I have two volunteer trees: one an oak and one a maple growing near the foundation of my house. The oak is 5 inches in diameter and 12 inches from the foundation and the maple is 7 inches in diameter and 24 inches from the foundation. I really like the shade from them on the wall of the house. Do I need to worry about them (cut them down) damaging the foundation of the house?
That is an example of a very common problem in our built environment. Tree seeds take root where they have the opportunity. Scrub jays and squirrels can carry acorns far from an oak. When dropped and forgotten, acorns use their stored energy to sprout and get a foothold, sometimes in unlikely and ill-advised places.
Here in our region, other energy rich tree seeds commonly volunteer, including walnuts, privets, cherry plums, Carolina cherry laurels, olives, camphors, and Canary Island date palms. Smaller tree seeds I sometimes see sprouting in gardens include Japanese maples, usually not far from the parent tree and where there is at least a little summer moisture, and some of the more dry-tolerant conifers, like Deodar cedar.
The fact that these species commonly volunteer indicates they are well suited to the local Mediterranean-type climate but, like smaller broadleaf and grassy weeds, they might not be the right plant for the location where they sprouted.
Secondly, aside from “volunteer” seedlings, people often plant trees where they will cause problems as they grow to their natural size. Sad to say, it’s a common mistake.
Thirdly, we often build things too close to existing, mature trees. I have seen this time and again, where the architects, civil engineers, and planning departments have all “signed off” on, i.e. approved, designs where mature trees have virtually no tree protection zone, with utility trenches, pavement, and foundations destroying root systems.
And, since some planners seem to have only a two-dimensional view of projects, tall buildings are sometimes designed go where large limbs already occupy the space.
Last week, I saw a three-foot trunk diameter coast redwood growing about one foot from a home. In that case, the wall by the trunk was an add-on. Apparently the owner or designer did not consider the nature of coast redwoods when they added a room near the tree.
With a little knowledge and thought they should have realized this type of tree can easily grow to 6-foot trunk diameter over time in a Napa garden, and far larger in parks and forests.
KD’s volunteer trees were providing some benefits but there is no exact way to know when push will come to shove. Who wants to bet their foundation to save a volunteer tree?
I responded: “That is too close. Eventual damage is possible. I recommend removing them. As an alternative you might be able to keep them dwarfed by pruning and still have some shade for the wall.”
One way to consider the benefits of a “right tree” in the “right place” is given in the tree appraisal system. When determining the value of a tree, the appraiser modifies value according to species, tree size, tree condition and location.
The location factor includes the site, the contribution (benefits) the tree provides, and its placement. Poor placement can drastically reduce appraised value.
Trees vary in compatibility with construction effects, mature size, and response to obstacles.
For example, coast redwoods grow quickly to phenomenally large size. They are inherently resilient when damaged and the roots tend to push obstacles out of their way.
In contrast, valley oaks grow to large size at a relatively slow pace. Oak roots tend to deform around obstacles, and older trees are very subject to decay following large wounds.
In landscapes and home grounds, it is pretty rare for a large-growing shade tree to “volunteer’ at the right location.
Whether you are considering saving volunteer seedlings, planting new trees or entire landscapes, or building near mature trees, know the species and think in three dimensions, plus time.