Coppice Road Allotments Association

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An introduction to Vegetable Growing

In many ways growing vegetables is more demanding than growing flowers. Generally, bedding plants are planted out at the end of May and more often than not left alone get on with it. Or, the herbaceous perennials are left to their own devices, just tying them up after they’ve flopped over and chopping them back when they’ve finished flowering.

Not so with vegetables, at least not if success is to be achieved. Vegetables need more cosseting to obtain a good, healthy, tasty and productive yield. Because vegetables are healthy and tasty, they attract all sorts of competition from weeds and pests and disease. To raise fast-growing succulent foodstuffs they need to be fed, given room to grow, kept free from competing weeds, and shielded from a myriad of pests and diseases. This takes time and labour, and only by putting in this necessary effort can the grower hope to be successful. It is not by pure chance that commercial growers produce the clean, healthy, attractive-looking fruit and vegetables seen on the greengrocers’ shelves, they really work at it. There is no reason why amateur growers should settle for produce that is second-, or third-rate, providing they apply the same effort. Whether an exponent of ‘organic gardening,' or follower of the traditional sustainable approach, there is no reason why the vegetable crop cannot be as good as the commercial grower, but even fresher and tastier.

Unlike many commercial growers, the amateur usually wants to grow a wider selection of crops, often in a limited space, rather than the fields and fields of monoculture. Therein lies the first problem, for not all soils are suited to every crop, and not all locations provide the ideal climate for every crop. So the first thing is to determine the nature of the climate and the soil, and then try and work within, or around, their constraints.

First, check the climate and the locality. The south of England enjoys more daylight hours and warmer average temperatures than the north of Scotland. The coastal regions enjoy more reflected light from the sea than inland regions. The lower altitudes have a higher mean temperature than the exposed higher altitudes. Exposed areas are windier and cooler than sheltered areas. Western areas tend to get more rainfall than more easterly ones. Southerly facing sites are warmer and more productive than northerly facing ones. All these regional, and local, climatic and topographical factors can play an important part in the successful growing of vegetables and they influence the choice of crop and or varieties to grow. Apart from minor changes, such as the provision of windbreaks, or the use of tunnels or cloches, there is little else the grower can do to drastically alter climatic conditions, short of moving to another location. Choose crops that are able to tolerate local conditions.

Next, check the soil. Most vegetables prefer to grow in a deeply dug rich moisture retentive but freely draining soil with a pH of between 6.0 and 7.0 containing all the plant nutrients in sufficient quantity. Clay soils hold onto moisture and nutrients but are difficult to work, are colder and slower to warm up, whereas sandy soils are easier to work, warm up more quickly in the spring, but lose their nutrients and moisture much more quickly. What vegetables prefer, and what they get, is often miles apart, but striving to provide the ideal, by cultivation, manuring and/or liming, is often within the growers’ capability, and will be rewarded with increasing success.

Thirdly, choose crops and varieties, that are able to thrive despite the constraints imposed by the limitations of soil or climate. Choose hardier varieties that are able to withstand lower average temperatures, or quicker maturing varieties for areas with a shorter growing season. Follow the guidance given in catalogues, books and magazines, but use judgement to decide when to sow seeds, waiting until the soil has warmed up, rather than a fixed calendar date.

Finally, regular husbandry in keeping down weeds and pests, providing sufficient food and water and supporting or sheltering the growing crop is essential to enabling it to mature through to successful harvest.

The guides on this website for growing specific vegetable crops also incorporate some references to the methods that the professional grower use. Although he is as much at the mercy of the vagaries of the weather as the amateur grower, his livelihood is dependent upon how successful he is. He will seek out those varieties that are successful in the locality, adjust his growing schedules according to the state of the weather and the land as well as the market demand. He will be rigorous in applying the required fertiliser regime, and attending to pest and disease promptly, in order to produce a high quality crop at the lowest possible cost. He cannot afford to plant his crop and leave it to chance. The same regular attention by the amateur grower is just as necessary if he too is to be as consistently successful.

There are some pitfalls that the amateur grower can encounter, usually of their own making. The main one is to make things over-complicated, rather than keeping it simple as the professional grower does.

