|
I've yet to see a nice columnar Buckthorn...in fact here in Zone 4b/5a (depending on microclimate) they mostly seem to be 3/4ters dead, leading me to question their hardiness classification, which Dirr gives as zone 3. Then again, maybe it is just bad nursery production, compounded by poor planting practices, that has rendered all I've seen "dawgs".
If a plant is predisposed to a quick death, can it be invasive?
Dirr mentions invasiveness several times in his entry on Rhamnus frangula, and if all else fails, trust in Dirr and higher taxes.
Replacements in the shrub category are scarce; I have several lists of fastigiate trees, and have seen some like the Newton Sentry Sugar Maple that are an impressive 30' tall and maybe 4' wide (Delavan Arboreteum, Delavan WI)...but I don't think those would do, would they?
Maybe try a multi-stemmed fastigiate understory tree that can have exterior-stems removed periodically to keep an upright form: say 'Regent' Serviceberry or 'Golden Glory' Cornellian Cherry Dogwood. Some of the newer Arrowwood Viburnum cultivars (like Morton ('Northern Burgundy')) would fit the bill and not produce so much height.
If you are willing to go with a conifer, there are plenty of choices.
Just wondering Stonehenge, in what situations do you use these columnar Buckthorns? Maybe there is a different design approach that wouldn't rely so much on columnar plants...
|