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Problem Rhododendrons are popular as foundation plantings and in shade gardens, but they aren’t the adaptable, carefree plants many people think, especially once winter comes calling. With broad, evergreen foliage, a shallow root system, and a need for consistently acidic soil, rhododendrons are quite sensitive to changes in their growing conditions. Freezing wind dries out the leaves, too much sunlight scalds them, and lime leached from foundations interferes with the plants’ uptake of iron. Low-maintenance they ain’t, but come bloom time, all is forgiven.
Solution If your rhododendron looks woebegone but you’re not sure why, check the leaves:
Leaves curled like a cigar mean that moisture is being lost to the wind and the plant is compensating by reducing the exposed leaf surface. Surround the plant with a windbreak made from burlap or apply an antidesiccant spray, and consider relocating the plant to a less windy site.
Browned edges can be sunscald, which is also caused by moisture loss. Water your plant well before the ground freezes and again if the ground thaws for a few days. Then cover the ground with a 2-inch (more is not better) mulch of pine needles, coarse bark or wood chips, or decomposed leaves.
Yellow leaves with dark green veins can mean chlorosis, a lack of iron. Your soil doesn’t necessarily lack iron, but its pH may be high enough to keep the plant from absorbing it. First get a soil test. If the pH is high (it should be between 4.5 and 6.0), add sulfur to the soil. Be careful cultivating the soil around the plant when adding amendments, because the roots are shallow and easily damaged.
