On Breeding Rhododendrons & Azaleas
Breeding good plants means growing large numbers, says Henry Hank Schannen, proprietor and breeder, RareFind Nursery, Jackson, New Jersey. (read about Mr. Rhododendron here) He tells of a breeder who grew 125,000 plants to blooming size; saved about 400; named 22 and 10 years later wished he'd only named nine.
“Nine out of 120,000 is what it takes to get a good rhododendron," Schannen says. “But there are exceptions. I grew only six seedlings of a plant I eventually named Solidarity and it's a superior plant and grown in England, Germany, the United States. That was one seedling out of six. But I can also tell you I had crosses where I bloomed 100 and not one was worth anything."
1. Elepidote rhododendrons freely interbreed with other elepidotes. They rarely cross the line.
2. Lepidote rhododendrons breed with lepidotes. They will not cross the line. (Except for a few successful crosses made with great difficulty.)
3. Evergreen azaleas breed within themselves, rarely across barriers.
4. Deciduous azaleas breed among themselves, rarely across barriers.
5. Vireya rhododendrons are tropicals that will not breed outside themselves.
“There are recorded variances to the laws but very rare," Schannen says. “They are terrible plants. They are not happy. They don't want to do that. The divergence, in an evolutionary sense, was so long ago and even though they are classified as rhododendrons they will not breed with one another."
The Hand versus The Bee
“You've got to get to it before the bees get to it. Most bees work one genus of plants at a time," says Schannen. “The reason a flower has parts is to attract insects. The insects get the pollen from the stamen and go from flower to flower and pick up pollen. They go from one open flower to another open flower and get nectar there. In the meantime, all the pollen that is adhering to all those little hairy bodies is dusting the pistils of the other flower.
“Once the pollen is on the stigma, then that pollen goes down that tube and seeds will form within two weeks, if the conditions are right - and they're not always right. When that happens, you don't know where that bee's been. You know what the mother is but you won't know what the father is and, if you're a serious plant breeder, you want to know what are the genetics of the father and the mother.
“If a bee does it, you don't know. So, hand pollination means that you take all the parts off a flower and protect it from the bees, sometimes with a bag, then you have collected the pollen from a plant that you want to be father, and you place it on the stigma and that way you know what it is that you got."
The typical rhododendron species has 26 chromosomes. Natural tetraploids with 52 (four sets instead of two) exist but will not breed with typical species. To get a cross, breeders sometimes chemically induce doubling of the chromosomes, such as with R. 'Epoch', a tetraploid of Carolineaum. The cross, R. carolineaum x Augusteria has a deep blue flower and is un-named.
For about 60% of deciduous azaleas, fragrance compensates for their delicate colors when it comes to attracting bees for pollination. But plenty of highly colored reds, oranges and yellows exist, mostly unscented. A few reds, some pinks and most whites have some degree of fragrance. And although most lepidotes are unscented, Schannen grows a fragrant few, as well as scented tropical lepidotes.
Deer like rhododendrons and azaleas. “Much of it depends on local herds," he says. “The mother teaches the babies. If the mother has a taste for rhododendrons and azaleas, I can assure you the babies will too. But they don't have a good taste for lead. So if you get out there and shoot them, there's no problem. My dogs keep me free of deer. I have two big German Shepherds over 100 pounds. They never had to be taught about deer. They are natural-born predators, God bless them, descended from wolves. And when they go out at night they go out looking for the deer and they go barking. The deer, if they come over the fence, turn around and jump back over the fence. (Schannen's five-foot high electric fence is to keep his dogs in.) They patrol at different times during the night. I don't have deer. They're all around, but not on my 11 acres."
Rhododendrons and azaleas continue to grow roots until the soil temperature drops below 35 degrees and then the plants become semi-dormant. Because soil temperature cools much slower than air temperature, roots can move until late December. It's good to get the roots down and established, so that when spring comes they keep right on growing and by the time hot summer comes, which can be tough on plants, they have the roots down and they're in good shape. Schennen plants in spring and fall.
Hank Schannen's Tips on How to Kill a Rhododendron
1. Southwest corner of house
2. Full sun
3. Heavy clay soil
4. Wet - poor drainage
5. Down spout nearby
6. Neutral/alkaline pH
7. Containerized plant is plunked into ground with root ball in pristine condition
(from Plant Catalog 2007, RareFindNursery, Inc)
More flowers articles
Print this story:
published October 26, 2007