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Why Did My Plant Die?

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Archive
Here's the Vast and Cavernous Archive of Enquiry that the Doyenne has already answered. Good clean fun for the whole family.

This week's questions:

  • Juniper Too Old For New Tricks
  • English Walnut Mulch
  • Pillar Vines
  • Bloomless Rhododendron
  • Ailing Japanese Maple
  • Pearless In Portland
  • Basic Camellia Pruning
  • Hacked Princess Bush

    Juniper Too Old For New Tricks

    Dear Doyenne,
    We live in Newtown, Connecticut in a house built in 1691. The soil is rich and very loose and has been cultivated for generations. I have a very old juniper which seems to have a disease. Two summers ago I began cutting it back and exposed its 7 inch diameter trunk. I've just noticed that much of the old growth is turning brown and there are touches of white powder on the limbs and trunk. Can you give me an idea of what it might be?

    Thanks
    Joan

    Joan,
    Junipers and other conifers are notoriously bad candidates for renovation pruning. They do not grow back well from old wood, leaving big bare patches that seem to take forever to fill. I wouldn't be surprised if, when cutting to expose the trunk, that all those branches previously in the shade are now exposed to high amounts of light: hence, the browning of the old foliage. It also could be that with the pruning, the resources in the plant are now going to the new growth (and cone development) that previously went to maintaining the old growth: hence, the dieback.

    I doubt whether the white powder is disease. My own gurus tell me it's more likely to be resin deposition, which junipers have in abundance, especially when under attack.

    At this point, I suspect less is more: just prune out the dead stuff and let things take their course.

    Hope this helps, KL

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    English Walnut Mulch

    Dear Doyenne,
    Do you know if English Walnut leaves are good to use as garden mulch?

    Thanks,
    JP

    JP,
    English walnut (Juglans regia), much like the native black walnut (J.nigra) contains toxins that may be harmful to other plants -- particularly members of the Solanaceae family, which includes tomatoes. When using the leaves as a mulch, make sure they are very well composted before applying around the base of plants.

    Best, KL

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    Pillar Vines

    Dear Doyenne,
    I live in a Seattle suburb (USDA zone 8) and just moved to a new location. We have a small patch on the North side of our house which is in the shade most of the time. Its also rather damp, but I am working on improving the drainage. What could I plant there that would thrive? I might like a flowering vine that would climb the pillars of the front porch but don't want something that will take over. Would Clematis work?

    Douglas

    Douglas,
    A clematis would work very well in that area provided you add a bunch of compost to improve the drainage. The evergreen C. armandii is especially well suited to moist areas (though it will need pruning since it likes to grow). Another evergreen idea is the vine, Holboelia corriacea; I'm thinking of using this one in just the same situation. Akebia quinata is a lovely plant with great foliage, as long as it isn't too happy (i.e., exuberant). I will that that your open north facing site is ideal for many vines.

    Have fun, KL

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    Bloomless Rhododendron

    Dear Doyenne,
    Why would a rhododendron not bloom? It has exceptionally dark green leaves, with some yellow spots (chlorosis?) and scant amount of chocolate brown dry edges (phyto-type blight?). It is growing in Marin County, California. Planted in "rhododendron" soil from the nursery and sun protected.

    Cheers,
    Jeannie

    Jeannie,
    When a rhododendron refuses to bloom, it's a good bet it's experiencing some kind of stress. It could be that the plant is not getting enough water, since rhodies have shallow roots that dry out quickly. You need to strike a balance between the plant drying out completely and not being overly soggy (think of the cool forest floors under the redwoods; those are the ideal conditions). The problem could also be that the rhodie is too exposed to hot sun and/or drying wind. Some forms are more sensitive to adverse conditions than others. Ultimately, I'd recommend a good soak, then mulch the plant with compost, but don't allow the mulch to touch the plant's trunk. Finally, feed it with a handful of cottonseed meal, an organic slow release acidic fertilizers that all rhododendrons love.

