good strong fork and probably a heavy-duty knife with replaceable blades to cut sections free.
Inorganically, it's the usual suspects again. Spray and wait. But it doesn't really help - you still have to dig it out! If you can cope with roots, then you could try and rotavate once you are sure it's dead, but one of the more annoying things about ground elder is its ability to regrow even after you're sure you've killed it or dug it all out. If you have it, expect to be battling for several seasons whichever method you choose to use.
This is pretty much endemic in most allotments, because it's another weed with really deep bright white roots which snap easily when you try and dig them out, and it can regenerate from a tiny fragment. Field bindweed (the tiny pink one) is the hardest to get out, and with deep roots the only method you've really got is to remove and burn every white root you find while digging. The hedge bindweed (huge white flowers) will climb up everything and is nigh-impossible when it's tangled up in the roots of a fruit bush or similar. Keep digging, and eventually you'll weaken it enough, so it doesn't regrow. It loves manure heaps too.
Glyphosate works well on bindweed: it's a good method to let it twine up a bamboo cane and then, wearing rubber gloves, to spray glyphosate onto the gloves then wipe your hands up the leaves. That way you treat the plant and not your crops. If you have an organic allotment you might like to cheat a little and apply to persistent or tricky to reach clumps in this way. Inorganically you'll just spray the lot!
Speedwell, fat hen, groundsel, chickweed and scarlet pimpernel are some of the more prevalent annual weeds. They are easy to remove when small but do run to seed extremely fast and so it's well advised to keep them down by hoeing or hand-weeding once your plot is up and running. Speedwell is particularly hard to eradicate since its seeds can mature after the plant's been pulled up: unless you have a very warm compost heap to kill seeds, you may well reintroduce it a few months later…
The usual method of clearing is to do it in sections, covering them over as soon as they've been dug until the time is right to plant up a crop. There are two main digging types: single digging and double digging. The latter is also sometimes referred to by a variety of rude names such as bastard trenching, simply because it is…
Single refers to the depth of the dig, measured in spits, which is the depth of a standard spade or fork. In this, you dig out a trench, throwing the soil forward onto the soil in front and then hitting it with the spade or fork to break it up a bit. This also reveals the roots or any perennial weeds and allows you to remove them as you go. Have a bucket or wheelbarrow next to you while digging to put the weeds in.
Here you dig the single spit trench as before, putting the soil either on the ground or in a wheelbarrow, then dig another single trench in front of it, putting the soil on top of the previous or in the barrow. Then dig down another spit, incorporating manure or compost into the soil. This deeper soil is known as subsoil and should not be brought to the surface. When you have finished with the trench, dig your next single trench, throwing the topsoil on top of the manured subsoil, then do the next deep trench etc etc. When you have worked your way across the whole plot, you barrow the topsoil from the original trench across to the final one and use it to fill in the hole. This is very hard work, but sets up the soil fertility extremely well for several years. It also means you get deep enough down to get out all the really pernicious weed roots. Rotavators cannot get deep enough to get into the subsoil, which is as well since you don't want it at the top.
This is possibly the easiest way of getting shot of weeds when you're first cultivating an allotment. If you have been lucky enough to inherit a plot which has bare soil visible and scatterings of weeds, then working your way across with a hand trowel will allow you to get rid of a lot of the smaller weeds into the compost heap. Then when you dig over the plot, you can just dig rather than having to keep bending over to pick out the weeds. It also allows you to be more confident about using or not using rotavators, since by forking it over to 3-4" you'll have a good idea if there are perennial weeds lurking.
