Lesson 2 - Planning your fruit growing
Most fruits are woody, perennial plants that live for a long time, so it’s important to consider their selection and placement carefully. Start by considering what fruits you like to eat and how much time do you want to spend growing and caring for them? While producing fruit in the garden takes some work, some crops are less labour intensive than others. Strawberries for example can be grown very easily with little effort, while some of the deciduous fruit trees will require inputs several times during the year, including tasks such as pruning and training. Look at the space and size of the area that you have for growing and match this to the dimensions of the plants that you are interested in growing. Some fruits will require netting to protect the harvest from birds and other pests, a task that can be relatively simple if the plants are small, but complex if they are large.
And just like vegetables in the previous module, do some research to plan your fruit growing journey. Start by looking across your neighbourhood and see what fruits are growing and producing well. Consider the opportunities and limitations of your site to support different fruiting plants. The available area you have for growing is critical as many are trees that require considerable space and light to grow well. Explore the mature dimensions (height and spread) of the fruits that you are interested in growing, although there are increasing numbers of dwarfing or semi-dwarfing cultivars that grow significantly less than the typical species. Many of these are also excellent for container growing. You can also use specialised training and pruning methods for some fruits, such as espaliers, to reduce their height while still being very productive trees. Also consider the rootstocks used for some fruit trees, to which the fruit has been grafted on to, especially those with resistance to certain pest and diseases.
Your garden or site will influence the growth and productivity of any fruits you grow and should be analysed prior to plant selection. Microclimate, especially slope, aspect and wind, should be assessed, and in smaller urban sites, look for any localised shadowing and shading. Wind can be particularly damaging, and, in some cases, you may need some form of protection or barrier to grow fruit successfully. Cold temperatures and frost can also be a problem, especially if you are trying to grow warm temperate or subtropical fruits. Again, some form of protection may be needed, particularly when plants are small. Your soil is of course very important to successful fruit growing. This should start with assessing your topsoil, specifically depth, texture and structure, but also include looking at infiltration and drainage. If you need to know more on these topics, go back to previous modules in this course, including Module 1 (Planning and design) and Module 2 (Soils and water).
The climate of your garden, particularly rainfall, light, wind and temperature, strongly influences the growth and the productivity of fruiting species. Many temperate fruit trees need a period of cold exposure over winter to break bud dormancy, initiate flowers, and in turn produce fruit. Described as the chill factor or ‘chill hours’, it is the cumulative number of hours below 7°C for a location. High chill fruits require 650+ hours, medium chill 450 to 650 hrs, and low chill 150 to 450 hours. Some fruits, such as apples, apricots and European plums need relatively high chill hours, which is why they are often difficult to grow where the winters are mild. Insufficient chilling causes uneven bud break and blooming, a reduction in fruit set and smaller-size fruits. However not all fruit trees have a chill hour requirement, for example avocadoes and citrus have none. And the chill hour requirement varies between species and also between different cultivars. So do your research. To calculate the chill hours for your location, you can use climate data from bureau of meteorology website and then match it with information from this interesting website Fruit chilling guide for Australia to see what will grow best. There are increasing numbers of ‘low chill’ fruit tree varieties that can be grown successfully in warmer climates (which is why we see stone fruit in stores during late spring!). With the right chilling requirement, most trees will have a good blossom after winter, although your microclimate and a mild winter (a feature increasing with climate change) will also affect blooming and fruit set.
Another climatic factor to consider when selecting fruits for your location is the relative warmth or growing degree days (GDD). More important for growing warm temperate and tropical fruits, GDD is a measure of accumulated heat over a growing season needed for different growth stages of the plant, in this case for fruit development and maturation. And just like chill hours, some crops have minimum GDD requirements to fruit successfully. Examples include grapes, tomatoes and citrus, although there is considerable variation between cultivars. In locations where you don’t reliably have long periods of warm weather, (i.e. months), it can be difficult to get fruit to ripen. Melons, such as rockmelon and watermelon, need minimum temperatures of 10-16°C and warm daytime temperatures between 21-32°C, over a long period (80-120 days) to reliably produce fruit. In cooler southern areas of Australia, these requirements can be difficult to satisfy.
Finally, when considering fruiting plants to grow at home, do some research around their pollination requirements. Pollination is where pollen, from the male part of the flower (anther), moves to the female part of the flower (stigma), resulting in fertilization and the development of seeds and fruit. Fruit trees tend to be one of two types – self-pollinated trees, where flowers on the tree are self-fertile and pollinate themselves, such as peaches, citrus and berries; and cross-pollinated trees, those that require pollen from different but compatible cultivars of the species to ensure fertilization, such as apples, pears and Japanese plums. Although some trees that are largely self-pollinating, such as apricots, peaches and European plums, will always have better yields when cross-pollination occurs (i.e. when different cultivars of the species are present). Successful pollination often also relies on having insects, particularly bees, to be active when flowers are blooming. Ensuring that you have other flowering plants nearby in your garden to attract pollinators will also benefit the pollination of your fruit trees.