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Journal American Rhododendron Society

Current Editor:
Dr. Glen Jamieson ars.editor@gmail.com


Volume 31, Number 2
Spring 1977

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Robin Hill Revisited
Reprinted from the New York Chapter Newsletter

        Gartrell's Robin Hill azaleas are on the point of wide dissemination, and have been a subject of great interest to the Chapters near his New Jersey home for some years. Bob Gartrell spoke to the Azalea Study Group at Planting Fields, sharing some of his experience and recounting the long years of work which have gone into producing the Robin Hill azaleas. This article was compiled from notes taken by Jane McKay and Fred Knapp at that informal lecture three years ago. An article by Mr. Gartrell also appeared in the Oct. 1970 Quarterly. Editor.
        Bob Gartrell came to azaleas by an unusual route, having originally been a delphinium enthusiast living in Canada. He fell in love with blue flowers, and had a great deal of fun winning local show prizes and investigating the variations of these plants. When he moved to Ramapo, New Jersey, he innocently expected to continue his life with delphiniums, and set out approximately 4,000 plants. It will be no surprise to local New Jersey or New York members that the plants did poorly in the Ramapo climate and soil, dwindling to extinction in three or four years. By this time another fault was also becoming an irritant, clonal propagation was not convenient, being carried out by division only. Mr. Gartrell then cast about for a different plant with which to work out his creative gardening urge.
        Azaleas seemed to possess the best combination of beauty, ease of propagation and space requirements. The latter criterion was important in choosing azaleas rather than their big brothers, rhododendrons. With Kurumes, Kaempferis, Chugais (now Satsukis), Gables both under name and number, Glendales, etc, Mr. Gartrell estimates he has grown over 600 named varieties. Of course, it was not enough to grow this host of existing hybrids without trying to create his own, and very soon he was in production again. He had to cultivate a new attitude toward his favorite delphinium blue, for nothing in the rhododendron family has ever attained such a color, while the "blue tinge" which underlies so many of our hardier pinks and reds has been thoroughly anathematized.
        In his earlier crossing, Bob chose to work from hybrids rather than species (the Morrison route rather than the Gable) and proceeded as do most of us, by crossing plants which he admired for particular characteristics in an attempt to combine his favorites into a single outstanding azalea. He found this disappointing, for while 90% of his yield was as good as the typical existing hybrids, the unique combination of all desired features eluded him consistently. Certain plants had characteristics which consistently occurred in their progeny, however, and this served gradually to focus the effort for more effective results. Prominent among these were a plant which Bob calls 'Oakland', and 'Louise Gable'. 'Oakland', an unknown which seems to be a Kaempferi, Bob purchased at a roadside stand. It has withstood 2 months of deeply frozen ground (including the water service pipe to Bob's house) with temperatures as low as -35 degrees F, and flowers well even planted in considerable shade. This hardiness seems to transmit quite reliably to its progeny. 'Louise Gable' also seems to pass along hardiness and a degree of doubling to its children. Working along these lines carried Bob to retirement, giving him much satisfaction but still not quite leading to the new azaleas he had wished to create.
        At retirement, Bob moved to Wyckoff, New Jersey. At that time, Tingle agreed to grow about 1800 of his plants. Also about that time, Dr. Creech and others were bringing in Satsukis, to which Bob was greatly attracted. Their foliage is attractive, habit typically low and spreading, and flowers impressively large. Their problem is hardiness, but he found that a typical Satsuki x 'Oakland' would look like a Satsuki and have enough of 'Oakland's' hardiness. There were many things to learn, however, as some of the most unusual colors in Satsukis turn out to vary from year to year, making them difficult to inherit! And some of the most attractive flowers simply will not produce good crosses. One of these latter was number 230613, an outstanding white. Working on with Satsukis and 'Oakland' and 'Louise Gable' and their derivatives (one much used was 'Louise Gable' x 'Tamagiku', for double flowers) brought Bob and his Robin Hill azaleas up to the present time. Bob says he has grown over 25,000 seedlings from 1, 500 crosses, and his records are 99% complete. This last makes him a truly remarkable hybridizer, for most of us lose control of our records long before we make 1,500 crosses. The last phase of his work, with the Satsukis, has brought forth plants which are unique and outstanding, immediately envied and coveted by all who see them. They meet the goals of his program, being Northeast hardy, low to medium height with large dark glossy leaves preferably with rounded ends, flowers with broad petals overlapping in a full circle effect. Many have six petals rather than the usual five, some even more. In selecting plants, he always looks at the habit and foliage first, then the flower.
        Lest you misunderstand the time involved in all this, the typical time to flower seedlings is four years. To evaluate the overall plant takes eight years. Bob gave us a description of some of the methods he uses in different stages of this eight year period. He cross-pollinates bare-handed, with no tweezers, brushes, etc., and does not cover his crosses. He remarked that he gets no seed on evergreen azaleas except where they have been hand pollinated. Seed, harvested around Thanksgiving, is sown in December on milled sphagnum moss. When ready, the seedlings are potted or flatted in a modified Cornell mix:

5 gal. peat
2 gal. vermiculite
2 gal. perlite
3 tbs. superphosphate
3 tbs. gypsum
6 tbs. 5-10-5 fertlizer
a dash Epsom salts
a little sequestrine

        He uses supplemental lighting on seedlings flatted in the bench. The lights are 150 watt floods 25 inches above the seedlings, and are used during the night on an intermittent basis. The time a plant requires to convert light energy is much greater than that needed to absorb it, and Bob gets good results with a schedule of 15 seconds light once in every 15 minutes. Once he used aluminum sulphate in the bench getting his pH down to 3.5, with no serious effects on the plants, although aluminum is now considered toxic. The plants grew more slowly than normal, and when put outside in the ground took off at a great rate, out of relief, no doubt. Meanwhile, his aluminum tags in the bench medium tended to disintegrate.
        Bob has experimented with radiation and chemicals such as colchicine, and found these avenues a dead end for him. He also experimented quite a bit with the question of seed parent vs. pollen parent and found it unimportant for this group of plants.
        Seedlings are permitted one year in the greenhouse and then are lined out in the open to take care of themselves. Bob prepares his beds by the book, with lots of peat, but remarks that his son-in-law grows the plants in straight Virginia clay and has better looking specimens than Bob's own. In general, he is opposed to mulch, particularly winter mulch, but has begun to appreciate it in summer for weed control. Pine needles are his favorite for this. He is experimenting with pine bark as a soil conditioner; and admits that his soil is probably too acid for ideal results. Bob fertilizes occasionally with sparing amounts of 5-10-5, but feels that very little fertilization is needed.
        Pest control has not been a serious problem with the Robin Hill azaleas, although we cannot say how much of this is plant and how much is due to other factors of the planting site. Bob uses Malathion just before the flowers open and just after they go by, and has no difficulty. Pruning is optional. The plants will respond to any amount, but he likes to leave them alone and evaluate the natural results. The plants propagate readily from cuttings, and Bob recommends 50-50 peat and perlite, with Rootone. Cuttings can be mailed to friends in baggies with perfect success.
        Bob's goal is to choose the 25 best of his Robin Hill azaleas. If you have bloomed any of your own crosses you can imagine how difficult this can be, and he admits he is "swithering" over the choice. (The word is his, and is expressive if unfamiliar.) Plants are under test at Planting Fields, the National Arboretum in Washington, Longwood Gardens, Tyler Arboretum, Callaway Gardens, with Dr. Wheeldon in Virginia and Mrs. Pennington in Georgia, with Bob's son-in-law in Virginia, in New Zealand, and now in our own Azalea Study Group. That makes a very wide-spread test sample from which to choose the 25 best. We hope we in the Azalea Study Group can contribute some useful data to the final choice. We also hope it may include one clone which Bob was kind enough to name after our own Betty Hager. That one will certainly always be known in New York Chapter Gardens.


Volume 31, Number 2
Spring 1977

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