The Bay Gardener
By Dr. Frank Gouin
Garden Math: Dividing and Multiplying Azaleas
Transplant now for a colorful spring
For a jumpstart on spring growth, September is the time for transplanting azaleas, rhododendrons, blueberries, leucothoe, andromeda and mountain laurel. Don’t wait long: Do it by September 15; November is the worst month for transplanting members of the azalea family.
Woody plants’ root growth and shoot growth do not happen simultaneously. When the shoots stop growing, the roots start lengthening and spreading; later, when the roots stop, the shoots grow. This month, the vegetative growth of these species slows in preparation for winter. As this growth slows, root activity increases.
When you transplant these species now, you favor root growth. Thus the plants will be established in time for winter and ready to get growing in the spring. Spring-transplanted azaleas and rhododendrons usually don’t produce healthy shoot-growth after flowering in early spring.
When transplanting these species, move them into soils with a pH between 4.5 and 5.5. If you’re unsure, have your soil tested by a reputable soil-testing laboratory. (I use A & L Eastern Agricultural Laboratory in Richmond, Virginia: www.al-albs-eastern.com.)
Acidic soils tend to be low in available calcium. If that’s the case in your yard, blend one-half to one full cup of gypsum in soil that will be packed around the roots. Also blend the existing soil with one-third by volume of compost, such as LeafGro. Avoid using peat moss around azaleas and rhododendrons in heavy soils. Peat moss holds a large amount of water, making plants susceptible to root-killing diseases. If you don’t have compost, use quality pine-bark mulch, pine fines or fir bark mulch, but do not use hardwood bark mulch.
Finally, plant azaleas shallow, because such species are shallow rooted, and the roots are easily killed if buried too deep. Make sure you’re planting at the right depth by scooping out a saucer-shaped hole for transplant. Plant shallow with the top of the root ball above the surface of the soil.
After transplanting, I mulch my azaleas in early October with an inch of nutrient-rich compost to keep foliage green all winter long.
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