In small gardens you don’t usually have a great deal of choice as to where to put your garden – it goes wherever there is enough sunny space (or even not-so-sunny space) and you make the best of it. If you are lucky enough to have a large garden, you may have several choices of location, in which case there are a number of factors to consider. It is very important to choose the best possible location, as it will make your gardening activities easier and more successful. The wrong choice can simply invite problems. When I put a garden at the wild edge of my land, close to a dense growth of poison oak bushes that provided excellent cover, it was plagued by quail who ate any succulent green leaf they could reach – I couldn’t direct sow anything without using bird netting (and transplants often got shredded too).
In most situations the choice of garden site is generally a compromise, you choose the place with the most advantages and the fewest disadvantages. If you can’t find a single site that is large enough for your requirements, you might be able to create several smaller gardens in suitable spots.
When evaluating a potential garden site, you first have to think about the natural benefits and disadvantages it offers, especially the microclimate. These are the most important because they affect how your plants will grow. After you have thought about these, you then have to consider the human aspects; how easy and pleasant it will be to work in.
Natural criteria for the site
Plants grow on sunlight, so this is by far the most significant factor when deciding where to put the vegetable garden. You need to put it where it will get the maximum amount of sunlight throughout the day. This is even more important for the vegetable garden than it is for other types of gardening, because you can’t choose your plants to match the amount of sun. If your vegetable plants don’t get at least 6 (and preferably 8) hours of direct sunlight a day, they will grow more slowly and won’t be as productive. Sunlight is the one thing you can’t afford to compromise on.
Sunlight doesn’t just affect plant growth directly, it also has other significant effects: how quickly the soil warms up, how hot it gets and how frequently you need to water.
In urban gardens getting enough sunlight can be a problem because of the shade cast by neighboring buildings, fences and trees. In such places you may have little choice about where to put your intensive vegetable crops and may have to make do with a partly shady spot. You can still have a vegetable garden with some shade, it just won’t be as productive. In such places you should concentrate on the most shade tolerant crops, such as leaf crops, carrot, pea, onion, radish, cauliflower and cucumber. The operative word here is tolerant – they will all grow more slowly and probably won’t yield up to their full potential. However any harvest at all will be a gain.
There are ways to (slightly) increase the amount of sunlight your vegetable garden receives. You might be able to judiciously trim the lower branches of trees (this is sometimes called crown lifting), or even coppice them (which means cutting them to the ground and allowing them to sprout from suckers). Some gardeners have increased the amount of light on their vegetables by painting surrounding surfaces white, or by using white gravel for pathways.
Large trees are not very compatible with vegetable gardens. They are most problematic when located to the south and west of the garden, as they will block out essential sunlight. However the roots of any trees within 50 ft of the garden may compete for water and nutrients.
Having spent most of my adult life in heavily wooded areas, I have frequently had to deal with trees. I love trees and don’t like to cut them down, but I also love growing things. I find the best compromise is to coppice them when possible. This means cutting the tree down to leave a low stump and then allowing the tree to send up suckers and keep growing. In my present garden I have done this with chestnut, oak, madrone and redwoods. If I ever stop gardening, the trees will be left to grow back again.
Though it is good to start with rich soil, this is actually one of the least important considerations when choosing a garden site. You can completely transform the soil with good gardening practices, but you can’t move a building to get more sunlight. This is good, because the soil around houses is often fairly poor, due to construction activities when they were being built.
In wetter climates you might have to think about drainage, especially in early spring. A low lying garden can be problematic in heavy rain, in which case raised beds can help a lot (I have had my garden paths completely underwater, with the beds sticking up like little islands)).
In very dry climates you may want to put your garden in the place that holds water longest, which will usually be the lowest spot.
Microclimate is the climate on the ground in your particular garden and can be very different from the climate (macroclimate) around about. Two gardens in the same area may have very different growing conditions. In winter the bottom of a north facing hill may be shady and frozen, while only a few hundred yards away the south facing top may be sunny and mild (the equivalent to being a hundred miles or more to the south).
You may have noticed that the growing conditions in your garden vary from place to place. Some places may be hard hit by frost while nearby spots may be completely untouched. This occurs because cold air is heavier than warm air and so moves downhill and settles in low spots, close to the ground. This effect can be surprisingly local and the air four feet up may be significantly warmer than that at ground level. You can sometimes see this clearly illustrated, when the lower branches of a shrub or tree may be damaged by frost, while higher ones are unharmed.
