Doing your part for Minneapolis urban forest

photo by tricia cornell

The Tree Trust offers tips on choosing and planting trees

When the leaves started to fill in this spring, many Southwest residents looked upward a little nostalgically: The lush green canopy has a few more holes in it each year.

The city of Minneapolis cuts down about a thousand of the city’s nearly 1 million trees every year, just as part of the regular life cycle, but during the last decade, thousands more have been lost to Dutch elm disease, including a devastating 10,000 trees in 2004.

That means more gardeners are adding another task to their spring list: planting a tree. But choosing and planting a tree isn’t quite like sticking some petunias in the ground or trying a new perennial, knowing you can always dig it up and move it if it doesn’t work.

Because — to state the obvious — trees are a lot bigger and a lot longer-lived, choosing and planting one takes a little more care. That can intimidate some homeowners.

We talked to Karen Zumach, community forestry manager at the Tree Trust, about what to look for when you want to do your own bit for the city’s urban canopy. The Tree Trust, based in St. Paul, helps promote the health of the metro area’s urban forest by planting and maintaining trees in public spaces and helping get inexpensive trees into the hands of homeowners.

In early May, the Tree Trust distributed more than 800 trees to Minneapolis residents through a city-subsidized program. As in years past, residents have been able to buy 6- to 8-foot trees for just $25. (Those of you who missed out, keep your eye out for notices next spring. “It’s a year-by-year budget thing,” Zumach says. “Mayor Rybak has been really instrumental in making sure that goes through every year. Hopefully we’ll be able to do it again next year.”)

Choosing a tree

The elms we’re losing make up about 10 percent of Minneapolis’s trees, according to a recent report by the U.S. Department of Agriculture. The vast majority of the rest belong to four other species: sugar maple, Norway maple, little-leaf linden and green ash. (Ash trees make up nearly 15 percent of the forest. They were the tree of choice to replace the elms lost to the first round of Dutch elm disease in the 1970s and are under impending danger from the near-inevitable arrival of the emerald ash borer.)

But you can look beyond the big five when choosing a new tree for your home. When asked about her own favorites, Zumach responds enthusiastically.

“I would definitely say the showy mountain ash is a big one for me, it’s a medium-sized tree that has something going on all year round as far as the bark or the fruit or the flowers,” she says, adding, “I always like crabapples. They’re just so sweet this time of year and tend to be more manageable.

“For larger trees, bur oak, I don’t think there’s any more beautiful tree than a bur oak. They just have really great architecture, which is impressive.”

As for those ubiquitous hackberries and ginkgos, she calls them “workhorses” that can thrive in all kinds of conditions. “I think our urban landscapes would look a lot different if we didn’t have those around.”

No matter your taste, two things that you must take into account when choosing a tree are height and hardiness. Always find out what the mature height of your tree will be and make sure it will stay well clear of houses and power lines when fully grown.

“Generally, because of the smaller lots that exist in South Minneapolis, you’d want to stick with a smaller tree, like an ornamental, not necessarily a big oak tree,” Zumach says

Also, while local garden centers certainly carry beautiful zone 5 trees (that’s the USDA hardiness zone south of us), Zumach recommends sticking to zone 4 trees. Be sure to ask where a tree was originally grown and insist on trees from local nurseries: A zone 4 tree that originally set down roots in Florida is going to have a tough time surviving its first Minnesota winter.

As for what size tree to look for — whether a tiny, stick-like sapling or a 6-foot tree in a No. 10 pot — Zumach says that decisions is driven entirely by cost.

Planting a tree

The first step in planting a tree is to find the right spot. Look up: Any overhead lines? And look down: Any power lines or sewer lines under there? Actually, for this part you’ll need some professional help. Call 311 to have someone from the city come out and mark any underground obstacles.

You’ll need a little professional boost in step two, as well: Order a soil test from the University of Minnesota. For a small fee, you’ll get an analysis of the nutrients in your soil and a recommendation on how to amend.

In order to take full advantage of the energy-saving shading properties of your tree, Zumach recommends planting on the east or west side, while avoiding the north and south sides because it “messes with the whole passive solar idea in the winter.”

When you have a site chosen and a tree in hand, it’s time to heed the cardinal rule of tree planting: Don’t plant too deeply! When transplanting annuals and perennials from pots, many gardeners are used to using the container as a guide for digging the hole. When planting a tree, instead, you need to look for the first pencil-sized root and use that as the ground line, Zumach urges. “[Planting too deeply] is the biggest tragedy that happens,” she says. “Roots start sprouting from the area above where they’re planted and it ends up strangling the tree. It commits suicide.”

You may also be tempted to fertilize your new tree to help it along, but if you purchase one in a container, this won’t be necessary for two growing seasons. “When plants are grown in containers, the soil in which they grow is very similar to steroids!” Zumach says.

Not out of the woods

With encouragement from organizations like the Tree Trust, more homeowners may be adding trees to their gardening repertoire. The city will continue to lose elms and it will take years, if not decades, to fill the holes in the urban canopy.

“Dutch elm disease has devastated a lot of trees. I don’t think we’re out of the woods yet. It’s still pretty ubiquitous,” Zumach says.

Meanwhile, forestry officials are looking eastward to Wisconsin, where the emerald ash borer has arrived and is eyeing the city’s ash trees.

 

Resources

Planting Trees and Shrubs for Long-Term Health
• By Rebecca Hargrave, Gary Johnson and Michael Zins. Available for purchase from the University of Minnesota Extension Service

Plant a Tree the Right Way and The Right Tree
• Available for download from the Tree Trust: http://www.treetrust.org/urban-forestry/training-and-resources.html