rate of growth

sunnytopSeptember 16, 2008

I planted a tiny Northern Lights azalea this past spring that was a six inch twig from Bluestone. It is now about 8 inches tall with a single 2" sprout. It is in a wooded area but the canopy does not give deep shade, it is bright, just not much direct sunlight and not for very many hours. I am worried it is not getting enough sun. I planted it in amended soil of compost and I add additives monthly to keep the soil acidic. Do they normally get off to a slow start? Does it take several years to get established enough to flower?

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rhodyman(SE PA, USDA Z6)

Usually a shady location causes tall gangly growth. I think the plant is just having a trouble getting started. Your adding additives monthly to keep the soil acidic troubles me. Either the soil is acidic or not. Trying to keep it acidic is not a normal struggle. That may be the problem. Usually if the soil is alkaline, a raised bed is used with acidic soil. Alkaline soil would definitely be a reason for the plant to not grow and perhaps die.

Liquid fertilizers for acid loving plants like Miracid are more of a problem than a solution. The liquid acidification is not effective in alkaline soil. The large amount of water soluble nitrogen fertilizer they contain is not healthy for azaleas and can prevent them from blooming.

In a raised bed the soil is normally acidified with sulfur when the soil is prepared. Sulfur is long lasting and only needs to be replenished with a light top dressing every couple years.

Here is a link that might be useful: How to grow azaleas.

    Bookmark   September 16, 2008 at 10:43AM
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I did put sulpher on it in the spring. I think the soil is acid enough around it, maybe the muracid is overkill. My holly and birch tree were ailing and adding soil sulpher did wonders for them all summer long. I am going to trim out some of the tree branches and try to get more filtered light through. Raised bed is not a good idea under shallow rooted established trees I've heard. All soil in this part of the country (great plains) is alkaline. Sounds like azalea might be a waste of time in the central part of the country. I've seen them in nurseries but not a lot of them around. Maybe I should try keeping it in a pot.

    Bookmark   September 16, 2008 at 12:28PM
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rhodyman(SE PA, USDA Z6)

Azaleas are not a good idea under shallow rooted established trees. Azaleas have shallow roots also and don't compete very well.

One way to put a raised bed, and hence azaleas, over shallow rooted trees is to put about 2 inches of gravel down first. Then use something like landscape timbers to define the raised bed. Then place landscape cloth over the gravel and up the inside of the timbers. Then place the acidic soil over the landscape cloth. This allows the original air layer to remain over the trees roots and prevents problems.

The raised bed only needs 8 to 10 inches of soil. But, it must be mulched very well to conserve moisture.

Sulfur works best when mixed with soil before planting. It is very slow acting. In general, azaleas don't need much fertilizer if any at all. I recommend using HollyTone once in the spring around bloom time and at half the rate on the package. If you are trying to stimulate a little growth, then perhaps one application before blooming and one after would be OK, but still at half the rate on the package each time.

Here is a link that might be useful: How to grow azaleas and their problems.

    Bookmark   September 16, 2008 at 12:47PM
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What a neat idea. I've never heard of that method here or anywhere. You say it only needs to be 8-10" deep, but how about diameter? How much spread are these roots going to need?

    Bookmark   September 17, 2008 at 1:06AM
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rhodyman(SE PA, USDA Z6)

The roots will spread out to the drip line, so you need to look up the mature size of the plant and then allow extra. Most of the Northern Lights Azaleas grow to 3 to 4 feet tall in 10 years, so this would be about an ultimate max drip line 4 to 5 feet in diameter. Since air can circulate under the raised bed, I would allow more depth so that you wouldn't have to water so often in a drought condition. I would probably make it 12" deep to allow a safety factor if there was a severe drought when I was away.

    Bookmark   September 17, 2008 at 10:37AM
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