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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Sarcococca, Soil compaction, Soil testing, Katsura

I have some dying Katsura trees. I created a dry stream to one side of them to redirect water (they don't like wet roots). The owner has put 1-2 inches compost/soil down for some good nutrition and a few tree stakes into the area. There is also landscape fabric (the gray kind rain can get through) and another inch of bark to stop a horsetail problem that creeps in every year.

I am wondering if the the soil around the tree roots has become compacted by rains and is prohibiting the trees from getting oxygen through their roots. The yellow is not in leaf veins like an iron deficiency usually looks; it is almost as if the plant is getting its chlorophyll drained from inside. No bugs present to my knowledge either. I would like to know both what I might do about the soil and about the trees.


Some solutions to the problem may be to take some dead branches or stems to a Master Gardener clinic and ask them to help you identify what could be happening. You may also want to check that the compost is not closer than 4 inches from the trunk of the trees. If it is, scrape it away. For further evaluation of the soil, take a sample from around the tree and send it to a lab for analysis. Our website has a Soil Testing Information section that includes a list of labs that do soil test analysis. Check the area for drainage by digging a hole and filling it with water or let the rain do it and then see how long it takes to drain away. Perhaps you have a layer of hardpan clay underneath the trees that is blocking the drainage in winter and preventing the water from getting to the roots in summer.

A great resource on Katsura trees (Cercidiphyllum japonicum) is Dirr's Hardy Trees and Shrubs: An Illustrated Encyclopedia by Michael A. Dirr. The author notes that the tree requires ample moisture in the early years of establishment. From the book, Trees and Shrubs for Pacific Northwest Gardens, by John A. Grant and Carol L. Grant, Katsura trees prefer deep soils and adequate summer moisture. There is a Katsura planted in the Arboretum on the edge of a pond in soil that is permanently wet and it is doing just fine.

Date 2018-04-05
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Garden Tip

Keywords: Sarcococca, Plant cuttings, Salvia, Lavandula, Propagation, Rhododendron, Gaultheria shallon, Penstemon, Holly, Cistus, Ceanothus

Make new plants by taking softwood cuttings. Cuttings Through the Year, a booklet published by the Arboretum Foundation(available for sale at the Washington Park Arboretum gift shop) suggests which plants to propagate month by month and how to do it. A few September plants include: Rock Rose, Salal, Lavender, Holly, Penstemon, evergreen azaleas, Sweet box, Salvia, California Lilac and many others.

For a tutorial on taking softwood cuttings go online to a Fine Gardening article complete with clear color photos: www.finegardening.com/propagate-your-shrubs-softwood-cuttings

Date: 2006-10-23
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May 31 2018 13:14:08