Fruit (and nut) trees provide an abundance of delicious food while requiring very little care (they are also beautiful) and should be in every garden. However you have to place them carefully because they are so big they influence everything around them. This influence is sometimes positive (they modify the microclimate and create shelter from wind) and sometimes negative (they create large areas of shade and their strong roots can take most of the water and nutrients from the soil). You just have to find the places where they will grow best and enhance the garden, without creating too many problems.
The biggest problem with trees in the food garden is the shade they create. A newly planted tree doesn’t cast much shade, but as it gets bigger over the years it can eventually shade a considerable area. The biggest mistake I made in the early years of my garden (and the hardest to rectify) was not being more careful where I planted my trees, which resulted in several sunny areas becoming partly shady. Actually I wasn’t careful at all, I just planted the trees where I thought they would do well, without taking into consideration what the area around them would be used for later. This is an easy mistake to make when you have a large empty area, because you may not have even thought of what you are going to do with it in the future. Planting trees should start with deciding what you will do with each area of the garden, so you can then avoid putting trees in areas that will need full sun (at least until you have a better idea of how you are going to use them). Above all you must avoid planting fruit trees anywhere near your vegetable garden, most common crop plants need full sun for maximum production and don’t mix with trees very well.
Of course the shade cast by your trees isn’t static, it varies continuously as the sun moves across the sky. In the morning the west side of the tree is shady, at noon it is on the north side and in the evening it is to the east. Shade also varies seasonally (and with latitude), in winter the shadows may be very long, while in summer they may be almost directly underneath the tree. The first rule here is to avoid planting trees to the south or west of your vegetable garden (or patio), as you need as much sun in those areas as you can get (unless you live in the desert, but if you do you probably know more about desert gardening than I do). As a general rule you should put trees to the north of any places that need full sun (making sure you don’t shade your neighbors though). Trees to the east of the garden aren’t usually a big problem because early morning sun doesn’t produce much growth anyway.
Another big mistake is not giving your trees enough room. Crowded trees have to compete with each other for water and nutrients and create such dense shade that nothing can grow underneath them (it also makes them taller and skinnier). The right spacing between trees depends upon their mature size of course (don’t be influenced by how small they are when planting) and especially their width. For maximum productivity you want your trees to grow to their fullest potential, which means giving them slightly more room than they need. Of course you don’t have to plant trees as close together as they will tolerate, if you have plenty of space it’s usually better to leave extra growing room between the trees and fill in with other plants (this is basically what forest gardening is all about). Be aware that the ultimate size of a tree isn’t completely predetermined by rootstock, it also depends upon the growing conditions: how much room they have, soil and climate. Even dwarf trees will grow bigger if they have good growing conditions.
Most fruit tree roots tend to be vigorous and fairly shallow and when well established they will take most of the nutrients and water out of the soil. This is another reason for keeping your trees well away from the vegetable garden (even on the north side). It’s a common practice to put a nice wide path between the trees and growing beds.
When placing your trees you also need to be aware of the growing conditions of the site (soil, microclimate, shelter, competition from other plants) and make sure these are suited to the species. This is particularly important for plants that are marginal for the area, as a warmer microclimate can allow you to successfully grow something that wouldn’t thrive otherwise. I planted citrus around the dripline of a large Live Oak (on the southwestern side) because it provides significant protection from frost. When I planted the first trees in my garden I made the mistake of planting several too close to established trees. They didn’t grow very well because they didn’t get full sunlight and their small root network couldn’t compete against the large tree roots. I tried to compensate for this by irrigation and feeding (more work) but it didn’t really work (I eventually moved some of them, but the ones remaining are about a quarter of the size of trees in more ideal conditions). The amount of shade a tree can tolerate varies according to species of course, but it also depends upon what you want it to produce. If you only need a few leaves for flavoring then a plant won’t need as much sun as if it has to produce lots of fruit (which requires lots of sunlight). You should also consider the vigor of the plant, you may be able to put an unusually vigorous plant in part shade (instead of full sun), where its vigor will be reduced, but it may still produce satisfactorily.
Of course garden trees also frequently have to perform landscaping duties, such as screening an area from view, creating shade for the house in summer, or blocking cold prevailing winds. These uses will often determine exactly where we put our trees, which simplifies your planning (don’t forget to take the other factors I mentioned into account too). The reverse of this is don’t put trees where they will negatively affect the look of the garden.
If (after all this) you do put a tree in the wrong place, it won’t usually be evident until it gets big enough to affect the area around it. Unfortunately by the time a tree is big enough to be a problem your options are limited. You can either remove the tree (if it’s not too big it’s worth trying to transplant it) or leave it and change the garden around it (this is the best option if you have lots of space). Of course it’s much better to plant the tree in the right place to begin with, so do your best to get it right first time.
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