Forest gardening draws on the way in which nature itself works for many things, from fertility to pest control. Therefore, when it comes to pruning, you might imagine that it would be best to leave aside such artificial practices and instead let trees and shrubs follow their own natural patterns of development. No-work permaculture at its finest!
This was my own assumption when I started forest gardening, but years of experience have taught me, often the hard way, that the opposite is true. Pruning is a very effective intervention that pays back the effort many times in terms of the accessibility, quality and size of your crops. It is also a great way of learning more about your plants and how they develop. With a little practice, you can use your secateurs as a baton to conduct a symphony of growth, flowering and fruiting in your garden.
I use pruning to achieve three main things. The first is access. The secret to a forest garden in its complex, multi-layered structure. This can also be a hazard as you battle your way through branches and wet foliage to get to your food or get poked in the eye bending down to pick from the ground layer. The main principle here is to prevent plants from branching too low down so that you have a clear view and easy access to the plants growing beneath them. You can also make trees and shrubs more robust and so less likely to be dragged down by the weight of their own fruit.
The second is yield. Pruning is your main method for persuading trees to put more energy into fruiting and less into massive amounts of woody growth. It largely isn’t a matter of cutting off growth after it has happened but instead of cutting back to the right buds so that you encourage the kind of growth that will bear fruit. A tree that is investing less in vertical growth will have more to put into fruit and the lighter, sunnier canopy will generally allow better ripening of the fruit. In a forest garden, there is also a knock-on effect in the lower layers. Many plants naturally produce more foliage than they strictly need for photosynthesis in order to shade out the competition and claim a greater share of the available water and nutrients. Creating a lighter crown gives you more light and productivity in your ground layer.
Finally, there is disease. Pruning is an opportunity to cut out diseases like apple canker and to stop them from spreading. A more open, airy plant is also generally less prone to diseases such as mildew that can attack both plant and fruit. A pruning saw is a double-edged sword though. Carelessly carried out or mis-timed pruning can spread infections or create opportunities for diseases to attack. I generally wipe my pruning tools with meths between trees to avoid transferring diseases.
There are three main principles to bear in mind when pruning. Much of the rest flows from these three. The first is that a bud will produce a shoot pointing in the direction that the bud itself is pointing. On a horizontal branch for instance, a bud on the top of the branch will produce vertical growth, buds on the side will grow out horizontally and ones on the bottom will grow down. The second principle is that growing buds suppress the growth of ones further down the shoot. The practical upshot of this is that you can cut a shoot back to a particular bud and this will be the one that will have the most growth. Leaving the end (or apical) bud will give strong extension of the shoot. The third principle is that plants prefer to fruit on some kinds of growth more than on others. The details vary from plant to plant and the biggest differences in pruning strategy are down to this.
Now, with these principles and a pair of secateurs in hand, let’s have a wander around the garden…
Raspberries (Rubus idaeus) are often grown up wire frames that support the canes and prevent them from being dragged down by the weight of the fruit. The downside of this approach is that canes that wander too far from the frame are usually pruned off, preventing the natural spread of the plants. Over time this tends to lead to the loss of the whole stand to disease.
An alternative approach, which I have now adopted for all my rasps, is to shorten the canes somewhat so that they are robust enough to be free standing. Allowing my plants to wander around the garden has allowed me to make some interesting observations. Raspberries are related to brambles (R. fruticosus agg) and while they don’t share the briar’s trait of making roots at the end of their shoots in order to spread through a wood at terrifying speed, they do share its ultimate dream – of getting up into a tree in order to co-opt its structure and reach the sun. The thorns of bramble and raspberry, like rose, both point backwards from the stem. They are as much about helping the plant to get a grip on the plants that it scrambles over as they are about protection – they are little grappling hooks designed to pull the shoots up into a tree.
Grown in the open, raspberry canes grow with a distinctive kink near the top. When they get near a tree, the purpose of this becomes clear: the canes first punch up vertically through the canopy then loop over, hopefully snaring a branch for support. In the open, I generally prune the canes just below this bend. It doesn’t remove too much stem but it seems to be enough to keep them vertical. Under a suitable tree, I just let them get on with it. The pruning is carried out in winter when the plants are dormant. At the same time I remove the previous year’s canes, take out any weak, spindly, damaged or diseased canes and thin out any areas that are too crowded. The old stems make great kindling; new ones go in the compost.
The exception to this pruning strategy is for autumn-fruiting rasps, which have to be cut right down to the ground at the end of every season and which generally need some support once they are grown up.
Brambles or blackberries are like raspberries, except that their shoots are designed to arch over and root at the tip, which makes them something like a cross between creeping buttercup and barbed wire. However, it’s possible to tame a bank of brambles with a little carefully timed pruning. In the middle of summer, when the shoots are growing at their fastest, cut the new stems in half, at the high point of their arc. If you’ve done the same the year before it is easy as you cut them just beyond where they pass the fruiting stems, so it can be done with a hedge trimmer if you have a lot.
The currants (Ribes) nicely illustrate the importance of knowing what kind of wood a plant fruits on. Blackcurrants fruit on new growth so they are pruned by cutting the oldest third of the stems down to ground level every winter, giving a constant supply of new shoots.
