We've all seen it, the tree lined streets with the volcanoes (Think Volca-NO!) of mulch carefully piled up knee high around the tree trunks. We spend a lot of money for that mulch, and unfortunately when it is piled high around the base of a trunk, it is not fufilling its purpose.
In fact many of our urban trees are planted with good intentions, but our current methods of care are actually contributing to their early demise. On average an urban tree life is 7 years. I don't know about you, but if I pay good money for something I would like it to last much longer than 7 years. Especially trees which provide benefits for storm water retention, property values, and the health of the planet.
Much of this ill advised care comes from lack of knowledge. Holden Arboretum and The Western Land Conservancy are seeking to change that with their Tree Steward training which is a major part of their Reforest Our City program. Two of our staff are in the process of becoming tree stewards and some of what we learned surprised us, and we think it may surprise you to. Here are a few items you might not know about urban tree care.
1) Mulch is important for urban trees. With some basic tree knowledge this now seems like common sense, but before the tree steward class I was under the impression mulch was just for aesthetics and preventing weeds! Our urban trees actually need mulch around the trunk out to the canopy of the tree to replace the leaf debris that we rake away every year. When you mulch a tree it should start about 1 to 2 inches away from the trunk and travel out to the canopy. It should not be piled up around the trunk. This piling can cause rotting of the bark. See this fact sheet for further details on mulching.
2) Trees have a trunk flare. In addition to poor mulch habits many of our urban trees don't get the right start when they are planted too deep. Take a look at your tree lawn trees, do they flare out at the bottom? If not they were likely planted too deep. This can cause the tree's roots to wrap around the base of the trunk and shorten the life of the tree. If it looks like a utility pole, it was planted too deep and you may need to do some careful flare excavation.
3) Urban trees require some planning. Many trees are planted without a plan for their growth. Avoid planting tall trees under utility lines and don't plant a tree with a heavy canopy right over your house. Make sure your soils are right for the tree you intend to plant. See this fact sheet for tips on avoiding placement conflicts.
4) Urban Trees need pruning. I was suprised to learn that you should prune urban trees. It seems like you should just be able to let a tree grow, but because our urban canopy is not as dense as a forest, urban trees tend to compete with themselves and can use some pruning to ensure the growth of strong healthy branches. Hire an arborist or get some training in the proper technique for pruning your urban trees.
Hopefully this post has piqued your interest in proper urban tree care as the Tree Steward Training has peaked mine.