Soil preparations are critical to the successful growing of
Rhododendrons. They require a rich well drained high organic content
soil mix. You can provide this by mixing into the existing soil a
very large amount of Peat Moss. The Peat Moss should be 50% by volume of
the soil. This will produce an acidic soil of about 6.0 to 6.5
pH. Check this estimate with a pH meter. After checking the pH of
the soil mix you will want to adjust the pH to 4.5to 5.5 using Garden
Sulphur according to the label directions. Never use Aluminum
Sulphate to adjust the pH of the soil for Rhododendrons because in
acidic conditions the Aluminum can become toxic to the Rhododendrons
especially to younger plants. You should also add some leaf mold
and coarse sand to the soil mix to encourage better growth.
When you plant Rhododendrons like this Duke of York prepare a hole at
least 2 to 3 feet wide and 6 to 8 inches deeper than the height of the
root ball. If you think extra drainage will be needed place a 4 to 6 inch layer of
coarse gravel in the hole ensuring that you still have the required 6
to8 inches between it and the bottom of the root ball. Back fill
with your soil mix and gently firm the mix around the root ball
while never pushing or standing on the Rhododendrons root ball.
The finished grade should be
2 to 6 inches above the original grade. You should now water in
your plants with a transplant fertilizer with a rooting hormone
in it. A mulch of pine bark, cocoa beans, pine needles or oak
leaves at least 2 to 4 inches thick can now be applied.
After the flowers are finished you must disbud. This is the
removal of the spent flowers and must be done very carefully because the
new growth is immediately behind the spent flowers, though some buds
will also occur in the leaf axils.
Their removal directs the plants energies towards producing new growth
and the flowers for next year.
After disbudding gently remove the mulch by hand carefully so as not
injure their very shallow root system. Now add a layer of
mulch. Alternatively you can just add the new mulch over the old
mulch. Do, which ever you feel is best for the Rhododendron.
Feed your Rhododendrons at this time with an acid based
Do not feed them after July 1st. Feeding after this time encourages late
season growth that may not harden off before the winter sets in and it reduces
If winterizing your Rhododendrons is required by the environmental
conditions i.e. northwest location then just before the ground freezes
pound in some wooden stakes at least 1 foot out from the ends of the
branch tips and taller than the plant. Now after the ground is
frozen staple a single layer of burlap to the stakes 2 inches above the
ground. The top should be
open to allow the snow to enter and insulate the plant. In very cold
climates you can carefully stuff leaves in between the burlap and the
leaves only after the ground is frozen.
Always remember never cultivate around the Rhododendrons because their
new feeding roots grow up and hence the need for an annual mulch.
Cultivating around them can kill them.
Truly Rhododendrons are the Kings of my garden!