Redcurrants, whitecurrants, pinkcurrants (all R. rubrum) and gooseberries (R. uva-crispa) all fruit on old wood, so the pruning strategy for them is completely different. Winter pruning is limited to taking out especially old or diseased branches and any shoots that are crossing or growing up from the base. Then, in early summer, all side shoots are cut back to two buds. Because the plants fruit on older growth this doesn’t remove any fruit, but does change the plant’s priorities from making new growth to producing fruit. Leading shoots can be shortened to create a robust, compact plant that will not be dragged down by the weight of the fruit on it.
Overall, the aim with redcurrants and gooseberries is to produce an open, ‘goblet-shaped’ plant that allows air circulation and resists mildew. They are usually grown on a ‘leg’ (the stem of the goblet), a short section of trunk free from any shoots. This is particularly useful when you have ground layer crop that you want to harvest and also helps to discourage gooseberry sawfly, which emerge from the ground every year and have to get up into the plant in order to strip its leaves.
Apples (and pears)
Apples and pears are pruned in the dormant season, between leaf fall and bud burst. The overall aim of pruning is to produce a robust, compact frame of sturdy branches and short fruiting ‘spurs’ that will support the un-naturally large fruits that we have selected the ancestral apple for. Spurs are side shoots that are kept short (just a few buds). As well as ensuring that the apples are borne close to the main stem this encourages the formation of fruiting buds.
The other main aim is to stop the tree putting all its resources into non-fruiting growth. The rule of thumb here is that vertical stems grow rapidly and produce little fruit while horizontal stems grow slowly and produce lots of fruit. As I said above, you don’t want to have to achieve this by cutting off lots of the wrong kind of growth but rather by pruning back to buds that are going in the direction that you want them to in the first place.
Before you start, it’s important to learn to distinguish fruiting buds (which will break to produce a spray of blossom, followed by fruit) from vegetative buds (which will produce a length of stem). In the photo below you can see some spurs pruned back to the large fruiting buds. The vegetative buds on the side of the stems are much smaller. Before you start pruning, check whether your tree is a spur-bearer, with the fruit buds closer to the base of the shoot, or a tip-bearer, with the fruit buds clustered at the end of the shoot. Spur-bearers are more common.
The first part of the pruning strategy is simple: reduce all vertical shoots to short spurs (or even cut them right back to the branch as they will always tend to want to make vertical growth). The only exception to this is for stems that you want to form the central trunk of the tree in the future. These are generally reduced by about half to keep the tree compact and the stems robust. I generally like to give myself options by keeping a few leading stems at the top of the tree – ones that aren’t needed can be pruned back in the future. Also cut out any diseased wood at this stage.
The second part of the strategy is to create a leading shoot at the end of the branch that will give horizontal growth. Pick a shoot (or two) near the end of the branch and prune it back, by about a third to a half, to a bud on the underside of the shoot. This will grow in the direction it is facing, giving a downward-facing shoot (the tendency of all shoots to curl upwards will translate it into a horizontal one). If all shoots on a branch are trimmed back hard then lots of buds will break, setting you up for a dense tree with lots of vertical growth in the future. The end shoots therefore achieve two aims: they give you a horizontal extension to your branch and they produce chemicals that suppress the growth of the buds further down the branch. The photo below shows the result. Right in the middle you can see a shoot that has been pruned back to a downward facing bud at the start of the year, resulting in a horizontally-growing shoot.
Finally, the side shoots behind the leading stem are your spurs. Here you can take your pick. Traditonally, spurs were cut back to a short stem of approximately five buds, ending again on a downward facing bud. More recent thinking is to do no more cutting back than is needed to avoid congested and crossing spurs. If the fruit buds are clustered at the tips (a tip bearer), this is definitely the option you need. I’m used to the old way, but will try experimenting with the newer recommendations this year.
Plums and cherries
Avoid pruning stone fruit like plums or cherries in wet weather or in winter as this makes them vulnerable to a disease called peach-leaf curl. A sunny day in July is ideal. Plums do not require a lot of pruning – mostly just cut out any diseased branches and any shoots that are growing vertically or towards the centre of the tree. Summer pruning may involve removing some shoots with developing fruit. Don’t worry about this. Plums always set too much fruit anyway. In fact you might want to thin out the developing fruit at this stage to avoid overcrowding, broken branches and exhausted trees.
An alternative to pruning on apples, pears, plums and cherries is festooning – tying down vigorous vertical branches to the hortizontal. This is more work but gives a quick way to achieve a more horizontal structure without removing lots of material and making lots of cuts. I use it, in combination with pruning, on trees that haven’t been pruned for a few years and need some drastic action.
If you are pruning a newly planted fruit tree, you don’t need to worry about encouraging fruiting as you shouldn’t allow it to fruit anyway in its first year. Instead, this is the time to think about the future structure of the tree. The traditional advice is to cut the leading shoot of a ‘maiden’ (single stemmed) tree at 75cm and then allow the shoots that come from the buds below the cut to develop into the main branches of the tree for a goblet-shaped structure (removing the topmost shoot if it is too dominant). For access to the ground layer, I prefer to have a little more unbranched trunk than this.