Clethra Alnifolia

getyourleash(z7 Mid-Atl USA)June 9, 2005

Hello --

I think I have made a mistake by planting a hedge of clethra alnifolia along the fence in my backyard. I planted it (last Spring) there for several reasons, but my original goal was to plant something that could handle what I thought was swamp-like conditions and clay soil.

My first problem is that when the clethra came back this Spring, it greened up very slowly and it still is not full-looking. Secondly, how much do these plants love water? This area gets inundated when we have these 3 day rainstorms that soak the backyard. It also sees plenty of water from massive summer rainstorms. In fact, we have seen both in the last week. Is it too much rain? Not enough?

Secondly, I'd like to know how fast these things grow. I see no real increase in plant size and I'd ultimately like a hedge, not just a row of clethra. Also I planted both the pink variety 'Hummingbird' and the white. Would this affect anything? Did I blow it? They just look like weedy seedlings.

I cut off all dead wood (there was a lot of it) and fertilized with an all-purpose fertilizer. Was that wrong?

I don't want to rip these out because they look like hell. I'm hoping someone will say it takes years for them to fill in and just have some patience. Or, is clethra just a scraggly, ugly plant?

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lycopus(z5 NY)

I wouldn't call it ugly but it does tend to develop an irregular shape. Pruning is needed to keep it in shape. It's also late to leaf out as you've already found. Wet soil shouldn't be a problem since I've grown it in soil that was constantly saturated and it was very happy. I think Clethra is best from mid summer on since the flowers make up for it's poorer attributes and it can develop some good yellow fall color.

    Bookmark   June 10, 2005 at 2:11PM
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viburnumvalley(z5/6 KY)


In case you were misled, Hummingbird is a white form, and not the best one. There are others, like Sixteen Candles that tend to "make up" better as young plants. Ruby Spice (among 5 or more others) is the pink form that has performed the best here in central KY, not fading to white like the others.

Agree with all Lycopus' points, and that generally you are experiencing what young Clethra alnifolia act like. You didn't say how big/small the plants were that you started with. 3-5G pots are pretty good looking plants most places I've seen them (24-30" tall and full). You should withhold pruning on these till they are well-established (based on vigorous new growth extensions) and then prune for shape.

Individually, Clethra can look leggy but it also wants to be a colony of stems if it's happy where it's growing, so this will add to foliage around the base. My brush with Clethra in its native haunts was on Cape Cod, along the national seashore in a swamp with Nyssa, Viburnum dentatum and the like. Pretty wet sandy clays. It was 15' tall and they had to whack it to keep it off the boardwalk through the woodland.

The cow's already out of this barn, but a freer root run always helps with more vigorous growth and quicker establishment. If you dare, loosen more soil in the future hedge line, and topdress with compost every year to increase organic matter in your clay soils. All purpose fert is fine, but a soil test can lead you to provide what's needed, if anything. If you are on the alkaline side, soil sulfur or iron sulfate can steer the pH back to the acid side of 7.0 where Clethra would rather be.

    Bookmark   June 11, 2005 at 8:40AM
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getyourleash(z7 Mid-Atl USA)

Thank You for your kind reply. I am slowly becoming less concerned about my clethra, as I made one intial mistake in my description of the clethra to you. My pink variety is 'Ruby Spice' which came highly recommended to me. The leaves have become much more full since my intial posting. Also, I'm being reminded of why I chose this plant-- I love that dark green color on the leaves!In addition, spikes are beginning to form, so it must have needed the fertilizer boost. It may also be that it just needs watering when we don't have a regular torrential rainstorm or flood in the yard! I gave them a nice big drink of water when I trimmed them and altogether look improved. I can't wait for the flowers!

Here is a link that might be useful: Clethra Alnifolia 'Ruby Spice'

    Bookmark   June 11, 2005 at 10:18AM
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i have found clethra to have a very regular, symmetrical shape. mine that are in full sun are leafy all the way to the ground. i have them growing in shade, in sun, and in sun/shade. all are nice plants. its one of the cleanest native plants out there, they don't look messy like some other shrubs. i did buy some from franks nursery a couple years ago that were very slow to leaf out and they were more woody and less leafy than my others. i think if i cut them back it will rejuvinate them. clethra have a nice yellow fall color too.

    Bookmark   June 12, 2005 at 12:36AM
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In nature, clethra grows in very swampy areas. It also likes acid soil. Among its favorite companions are spicebush. I don't know how it would take to clay.

    Bookmark   June 12, 2005 at 9:15AM
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fatso(z5 OH)

I had it in some heavy clay soil and am not sure how it really did because rabbits chomped it every year. I finally had to move it to raised beds to protect it from them.

    Bookmark   June 12, 2005 at 3:43PM
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joja(Z7 Md)

Does Clethra Alnifolia need any light . . . the store sign said "shade" but the tag (I now see) says "full to partial sun," which it will not get in my urban Baltimore garden.

    Bookmark   April 12, 2009 at 11:38AM
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loris(Z6 NJ)

I think Clethra Alnifolia will be ok with shade as long as the shade isn't too dense. I went a bit overboard with this plant a few years ago, and bought about 6 of them over a period of a couple of years. Most of them are fine, but the one or two I had in very shady areas or dry areas didn't make it.

    Bookmark   April 12, 2009 at 8:18PM
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just planted ruby spice and love the look...they were 3 gallon size. we just had a heavy downpoor and the "leggy limbs" are bant back and look as if they need to be staked. is this normal? should i be concerned? should i prop them up with something in the morning? they aren't broken, just flopped over and laying over on the ground...will they bounce back to normal after rain???

    Bookmark   May 15, 2009 at 9:47PM
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I've seen Clethra growing wild in pretty heavy shade in the woods south of Boston. The plant was quite leggy, just a few stems, and leaning hard towards the path where there was more light, but it was blooming. It doesn't require standing water to grow successfully, but if that's what you have Clethra will grow happily in it if it gets enough light and the soil's okay for it.

    Bookmark   July 11, 2009 at 2:04PM
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I have a garden plan that calls for clethra alnifolia Summersweet. It says in the book that it can take full shade but after reading up about it it doesn't look as if it will do well in full shade. I am looking for something for the north side of the house in front of my front porch. So it is mostly shaded for the whole day may get 1 hr of sun or so. I'm just not sure if I should give it a try or is there something that might be better in this area (we have sandy soil)

    Bookmark   April 22, 2014 at 6:57PM
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getyourleash(z7 Mid-Atl USA)

PinkPeony: I would avoid the clethra alnifolia for full shade. The original post here is very old, I don't even live in that house anymore and had to say goodbye to my gardens there back in 2010. I do recall that the clethra never did become gorgeous or anything close. Perhaps some Calycanthus floridus? It needs the good drainage a sandy soil would provide, has lovely fragrant flowers and can handle true, full shade.

Here is a link that might be useful: Calycanthus floridus or Carolina Allspice

    Bookmark   April 23, 2014 at 3:38AM
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Thanks for your advice I will check that out.

    Bookmark   May 7, 2014 at 4:06PM
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