When faced with a plot of land the enthusiastic amateur is often tempted to reach for the hammer and nails and planks of wood and divide the plot up into small beds with interconnecting pathways. This is wasteful of growing space and imposes limitations on flexibility of layout. There is a case for creating raised beds if the ground is heavy and drainage poor, or if the grower has difficulty in bending. In many instances drainage is adequate and growing ‘on the flat’ involves less ‘engineering’, is just as effective, cheaper and more flexible. In any event, raised beds can be created just by mounding up the soil where needed for that crop or that season, rather than frequenting the timber merchant. Pathways need only be temporary to gain access to the growing crop for that season; they can be created elsewhere for the next crop or season. A layer of woodchippings or a strip of ground-cover plastic can be used to reduce muddiness.This way the ground can be cleared of obstacles at the end of season and prepared for the next season more easily.

Having a fixed-sized bed often means that it is either too small to contain all the desired quantity of crop, or too large. In the former case, the crop has to spread over more than one bed, and in case of the latter there is the temptation to plant more than one crop, which may need differing growing conditions or treatments.

This is not to say that beds shouldn’t be created. The professional grower will often create beds as wide as the wheels of his tractor, so that the actual growing area isn’t trampled and compacted and the soil structure damaged. The amateur grower can create temporary beds with pathways at the sides, so that he can reach his crop from either side, without trampling and compacting the growing area, or he can use a plank, to spread the weight and reduce compaction.

Planting or sowing in rows, rather than random broadcast fashion, is not just because of an overwhelming desire for regimentation and neatness; it actually makes tending to the crop, weeding etc., easier.

Failing to give the crop the correct growing space is often a shortcoming of the amateur grower, who often tends to overpopulate the growing area. This has a profound effect upon the yield and quality of the final crop. The final planting distances given on the seed packet or gardening book haven’t been plucked out of the air. They are the result of long experience and detailed study.The idea is to give just sufficient growing space for each individual plant of each crop variety to reach maturity. Allowing too much space is wasteful, not only of space, but of sunlight energy. If the leaves of the crop don’t intercept the sunlight, then it falls onto the bare ground, which warms up and encourages weeds to grow, which then compete with the crop for nutrients and water. If the crop plant utilises the light to its maximum extent by being planted at an optimum distance apart it cuts down the amount of light reaching the ground and suppresses and minimises weed growth.

However, if planted too closely together, the crop plants themselves compete with each other for light, nutrients and water, and fail to thrive. They give a poor yield per plant, can become stretched or ‘leggy’, or can run to seed (bolt).

There is also poor air flow which creates ideal moist still conditions for pests and fungal disease which will quickly spread through the plants. Planting too closely together can also have other undesirable effects on some crops, cabbages and lettuces can fail to heart-up fully, and peas produce a reduced number of pods all in one flush rather than a greater number of pods spread over a number of weeks. Of course this can be used to effect if baby carrots, mini cauliflowers or ‘cut and come again’ salad leaves are required , but extra vigilance against pests and disease may be required.

A number of vegetable crops need to be sown directly in the growing position as they do not transplant readily. These include radishes, carrots, parsnips and turnips as well as others. Seed may be sown either by broadcasting, drilling, or ‘station sowing’. This is, respectively, scattering the seed randomly over the growing area, sowing in rows (or drills) or sowing a couple of seeds in the final growing position. In each case the soil must have been prepared to a fine sowing tilth and be warm and moist enough to encourage the seed to germinate readily.

The seed bed may be prepared some time before sowing and weed seeds allowed to germinate. These weed seedlings can then be removed whilst disturbing the soil as little as possible, either by hand, contact herbicide or a flame gun. Thus when the crop seeds are sown subsequently, they will not be swamped by germinating weed seedlings. This is known as the ‘stale bed’ technique.

Packets of seed usually contain far more seeds than required, and they are often marked on the packet how many seeds are contained, or how long the row that the packet will stretch to. The number of seeds required for a given row will depend on the final spacing, but in all cases some excess seed is sown. All vegetable seeds are laboratory tested for their ability to germinate successfully and must achieve a minimum standard by law.

