(kamm) wrote:
I planted a rhododendron (dwarf rhododendron "baden-baden") in the
alkaline limey soil in my garden, before realising that these plants
hate lime. It was planted about 6 weeks ago and so far it is doing
fine. It had two flowers when I planted it, which have now fallen,
and although it has had no new flowers, it has loads of new shoots
growing.

It will flower once each year on buds formed the previous fall and the
flowers last 2 to 6 weeks.

If your plant came from Europe, your Baden-Baden may be grafted onto
root stock of Cunningham White which is somewhat tolerant of alkaline
soil. If it is of American origin, it is just rooted from a cutting
and needs acidic soil. It is best to dig it up now and plant it
correctly. The most important factor in achieving vigorous growth is
an acid soil mixture high in organic content. Rhododendron and azaleas
need an acid soil with a pH of 5.0 to 6.0, well mulched with organic
material. Rhododendron thrive in a moist, well-drained, humus-filled
soil, enriched with peat moss or leaf mold. Prepare the soil by
thoroughly mixing equal parts of loam, coarse sand and ground oak
leaves or redwood before planting. Many commercial growers root
rhododendron and azaleas in pure sphagnum peat, or in a 50-50 mixture
of sphagnum peat and coarse sand or perlite. A favorite mixture on the
West Coast is 1/2 sphagnum peat and 1/2 ground bark dust, but in such
mixtures, plants must be fed regularly. My favorite soil mix is a
50-50 mix of peat humus and the natural soil. Soil around the
rhododendron's shallow roots must be kept cool and moist but well
drained. If the soil is too alkaline, acidity may be increased by
adding flowers of sulfur (powdered sulfur) or iron sulfate. I add 1
tablespoon of sulfur powder around the base of any plant showing signs
of chlorosis. Do not use aluminum sulfate. Aluminum can build up in
the soil to toxic levels eventually.

Because the roots grow near the surface, a bed prepared especially for
rhododendron and azaleas need not be more than 12 inches deep; deep
planting or too much mulch in the growing season keeps the roots from
getting the air they need. In fact, it is a good idea to set
rhododendron about 1 inch higher than they grew at the nursery.

Visit my Rhododendron and Azalea web pages at:
http://www.users.fast.net/~shenning/rhody.html
Also visit the Rhododendron and Azalea Bookstore at:
http://members.aol.com/rhodyman/rhodybooks.html

Cheers, Steve Henning in Reading, PA USA