Lesson 1 - How to grow healthy plants
Plant health is an overarching term that covers all aspects of the condition of plants. A narrow definition tends to focus on the effects of pest and disease organisms on crops but in this module, we will take a broader approach that includes plant interactions with the environment in which they are growing. Plant health is important to us as food growers as unhealthy plants are not as productive as they can be, and the quality of their produce may be reduced.
The starting point for creating and sustaining healthy environments for growing crops is, once again, understand the climate and soil conditions at your location, identifying the limits that these might impose on your crops, and then identifying which, if any can be modified to suit potential crops. Some of these factors are listed later in Lesson 2: Abiotic disorders, and we have discussed these in earlier modules.
The key to growing healthy crops is to grow those species and cultivars that are best suited to your location. Crop plants have specific tolerances and susceptibilities and growing plants in locations where they are not suited will always be difficult. We suggest you research your location, and the crops you hope to grow, and then look for species and cultivars that tolerate your conditions. This information can be hard to find and sometimes you need to experiment. With annual crops like vegetables, because of their short life cycle, you can relatively quickly find varieties that work (or obviously don’t work) for you. Don’t set yourself up to fail by trying to grow late ripening tomato varieties in cool areas, or disease prone species in wet summer locations. With perennial crops like fruit trees the importance of good early research is invaluable. You could waste years only to find that the particular plant you wanted isn’t suitable, either because of environmental unsuitability, soil incompatibility, or pest or disease susceptibility. Good plant selection before you start a project is just as important as any other aspect of food crop growing. If you are completely new to food growing, finding local growers who can share their experiences is another very useful way of beginning to understand your situation.
Once a site is prepared, and crops are established, maintaining soil health, suppressing weeds, providing adequate irrigation, and providing protection from pests and diseases, will all contribute to keeping your plants in as good condition as possible. This will ensure that the produce you grow is of good quality, and that it is worth the time and effort and money that you have spent to grow it.
In summary, a healthy plant is one which is growing in an environment to which it is well – suited, that provides it with adequate levels of the resources it needs for growth, and that is free from harmful agents. Additionally, it is a plant that is not subject to uncontrolled predation by animals, or invasions by pathogens, or subject to severe competition from weeds.
Broadly speaking, plant disorders can be subdivided into two classes, abiotic and biotic. Abiotic disorders (sometimes called environmental, or physiological disorders) arise when the crop is being grown in an environment that the crop does not tolerate, resulting in a stress. Biotic disorders on the other hand are caused when a living organism attacks the crop, resulting in damage, and reduced yields. Whether the cause of the damage to your crop is abiotic or biotic, there will often be visual clues that damage is occurring (these visual signs are called symptoms) and the symptoms are typical of the problem. Developing a mental library of these symptoms is one of the skills one develops as a grower. Image searching on the internet can be a useful way of starting to learn what different disorders look like. Bear in mind however that similar symptoms may occur with different stresses (for example, wilting can be caused by water shortage, waterlogging, and root rot or wilt diseases).
Side Bar: Commercial fruit and vegetable growers are under pressure to grow produce that is in very good condition, with no blemishes, spots, or other imperfections. This usually requires rigourous crop protection, often with the use of pesticides (even in organic production systems pesticides are used, as long as they are of types approved by organic regulatory organizations). As a home grower, you are not necessarily under the same pressure, as areas of imperfection can be removed as food is being prepared (codling moth damage cut out of apples, the occasional caterpillar removed from a head of broccoli). Consequently, home growers can be a bit more relaxed about plant health. This is not to suggest that you don’t have to do anything about crop health. After all, you are expending resources on this activity, but a few blemishes aren’t the end of the world.
Diggers tip
Don't be a bad neighbour. Please keep in mind that neglecting infected or diseased crop plants could spread the problem to neighbours is the act of a bad neighbour. You need to provide some care and stewardship for the crops you grow. It’s like sending your kids to school when you know they have chickenpox.
Commercial fruit and vegetable growers are under pressure to grow produce that is in very good condition, with no blemishes, spots, or other imperfections. This usually requires rigourous crop protection, often with the use of pesticides (even in organic production systems pesticides are used, as long as they are of types approved by organic regulatory organizations). As a home grower, you are not necessarily under the same pressure, as areas of imperfection can be removed as food is being prepared (codlin moth damage cut out of apples, the occasional caterpillar removed from a head of broccoli). Consequently, home growers can be a bit more relaxed about plant health. This is not to suggest that you don’t have to do anything about crop health. After all, you are expending resources on this activity, but a few blemishes aren’t the end of the world.