Mountain Gardener by Betty Hensley
Rhododendrons: Endless Color and Variety
This is the amazing gift you get from rhododendrons in early spring to the first part of summer. When the blooms are gone, you have a bright multi-green shrub that continues to be an asset to any part of your semi-shaded garden. This month I choose to write on the topic of rhododendrons, because after the long, color show they provided to me in my garden, I began to notice that even though the tips of the plant looked fresh, young and happy, some of the older leaves were getting unsightly brown spots on them. Out came a multitude of gardening books and I began to discover all kinds of helpful information about these beautiful plants; information I’d like to share with you.
WHEN do you plant rhododendrons? In most regions it is best to plant them from mid to late fall through winter.
WHERE do you plant rhododendrons? Choose a garden spot that gets either filtered sunlight all day or some sun in the morning but light shade from noon onward.
HOW do you plant rhododendrons? These plants must have soil that drains rapidly yet retains moisture, so be sure to liberally amend your soil with organic matter prior to planting. When planting, dig a hole roughly three-quarters as deep as the plant’s root ball and twice as wide. When placing the plant in the hole, be sure the juncture of stems and root ball are above the soil grade about 1-2 inches.
CARING for rhododendrons: For optimum performance, water regularly, and apply a commercial acid fertilizer twice a year. Do this before plants bloom-as buds begin to swell, and again just after flowers fade. It is good to maintain a mulch beneath the plants for moisture conservation and to keep the soil cool.
PROBLEMS that may surface: (1) Salt burn may be the problem when leaf edges are brown and dead. This browning usually occurs on older leaves first, which distinguishes the problem from windburn, which develops on the younger leaves first. Salt burn is more common in areas of low rainfall, and occurs in soil with poor drainage or where too much fertilizer has been applied. Excess salts dissolved in the soil water interfere with water uptake by the plant. The solution: Avoid the use of bagged steer manure, which may contain large amounts of salt, and leach accumulated salts from the soil with a monthly heavy irrigation. (2) Sunscald is a problem during warm sunny weather. The center portion of the leaf bleaches to a tan or off white color. The injury is unsightly but does not damage the plant, yet these weakened leaves are more susceptible to invasion by fungi and bacteria. Also plants that do not receive enough water are more prone to sunscald. The solution: Provide more shade and regular watering. (3) Iron deficiency is a common problem with acid-loving plants. These plants prefer soil with a pH between 5.0 and 6.0. The soil is seldom deficient in iron, but iron is often found in an insoluble form that is not available to the plant, especially in soils with a high pH. The solution: Spray the foliage with a chelated iron fertilizer, and apply the fertilizer to the soil around the plant to correct the iron deficiency. Lower the pH of the soil by treating it with aluminum sulfate and watering it well.
If you have problems of your own with the rhododendrons in your garden, call for FREE advise from a Master Gardener by contacting the University of California Cooperative Extension. 209-533-5696 or email me at bettyhensley@mlode.com
