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Tree of the Month - May 2006: Azalea
By Ken Schultz
Azalea are among the most popular of the flowering species used for Bonsai. In Japan there are entire shows devoted to just this one species. While a truly outstanding specimen can cost over $800, good nursery stock that can be trained into bonsai can be purchased for $5.00 to $30.00. If you like to start cuttings, a select branch from an azalea in your yard can be rooted for free.
Azalea has the unfortunate reputation of being difficult. They aren't, they're just different. If you have grown them in your flowers beds, you are probably familiar with some of their likes and dislikes. My first attempt at keeping an Azalea, as a bonsai was a variety sold for Valentines Day with pink and white-stripped flowers. Being a non-hardy variety, I kept it indoors in the winter. It lived for 4 years before I over-watered it to death. Since then, I have focused on using nursery stock with much better success.
The natural growth pattern of azalea is that of a shrub. This means they want to be a multi-stemmed bush, with weak apical growth, so their lower branches grow vigorously compared to their apex. Growth starts about mid March. Normally, they flower late May to early June. In Japan Satsukie azalea mean "Fifth Month" because they flower in May, the fifth month. Their flower buds begin to develop in August for the following year. Leaves grown in the summer turn color and drop in the fall, leaving a cluster of leaves around the flower buds. Because azaleas are shrubs, they will resist developing the trunk. Interestingly, this trait causes them to easily back bud. Shoots will actually need constant thinning.
The Japanese swear by the use of Kanuma - Acadama Soil to grow azalea in. So far, I haven't tried it but those who have swear by it. I use our soil mix with an extra dose of Zack's favorite organic additive, used coffee grounds. Since azalea does best with a pH of 5.0 - 5.4, the acidity must help. Also, while the soils must drain well, it must retain some moisture, again the coffee compost helps. Peat moss is too wet. The roots of azalea will form a dense mat. If you don't repot them every 2 - 3 years the root mass will become like a brick. Whatever you do, don't leave nursery stock in field soil or straight peat moss. Repotting can be done from mid March until new spring growth gets active.
Fortunately, most insects do not attack azalea. Planted in a flowerbed they can be attacked by black vine weevil. But this is not a problem in a pot. However, fungus and mildew can be. This can be controlled with Orthene or Mifenoxan. Neem oil may also be used.
If you are looking for nursery stock, try "Hino Crimson "or "Coral Bell". Look for small leaves and a good trunk line. Wait until early March to do major root work and repotting the first time. When you select the branch structure you plan to keep, leave a stub. Taking a large branch can kill a section of the bark down the trunk. Similarly cutting major roots can lead to specific branches dying.
Following repotting or significant branch styling, flower bud removal will help the plant's health and will result in vigorous back budding. This is best done right before the buds become active. Remove them at their base. The energy traveling up from the roots will be diverted to dormant buds all along the branches. If you missed an early repotting, it can be done just as the flush of new leaves begins to appear but avoid a major root or branch removal.
Do not fertilize while the azalea is flowering. And meticulously remove all the dead blossoms. If you don't, the plant will send energy to develop a rose hip like seed structure. This will weaken the plant itself. Once you fertilize, growth will be rapid. Allow the stems to put out 6 - 8 leaves (more on weak parts, such as the apex), and then pinch back to two leaves. Thin small extra branches after flowering or in late May if you de-flower the plant. During the summer, you will need to continue the pinching regimen until late July. Stop then to avoid pinching off next year's blossoms. Continue to fertilize unless temperatures are hitting the 90's. Full sun is ok except in mid afternoon. I keep my azaleas in light shade.
In the fall it is ok to remove the inner leaves, they will fall off by winter anyway. This exposes branches to light and air and encourages dormant buds to develop. This improves ramification. After flowering the azalea will send out five branches from virtually every branch kip. You will need to keep only two of them. Usually one of these new branches will be growing straight up. Except for the apex, remove these. Of the remaining four branches, remove the strongest, normally the longest. I usually take out the one growing in a direction that I don't need.
Azaleas also have the reputation of having brittle wood, resistant to bending. Everyone has a story about snapping a branch while trying to bend it. Interestingly it is recommended to wire in late winter or early summer after flowering is done. If you remove a branch, apply cut paste to reduce die back. A clean cut with a very sharp tool is essential. There are many photographs of beautiful azalea bonsai to use as your model. Usually, they are grown in as informal upright "pine" style. I do have a Hino Crimson raft planting. Azalea are also used in Saikai; I have even seen them used to simulate the mountain laurel under story as its mountain pine trees. I have even seen a mini rhododendron ("Blue Gem") in a literati style.
I know this sounds complicated, but the results are well worth the effort. No bonsai collection is complete without an azalea or four or five.