    Best of luck, KL

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    Ailing Japanese Maple

    Dear Doyenne,
    I garden in Cincinnati, Ohio. Summer, 1999 I planted a 3-4 foot Japanese maple. The first winter the leaves turned brown and fell off. In the spring it leafed out beautifully. This past winter the leaves turned brown but did not fall off. This spring there is one new branch near the bottom with leaves. The rest of the tree is bare. Are the upper branches dead? Should I prune it or see if it leafs out again next year?

    Thanks,
    Margie

    Margie,
    First let me say that Japanese maples are listed as hardy to Zone 5. With that in mind, it could be that some combination of events (summer drought, cold winter, late frost) might have conspired against your tree. Certainly the brown leaves hanging on through the winter is a sign of something being awry, as is the fact that the tree hasn't leafed out. To determine whether it's even alive, give it the old fingernail scratch test and see if it's still green. Re: that new branch. If it's come up above the tree graft (Japanese maple cultivars are grafted on to straight species understock), it's still the maple you purchased, but you'll have to judge whether it's worth keeping. If the branch came up beneath the graft, all you've got left is a straight species which is unlikely to thrill you. Sorry I don't have better news!

    Best, KL

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    Pearless In Portland

    Dear Doyenne,
    We live and garden in SE Portland, OR and noticed that our pear tree had a profusion of flowers up until the driving, hard rain this week. Many of the blossoms were knocked off the tree and today I noticed the ones that were left are all shrivelled and dark. What fruit had started is misshapen and nasty looking.

    Was it the rain, do you think? Or are we looking at a bug or blight of some sort?
    Susan

    Susan,
    The irregular weather that we've had this spring -- hot, then cool and wet, and now hot again -- has not been ideal for trees to set fruit. You're right to assume that the rain may have affected pollination; no doubt substantial amounts of pollen were washed away, which seriously inhibits fruit set. Just give the pear a good deep soak occasionally through the summer, and I mean deep: put the hose on a trickle and leave it there for several hours -- this encourages the roots to go deep. I'm sure it'll pull through, perhaps even this year.

    Best, KL

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    Basic Camellia Pruning

    Dear Doyenne,
    How and when should I prune a camellia?

    Thanks,
    Kathryn

    Kathryn,
    You can prune camellias after they're both finished blooming and the new growth has stopped growing. You have a 10 week window before you're affecting next year's flowers. Standard pruning practice: good clean cuts with a sharp saw at an angle of 45, pointed down. Bear in mind that camellias sprout from dormant buds on the wood, so you can cut wherever you want. Stand back often to make sure you're creating a well-shaped shrub.

    Enjoy, KL

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    Hacked Princess Bush

    Dear Doyenne,
    When I was doing my winter pruning, I took some friends' advice and pruned back my princess flower bush to get a handle on the long and spindly branches. So I cut it back, leaving about 1 to 1.5 feet of branch shooting up out of the soil. And now, four months later, the plant has this whitish mucus that's seeping from the top of the stumps of the main branches I left -- and no new growth. The plant sits in a large pot in my back yard in potting soil, and it gets about 6-8 hours of sun (the sunniest part of my San Francisco garden). I don't think it's my pruning methods as I did the same thing to my princess flower bush in my front yard, and that has no seepage and lots of new growth. Where have I gone wrong?

    KC

    KC,
    Sounds like a case of shock. Princess flowers have huge, voracious root systems; in the ground, your plant might have found the resources to regrow its top. But in a pot, it has likely used up all the available nutrients and could find none with which to regroup. In the future, the best way to prune a potted Princess flower is to tip pinch it back gradually, thereby avoiding the legginess that required drastic pruning.You might also fertilize it every time you water with a half dilution of liquid fertilzer. Repotting into fresh soil and then cutting back the plant works well, too, all advice too late to help you now, but at least you know what went wrong. Better luck is ahead! KL

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