New, improved Japanese maple blog

A new, improved Japanese maple blog has now been set up and can be found at the Japanese maple guide.

Pruning a japanese maple - don't be scared!

Pruning a Japanese maple requires no special skills and is quite straightforward providing a few basic rules are followed. For older trees much of the pruning will have been done already by the tree itself. Smaller branches in the centre of the tree and branches low down on the trunk that are shaded by others will die back naturally and older trees will form the proper shape of their own accord. Pruning a Japanese maple tree is then essentially one of maintaining the shape and dealing with any straggly or lop-sided growth.

So, how to prune a Japanese maple? Firstly, try to visualise the shape you are hoping to achieve and cut to that imaginary line. If there are one or two strong growing branches that need to be pruned, cut back inside the line by a few buds as there will be more subsequent growth from these branches than other, smaller branches. A second cut can be done in the summer when light trimming of the subsequent growth will bring the tree back within your imaginary line.

When to prune is quite critical and many commentators will say you should prune Japanese maples in the spring. This, unfortunately, is bad advice as two things will happen if done at this time. Firstly, the cut surfaces will bleed. This attracts insects and is a possible route of entry for fungal infections. Painting the cut doesn't help as this just traps fungi and bacterial spores that have landed on the surface the moment it was cut. Secondly, the sap that is coming out would have been used to produce new growth and the amount of growth produced will be reduced, depending on how hard you have pruned.

The optimum time to do any major pruning is going to be between November and January but ideally it should be done before Christmas. If you have very cold winters and new growth doesn't appear until April, then January and early February is a safe time. In areas with a mild winter, root activity never fully stops and as a result sap bleeding can be quite profuse depending on how vigorous the plant is. A light trim can be done once the tree is in growth by pinching out the tips after the first two or three pairs of leaves have developed.

Slightly more substantial trimming of your Japanese maple can be done in the summer once the new shoots have lignified, ie, ripened. The plant is now concentrating on building up food reserves in the roots so sap bleeding is not an issue but remember that the plant needs the leaves for energy production so try to keep shoot removal to the minimum. Far better to wait until winter when the branch structure can be clearly seen and you can visualise your cutting line better.

One suggestion you will sometimes come across is to prune inside the tree 'to let the air in'. A moments thought will realise the fatuity of that statement; the centre of the tree does not exist in a vacuum and air is always going to get in! As I mentioned at the beginning, if the leaves of a particular branch are not getting enough light because it's being excessively shaded, it will die back of it's own accord.

Sometimes, when branches cross and start rubbing against each other, the temptation is to cut one of them out. A better course of action, especially if the bark has been rubbed off from both branches, is to tie them together. Two things will then happen; the obvious one being that they will stop rubbing. The second thing that will happen is the branches will callus and fuse together resulting in stronger growth of the dominant branch. This will normally take one or sometimes two seasons, after which the weaker branch can be cut back to the joint (but only in winter!). Polythene tape or insulation tape can be used but remember to replace it every few months or it will cut into the bark.

Heavy Pruning of a young plant should preferably be avoided for the first few years to allow it to build up strong root system but during this time it will be amenable to basic shaping depending on what type of plant you've purchased. Upright, spreading or low growing dissectum types can be encouraged to form specific shapes at an early age by appropriate staking and trimming rather than allowing them to become too open and sparse.

If you want any more information on pruning or any other aspect of their care, visit Growing Japanese maples

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Mycorrhiza in the garden

I was probably overly harsh on the subject of Japanese maples and mycorrhiza on Friday. In practice, some benefit can be obtained from mycorrhizal treatment but overall, the difference in growth is going to be marginal, assuming that you have a healthy plant to start with. What mycorrhiza can't do is revive or improve the health of a poorly performing maple. As far as the soil microflora is concerned, boosting bacteria numbers and variety will have a far more impressive effect on the overall well-being of your Japanese maple and this is a subject I'll go into in more detail in a future post.

