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Why Did My Plant Die?

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

This week's questions:

  • Asymmetrical Rose
  • Diseased Peony
  • Never Rototill Tree Roots!
  • Stunted Lilacs and Flowerless Crabs
  • Hydrangea - Heal Thyself
  • Another Stressed Japanese Maple
  • How to Kill a Rosa Rugosa

    Asymmetrical Rose

    Dear Doyenne,
    I am new to the world of roses and have recently planted a rose bush in my front yard which is yielding magnificent flowers. The bush is growing asymmetrically with one side far taller than the other. I don't want to lose the extended growth. How can I graft this part into a new plant?

    Sincerely,
    Isa

    Isa,
    Grafting roses is difficult, especially for a beginner. Quite frankly, the cutting will probably not take. You're better off cutting back the erratic growth and making the plant more symmetrical, if that's your preference. Roses grow quickly and pruning helps to promote new growth and flower buds.

    Enjoy, KL

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    Diseased Peony

    Dear Doyenne,
    I highly suspect that my peonies are suffering from botrytis. Is botrytis treatable? Does a treatment exist that is not harmful to the environment, including the birds, bees and children?

    Thanks,
    Sally

    Sally,
    The typical symptoms of botrytis blight (gray mold) appear on young leaves of peony in the spring on 12" shoots. The leafy shoots develop irregular spots and often wilt. Infections occur in cool, wet weather as leaves are emerging.

    For control, good sanitation is a must. Clean up all infected plant parts and discard (do not compost), as the disease is carried in spores that will reinfect next year's plants. As for general culture, peonies should be planted in well-drained soils, with mulch kept away from the base of the plant. Some gardeners use over-the-counter fungicides in early spring and follow with a second application ten days later. That's your call entirely.

    Best, KL

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    Never Rototill Tree Roots!

    Dear Doyenne,
    About 35 feet in front of my home in Portland, Ore., there are three very mature, well-established maple trees planted between the sidewalk and the street. The trees are great, but I cannot get much of anything to grow in my front flower beds. The flower beds are just about even with the "drip line" of the overhanging trees, although the beds do get several hours of direct midday sun, so they aren't in deep shade. But when I dig in the beds, they are penetrated by a tangled mass of small roots and some occasional larger roots I think must be from the trees.

    So I'm thinking that the tree must be sucking all of the nutrients and water from the flower beds. I've thought about scaling back my expectations and starting over by doing this: Pull up all the plants; rototill the soil and add lots of organic mulch; put in a few plants that can compete with the voracious tree root system -- perhaps a ground cover of some kind?

    Thanks,
    David

    David,
    Please, please do not rototill your maple tree roots! Unless your intention is to kill the trees. If they don't die outright, they will probably become hazardous and, at some point, fall. The roots of these trees extend two to three times the crown diameter, and generally no lower than 18".

    The best drought-tolerant groundcover in this situation is probably epimedium, of which there are many, colorful varieties (early spring blooming). Staying with low-water needs, given that you've got sun, there's a chance you'd succeed with kinnickinnick (Arctostaphylos spp.) and perhaps even low-growing ceanothus (sun will be key here). The list of possibilities is long; I recommend you discuss your exposure with the folks at one of Portland's better nurseries. Just be sure to mulch well, whatever you plant -- this will help the soil retain moisture.

    Best, KL

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    Stunted Lilacs and Flowerless Crabs

    Say Ketzel,
    Two quick questions:

    1. What can I feed my lilacs to make them grow faster? I planted 10 slips about 10 years ago that I received from the National Arbor Day Society and of the six that survived, the biggest one is no more than two feet high and the smallest is still a twig with a few leaves on it.

    2. Why doesn't my flowering crabapple tree flower? When I bought the tree six years ago it was about five feet tall and solid blooms. Now it's a healthy tree over 12 feet high and branched out beautifully, but I seldom get more than a few blooms each spring and this year - nothing!

    Thanks,
    Dan

    Dan,
    First, your cuttings. Whoa, not too impressive after a decade. What type of soil do you have them planted in? Lilacs prefer full sun in well-drained soil. It also helps to amend the soil with leafmold, compost, or something that will loosen the clay soil. Use a balanced fertilizer, something with the numbers close together (10-10-10) to help push some growth on these small plants. I also would dig one up and check the root system to see if the roots are white and healthy (it can always be replanted).