Once you have some bare soil ready for planting, you need to look at soil types and pH before you go ahead. You'll have a good idea of soil type after the first attempt at digging! Heavy clay needs no introduction, but the general definition is to take some damp soil and try and roll it into a cylinder. If it sticks together nicely and allows you to do this and bend it into a U-shape, then you've got clay soil. Fantastic for fertility, grows everything well, but is a pain in the back to dig. It gets very hard when dry and turns to gloopy glue when wet and doesn't tend to drain well. Neutral to acidic pH. Sandy soil is literally that - very coarse grains which are generally dry don't have much organic matter in between then and don't stick together. Tends to be neutral pH. Chalky soils can also exhibit the same tendency as sand to be dry and very free draining, with the added alkalinity and chunks of flint (making rotavators rather lethal to use!) Loam is what everyone aspires to - lots of organic matter, not hard to dig, no stones and neutral pH - needless to say not many people have this!
Don't assume your soil's pH. Measure it. Small testing kits are only about a pound in cost and are simple to use. Take soil samples from around your plot from a few inches’ depth, mix them together then fill the testing tube to the indicated level. Add distilled water or rainwater, as tap water may be too alkaline for accuracy depending on where your water supply comes from, shake well and leave. Wait a few minutes and then compare the colour of the sample to the chart provided. You'll then have an idea of what the average pH is on your plot. You will manipulate this with all the things you add to the soil, so re-testing is needed every 2-3 years.
These grow great raspberries and other soft fruit, especially blueberries. Brassicas (cabbage family) will hate it so you have to add lime where you grow them. There are charts of which vegetables like lime and which don't, so you add as required.
Great for most things: may not be acidic enough for blueberries but everything else will do well. Again you'll have to lime for brassicas.
Alkaline (chalk) Soils
You won't have a problem with brassicas but your potatoes will be scabby, and soft fruit will have to be fed with acidic fertilisers to be at their best.
One thing you probably won't find out quickly is what lurking nasties are in your plot. Lots of pests and diseases can persist in the soil for years after their introduction, and will take off at the first sign of their favoured crop. Bear in mind just walking over an infected plot can transfer the pathogens to your own, so be careful and considerate! But if yours hasn't been dug for what seems like decades, this can work to your advantage as it's less likely to be infected.
This is the main problem for brassicas, and causes incredibly twisted and deformed thick roots on the plants, so they can't feed properly. This stunts them. Once in the soil, it's there for good. It prefers acidic and neutral conditions - heavy liming will deter it from having its worst effect. Most surrounding plot holders will tell you if the allotments have club root. You deal with it by growing your brassicas in compost to as big as you can before planting out, so they develop a decent root system.
Onion White Rot
Another horrible fungal disease. It persists at least 8 years in infected soil from the last date an allium (onion crop) was grown there. So you really do need to quarantine an area if you've white rot. Symptoms are fluffy white mould on the roots and discoloured, slimy outer layers of the onion concerned. Garlic is the usual way in which it gets onto a plot: never use supermarket garlic bulbs as they are not certified to be clear of rot! (Also commercial crops are usually grown in hotter countries so are not bred to be good croppers in the UK anyway.) Leeks tend to be fairly resistant to the rot, but over wintering onions and summer onions tend to be worse.
Best bet if you've got it: create a raised bed (at least 8" deep) with wood, line it with black polythene and punch drainage holes in it, add at least an inch layer of grit for drainage and fill with topsoil. Grow your alliums in that, and do NOT put your garden tools (or unwashed hands/gloves or feet!) into it from the main plot or you'll be back to square one…
Persistent Potato Diseases
Potatoes seem to win hands-down over other vegetables for problems. These are just the problems which persist in the soil from year to year - and do not include diseases which appear on a random annual basis, such as blight.
These tend to build up. The 1st year they are not usually a problem, not enough to affect yield. They become more of a problem if you save your own seed potatoes. The second year’s disease is usually much worse. Examples: potato mosaic virus (blotchy leaves), potato leaf roll virus (leaves roll inwards along the main vein). ALWAYS use certified healthy seed potatoes, and if you do intend to save any, protect from aphids by growing in fleece.