The reason mycorrhiza have little effect on maples is due to how they originally evolved and the types of plant they developed a symbiotic relationship with. Although it's not immediately apparent, the fine feeding roots of a Japanese maple are covered with a mass of root hairs. If you grow a seed and the initial root hits a small air pocket in the growing medium, the root hairs are easily visible. Under normal growing conditions, if you pull up a maple you won't see anything as the root hairs will be within the soil or are easily pulled off. You can see a more obvious picture of root hairs on something such as a lily bulb, particularly the roots that grow above the bulb from the base of the stem.

Root hairs serve the same purpose as mycorrhiza and specifically arbuscular mycorrhizae, as these are the symbiotic fungi most closely associated with garden plants. The root hairs penetrate the soil and provide the plant with it's nutrients in the same way as mycorrhiza do and no symbiotic relationship is required for the plant to perform 100%.

The root hairs also serve another purpose and that is as a barrier to fungi, good or bad and inoculating the soil will mean the fungal hyphae can't reach the roots and develop within them. This barrier to mycorrhiza is only present in plant species that are relatively 'new' and have developed more sophisticated forms of nutrient uptake. Acer palmatum is a very 'young' species in terms of evolution and is still unstable. This manifests itself in it's inability to produce offspring that look identical to the parent; sow a thousand seeds and you will have the majority of them unique in leaf shape and form. They may all look very similar, either red or green, but there will be subtle differences in shade of colour, the serration on the lobes or leaf size.

Where mycorrhiza can make an appreciable difference, however, is with the more 'primitive plants and I shall, hopefully, cover that tomorrow, as this type of plant is the reason for the existence of mycorrhizae.

Mycorrhiza, nature's root extensions

Looking through all the information I have on mycorrhiza, to put in this post or spread it over several days would produce an impossibly long article. For the moment, the best introduction I can give is to send you to the following site: Introduction to Mycorrhizas

I'll discuss how best to manage mycorrhiza in the garden tomorrow and provide some information for growers of exhibition vegetables.

What not to buy

Following on from yesterday's post, I thought it would be a good idea to illustrate some typical aphid activity. If you click on the picture, I've put two larger versions on my web site. You'll notice they're starting to congregate at the base of the dying leaf stems and around the base of the current season's shoots. These are all ideal hiding places to lay eggs; not to get away from you but to protect the eggs from birds. Again, the same advice as yesterday; kill them before they kill your plant! And yes, small plants can be severely weakened in the spring and can die.

When I'm browsing on the Internet I sometimes suffer from WILF (what was I looking for!) and I ended up on a Technorati page listing that had links to some Youtube videos. I clicked on one of them and it turned out to be a clip from Garden Time tv and an interview and product plug with a garden centre owner describing some Japanese maples. So far, so good, although I never take any notice of people telling me a particular variety is only going to get to a specific height; a good rule of thumb: take the height and double it!

What they were advertising at the end illustrated the danger of jumping on a bandwagon without having the facts to back it up. In essence, they were promoting mycorrhiza as a 'must have' for improving the quality of your Japanese maple. The product contained lots of different strains that would, apparently, all help to make your maple healthier and more vigorous, protect it from soil-borne diseases and generally act as a universal panacea.

The reality, however, is somewhat different. Mycorrhiza have little or no effect on the well-being of your Japanese maple and applying beneficial fungi to them will not be cost effective.

As a professional nurseryman, I started using mycorrhiza in the late nineties when reliable strains first became available, although having said that, there was a lot of rubbish about just as there still is and considerable testing of their effectiveness had to be done. Initially, it held some promise, at least in theory and I started using it extensively but more research and field trials showed that, on it's own, it was doing nothing. There were other elements of the soil microflora that had a far more important role as far as Japanese maples were concerned; specifically, bacteria and some of the most important of these are Azotobacter, Pseudomonas and Rhyzobium.

The subject of soil microflora is an important one, not just for Japanese maples but for most garden plants. I'll come back to this subject next week as there is a large amount of information that can be of great benefit to all gardeners and I'll also have a secret tip for growers of exhibition vegetables that probably no one, outside of a laboratory, is aware of.

Need more information? find it at growing Japanese maples.