One of the best-known examples of a useful beneficial microclimate is the south facing side of a stone wall. This traps the sun and stores heat, while sheltering the area from cooling winds, thus creating a microclimate that is considerably warmer than the surrounding area.
The value of a particular microclimate depends upon the climate and season. In a cool climates a south facing wall will be prized for being warm and sunny, whereas in a very hot climate it may be too hot and dry for most plants. Conversely a cool shady moist spot may be a problem area in a cold climate, but just what you need in hotter areas.
Microclimate isn’t set in stone, it can often be altered to better suit your needs, for example by adding a windbreak or pond. Careless activities can make the microclimate worse, for example if you plant trees on the south side of the garden, or if a poorly sited building creates a wind funnel.
The topography of the land can be a significant factor in its suitability for a garden. Low lying land may have good soil, but there is often the potential for flooding and if surrounded by higher ground, it can be prone to frost (as I mentioned under Frost Pockets).
Flat land is convenient for the gardener to work on, but sloping land can often provide a better microclimate. Some of the best garden sites can be found in the middle of gentle south facing slopes. Slopes also drain faster than flat land, which can sometimes be a significant advantage in rainy climates. Of course if the slope is too steep, there can be problems with getting around and creating growing beds. It may also be prone to erosion in wet weather.
One microclimate you need to know about is the frost pocket, which is caused when heavy cold air flows downhill (rather like molasses) at night and collects in low lying valleys. This effect makes low flat areas more vulnerable to frosts than somewhat higher elevations (contrary to what you might expect, as it is supposed to get colder at higher elevations). These low lying areas can suffer from severe frosts, even when higher areas nearby are frost free. If you have any choice in the matter you should avoid putting your garden in a frost pocket. Put it a little up slope, so any cold air will move on through and continue its way downhill.
Frost pockets can also occur higher up on a slope, if a solid barrier (wall, hillock, fence, hedge) blocks the free downward flow of cold air. Such a barrier is known as a frost dam and causes cold air to accumulate above it, creating an area that is much colder than the slope around it.
It may be possible to divert the downhill flow of cold air around your garden, by putting a solid barrier on the uphill side. This should be angled slightly, so the cold air keeps on moving and so misses your garden area. If this isn’t possible you should at least avoid creating a frost dam on the downhill side of the garden, by using open fences which allow cold air to pass through them. You might also raise them up off of the ground slightly, or angle them downhill. All of these ploys keep the cold air moving, rather than accumulating. Frost pockets can also be dissipated by wind, but of course too much cold wind can chill plants also.
Frost pockets aren’t always bad, they are sometimes used in mild winter areas to ensure that fruit trees get sufficient chilling.
The orientation of a slope has a considerable effect on its’ microclimate, because the maximum solar gain is received when the sun strikes the soil at right angles. The desirability of a particular slope orientation will be determined by your climate. In temperate climates you will usually be looking for warmer conditions, but in the desert you might want cooler ones.
Eastern slopes: These warm up fast because they receive morning sun, which is useful in spring and autumn (but not good on cold mornings as it can increase frost damage). Such slopes are commonly sheltered from prevailing westerly winds, which makes them somewhat warmer and slower to dry out.
Southeastern slopes: These are probably the idealgarden sites. They warm up rapidly like eastern slopes, but get warmer. They aren’t as hot and dry as south or western facing slopes.
Southern slopes: These have the warmest growing climate, because the sun hits them more directly. If flat land gets 100 units of sun, then a south-facing slope may get 106. This is effectively like moving the land further south. These slopes warm up faster in spring and get hotter in summer. On the negative side they also dry out more quickly.
Western slopes: These are exposed to the afternoon sun, so get very hot and dry out rapidly. Prevailing westerly winds can exacerbate this drying effect. These winds may also cool the soil in spring and fall and if very strong they can cause physical damage. On frosty mornings these slopes thaw out more slowly, which can mean less frost damage.
Northern slopes: These receive sunlight at a very oblique angle and so get less solar gain than flat land. They may only receive 86 units of sunshine, as compared to 100 units for flat land. This means they have a cooler and somewhat shorter growing climate, just as if the land was further north. This is most drastically illustrated in mountains, where snow stays on north facing slopes much longer than it does on south facing ones. In addition these slopes are often exposed to cold northerly winds, which further lowers the temperature. Like western slopes they thaw out slowly in winter, which can reduce frost damage. In temperate climates such slopes don’t make very good garden sites, but in very hot climates they may be preferred for growing many crops.
