FW: FW: [AZ] [this is from the ASK US page, so please send me a CC]
This is a reply from Cliff Pottberg, An Oconee Bonsai expert
It sounds as though you have a fun project ahead of you. There are a number of considerations you must keep in mind, though.
You've understood several of them, so I'll discuss them first and then add a few more.
Your primary concern, I take it, is how to most safely repot the azalea/rhododendron into a better and/or smaller pot which is better for cultivation of bonsai.
There are a number of questions you must ask yourself before doing anything. The first is: what is the size of the aboveground plant relative to the size of the root mass? I assume that the root mass fills its present pot, and if the plant hasn't been in that pot for many years and hasn't become totally root bound, then the plant's trunk size is probably between 1/2" and 1 1/2" thick, though the trunk may be thicker than this estimate because of the amount of foliage you mention that is on the plant.
You can tell the health of the plant by the color of the roots at their tips. Light or white tips indicate that many feeder roots are alive and will make your repotting easier and safer.
If there are no white roots but the tree seems generally healthy, it is likely that it is just deep in dormancy. In that case, the very best time to repot is just when the plant begins to break dormancy; just as the tree's roots begin to show a color change at their tips and before any growth shows on the aboveground part of the plant. Generally, you will be able to tell when all this is happening or about to happen, by the swelling of the buds on the plant. Here I am talking about the vegetative buds as they swell. Flower buds in general swell and grow before there is a vegetative growth. In fact, many azaleas and rhododendrons flower while they
are otherwise still fully dormant. Here, it depends on the genus (rhododendron, azaleodendron or azalea), the species, the variety, and where the plants are growing (deep south or farther north).
You didn't mention your location, but since this may be a rhododendron, I assume you aren't located in the deep south, where few of them grow well. I assume it also because of the size of the leaves, which indicate it is a dwarf rhododendron as well.
You also didn't mention the kind of potting soil the plant is in, and since you've had it a while, you must be doing something right.
Just remember the primary considerations for the soil are that it:
is slightly acid
has good moisture retention but not so much as to stay soggy
has good porosity
Any good horticultural text can explain how to create such a potting soil, or where to procure some.
One thing to add here is regarding the creation of a drainage layer at the bottom of the pot. Usually that's counter productive and results in a double layer of saturated soil, thus reducing further the amount of unsaturated soil that the plant roots can make use of in the pot. This is particularly important when planting into a bonsai pot, which is typically quite shallow.
Unless you know the criteria of a good soil to use as a drainage layer, don't use one.
Regarding removing the buds, I'd suggest you don't remove any vegetative buds, only flower buds. However, if the plant is healthy, you definitely might want to keep some so as to enjoy the bloom.
When you repot, and are removing some of the top foliage and/or roots (to make the plant fit in the pot), do so that you don't cut more of the roots than you do the top. They are in their balance you find them because was a healthy balance
In answering again your specific question about when to repot the plant: it is just as the roots begin to show the smallest bit of new white growth on the tips of the feeder roots. To know this, you may have to carefully tease the roots out of their present container (which you'll have to do eventually anyway when you repot the plant)
If, by knowing your general climate you can know when plants are beginning to break dormancy, that will be close enough so you don't have to check even more closely as to timing.
Hello Im hoping to get some advice I have been learning Bonsai cultivation and in it 2 years My favorite is Azalea. I have on in paticular that I dug up from my neighbor and it was 10years old it has been in a 5 quart pot to let rest and establish itself for a Bonsai pot in order to save the tree I was told to remove the buds in order to reserve the energy of the plant and focus on root development. the apex is approx 2 feet wide and has well over 40 small buds this type has small leaves all one quarter inch in size and I believe to be a rhododendron and not a true azalea. should I do now while it is the end of january. Thank you for any advice. Todd