Back in 2018, I spotted a listing for Korean germplasm of Magnolia sieboldii on the seed exchange list for the International Magnolia Society. For those who don’t know magnolia species, Magnolia sieboldii is considered one of the most beautiful in the genus, but it’s widely known not to grow in hot, humid climates. I had actually seen this pendant-flowering species on Korea’s Mt. Sorak in 1997, but didn’t gather seed because I assumed it ungrowable. Subsequent to that trip, we would try in our garden, but we stopped after killing it on our requisite three attempts. Good sense would tell us to stop trying, but that’s not something we seem gifted with.
As with all plant breeding and selection, it’s a numbers game. If the desirable trait exists in the species, you’ll eventually find it, if you grow enough seedlings. Since there were plenty of seed available from the exchange, I reasoned that if we grew enough, perhaps one would show some heat tolerance.
I don’t remember exactly how many pounds of seed arrived, but they were promptly sown, and germination soon followed. Each time the seedlings were transplanted, only the most vigorous ones were selected. These were then grown in our research cold frame for the next year, subjected to full sun and through a typical NC summer. By the following spring, we had whittled down our selections to nine clones that had thrived in containers, and in early spring 2019, they were planted in the ground. Over the ensuing years, four passed away, leaving five. This spring, four years after planting, two clones have topped 7′ in height and are flowering beautifully, as you can see below.
There are less than 20 named selections of Magnolia sieboldii, most selected either for double flowers or blush pink tips, but none for heat/humidity tolerance. The next step will be to make a final selection which we’ll name Magnolia sieboldii ‘Southern Pearls’. Scion wood will then be shared with Magnolia grafters who will assist with our mission to propagate and share. Winter hardiness of this clone should be at least Zone 5b – 7b.