Dear Inconstant Weeder!
If you own a car, someone wants to sell you car maintenance. If you have a face, someone wants to sell you face maintenance. If you have a tree, chances are someone wants to sell you tree maintenance.
You may be aware that some kinds of car or face maintenance are not really necessary: fuel injector flushing, pore injector flushing, windproof windshield waxing, age-proof hoof toning, and skilled manual agitation of perfumed air around your potential problem areas.
Well, tree maintenance, too, has its upsells.
One of them is deep root fertilization.
Arborists and landscapers sell deep root fertilization to the homeowner under the premise that since trees are big, their roots go deep. “Deep” is a magical little-understood stratum where there be magma and dragons; therefore, trees need fertilizer pumped through a hole in the ground directly to their roots inside the Deep, lest they die.
Dear Weeder! Please see the forest. For the trees.
In a forest, have you ever seen anyone drilling an expensive hole into the earth and pouring fertilizer into it?
No – and yet the forest thrives.
Many trees do grow a taproot when they are babies. It first helps them get anchored in the ground, and then it grows fibrous (thread-like) roots in all directions, spread close to the surface of the soil. The fibrous roots are the ones responsible for the uptake of nutrients. Most feeding occurs right near the surface.
In a forest, there is a lot of composting activity on the surface. Leaves, fruits, bugs, worms, fungi and other things make this life-and-death soup, which leaks nutrients, which the surface roots drink up.
Most likely, the trees in your backyard need no fertilization at all. But if it makes you feel better, you can buy a ten-dollar can of fertilizer granules at the hardware store, and sprinkle them on the ground under the tree by yourself, in accordance with the label instructions: tree fertilization achieved.
Pouring big unusable deposits of synthetic fertilizer in deep holes in the ground is actually not good for our water.
Now let’s talk about mulching trees.
We are told that putting a big pile of brown wood chips around the tree will conserve moisture in the soil, and so is beneficial.
Again, consider the forest.
The forest is self-mulching.
A lot of tree owners remove all leaves from their property in the fall. If we kept the leaves under our trees, the rotting leaves would feed and moisturize the trees nicely.
But even when we remove leaves from under established trees, mulching them does not make things better.
Young seedlings can indeed benefit from an application of mulch. They are still growing their roots, and a moister surface soil will make early life easier for many species. Smothering nearby weeds with wood chips also does a little bit of good.
Big trees don’t need this service; they got a good handle on growing themselves.
Many people simply like the tidy cultivated look of a freshly mulched tree.
That’s fine. But first, do not harm.
No piling mulch right against the trunk or over exposed roots: bark will decay and expose the tree to pests and fungi. No piling mulch more than two inches high: enough water may not reach the ground in high mulch and younger roots – gasp! – may even start to curl upward to drink from the mulch instead! No good.
Deep fertilization and mulching mature trees may be good for business, or for our sense of accomplishment.
It may not be good for our wallets and our trees.
Dear Inconstant Weeder!