These are clickbeetle larvae (copper coloured, three pairs of legs at the head end) and they will tunnel in and through tubers with ease. They tend to be worse where you’ve just dug over grassland to grow crops for the first time, and the best solution is to avoid growing potatoes in such areas for 3-4 years after first cultivation since the lifecycle is eggs laid in grassland and weedy soil, early midsummer. Larval stage is long, up to 5 years.
Potato Cyst Eelworm
These are microscopic nematodes which infest the roots of potatoes and tomatoes. There are two types - golden and white eelworm.
They feed in the roots then the mated female blows up to become the egg case, a hard cyst with several hundred eggs inside. You see little globes on the roots with a hand lens, July-August. Colour varies from white to black as they mature. Most hatch in the first year but they can remain dormant in the soil for 10-20 years, so normal rotation doesn't really help once you've got it! The cysts are stimulated to hatch by the chemicals secreted by potato or tomato roots.
Now you've got a clear plot (or part of a plot), an idea of your soil type and pH and you hope your soil has no diseases. Now where do you go? You need to get out a pen and paper and plan what you are going to grow and where. Chances are that you have only room for a few things if you're progressively clearing a plot, in which case choose your favourite vegetable and grow it! Record what you planted and when, and next year, rotate the place you grow that type of crop to somewhere else. Rotation means growing different vegetables in a given patch of soil each year, for a number of reasons.
1) Different crops take different nutrients out of the soil, so rotating makes sure a given area isn't depleted of too much of any nutrient too fast for it to be replenished.
2) Different crops also use different cultivation techniques, e.g. potatoes need regular earthing up, which means the soil is continually disturbed and weeds are not allowed to take hold. Also the potatoes break up the ground with their roots. This means that soil is ‘cleaned' by the weed removal. Other crops don't like disturbance once they're in, so weeding is tricky. Rotating means that weeds get clobbered every few years by the potato rotation even if you're not as careful about hand-weeding the carrots!
3) Different crops need different levels of plant food and humus. Some crops prefer more fertilisers than others and some hate it. Rotating means you can manure just the sections that are due to grow heavy feeders and 1) doesn't become a problem.
4) Rotation helps to control pests and diseases. This is probably the most important reason. The longer the rotation the less chance there is of a particular pest or disease building up to significant levels. A lot of insect pests over winter underneath the place where the plants they fed on were: if another crop is there the next year, a large number will die before finding food.
Typical rotations are three-year, four-year or five years. The longer the better, but the smaller your plot, the shorter your rotation invariably is.
Three-year (simplest method)
1) Brassicas - add general fertiliser and lime
2) potatoes, alliums - add manure in the previous autumn
3) root crops and legumes (beans)
Four-year (HDRA recommended method)
1)potatoes and tomatoes - add organic matter, high nitrogen (manure)
2)roots - add nothing
3)brassicas - add general fertiliser and lime
4)legumes - add organic matter, low in nitrogen (compost)
In this rotation, the alliums go with one of the other groups, but chosen so they are grown in a different place and with a different group each year.
Five-year (RHS recommended method)
1)potatoes and tomatoes - add organic matter, high nitrogen (manure)
2)roots - add nothing
3)brassicas - add general fertiliser and lime
4)legumes - add organic matter, low in nitrogen (compost)
5)alliums - add organic matter, low in nitrogen (compost)
Either way, potatoes are always followed by roots followed by brassicas. Sweet corn and marrows/squash seem to go wherever there's space, though rotating the sweet corn is a good idea as it's subject to a fungus called smut which can persist for 5 years in the soil.
Covering the soil when not planted with a crop
This stops weeds growing (good if you've just cleared it and don't want to start again in a month) and also prevents nutrients washing away. Covering the beds can be with exactly the same things you covered plots with while getting round to the digging, with the addition of green manures and mulches if and only if the rotation permits it. If your next crop is potatoes, corn or marrows then growing green manure is a good idea, as it will incorporate high nitrogen matter into the soil. Field beans are especially good here as they fix nitrogen for the next crop. Some green manures are quite low in nitrogen so can be grown prior to brassicas, for instance. Whatever you decide, leaving a bed uncovered is a bad idea, as all it will do in increase the amount of weed clearing you have to do the following season or before the next crop is sown or planted out.
