If a cold snap last November wasn't enough, Mother's Day really took a toll on trees across Douglas County, experts say. Just as hackberries, honey locust and ash trees were trying to leaf out for spring, a drastic freeze set them back.
“We are just getting totally inundated with calls about people's trees,” Douglas County horticulturist Jane Rozum said.
It all started last fall, when temperatures plummeted from 50 degrees to well below 0, and for trees that's a very stressful event, especially if they're young and haven't acclimated yet, Rozum said. Then the temperature hit 26 degrees on May 9 and just as some were trying to grow new life, they froze.
But things may look a little different now, said Highlands Ranch Metro District forestry supervisor Dennis Donovan.
“Our trees are leafing out, as we speak,” he said. “We have to let Mother Nature take its course and have a wait-and-see kind of attitude.”
Donovan helps take care of roughly 14,000 Metro District-owned trees in what the municipal services department likes to call an “urban forest.” His job, as well as that of other forestry employees, includes pruning, watering, pest control, planting and tree-limb recyling. Highlands Ranch alone has about 50 different tree species, with about 1,500 ash trees.
While new life is springing, the downside is that trees may look sparser in appearance and have more dead twigs and branches, Donovan said.
“Trees are pretty resilient and will push new growth, but after several freezes they don't have the energy reserves to come back,” Rozum said. “These climatic events make it tough for them to grow, but they still have to get ready for the next thing that could possibly come their way.”
Another upcoming challenge could be a dry, hot summer. Rozum encourages tree owners to water under the canopy every two weeks if the summer's extreme heat has an effect on the trees' reserves.
Rozum's biggest advice is to be watchful.
There's no crystal ball, but it does take a good three weeks — at least — to recover, and that's being optimistic, she said.
“Give them at least until the end of June,” she said. “If anyone wonders if their tree is dead or alive, they can scratch with a finger anywhere on a twig — if it has a greenish-whitish tissue and is expandable, it's still alive; if its brown and brittle, it may not be.”
People will have to make a decision on their own if they want to treat their trees, but it's not recommended to fertilize or prune until next spring, she said.
Rozum said Douglas County loves it when people snap photos and email them into the Colorado State University Extension Office, where she works.
“We can tell a lot about these trees from how they're planted and the way they look and those photos help us,” she said.
Arbor Valley Nursery, which has locations in Brighton and Franktown, is a wholesale nursery that supplies roughly 15,000 large trees to landscape contractors and commercial gardeners a year.
The freeze in November was a stark 60-70 degree drop and it damaged a lot of evergreens, said Tom Halverstadt, Arbor Valley's general manager. Mother's Day was more of a short polar plunge, and thankfully the last one of the year, he predicts.
As with the recent hailstorms, Halverstadt said, there's really no way of avoiding damage. If residents have young trees, cover them with a blanket, but as for a large tree, there's not much to be done other than pruning off the damage after the storm.
About 60 different species are sold through Arbor Valley, including those sold to residential landscapers around Douglas County, and he's heard what everyone's saying about their trees.
“The four species that seemed to be slow on re-leafing are honey locust, oaks, ash and hackberries,” Halverstadt said. “Last week, I had no leaves on one of my trees and this week because of the heat, they're coming on strong and I've noticed a big difference. Ash trees around Sedalia are really popping out now.”
The best part is, almost all trees have two sets of buds, for this very reason — to protect them from harsh weather. They're well equipped, so everyone just has to be patient, he said.
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