Plant propagation is somewhat more difficult than planting a container-grown
azalea. We have included a list of resource material at the end of this
section that includes the sources of the information printed here.
You may root cuttings and grow plants many ways. Whatever method of propagation
is used, sanitation and cleanliness is very important for success. The stock
plants should be healthy, and the equipment used, the propagation preparation
area, and the propagation area, greenhouse, or cold frame should be disinfected.
Generally, most evergreen azaleas are easy to propagate. The problem is
that not all species can be propagated using the same method. Each of the
several methods of propagation have advantages and disadvantages. Azaleas
are propagated from seeds, stem cuttings, root cuttings, layers, and grafting.
Stem cuttings are the most popular method.
Seed Propagation
Propagation by seed is a good method for many deciduous azaleas and
other cultivars that are difficult to propagate by cuttings or other methods.
Seed capsules are green and turn yellow to brown when mature. Capsules
should be collected when they begin to turn brown, mid- to late autumn.
If the capsule has split open, seeds will readily drop out. Store the seed
capsules at room temperature in paper envelopes or open-top containers.
Each capsule contains 100 to 500 seeds. The seeds can immediately be germinated
or stored at 20°F in an air-tight container for later use.
The sphagnum moss method is generally used for germination. Sphagnum
should be shredded or milled, saturated with water, squeezed dry, and fluffed.
The ideal container for germination would be a 3-inch deep, plastic container
with a clear lid. Punch small drainage holes in the bottom. Rinse the container
with a 10-percent chlorine bleach solution (1 cup bleach to 9 cups water)
to sterilize the container. Fill the container to within 1 inch of the
top with sphagnum. Scatter seeds over the moss and mist them lightly with
water. Covering the seeds is not necessary. Close the containers and place
them in indirect or fluorescent light. Keep the temperature between 60°
and 75°F. Germination should begin within 2 to 4 weeks. Seedlings can
be transplanted into individual containers or flats within 8 to 10 weeks.
Propagation By Stem Cuttings
Propagation by cutting is used most frequently for evergreen azaleas.
Cuttings should be made from new wood (June and July) of healthy, mature
plants. Suitable new wood should snap when broken. Cuttings should be 3
to 6 inches long with the leaves removed from the lower one-third to one-half
of the cutting. Insert the cuttings 1 to 112 inches deep in the rooting
medium. Rooting medium varies from (a) equal parts of perlite and peat;
(b) 1 part peat and 2 parts perlite; to (c) bark, peat, and perlite. Before
sticking the cuttings, the rooting medium should be thoroughly moist (not
wet) and firm.
Flats or individual pots may be used, depending on preference or the
quantity of cuttings. Azalea cuttings can be rooted outside in a shady
area if humidity is high, in a greenhouse under a mist system, or under
enclosed plastic structures in shady areas. Rooting will normally occur
in 4 to 6 weeks. The problem in rooting all cuttings is trying to get roots
initiated before the cuttings dry out. You prevent drying by increasing
humidity, increasing shade, reducing air movement, and maintaining 100
percent humidity. Rooting hormones such as Hormex, Hormodim, Dip &
Grow, and others also help in increasing the number of roots on the cutting.
Propagation By Layers
Layering is a modification of propagation by stem cuttings. It is a
slow process, but it can be useful if the number of plants to be propagated
is small. Branch layering is the easiest method of layering. A low, sweeping
branch is selected and bent to the ground. A wound is made on the stem
by making an upward cut 1 to 12 inches in length along the underside of
the branch. The branch is buried 3 to 4 inches deep at the cut. The top
of the branch is bent upward. The buried part of the branch should be pegged
down with wire or a rock and covered with mulch. It frequently takes more
than a year before the new plant can survive on its own roots. However,
for the home gardener, this is often the easiest method to get a few extra
plants.
Propagation By Grafting
Propagation by grafting is used in Europe, but it is not commonly practiced
in the United States. It is frequently used to produce unusual plants,
such as tree azaleas. Grafting is a means of propagation where a desirable
bud or cutting (scion) of an azalea or other plant is attached to the roots
or understock of a plant of a similar kind. The two parts join together
and grow as one. The understock should be actively growing, but the scion
should be dormant. A side graft is recommended, with the cambium layers
of the understock (the light green tissue immediately under the bark) and
scion matching before securing. Wrap the graft union with damp sphagnum.
Cover the entire graft with a plastic bag. Once the scion begins to grow,
gradually increase the volume of air by punching holes in the plastic bag.
When the scion has hardened off, the top of the understock should be removed
above the graft union.
To be successful, sanitation and cleanliness must be observed no matter
which method of propagation is used. Remember, the stock plants should
be healthy, and the equipment used, the area processed, and the greenhouse
should be disinfected.