Why won't Karen Azelea's grow?

jellicoeMay 3, 2006

I'm trying to grow some Karen's Azelea's in a large bed under a shagbark hickory tree, along with pulminaria, heuchera, daylillys and vinca. Everything else is doing beautifully. They get several hours of late afternoon sun. My landscaper replaced 3 of the 5 last fall (after 1 year and nearly total leaf loss) and this spring 4 of the 5 look like they are dying, though a number of the bare branches have flowers on them. You can still see the outling of the original soil from the container, as if the growing soil is not blending at all with my own soil. They also seem to have quite a bit of winter heave pushing them up. I see this azelea in other people's gardens with lots of green leaves and covered with flowers in season. I have mostly bare branches or spotty leaves. What is going on? Am I doing something wrong? I think my landscaper is going to replace them one more time, but she is also confused. Any advice is very welcome!

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bboy(USDA 8 Sunset 5 WA)

Rhododendrons and azaleas have special soil requirements, in noticing the contrast between the soil your azaleas were grown in and what you have them planted in you are probably seeing the problem. Maybe you even have alkaline clay soil, not very suitable at all (did the neighbors plant theirs in special beds?).

    Bookmark   May 3, 2006 at 10:48PM
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morz8(Washington Coast Z8b)

Janice, do I understand your post correctly that both times the azaleas were planted in Fall? I have no experience in a cold climate to share, but I do find the suggestion that Fall planting in Illinois may not give rhododendrons and azaleas enough time to establish before ground freezes, then winter takes its toll...earliest Spring may work out better if you are willing to pay attention to summer water needs.

If others around you are growing them casually and not going to extremes to make them thrive, you can probably assume you have the right conditions for them. Good drainage but moist soil...sounds odd, but they won't take soggy saturated soil any better than they do drought. Shall we also assume your landscaper knows to rough up or root prune that rootball before installing them in the ground, paying careful attention to making sure they are no deeper
(preferably slightly higher) than they were growing in their nursery containers?

    Bookmark   May 4, 2006 at 12:11AM
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rhodyman(SE PA, USDA Z6)

I agree with bboy and morz8. Azaleas need a moist, well-drained acidic soil. The other plants you mentions all thrive in a "sweet" (non-acidic) soil. You may have to use a raised mound or raised bed approach with an amended soil that is acidic. I like to use bags of peat humus to plant my azaleas.

Fall is a poor time of year to plant in an area that has frost heaving. It doesn't give the plants enough time to get established. Plant heaving is also a sign that the plants were not mulched enough. The best way to avoid heaving the first year is to wait for the soil to freeze, then add mulch to keep it from thawing out. Also, without mulch, the root temperatures will get too hot in the summer.

A third consideration. Azaleas have shallow roots and don't compete with other plants. The Vinca may be a problem, if not now, in a couple years. It is not a good ground cover for azaleas. Its roots are too aggressive.

Last, too much fertilizer or fertilizing too late will keep them from hardening off for the winter. In general, evergreen azaleas take about 3 years to achieve their rated hardiness, which for Karens is -25F. The first 3 years of being field planted, I recommend using a wind break and sun break in the winter.

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

    Bookmark   May 4, 2006 at 8:30AM
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dwk001(z5 IL)

The problem could be exascerbated by sensitivity of many rhododendrons and azaleas to the plant "toxin" juglone, produced by the roots and other tissues of many (but not all) kinds of walnuts, hickories, pecans, and their relatives.

    Bookmark   May 4, 2006 at 6:17PM
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rhodyman(SE PA, USDA Z6)

Juglone (5-hydroxy-alphanapthaquinone) is produced by the roots of Black Walnut (Juglans nigra L.) and Butternut (Juglans cinerea L.)

Here is a link that might be useful: Juglone poisoning

    Bookmark   May 5, 2006 at 11:27AM
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