    A couple of possibilities for your non-flowering crab: How hardy is the crabapple cultivar in your area? If you have below normal cold winters or mild autumn temperatures followed by sudden freezes flower buds may be damaged before they have a chance to open in the spring. Pruning at the wrong time is another possibility. Crabapples set flower buds on old wood for next year's growth. If you do any pruning on the tree after July, more than likely you are also cutting off the flower buds. Also, some crabapple cultivars only flower every other year. Finally, stay away from high nitrogen fertilizers (first number); instead use a balanced 10-10-10.

    Good luck, KL

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    Hydrangea - Heal Thyself

    Dear Doyenne,
    I have nikko blue hydrangeas in a shady spot (zone 7) that are growing but the leaves are puckered, twisted and distorted. Few flower heads are being formed. There are mushroom-like fungi growing out of the mulch in that area. Too much water? Not enough sun? Fungus? Help!

    Thanks,
    Karin

    Karin,
    Hydrangeas have a few diseases and insects, and aphids are one of them. Infestations can cause the leaf curl you're describing. Fortunately, as long as the plant is healthy, it can fight off minor infestations; what your bigleaf hydrangea (Hydrangea macrophylla 'Nikko Blue') needs is moist soil and dappled shade. Don't sweat the fungi, it's feeding on the mulch.

    Best, KL

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    Another Stressed Japanese Maple

    Dear Doyenne,
    I purchased a Japanese maple a week ago that is about four feet tall. Two days passed after transplanting, when some of the leaves began to turn light tan. It is most prevalent in one section. I believe that these leaves have been dried by excessive wind, which occurred the day I purchased and planted the tree. I have planted the tree properly and it is kept moist and well-drained. Will these leaves drop and return? Is there anything I can do to promote their return? Also, there are several dead twigs (smaller than a pencil). Can I remove these now?

    Thanks,
    Barry

    Barry,
    Abnormal coloration of the leaves might have been caused by stress such as drought, strong winds or extreme soil pH (preferred soil pH ranges from 6 to 7). Not much to do but wait and see. The rule of thumb about maples is to prune during the dormant season but before the spring sap starts flowing. Pruning during the actively growing season may open up wounds through which fungal disease such as Verticillium Wilt can enter and cause more serious damage. However, if the twigs are as small and as dead as you're describing, I would just go ahead and prune them now.

    Best, KL

    A Diagnostic Plant Pathologist Begs to Differ

    Dear Ketzel,
    I was reading the June 14, 2002 "Ask Ketzel" topics and must correct part of your answer about the stressed Japanese maple. "Pruning during the actively growing season may open up wounds through which fungal disease such as Verticillium Wilt can enter and cause more serious damage." This observation would be true only if the roots were being pruned. "Verticillium invades the root system directly or through wounds caused naturally by root growth through the soil or soil organisms. Once in plant tissues, the fungus produces toxins and invades the xylem (water conducting tissues), moving upward in the plant via spores. Where new spores lodge in the vascular tissue a new infection begins. Toxins produced by Verticillium may kill plant cells at some distance from those directly invaded." from: Verticillium Wilt of Trees and Shrubs, UMN Cooperative Extension FO-01164, Cynthia L. Ash

    Best Regards,
    Ellen

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    How to Kill a Rosa Rugosa

    Dear Doyenne,
    I think I am the only gardener in the world who can kill rosa rugosa! Late last fall I cut back my bushes. I left about six to eight inches. Four of the six plants seem to be happy and are sprouting lovely new growth. The other two are not happy. They have only one tiny bud-like growth each. All six had been very happy for the past two summers. Did I do a deadly deed in the fall? I had to get these lovelies under control, hence by pruning. What should I do?

    Thanks,
    Lois

    Lois,
    Rosa rugosa is an extremely hardy plant that grows on its own roots. Usually shrub roses require very little pruning, except when plants become old and scraggly. Late fall pruning probably exposed more of the crown to winter damage and could be the reason for your winter kill. Wet soil could also contribute to its demise. It is safer to prune in early spring, after winter. Then prune only dead wood. No doubt, you are neither the first nor the last to kill a rugosa! but I will say, I'm impressed.

    Best, KL

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