Late Spring plant series for Boulder Colorado area landscapes
Spring, 2019: Rhododendron
Rhododendron….in Colorado, true gardeners, those with a passion for the ‘sport’ either love them or hate them. It all depends on whether said gardener has the time to care for them. In the Appalachian mountains, in the highlands, they are found growing natively. But here in Colorado, the dryness, the winds, the extreme temperature changes, the winter sun, all work against the avid gardener trying to cultivate and maintain healthy Rhododendron. That said, it can be done, if one finds the right location, soil and water.
Rhododendrons are a member of the heath family, of which there are over 1,000 species. In Colorado, there are only a few which are viable. Azalea are a sub genre of Rhododendron, and there are about 10 varieties that can flourish in Colorado, again, with the right conditions. The most common of the “true” Rhododendron are the PJM variety that can grow well here in Colorado, named after Peter J. Mezitt of Weston Nurseries in Massachusetts.
There are over 28,000 cultivars of Rhododendron in the International Rhododendron Registry. But to have success here in Colorado, here’s what needs to happen. Soil….it must be amended heavily so there is little clay and mostly loam or sandy loam. It should have good drainage, but Rhododendrons like water so it needs to hold moisture as well. The soil must be acidic, and since most soils along the Front Range of Colorado are alkaline, it is important to amend with something acidic…..pine bark, pine needles, peat moss, etc. They like regular fertilizer to bloom vigorously. Careful watering is important. Having them on a drip system is not enough. They like a humid environment, so Maxijet irrigation stakes spraying the area around them are a good way to water. And, winter watering is very important, including wetting the leaves on a regular, weekly basis. Keeping the area around the plant moist and humid is a tough task in Colorado, but the avid gardener will reap the rewards of meticulous watering. Exposure is also important. They must be kept protected from drying winter Chinook or Bora winds. They must be somewhat shaded from intense winter low angle sun, as well as remain shaded in the summer sun. Northeast exposure is good with some overhanging canopy trees. This keeps them out of the winter west winds, but care must be taken to keep them from the northeast winter storm winds that bring snow. A woodsy type setting is best.
If you have the time, Rhododendrons can be an extremely beautifying asset to your landscape. They are not cheap, but the rewards are extensive. Plant a few in select locations of your landscape, tend to them, and don’t give up if you fail a time or two. They are not for everyone, but if you succeed, everyone will notice them.
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