Power Trees

Scientists at the U.S. Nat'l. Arboretum have spent the last 4 years studying trees that can stand up to the rigors of urban environments. The Power Trees Project http://www.powertrees.com/index.html identified cultivars that exhibited pest resistance and tolerance for environmental extremes. Trees that made the cut include Ulmus 'Frontier,' Prunus 'Dream Catcher' and Lagerstroemia 'Natchez.'

So in a few years, everyone will be planting these, then along comes a new disease that rips through them, and back to square one . . .

The way to keep secure against problems is to maximise diversity: plant lots of different species, and use genetically diverse seedlings, not clonally propagated cultivars. That way, when a new pest or disease appears, it only takes out one or two plants here and there, not nearly everything in one go.

Resin

lol Resin. You are right though. The City of Vancouver overplanted Prunus, all the flowering Cherries, and now Honey Fungus seems common. I'm surprised there is no selection of Ginkgo - the tough-as-nails tree proven to take the worst city conditions. Diversity is far smarter.

Resin, you couldn't be any more correct. In my small town, when we plant a new subdivision, or old neighborhoods that have lost trees due to street imrpovements, we plant a minimum of four different trees, either Genus or species or preferably both. We choose from a selection list of roughly 30 trees adaptable to our particular soil and climate conditions and that can take tough urban sites. We do get some complaints from residents that they want a more "uniform " look. There are no longer any "sweeping vistas" of one species.

Municipal governments always fight budget constraints. Believe me they learn quick about over planting one variety when they lose them all and suddenly have to find the money to remove and replant. As chair of the Municipal Tree Commission I have had to plan the removal and replacement of 464 ash in one area alone. They weren't planted on my watch,
however had I been chair then I would have used the best information available from the State Department of Forestry and I might well have done the same thing.

I'm always grateful when there are new introductions to the stock of available street trees.
Used properly they can only increase the diversity.

growin, Ginkgo "Autumn Gold" and "Princeton Sentry" are two trees we regularly use. "Princeton Sentry", though gawky in youth, is a tree of great stature and downright majesty in maturity, if you are lucky to live long enough to see it!

My city is using jap tree lilacs quite a bit now. Some crabs,linden and tartarian maples. I do get a little worried when they plant 20 of the same thing in a row.

We've not planted many Malus, but the lindens and maples are frequently chosen. Also the Japanese Lilac. They work great under power lines and other small areas. Some cities around here will plant one block with one species, then switch to another Genus or species in the next block and so on. Diversity - yes, but a little riskier. About the only place we plant crabapples are in cul-de-sac islands. A grouping of two or three looks really nice in that setting. They dont get so large as to require much pruning to keep good sight lines for traffic.

We're in crape myrtle overload here, they're must be thousands in this small town.