astilbies and cannas - Knowledgebase Question

kalamazoo, MI
Question by dfgquilter
June 17, 2007
Hi.... I REALLY appreciate all your help in the past few months!!!!!

Several times I have bought huge astilbies with about 9 inch gigantic blooms on them. However, I have never been able to get much of a bloom on any of them.. or about a few 3 inch whimpy ones.
What am I doing wrong? They are on the north side and get 1/2 day of sun and are in good soil. I think I put cow manure in the soil too.
What else do I need to do?

Cannas. I have a few big ones sprouting OK in my pots outside.
However, I have a lot of them that are doing nothing. The roots are damp but the tops seem dry. Should I put Miracle Grow on them or do anything to encourage them? Should I soak them like they do with dahlia tubers or will that rot them? Do they rot easily like dahlias?
Are the

Answer from NGA
June 17, 2007


Glad we've been helpful in the past - feel free to drop by anytime!

It sounds as though you're doing everything right with your astilbes. They prefer growing in partial shade and like rich, moist soil. If the foliage looks good but they simply are not flowering, especially in your well amended soil, I'm wondering if the soils pH is a little too high? I grow them in acidic soil and they bloom wonderfully for me. If your soil is alkaline, that might account for their behavior. When soil is too acidic or too alkaline for a plant, although the nutrients are there, they will be bound up in the soil and unavailable to the plant roots. You might want to check the pH with a test kit. If it is much higher than about 6.5, you may want to lower it.

Cannas rest but they never really go dormant so they shouldn't ever go completely dry (the way dahlia tubers do). Soaking isn't necessary, because they should be stored in moistened peat moss which will keep them hydrated. Here's how:
After digging the clumps of bulbs, remove soil by shaking or rinsing with water.

Divide clumps into 3-5 eye bulbs.

Place clumps in a plastic bag with several air holes, adding peat moss or rice hulls to maintain moisture balance.

Store in a cool, dark place between 45 and 60 degrees. Do not allow bulbs to dry out completely; this is the most common cause of failure.

So if yours are looking puny, it's possible they dried out too much during storage, or they were divided into clumps which were too small. They should live, but they may take a year to develop enough foliage to store enough energy for flowering.

Don't give up on your plants. Keep giving them good care and they should reward you with flowers next year.

Best wishes with your garden!

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