The commercial grower will be supplied by the seed house with the germination percentage for a given batch of seed, but the amateur will need to assume that only around 80% of the seed will germinate. This is under ideal laboratory conditions, but the open ground won’t be ideal conditions, so the percentage of seed that does germinate successfully will probably be lower than this, depending on the condition of the seed bed and the prevailing weather conditions. Based on his experience and judgement a commercial grower will apply a ‘field factor’, a figure between 0 and 1 and increase his sowing rate according to the conditions of his seed bed and weather. An experienced gardener can also do this. For example, a 15 ft row at 2” final spacing will require 90 seeds assuming every seed grows into a finished plant. Allowing that 20% won’t germinate successfully to grow into a finished plant under ideal laboratory conditions, a further 18 seeds would be needed. If the sowing conditions are less than ideal a further quantity determined by the ‘field factor’ would be needed.  If the grower decides that the field factor is 0.7, that means only about 7 out of 10 seeds will be successful and so would need to increase his sowing rate by a further 30%, giving (90+18) + 30% (33) = 141 seeds per 15 This may seem an awfully precise and fiddly thing to be doing, but bear in mind that the commercial grower will be sowing thousands of yards and using lots of seed. Seed is very expensive, particularly the newer F1 hybrid varieties, so the grower will not wish to use more seed than he needs.. He will rarely sow if he judges the field factor to be less than about 0.7 or 0.8. If his judgement is correct he will have a good ‘stand’ of crop, correctly spaced, with a minimum of ‘thinning’ out and few large gaps in his rows. This means that he has to spend less labour on thinning out, or ‘gapping up’. If the amateur carries out a similar exercise, then the seed packet will go further, the seedlings won’t need thinning out so much and there is an improved likelihood of the seedlings getting away more robustly with less chance of root disturbance or attack by pests and diseases.

Some weed seeds will inevitably germinate along with the crop plants even with the stale bed technique. It is important to let the crop seedlings become fully established and growing strongly before attempting to weed between them.  Weeding too soon will disturb the fragile roots of the crop seedling while it is at its most vulnerable and prevent them from getting away without check. It is better to wait a few weeks before attempting to weed them, then once they are established weeding should be carried out regularly, usually by a light hoeing. Studies have shown that the weeds between rows pose more of a competitive threat that those weeds within rows which are usually crowded out or shaded out by the crop plants. As the crop grows it will increasingly shade out the bare earth and suppress the germination of  further weed seeds, many of which require light to germinate. As the crop approaches maturity the need for further weeding is lessened as the competitiveness of the germinating weed seedlings will, by this stage, have little effect on crop yield. Only if the weeds are likely to set seed will they need to be removed to avoid increasing the weed seed bank for the subsequent seasons.

In addition to not sowing too thickly, it is also important not to sow  too deeply as many seeds require some light to initiate germination. Generally, the smaller the seed the shallower it should be sown as otherwise it will not have the food reserves to support the seedling while it grows up to the surface and then begins to photosynthesise. In heavier wetter and colder soils it may be necessary to take out a shallow trench and back-fill with finer soil or compost before sowing.. In silty soils care should be taken to avoid the formation of a ‘crust’ on the soil surface (capping) to form a barrier to the germinating seedling and preventing it from reaching the surface light. On sandy soils it will be necessary to ensure that it doesn’t dry out before the seedling can get its roots down to seek out water.

If a soil is very wet, it is also colder than a soil that is only moist, water needs more heat input to warm up than air, and very cold soil will inhibit germination and may lead to the seed actually rotting before germination. If unsure whether the soil is warm enough to encourage rapid germination it may be a good idea to invest in a soil thermometer. The use of cloches, or plastic tunnels, to warm up the soil both before and after sowing is often advantageous, providing care is taken to provide sufficient water and not let the seedlings become overheated in strong sunshine.

Until a plant is established it cannot take full advantage of any nutrients that are there. In fact too much fertiliser is like feeding raw steak to a suckling babe; it won’t do it much good.  Although the ground may have had a base dressing of fertiliser before sowing, it is usual to follow this up with top dressing further fertiliser as the plant grows and is able to use it. Remember that the fertiliser needs to be dissolved in the soil water before the plant can assimilate it, so a moist soil is always required.

At certain times in some crops’ development they need more water than at other times. These are called ‘moisture sensitive periods’. Unless adequate supplies of water are supplied during these periods the crop will fail to grow to its full potential. For example, potatoes become moisture sensitive when the forming potatoes are about the size of a marble. Failure to keep the potato plant supplied with sufficient water from then on will give a significantly reduced yield in the final crop. Similarly, cauliflowers, although needing adequate water throughout their growing life, they are particularly sensitive and require plenty of water from about 20 days before they are ready to harvest up until harvesting. Failure to supply sufficient water can lead to ‘buttoning’, the formation of tiny malformed curds. Some plants, like lettuce, are moisture sensitive all the time throughout its growing life, so they must never be allowed to dry out at any stage. Failure to ensure this can lead to bolting. Many popular gardening books sometimes neglect to give sufficient emphasis to the significance of these details, leaving the novice grower puzzled as to what went wrong.

This is not to decry the worth of these gardening books, for there is only so much information that can be ‘crammed’ into a given space, but in the following guides these small, but important, details will be highlighted for emphasis.

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