Rhododendrons are the beautiful large bushes that flower with pom-pom like blooms during the spring. They have been popular for years and years and will continue to be because of their hardiness, ability to grow very large, and blooming capacity.
Rhododendrons and Azaleas are related but the one difference is that in most cases the Rhododendron is an evergreen and will not lose its leaves in the winter while the azalea does. Rhododendrons are larger than Azaleas having the ability to grow to up to 80 feet in height and their blooms are much larger. Rhododendrons have a lance shaped leathery leaf while Azaleas have smaller, softer leaves.
Propagation
Since it takes about 5 to 10 years to produce a bloom on a plant grown from seed it is much better to purchase a plant at your nursery. Taking a graft from an established plant is possible but home gardeners rarely have the equipment to do this. Planting and/or transplanting should be done in early spring or early fall. Plant a nursery plant by digging a hole 2 to 3 times the size of the root ball. The top 1 or 2 inches of the root ball should be above the soil line. Be sure to mulch after planting.
Growing
Rhododendrons are acid lovers. They love a pH of about 5.5. Mulch them with pine needles (acidic) as their roots tend to lie close to the surface of the earth and dry out if not mulched. They do not appreciate bark or wood mulch. They also enjoy shade and don’t particularly like to be planted where the sun would hit them directly. They do like moist, yet well drained soil and do very well in raised beds where the water will drain readily. You may see many Rhododendrons planted near buildings. That is because wind tends to damage them and it is best to plant them near buildings to give them protection. Their roots are very shallow and wind will knock over a large plant very easily since there isn’t much to hold it in the ground.
Flowers will appear in the spring but if your plant is placed in a densely shaded area it may not bloom. Full sun will cause the plant to bloom but will also attract the pests to the plant and too much sun will cause other problems as well. This is a shade loving plant so remember to never plant a Rhododendron in full sun.
Never cultivate under a rhododendron as you will have the risk of disturbing the shallow roots.
Pruning
Prune right after blooming. Rhododendrons set bloom by mid summer so if you prune past June you risk cutting off all blooms that would develop the next year. If you need to prune back an unruly bush it may not bloom for a year or two.
Varieties
There are so many different varieties including those that are cold resistant and those that are almost tropical. Some grow very high but there are dwarf varieties as well. Some varieties have slow growing attributes that some gardeners love since they don’t need to be pruned as often. Please see the note at the bottom of this article to go to a website that will explain the different varieties and what is best for your zone.
Problems
When rhododendrons are planted in a location that is not suited for them they can develop yellowing leaves that will fall off. This is called chlorosis and can be caused by an alkaline soil, potassium, calcium or iron deficiency, to much nitrogen caused by nitrate fertilizers, too much sun, and too much water and no drainage. Rhododendrons are left alone by most pests but if you detect one call your local nursery to find the best antidote for them. There are other diseases that can harm rhododendrons and make their leaves turn a different color and fall off. Check your nursery to find the best cure and what works best in your area. If you plant a tender variety of rhododendron in a cold area you may see damage from the cold. The leaves will be brown and brittle. Cut those leaves and branches off once the weather warms up.
Fertilizing
A fertilizer specially formulated for rhododendrons can be purchased at your local nursery and is best applied during spring prior to the appearance of blooms. Generally it is said that Rhododendrons rarely need fertilization and if it is done it should be done carefully as their close to the surface roots can be harmed by too much fertilizer. Fertilizing should be done in May and not after the end of June as this would cause new growth that would be killed by the cold of winter. Do not fertilize at initial planting as this could harm the roots. Interestingly enough established Rhododendrons that may not look as green as they should do well with a tea of 2 tablespoons Epsom Salts in 1 quart of water. Spray this on the entire plant and let it drip onto the soil beneath. This will green up the leaves and make the plant look healthy. Some people say that putting coffee grounds around the bottom on the soil benefit the plants as well. It certainly would make the soil more acidic.
Detailed information about any problems concerning rhododendrons and the best varieties for your area can be investigated at the American Rhododendron Society Webpage.
See other information from this author at PrymeThyme OnLine
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