Where Has 'Harkness Hybrid' Gone?

July 12, 2007

Dear Friends,

Many years ago, I saw a tall mullein, verbascum, known as 'Harkness Hybrid' growing at Willowwood Arboretum in Chester, New Jersey. Willowwood was the home of the Tubbs brothers and then their ward, Dr. Benjamin Blackburn, upon whose death it became a public garden. Besides 100 species and varieties of willow, there are meadows, ornamental plants, rare and unusual trees. Tubbs and Blackburn turned the 130 acres of former farmland the into a home for 3500 species and varieties.

'Harkness Hybrid' grew to seven feet tall and produced numerous flower spikes with a profusion of two-inch-wide yellow flowers for over a month. When I finally had a spot with enough sunlight - the gravel garden on the island - I tried to find seeds for the plant. The English seed company Thompson & Morgan used to offer it, but it was no longer in their catalog. Today, searches in places like the Royal Horticultural Society's Plant Finder yield nothing.


I telephoned Willowwood, but no one working there today had heard of the plant which has been lost over years of renovation. About four years ago, I got two seedlings purported to be the one I sought from a gardener in Pennsylvania. They grew and flourished and bloomed the second year (these are biennials). The plants were multi-stemmed, but not really as spectacular as the one I had seen at Willowwood. The following year, volunteers appeared in the vicinity, but the seedlings that grew to maturity were not like 'Harkness Hybrid,' either. Perhaps the seeds passed from person to person had hybridized with local mulleins and others in the garden, making the offspring something similar, but definitely not 'Harkness.'

This summer, a plant appeared on the gravel driveway, which looks a bit like the amazing old mullein variety. And what it lacks in stature, it makes up for in tenacity -- it is a tough, determined plant.

A couple of weeks ago, I had several tons of gravel delivered (I have wanted to expand the gravel garden for years) and when the dump truck arrived they had to unload the crushed rock very near the verbascum in the driveway. The large pile spread onto the base of the mullein-but the stone did not kill it - -just gave it a decided lean to the west. The candelabra turned into a menorah!

I plan to collect and save seeds (perhaps select seeds only from the chunkiest offspring) and see if I can re-establish a 'Harkness Hybrid'-like mullein. There are many mulleins that happily grow from seed like the roadside escapee we often see (V. thapsus), and the satisfying species V. chaixii. There are, however, superb hybrids like 'Southern Charm' that actually seem to be perennial. On the other hand, several of the newest verbascum hybrids simply will not survive a winter for me. Although purported to be hardy in my Zone six garden, and despite being given excellent drainage, these showy plants bloom their heads off for the first summer from purchased plants, and perhaps, bloom themselves to death. I once tried cutting all the flower spikes off to see if that would prolong its life, but it didn't. I've never seen a seedling, and even if one did appear, it would not "come true" (be identical to its parent). The hybrids could be sterile, and since they are the products of specific crosses they can only be propagated vegetatively, via cuttings. If you can grow plants like 'Helen Johnson,' Jackie,' 'Caribbean Crush' (at right) and 'Honey Dijon' (my favorite) for more than one blooming season, please share your know-how. Thanks so much for reading, and happy gardening, Ken