Plants don’t like strong winds for a variety of reasons, but the most significant one is that it can increase the amount of water they lose by transpiration. In dry conditions this may occur to the point where plants have to shut down and stop growing to conserve moisture. In extreme cases this has been known to cut total crop yields in half. Wind can also increase evaporation from the soil, which means more water is required for irrigation.
Wind also lowers air temperature (exposed areas may be 5°F cooler than sheltered ones), inflicts physical damage to the plants, causes erosion of dry topsoil and blows heat out of cloches and cold frames.
If your area is particularly windy, you might be able to site the garden where the topography of the land will protect it. If this isn’t possible you will have to create a windbreak, which can be expensive and time consuming
A good windbreak should be fairlypermeable (only about 50% solid), so that it slows the wind, rather than merely deflecting it over the top and causing increased turbulence on the other side. It is said that a windbreak will block the wind for a distance of about four times its height.
Hedgerows and trees make good semi-permeable windbreaks (and also provide habitat for predators), but they take a while to get established. A problem with using living plants is that they send out roots towards your beds, where
they compete for nutrients and water. They may also reduce rainfall immediately around them by as much as 75%.
Wire fences with wooden or plastic laths attached can make good and inexpensive windbreaks. Open wooden fences are a quick and fairly attractive windbreak solution (even a 3’ tall one will help) and don’t create too much unwanted shade.
Some crops make good windbreaks (fava beans, sunflowers), but you will probably have to reinforce them with stakes if you want them to withstand strong wind. Blackberries trained on a trellis make a great windbreak.
In very windy areas it may help to orient your beds to act as windbreaks and plant vulnerable crops downwind.
Human criteria for the site
Distance from your living space
This may seem like a trivial matter, but the further the vegetable garden is from your house, the less you will take care of it and use it. Someone once estimated (don’t ask me how) that the amount of food harvested declined by 30% when the garden was over 100 feet away. You might think this doesn’t really apply to you, because you are so enthusiastic and one hundred feet really isn’t that far, but it will make a difference as to how often you enter your garden. Ideally the garden would be located right outside the kitchen door (if this isn’t possible you might have a small salad and herb garden there).
A garden that is close to the house gets tended more conscientiously, not only because it is more convenient, but because it is so visible. You make more effort to keep it looking good because otherwise it would be embarrassing every time someone comes to visit.
It is a good idea to have the garden as a dead end, rather than a thoroughfare. If it is en route to somewhere else, plants may get damaged by passing children, dogs, wheelbarrows and more.
Contamination of the soil from human made chemical pollutants is an increasing problem for gardeners and one you should be aware of. Though the possibility of serious problems is fairly remote in most places, once a toxic substances gets into the soil it may be impossible to remove.
Make sure the garden is a minimum of 100 feet away from well traveled roads, as they are a source of many dangerous pollutants. The soil around old buildings may contain high levels of lead, leached from old paint. Heavy metals such as lead and cadmium have been found in composted sewage sludge. Wood that has been pressure treated with chromated copper arsenate (or other highly toxic preservatives) will slowly leach toxins into the soil (it may also have been burned). Anywhere people have worked on cars or heavy machinery can contain waste oil.
If you have a farm, or your garden was once farmland (this includes most suburban areas) the soil may contain the residues of persistent pesticides such as DDT, chlordane, dieldrin or lead arsenate. If these are a potential concern you can test for these.
This isn’t exactly a necessity, but it is good if your vegetable garden has a view, simply because you will be spending quite a bit of time there. It’s nice to have something pretty to look at when you look up from your turnips (not that they aren’t beautiful).
Alternative garden spots
If your garden simply doesn’t have a good spot for a vegetable garden, or you don’t have any garden space at all, you don’t necessarily have to give up on vegetable gardening. You might find a relative, friend or neighbor who doesn’t garden for themselves, but would be happy to have you do it (perhaps for a share of the produce). This can also help you to get to know your neighbors and encourage people to share a little more.
You might also find a plot in a community garden. This will not only give you a place to garden, but comes with a whole community of gardeners too. They can be of enormous help when you are first starting out.
If you want a bigger plot, or a commercial market garden, you could try renting a piece of land. There are landowners who would like to have the tax advantages that come from having their land farmed. I recently heard of a couple who created a small urban farm out of a number of other peoples gardens!