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Dr. Gouin's Bay Gardener |
The best time to transplant azaleas, rhododendrons, leucothoe, mountain laurel, andromeda and blueberries is from mid-August to mid-September. When these species are transplanted during this time of year, they rapidly establish roots into the new soil so they can resume normal growth the following spring without ever exhibiting transplant shock. When these same species are transplanted in the spring, they generally do not resume normal growth until the following spring.
Successful transplanting of these species is highly dependent on soil pH, organic matter concentration, shallow planting and an abundant supply of calcium. The soil pH should be between 4.5 and 5.5, which can only be measured by having your soil tested. The organic matter concentration of the soil should be near 5 percent, which is also measured by soil testing. The roots must be planted as shallow as possible because the roots of these species demand oxygen. Their rapid root establishment depends on readily available calcium, which is generally minimally available in acid soils but can be supplied without altering pH by adding gypsum, (calcium sulfate) at planting time.
If the soil pH is excessive, you will need to amend the soil with iron sulfate for flowers or sulfur if the soil contains adequate amounts of organic matter. However, if the soil is low in organic matter, you may increase the organic matter concentration while lowering the pH of the soil by amending the soil with pine-bark fines. Do not use peat moss. If the pH of the soil is less than 4.5, you will need to add ground dolomitic limestone but only a sufficient amount to raise the pH to 5.5. Because gypsum releases its calcium rapidly, mix one-fourth cup to one-half cup per plant to the amended soil placed around the roots. To prevent the soil from drying out rapidly, apply only one inch of pine bark mulch — or preferably compost — after the soil has been thoroughly irrigated.
You say you’ve misplaced the addresses of soil-testing labs?
- A & L Eastern Agricultural Laboratories ~ 7621 Whitepine Rd., Richmond, VA 23237; 804-743-9401; www.al-labs-eastern.com.
- Pennsylvania Agricultural Analytical Services ~ State Univ. Laboratory, Penn State University, University Park, PA 16802; 814-863-0841; www.aasl.psu.edu/SSFT.HTM.
- Virginia Tech Soil Testing Laboratory ~ 145 Smyth Hall, (0465) Blacksburg, VA 24061; 540-231-6893; www.ext.vt.edu/pubs/compost/452-129/452-129.html (Soil Sampling for the Home Gardener).
- University of Delaware Soil Testing Program ~ 149 Townsend Hall, University of Delaware, Newark, DE 19717; 302-831-1392; http://ag.udel.edu/other_websites/DSTP.
Professor Emeritus Francis Gouin retired from the University of Maryland, where he was the state’s extension specialist in ornamental horticulture. Follow his column of practical gardening and plant advice every week, only in Bay Weekly. Ask Dr. Gouin your questions at [email protected]. Please include your name and address.
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