Hybridizing, or crossing one azalea with another, is usually done to produce azaleas with characteristics better than the thousands of hybrid azaleas now available. Some examples of areas for improvement include increased cold hardiness, more compact growth, increased tolerance to adverse growing conditions (sun, shade, wet, dry), more-intense or less-intense colors, specific unusual colors such as a yellow evergreen azalea, increased fragrance, increased flower retention, earlier or later bloom time, and better summer and/or fall leaf colors. Since it will take considerable space to grow the seedlings, and two to four years to see the first blooms, and many more years to see the overall plant characteristics, it is worth having a plan.
Seedlings will exhibit characteristics ranging from one parent to the other, with many of them somewhere in between. Thus, the greater the difference between the parents, the more seedlings you must grow for a good sample of the variability. For a self-pollinated species azalea, a handful of seedlings might be enough. For two different hybrid azaleas with different colors, parentage and plant habits, even hundreds of seedlings may not be enough.
To make a cross between two azaleas:
- before the flower which is to be the seed parent (female) fully opens, remove its petals and its stamens, and remove adjacent flowers completely to reduce the possibility of accidental or self pollinization
- remove the stamens from the flower which is to be the pollen parent (male) immediately after the flower opens and before it loses its pollen
- take the stamens to the seed parent, and shake the pollen from the end of a stamen onto the stigma of the seed parent flower, which will have a sticky surface when it is ripe and ready to receive the pollen
- tag the stem to record the seed parent and the pollen parent, in that order you can bag the pollinated flower to prevent accidental pollinization by insects, although studies have shown this is not needed.
Cold and wet weather reduces the probability of success, as does very hot and dry weather. When a cross does set seed, collect the seed pod as it begins to turn brown and before it opens, around the time of the first frost. Even quite green seed pods can be collected, and will dry and open after several weeks indoors. Putting the pod and its tag into an envelope or a small paper muffin cup is convenient.
If the parents bloom at different times, pollen can be stored for years by drying and freezing it. Follow this procedure:
- from a drugstore, obtain empty gelatin capsules, size 1, 0 or 00, which may requre a doctor’s prescription
- also from a drugstore, obtain a supply of silica gel dessicant
collect the anthers (the ends of the stamens) and place them into a capsule, and label it with the variety
- let the capsules air dry for a few days in a refrigerator
place the capsules on cotton padding in a sealed glass jar with a quantity of dessicant
- place the jar in the freezing compartment of the refrigerator at about 0 degrees F.
- When the pollen is to be used, remove and warm the glass jar in warm water. (Repeated freezing and thawing has no effect on the longevity of the pollen.) Then open and remove a capsule, and tap it to shake out the pollen onto the surface of the capsule. Take it to the seed parent and either shake some onto the stigma of the seed parent, or insert the stigma into the capsule.