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Pruning
Common sense could tell you that the best time to prune any tree is when it's in it's peak health. This really is true of the Chinese elm as well, and the best time is in spring or early summer. The elm grows quickly at this time of the year so be sure to keep up with the trimming. It doesn't take very long for the Chinese elm to develop great branch ramification. After four to five sets of leaves have grown out on a new shoot, cut the shoot back to the first 1 or 2 sets that are nearest the branch or trunk of the tree. How frequently you prune will vary depending on just how quickly your tree grows and when it starts to appear out-of-shape. You may cause your tree to become weak if you happen to cut too much off in the course of any given pruning. But don't be so timid about pruning that you simply allow your tree grow to be out of shape. This technique of pruning ought to be continued througout the growing season, and when carried out properly it results in the tree maintaining it's vigor.
Re-Potting Your Chinese Elm Bonsai Tree
How frequently you need to re-pot your Chinese elm is dependent upon several factors among them how old the tree is, how big is the tree, and what condition it's roots are in. A more youthful tree may require transplanting every year. If the tree is 5 years old or older then it really only needs to be re-potted every 2-3 years. Repotting happens to be an essential procedure which often requires root pruning, and must be done correctly. Early spring is the best and safest time of the year to re-pot and prune the roots of your Chinese elm. You shouldn't re-pot your elm tree less than 30 days after you've pruned any of the tree's limbs or new shoots. This waiting is done as a way to minimize the amount of stress that the tree must endure.
When and How to Prune Your Chinese Elm Bonsai Tree's Roots
Plants require new root growth in order to maximize food and nutrient absorbtion. The optimum time of year to do ambitious root pruning would be the winter or very early spring when the tree is dormant.
It is actually good for the plant to have it's bigger, aged roots cut off because they'll be replaced by younger, smaller roots which do a better job of taking in water and nutrients.
The first step in this process is to remove your bonsai from the pot. Once the plant has been taken out, you must pull the roots outward in a radial-type pattern.
After the roots have been separated you will shorten the plants storage roots and get rid of any leftover part of the plant's tap root. The smaller, finer roots are the ones that you need to keep so don't cut any of these. You don't want to need to fold any of the plants roots so as to get them to fit when you put the root ball back in the pot so trim them keeping that in mind. To be on the safe side never remove more than one-half of the roots, particularly if root pruning is being done during the dormant season.
