Hi, I'd like to here from anyone in the north, who blooms cornus Kousa, as to which ones are the hardiest. They are said to be hardy to zone 5. We are zone 5 here in Ottawa, but nobody grows them. I have a couple that grow but never bloom or bloom very little. Kousa is said to be hardier than C. florida. I have it as well but no blooms. i have an acid soil, good mulch, light shade. I never have winter kill. they are 4-5 footers and established for 3-5 years. Anybody got any ideas?? Rich
"Hardiest and strongest grower of all the dogwood species we have in production. Exceptional vigor. No visible dieback or winter burn during our most severe winter blizzards and subzero temperatures of the past 25 years." http://www.lakecountynursery.com/galilean.htm "Cornus kousa is cold hardy to USDA zone 5, although it has potential for solid zone 4 with some new introductions likely to come onto the market over the coming years. In 1984, a U.S. expedition including Paul Meyer of the Morris Arboretum, Daryl Apps, Peter Bristol of the Holden Arboretum, and several others collected seed in South Korea. This Korean collection has yielded plants with excellent cold hardiness. John Wachter, who was working with Paul at the Berheim Arboretum, Clermont, Kentucky, at the time, tested several accessions in their lab and found more than one plant able to withstand -30F (-34C) or better. Stay tuned." --Cappiello/Shadow, Dogwoods (2005, Timber Press) If your plants were raised from seed they may not be old enough to bloom yet.
I'm in Omaha, Nebraska, which is also zone 5 and I've got a Cornus kousa 'Gold Star' that hasn't had any problems growing in the three years since I planted it. It has yet to flower, but it was just a wee little guy when I got it so I'm going to give it some time. There is a species kousa at the botanical gardens here that has had some spectacular blooms in years past.
