Two Pennsylvanians Share Thoughts on Cuttings
Some Thoughts On Vegetative Propagation As Related to Dormancy
Dr. Mark Konrad
Sewickley, Pennsylvania
There are certain aspects of vegetative propagation which have a hidden agenda. To have reasonable success, one must become quite familiar with the characteristics of each plant. With ever increasing knowledge, the art of propagation becomes easier. There are four different categories of plants in the
Rhododendron
genus. Each should be considered separately for propagation.
The evergreen azaleas and small-leaf rhododendrons have indeterminate growth, i.e., they will grew on immediately and continuously after rooting if the light and temperature are ideal. Dormancy only occurs with seasonal change. This probably explains why they are relatively easy to root. They do best when taken early, which is usually at the end of June and early July in the Pittsburgh area. The plants are significantly removed from the dormancy influence at this time. Tip cuttings from newly rooted plants with growth root even more readily. The implication is that the dormancy factor is much less operative with the physiologic state, thereby creating a condition more conducive to rooting.
The deciduous azaleas pass rapidly and deeply toward dormancy soon after new growth. That is why the cuttings should be taken as early as possible, around June 15 in the Pittsburgh area. This probably also accounts for the success I have had with leaf bud propagation, i.e., stimulation of the axillary buds, following removal of the stem tips (
JARS
Vol. 50, No. 3). I have also proven that tip cuttings from shoots of newly rooted plants can be rooted within 60 days, although they are not as easy or consistent as these with the evergreen azaleas or the lepidotes (small leaf).
The large-leaf rhododendrons are much more difficult to evaluate. The dormancy cycle is quite pronounced. They key, I think, is to find which ones do better in July when the dormancy factor is less pronounced, i.e., when the plant could still be active in growth. Some plants are very resistant to rooting but some root readily in July. 'Catalgla' is one such plant.
Many of the large-leaf rhododendrons do best in September and early fall. Since timing is of the essence, perhaps we should be thinking more about each individual plant and which month might be best, anticipating a change in the dormancy physiology. Could winter cuttings be the right time for some? Perhaps the passage of dormancy would be helpful with certain plants.
Summary: I have not covered all the complex aspects of vegetative propagation. Instead I have tried to associate the dormancy factor with the physiologic state and how it relates to successful rooting. One last thought might be to ask: when do plant hormones become the most interactive in the cycle? Or if potted plants were brought indoors for a week or two to break dormancy would the cuttings be any more apt to root?
Rooting Cuttings Lazy Man Style
Edward S. Rothman
North Hills, Pennsylvania
Whatever the Pacific Rim people suffered with their "ring of fire," we Pennsylvanians suffered equally. Only we did it first. Some 2 million years ago our monster Proto-appalachian mountains - now worn away to stubs - shoved a 50-foot mudslide very like Mt. St. Helens over this area. While it does make nice bricks the dense, airless clay is not what is considered optimal for rhodo culture. Our forest of acidic 150-year-old oaks lays down a mulch layer of such buffered nature that its pH is unreadable by meter measuring devices, but by titration with concentrated lye calculates to about pH 1! Our summers are African and our winters Alaskan.
Nevertheless we raise some wonderful specimens on our well-drained raised beds, and unlikely plants like 'Loderi Pretty Polly' and 'Sue' ('Loderi King George' selfed) are quite happy here. Needless to say, we use large quantities of limestone to temper the excessive acid and we like raised beds which form little archipelagoes right atop the grassy lawn. My "yaks" like as much sunlight as I can provide, but the closely allied
R. metternichii
(now
R. degronianum
ssp.
heptamerum
) demands much shade. So as the modern proverb puts it, "Different strokes for different folks and different ways on different days."
My small half acre garden surrounded by 150-year-old trees I would never consider defiling with a greenhouse or even cold frames. These break into the mood of an intimate garden and need some attention robbing us of time for more useful activities. Yet, when a fallen branch rips off a rhododendron branch it seems wasteful not to attempt to make new plants of the more beloved plants. My yaks on their raised beds flash their underpants in every breeze like can-can girls. I love the indumentum colors. So the question is how to utilize these fallen fragments?
I found some clear plastic dishes in the store like so many pie plates in their dimensions, e.g., 11-inch diameter x 2-inch depth. They were sold as under-pots to protect window sills from drippy house plants. I hide these behind bushes, perhaps alongside a stone house wall whose light reflection makes them function exactly like a Nearing frame. I wound cuttings but am too busy to look for a sharp knife. I tear off some micro strips from the cutting base with my fingernail. Synthetic hormones are not necessary because a good year is required for rooting. The cutting leaves are often plastered flush against the dish's roof and heavy water condensation coats the plastic roof and every leaf. I do not mind overcrowding cuttings of small-leaf yaks. When one roots, it seems to stimulate its neighbors to join the act too. Rooting weeds also seem helpful, although giants get topped off to allow light to contact the plantlets.
I like to take extra cuttings in autumn. The cuttings survive 0°F temperatures with no rooting taking place until cooler autumn temperatures the next year remind the cuttings to "shape up or ship out." This is a slow process, but the time of labor is insignificant and the freed time of the gardener can find happier uses.