wrote in message
oups.com.

[snip]


I water this
plant (and the tree) usually once a week, and less if it rains, and I
don't water them for 30-40 minutes, that's for sure. I water them
until the ground looks like it can't hold any more water, i.e. puddles
start to form and don't immediately disappear. That's usually within
5-10 minutes. Sometimes I just go out there with a gallon can of
water and empty it.

Should the soil be getting completely dry between waterings or should
it be kept moist? And how deep are the roots of a rhododendron?


There's too much left out to even suggest a comprehensive answer. The
reference to 30-40 minutes is for a sprinkler that wil add 1/2" - 3/4", but
it sounds like you're using a hose end or jug to deliver a lot of water in a
short time. How much sinks in? How much runs off? (ie, how much is
actually available to the plant?) Is your soil heavy clay that may be
waterlogged, or hardpan that allows all water to run off rather than be
absorbed by the plant? Your rhodo needs both regular, deep watering, plus
good drainage that keeps it from becoming waterlogged.

Here are a couple of references I found --

--Fraser South Rhododendron Society - Rhododendron Basics - What
Rododendrons Require --
http://www.flounder.ca/FraserSouth/b...quirements.asp

(" . . . [It] is important to understand their basic requirements.

First: Rhododendrons must have a constant supply of moisture. You may
occasionally see a rhododendron that will survive without being watered, but
it does so only under protest.

Second: Rhododendrons must never sit in stagnant water. Roots submerged in
poorly oxygenated water will likely die, though a plant may survive through
better drained surface roots. Hot, wet conditions are more dangerous than
cool, wet conditions. That is why a rhododendron will survive in a wet spot
in the Northwest during heavy winter rains but would not survive in a wet
spot in the Southeast's heavy summer rains.

Third: Rhododendrons must be grown in an acid medium (pH 5-6) that is
coarse enough for the roots to have access to needed oxygen.

Understand and provide these three conditions and you will succeed
wherever you live.")

-- Clemson Extension Service:
http://hgic.clemson.edu/factsheets/hgic1073.htm

("Rhododendrons are shallow-rooted plants and require irrigation during
dry periods. This is especially true of those planted in the preceding
spring. Rhododendrons planted in warm weather in sandy soils may require
watering of the root system twice a week during the first year. Newly
planted rhododendrons require regular watering during dry spells for the
first several years.
Pull back a small area of mulch beneath the canopy of the plant and check
the soil moisture level. When the soil feels dry, wet it to a depth of 8 to
12 inches. Use soaker hoses or drip irrigation to slowly water the base of
the plant.

Be mindful that rhododendrons in waterlogged soils will decline and become
susceptible to root rot diseases. It is important to reach a balance between
regular, deep watering and good drainage to promote a healthy plant."

-- Somerset County Chesapeake Watch Planting Requirements and Plans:
http://www.somersetbaywatch.org/PlantingReqs.html

These should help you understand how to treat your rhododendron -- best of
all, consult your extension service Master Gardener program. Regards --