Rhododendrons 101

Rhododendrons are synonymous with the landscapes of the Pacific Northwest. In fact, it’s hard to imagine a garden without one. There are many reasons that rhodos are so popular. The magnificent flowers that cover the shrub in early- to mid-spring, and their thick green leaves and shape, which provide a much-needed framework to a herbaceous garden, are just a few.
They also thrive here. Our wet, rainy winters create the perfect balance of acidic soil that rhodos thrive in. Rhododendrons grow well in dappled shade and are the perfect understory to other taller native species. Rhodos can also “culturalize” to sunnier locations, but ensure that they don’t drought out (regular irrigation is a must), and that you feed the soil with nitrogen-rich fertilizer.
The only problem that seems to re occur with rhododendrons is questions related to pruning them. Unfortunately, in many cases, it stems from a classic case of right plant, right place.
All too often I have seen well-meaning individuals pick up a cute two-foot rhodo from the nursery and site it directly in front of a window, walkway, etc. Unbeknownst to the buyer, the cultivar that looks so perfect at two feet actually reaches a mature height of 15 or 20 feet. Herein lies the problem.
There is an old gardener’s saying that “inside every rhodo is a 15-foot tree trying to get out.” Truer words were never spoken. A well-meaning pruner can try in vain to “control” the size of a rhododendron, but the best solution is to re-site the shrub to a spot where it can reach its full height potential without pruning.
In a perfect world, if you found yourself with a rhodo too big for its current spot, you can try increasing the size of the shrub’s bed to accommodate the plant, or you can move it. Rhododendrons are surprisingly easy to move and have a broad, flat fibrous root system that lends itself to digging up and re-siting.
Get a lot of strong people and a tarp to slide the large rhodo out of its home and move it to a new one. You can also root-prune once you have it dug out. This entails pruning up to 50 per cent of the roots coming out of the root ball, and will help to slow the growth and rejuvenate the plant. Most importantly, once you have dug your rhododendron into its new home, soak the entire root ball and keep it on a regular and deep watering program for its first year in its new home.
Remember that if absolutely necessary, you can prune a rhododendron. Real pruning for health and good shape are possible, but just go easy. Start by taking out all the deadwood and the damaged or diseased branches. Prune out all the crossing and rubbing branches and any branches that don’t fit the overall shape of the shrub, or that hang over a walkway or block a window.
To selectively reduce the size of your rhododendron you can make a few heading cuts every year. Follow the tallest branch down inside of the shrub (never shear the tips) where it meets up with a lower lateral. Cut it off at that point. Repeat with the next-tallest branch but go slow and carefully and never reduce the size by more than a third at any time. Repeat this process on a yearly basis. It takes patience, but you can reduce the size over time if you are cautious.
There are many smaller and dwarf varieties of rhododendrons available at your local nursery. Take the time and do your research before buying and plant the right shrub in the right place.

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