Beds vs Rows, and no-dig allotments
The traditional way of growing crops in an allotment is straight across the width of the plot, walking a path in between rows for access. Each autumn you dig over the entire allotment, digging up the compacted paths and start again the following year, adding manure as appropriate to your rotation as you go. Newer ways involve smaller beds, perhaps edged with wood, but no more than 4-5' in width (1.2-1.5m) so you can kneel at the side and reach over to the middle without having to tread on the soil. This has two effects: your soil doesn't get compacted, so it makes it easier to dig, and if you don't want to dig again (a typical sentiment after clearing a plot!) then you don't have to. Just cover. This retains soil structure, doesn't slice all the worms in half and you don't have as much work to do. If you need to add manure for the rotation, spread it on top then cover with plastic or carpet, and the worms will do all the hard work for you over winter. You don't have to edge the beds and raise them, but it does stop soil slipping onto the paths, which you can make permanent by covering with bark, woodchip, weed-suppressing fabric, carpet etc.
Once you've got your allotment you need to decide what you want to grow. Make a list of what fruit and vegetables you like to eat, and consider areas such as a fruit cage, herb garden, cut flower border, wildlife patch and green manures. Ask your allotment neighbours about local pests such as badgers and deer and think about incorporating suitable defences if none are already present.
Larger structures can be costly so consider how much use they will get before installing them. A greenhouse is a luxury whereas a windowsill is normally sufficient to raise transplants. Compost bins and rain water butts also need careful placement in the early planning stages.
Consider how much time you will be able to spend at the site. If time is limited then incorporate low-maintenance ideas such as planting through plastic mulches to reduce weeding time. Allotment crops will rely on regular watering if they are started off using over-exuberant irrigation. Some crops, such as runner beans, need regular harvesting to ensure continual yield, so if you're off on holiday offer a PYO beans scheme to your neighbours.
It can be rather daunting when faced with a blank allotment plot, but the whole area doesn't have to be dug over (especially if you employ a 'no dig' system'). Crops can be laid out in rows (which makes hoeing easier) or beds (which provides more even competition between plants). Individual raised beds can be managed intensively, leaving pathways between beds uncultivated.
Any areas not required immediately are best covered with carpet or similar, smothering the worst of the unwanted vegetation and weakening perennial weeds. Rotavators can be hired to make quick work of large areas, but perennial weeds will be chopped up and spread around if not dealt with first. Systemic herbicides are useful for this purpose, as some perennial weeds such as bindweed and horsetail are difficult to dig out.
In the first year of cultivation crop rotations usually aren't feasible unless the whole area to be cultivated is ready. In successive years however rotations can be incorporated, thus assisting in the prevention of soil-borne pests and diseases.
When planning what crops to grow try to estimate their harvest time to avoid gluts. Some crops, such as broad beans, are at their best for less than a week but can be preserved well by freezing. Others, such as garlic and onions are generally harvested all at once, leaving new, bare ground ready for cultivation. If you don't plan to visit your allotment regularly then grow quick-maturing crops such as radish and lettuce at home, using the allotment for low-maintenance crops such as winter squashes and maincrop potatoes. To avoid gluts of one particular crop stagger sowings and use different cultivars that take varying times to mature. The cropping season can also be extended by using cloches, fleece and transplants to get maximum cropping from your plot at the beginning and end of the year.
When bare patches of ground appear, especially in autumn, cover them with plastic or low-nutrient organic mulches, or sow over wintering green manures. If left bare weeds will quickly dominate, leading to lengthy periods of yet more ground clearance.