If you would like your own orchard but only have a small amount of space in your back garden, what can you do? Apple trees are usually grafted on to size-controlling rootstocks. The typical garden apple tree is probably grafted on the popular MM106 rootstock, which produces a nice-looking tree about 12ft-15ft in height and a similar spread. That is great for a feature tree, but not much use if you have got the apple bug and want to have a lot of different apple varieties in a small space. This is where M27 comes in. The M27 rootstock has an extremely dwarfing effect on the scion variety, and produces a mature tree of about 5ft-6ft or so - no bigger than a person.
Gardening books sometimes warn readers away from growing apple trees on M27, because they are allegedly too difficult. That might be true for the casual domestic gardener, because M27 trees are not a "plant and forget" affair in the way that MM106 trees are. However M27 trees actually need no more effort than is required for growing many other garden flowers and vegetables.
The big advantage is that apple trees on M27 are just so compact that you can pack them in at spacings of just over one metre between trees - maybe 1.5m if you are feeling generous. So you can grow 10 different apple trees on M27 in a space about 7m by 3m. Alternatively, as a rule of thumb, you should be able to get 4 or 5 M27 trees in a row about 7m long. The small size also means you can grow M27 apple trees very happily in large patio containers.
Smaller trees means more trees in the same area - and that in turn means you can grow more varieties, allowing you to spread your cropping from the really early varieties in late July right through to November in a good year. Although the trees are very small, M27 is so productive that you will probably find the total crop produced is greater than you would get with a single much larger tree. Depending on the variety, each M27 tree will produce about 3-5kg of apples - the equivalent of about 5-7 supermarket polybags.
What's more, M27 trees mature very quickly - you will be producing reasonable crops just 2 years after planting, and the trees reach full size after 3-4 years.
There's one other unusual advantage of M27 apple trees. They are the only apple trees that are truely on a human scale - pretty much the same size as us. That makes them an interesting option if you want to introduce your children to the joy of growing their own apples.
So what are the drawbacks? Well, nothing that a keen gardener will find too difficult. If you are planting in open ground in the garden, the most important thing is to buy some proper tree posts, about 6ft high by 2" or 2.5". Bang these in about 1-2ft before planting. (Sorry for mixing metric and imperial in this article, but tree posts seem to still come in imperial sizes). Then you can plant the trees alongside them. Put the trees on the south side of the posts, unless you are in an exposed situation in which case it is best to put the trees on the leeward side of the post. The posts are essential because M27 trees cannot support themselves - the roots and stem are just too weak.
If you are planting in patio containers, make sure you put a heavy-duty bamboo cane into the base of the container, which can then be used to provide some support for the tree.
The other disadvantage is that M27 trees need good mulching and a lot of watering, because the roots are so small. In other words, they do need looking after, in a way that traditional large apple trees do not - but they are no more demanding than many other garden plants. You should also keep the area around the trees completely free of weeds and grass as M27 trees cannot tolerate any competition.
Perhaps the most difficult part of growing M27 trees, but in some ways also the most interesting, is the early training of the tree into a productive shape. M27 trees mature very quickly, so you do have to pay attention to training in those first few critical years. The best method of training for M27 trees is as a centre-leader, in other words, a bit like a Christmas tree. Buy the trees as 1 year bare-root "maidens", plant them beside the post in the autumn and, although it sounds counter-intuitive, immediately cut the tree down to about 40" high (about 1m) - make a sloping cut just above and away from a bud. The following spring the top bud will grow and become the central leader, and other branches should radiate out below. As these lateral branches grow upwards and outwards, tie them to the horizontal - this is a key part of the training. Ideally you want about 4-5 branches forming the first whorl at around 3ft above ground-level. Note that apart from that initial cut there is no pruning, the emphasis is on training.
Alternatively, buy 2-year container-grown trees - these will have had initial training and pruning in the nursery so you won't need to do anything yourself except plant them.
In either case, after the first couple of years, once the tree is mature, there is very little further pruning or training to do.
So, if you want to grow lots of different apple varieties in a small space, have a think about the M27 rootstock.