So you have ripped out all the old “ornamental” plants in a garden bed, and intend to replace them with delicious edible fruits and vegetables. But cool your boots, would-be gardener: have you done a site assessment yet?
A wha? A site assessment. Okay, you’ve already identified the plants on site (and for the purposes of this post removed them all) but have you assessed other site issues? These also apply to building a completely new garden from scratch, too. Things like soil type, slope, nearby structures, drainage, water supply, lighting, position in relation to buildings, especially how close it is to the kitchen. Lets break these issues down into simple categories, starting with
What kind of soil do you have? Soils are usually classified according to texture, on a scale that ranges from sand at one end to clay at the other. Here is an example from the USDA of how to perform a simple soil texture analysis. The proportion of the soil that is actually sand, silt or clay particles will give the soil different properties, and every soil has advantages and disadvantages. For example, sandy soils have fantastic drainage, but are usually poor in nutrients. Clay soils hold on to water so well, drainage issues may be an issue, but they are the best soils for retaining nutrients. Though each soil is distinct, and requires slightly different approaches, it should be noted, that unless there is some kind of serious toxicity in the soil, there is no such thing as “bad” soil!!! In 100% of cases, poor soil structure can be fixed by the addition of organic matter. More on this later.
The degree of slope of your garden bed will determine a number of things, mostly to do with water flows, but can also influence things like how well mulch stays in position in the garden, as well as access to the garden bed. Ideally for most situations, the garden should be as flat as possible, too allow water to be applied and soak in as easily and evenly as possible. The greater the slope, the more problems will be caused in the garden later, so if any levelling works are required, before planting is the time to address this.
Tied closely to slope and soil, drainage is an issue which can be remedied, but it is easier to do so before planting a garden than after. Sandy soils have better drainage, and clay soils poorer drainage, though between the extremes there is a great continuous scale of variation. If you wish to see how fast your soil drains, dig a hole of an approximately 100 mL volume, fill it up with 100 mL of water and see how long it takes to disappear. This is important information when it comes to irrigation of your garden, which we will come back to.
This is probably the single most important consideration when growing plants. It is also something you can’t change, if you don’t have enough light, you will not be able to grow the plants you wish. For most popular garden plants, especially vegetables and herbs, at least 6 hours a day of direct sunlight are required. If you have less, your garden will be less productive, though you may be able to grow things, your harvests will be fewer and farther between. In the southern hemisphere, the sun moves slightly north in winter, so any gardening should have as far as possible an unobstructed northerly aspect. That is to say, nothing higher than the plants on the northern side of the garden. Protection to the south is probably desirable, and a building or fence to the south may be used as a growing surface, too. Shade to the west is more desirable than shade to the east, as morning sun is less harsh than hot afternoon sun, especially in the summer.
Unless you enjoy carting water in bucket or watering cans long distance to water your garden, the location of the taps or water tanks in relation to the garden need careful consideration. Obviously it’s best to have water available close at hand, both to avoid work when hand watering, and to reduce other risks, such as water heating up in hoses in the sun, and long hoses becoming a tripping hazard, or getting munched under the mower (if you persist in keeping up that ritual penance to the society of the 1950s).
Light & position
Lastly, it’s best to put a productive garden close by the house, especially for herbs and constantly picked vegetables, preferably in an area that is well lit. This is because on a dark and rainy night, you are less likely to sprint all the way to the back of the yard to grab a handful of basil or parsley, or on a hot day trek there for the ingredients of a salad. Simply, the closer you are to the garden, the more time you will spend in it, the more you will get out of it, and the more successful and fulfilling the whole process will be. Check also, especially if you are going to do any serious digging, for underground service such as water supplies, electrical cables, phone cables, sewerage and gas. You don’t want any nasty surprises to be uncovered with your spade or pierced with a garden fork.