JARS v37n1 - Seeds from Korea

Seeds from Korea
Frank Doleshy, Seattle, Washington

Seeking background facts for a forthcoming article on the geographical distribution of Japanese rhododendrons, Mrs. Doleshy and I went on a "horticultural and botanical tour of Korea", from September 18 to October 11, 1982. Under different circumstances we might have accomplished more. Yet we did learn a little bit about the rhododendrons, and we collected seeds which will be available from the ARS Seed Exchange.
Two particularly interesting places we reached were:

—  Mt. Halla, on Cheju Island. The 6298 foot summit is the highest point in all of South Korea, and low-growing R. mucronulatum is plentiful above 5400 feet.
—  Ulleung Island, 85 miles out in the sea toward Japan. Although this island is only about 7 miles across, it is a meeting place of numerous warm-temperate and cool-temperate plants, one of the latter being R. brachycarpum .

Besides the stops at these two places, the pre-departure plan included a full day each (i.e., two nights) at 5128-foot Mt. Odae and 5604-foot Mt. Sorak. In addition, we noticed a 5-day period when most of the tour activities would be outside our range of interests; therefore we planned to branch off from the group and visit 6284-foot Chiisan (Mt. Chiri), not on the list of stopping places but located between two of them. At Odae, Sorak, and Chiisan, together with Ulleung Island, we thought we could get a good idea of South Korea's apparently-little-known stands of R. brachycarpum and R. aureum , perhaps at the same time obtaining seeds of a R. aureum with yellower flowers than those found in Japan.

Map of S. Korea

These were our expectations; actually, as a result of itinerary changes, the tour group had only a few daylight hours each at Odae and Sorak - adequate for fall foliage viewing but not for mountaintop rhododendron hunting - and the rerouting did away with our opportunity for a Chiisan visit. (If you wonder where the time went, you don't realize how many temples there are in Korea.)
For the entire trip, our rhododendron seed collections were as follows:

R. mucronulatum

No. 703, from upper slopes of Mt. Halla, Cheju Island, elevation ca. 5575 feet, September 23, 1982

At this place, the Warren Bergs and Hideo Suzuki collected during May, 1976, with results that Warren reported in the Winter 1977 ARS Bulletin . His photo on the cover of that issue gives a good idea of the locality.
Most of the plants we saw there, in our fog-limited field of view, were about knee-height, some taller and some considerably shorter. In the early part of fall, leaves had turned maroon-purple but were firmly attached. These were leathery and stubby, 0.38-0.80 inches long x  0.19-0.44 inches wide (10-20 mm. x 5-11 mm.); the leaf tips varied from acuminate, or "drip-tip", to blunt or even rounded. Although we saw no flowers in September, the ones from our collection will perhaps match the Bergs', i.e., have colors so bright and clear that a casually-entered sprig will take a blue ribbon in an early competition. 1982 seed was scarce, but the Seed Exchange may be able to dole out a small pinch to each of 3 dozen or more recipients.

No. 705, from wooded, rocky ridge of Mt. Nae-jang, southwestern Korea, elev. 1300 feet, September 27, 1982; also No. 714, from rocky roadside in foothills near Mt. Odae, northeastern part of S. Korea, elev. 3300 feet, October 4, 1982

Both of these came from plants that fit the description of R. mucronulatum . Their rather thin-textured leaves were elliptic, with narrowly-pointed or acuminate tips. Those of No. 705 were 1.25-2 inches long x 0.56-0.95 inches wide (32-51 mm. x 14-24 mm.) and were still green when collected; those of No. 714 were 1-1.75 inches long x 0.38-0.75 inches wide (25-44 mm. x 10-19 mm.), and the leaf color had changed to clear, deep maroon above, pale, pinkish maroon beneath.

No. 716, from a steep, nearly treeless slope near Mt. Sorak, northeastern part of S. Korea, elev. 3875 feet, October 8, 1982

