New dahlia plantings have yellowing leaves?

annewaldron(SoCal,10)November 18, 2005

Not sure what the problem is- I've watered only 3 times in the last 8 days, so for once it's not an issue of overwatering! (has been a problem in the past) Just the bottom leaves are yellowing. And this is only happening in one of my flower beds...the others have nice green leaves.

(They dropped their petals within the first 2 days of my planting them, but I was told this would happen and that they would be back in the spring.)

Any ideas what could be wrong?


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tapla (mid-MI z5b-6a)

I don't know much about your climate, Anne, but yellowing of older leaves can signal several things. Mites usually attack the older leaves, which would be the lowest, and favor those on the shadiest side. Nitrogen is quite mobile in plants. If there is a N shortage in the soil, plants rob N from older leaves to use in building the newly emerging leaves. Of course, there are other causes - watering issues, over-fertilizing, pH problems, insects other than mites, etc.

Did you mulch the bed heavily with a wood product, or mix last years woody mulch into the soil before planting?


    Bookmark   November 18, 2005 at 10:18PM
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jean001(z8aPortland, OR)

"Tis the time for them to go dormant. So, avoid keeping them too moist.

As you were told, they'll be back next year.

    Bookmark   November 19, 2005 at 10:11PM
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I did mix old mulch into the soil, plus some low-numbers fertilizer (for new plantings), plus some gypsum (recommended by the nursery to aid in drainage, since that has been a bit of a problem for me). They definitely look like they're on their way out, so I will remain hopeful for the spring...

    Bookmark   November 20, 2005 at 3:31PM
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tapla (mid-MI z5b-6a)

As I mentioned, I don't know much about your climate or how plants behave there. Jean's much closer to 10 than I, so perhaps her observation that it's normal for plants entering dormancy is accurate. Here, they bloom & stay green until frost bites them.

Regardless, it's still good to know that wood products mixed into soil can tie up Nitrogen. Hardwoods and those that contain sapwood (wood other than bark) are more likely to "rob" soils of N. The size of the pieces also has an impact. E.g. sawdust incorporated into soil can cause a severe temporary N shortage but large mulch nuggets of conifer bark placed on the soil surface will have minimal impact.

It's possible that some additional N might be required to insure good plant vitality. Can't tell from here, though. ;o)


    Bookmark   November 20, 2005 at 4:16PM
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