Enjoy your column. I have several rhododendrons. They have long,
woody branches with greenery at the end, making an ugly-looking bush.
The limbs are mostly on the ground. Is there any way that I can prune
these bushes to help them fill out?
Rhododendron is a broadleaf, evergreen shrub that is putting on its
show of colorful, springtime flowers right now in the landscape. It's
a shrub that tends to grow large and often outgrows its spot. There
are ways to rejuvenate an already-overgrown rhododendron and ways to
keep a small rhododendron compact.
It's possible to make an overgrown rhododendron attain
its former shape through pruning. This process is accomplished
through several years of selectively removing older branches. In late
winter or very early spring, prune away one third of the oldest
stems. Do this for two or three more years each winter. Tall stems
can also be cut back at this time. Cut tall shoots back to just above
a lower side branch. Removing the older stems and reducing the height
of the remaining branches encourages new shoots to develop. If the
plant is very healthy and growing vigorously, it is possible to cut
back all its branches to just above the ground and allow new branches
to grow out. It will take a few years for the rhododendron to attain
an attractive shape after this drastic pruning and it's possible it
won't grow at all if it's not a healthy plant to begin with.
To maintain the shape of a smaller rhododendron and to
encourage more flowers, pinch out the tips of the new growth. This
should be done immediately after the rhododendron finishes flowering
this spring. Remove about an inch of the new growth once it reaches
several inches long. Pinching the ends of the stems will force buds
along the sides of the branches to grow. Pinching the growing end
also increases the number of flower clusters for next year since
several new shoots will grow from the pinched end. Don't wait too
long to pinch the new growth, however. Rhododendrons form next year's
flower buds in midsummer, so any pinching should be done before then.
If it's done too late, you'll be removing next year's flowers.