Near the end of the trip, Mrs. Doleshy and I detached ourselves from the tour group so we could have a few more days in the vicinity of Mt. Sorak. Although on the wrong side of the mountain for access to high-elevation plant communities, we made long probes toward the central mountain mass, and this R. mucronulatum was our most interesting find. Even though 2½ or 3 feet tall, it resembled the compact Mt. Halla plants. Leaves were just as thick, leathery, and densely arranged; also they had similar blunt tips. Size however was larger: .88-1.38 inches long x .44-.75 inches wide (22-35 mm. x 1-19 mm.) The leaves were shiny for this species and varied from red-maroon to deep gray-purple. To us, this plant stood out as the best R. mucronulatum seen. By picking every capsule, we got about three-quarters as much seed as for No. 703.
Tentative conclusions about variation in R. mucronulatum
The differences between low-elevation and high-elevation R. mucronulatum were conspicuous; plants growing at 1000-3300 feet generally conformed with the description of this species, but those at higher elevations had leaves more like those described for R. dauricum . This latter species, a native of far-northern Asia, is generally considered separate from R. mucronulatum but closely related.
If this variation in R. mucronulatum is the result of inherited genetic traits, rather than weather and soil, the high-elevation plants are likely to retain some distinctive features when brought into cultivation. To determine whether this has actually happened, I recently looked at some of the Berg introductions from Mt. Halla; these plants, I found, have features that are indeed at odds with the description of R. mucronulatum . One plant spreads its branches across the ground, and its leaves are very small, yet as slender and thin-textured as those of low-elevation plants. A group of recently propagated plants (not documented but almost certainly from a Berg introduction) is so compact that the eventual heights may not exceed 2 or 3 inches; leaves are maroon-purple, as on the Mt. Halla plants in autumn, and they are nearly the size and shape of a penny. Other plants, from Berg seed, look like half-size versions of low-elevation R. mucronulatum but have more leathery leaves.
Since these characteristics appear to be inherited rather than caused by environmental factors, perhaps we should call the plants something other than R. mucronulatum . Yet we first need to improve our understanding of the situation; to do this, I suggest that each person requesting high-elevation No. 703 or 716 from the Seed Exchange should also request lower-elevation No. 705 or 714, and observe the differences in the resulting plants. I'll be very happy if I can get the results of 10 or 20 such comparisons during the next few years, since I think this will be information beyond that available from dried specimens. For a parallel check, it would be interesting to obtain seed and dried specimens of R. dauricum from Siberia or northern Japan, so that plants grown in our climates from this seed could be compared with the source material.

R. schlippenbachii
The leaves of this species react promptly to the approach of fall weather, turning first maroon then brown and dry. Walking for miles through plants at these stages, we could see no clues to flower quality and few clues to foliage quality. Therefore I am suggesting to Bill Tietjen that he simply group our collections by geographical area and offer them in two lots as follows:

Lot 1, southwestern Korea

No. 706, from wooded, rocky ridge of Mt. Naejang, elev. 1450 feet, September 27, 1982

Lot 2, northeastern part of S. Korea (all from rocky places)

No. 713A, from roadside in foothills near Mt. Odae, elev. 3300 feet, October 4, 1982;
No. 713B, from wooded ridge above Kwongum cable car, Mt. Sorak area, elev. 2300 feet, October 5, 1982;
No. 713C, from ridge connecting Mt. Sorak with more northern mountains, elev. 2750 feet, October 8, 1982

R. brachycarpum
The scrutiny of R. brachycarpum-aureum territory had been our foremost objective, and we were disappointed at the loss of opportunities for this. The only wild stands of R. brachycarpum we saw were on Ulleung Island, where R. aureum is apparently absent. While walking across this island via the highest peak, we encountered R. brachycarpum first at an elevation of 1640 feet, then at the 3225-foot summit, and finally at 2525 feet - seeing no seed at any of the three places.
Tor Nitzelius (in a letter dated 1/1/77) said these Ulleung plants corresponded very much with his Korean R. brachycarpum subsp. tigerstedtii , described in the July, 1972 ARS Bulletin , pp. 165-8. The distinguishing marks of this subspecies are comparatively large shoots, leaves, and flowers. Yet, seeing the Ulleung plants, we thought a more exceptional trait was the colorful indumentum on newly-matured leaves.
Certainly this race of R. brachycarpum seems worth trying, and we do not know of any previous introductions to the U.S.A. or Canada. Therefore we regretted the lack of seed in the wild, and were interested the next day when we heard that an Ulleung Catholic church had a large plant with seed capsules. Going there, we met the "pastor" (probably his modest translation of the Korean word for "priest"); he was familiar with the native plants and told us this particular rhododendron had been brought down from the central peaks. Since there appeared to be nothing in the vicinity to cross with it, we accepted his offer of seed and received an enormous quantity, which now goes to Bill Tietjen as our No. 712.

In case you are wondering about the pleasures and problems of travel in Korea, I can say that we enjoyed the days when we made our own way, independent of the tour group, and dealt directly with Koreans in many walks of life. Their history and traditions are highly exotic, yet human nature in Korea seems the same as in the U.S.A. Regardless of the language barrier, it is easy to communicate with a merchant, a policeman, or the ticket seller in a bus station; only a few words require specific translation. We enjoyed the resulting sense of fellowship, and we think almost any independent traveler will find Korea very rewarding.