Many is the time that I get a call about an old, ill oak tree. “It’s been there for generations.” “I used to swing under it as a child.” “It’s was planted by my great grandparents.”
You get the idea. There is huge sentimental value attached to it. And it is doing poorly.
The honest truth is (and it needs to be said up front) is that I don’t have any great solution for saving an old oak tree that is in decline. We can treat for insects or surface fungal problems, but how do you treat a treat for a virus or bacterium? There’s no “Z-packs” or a shot in the hip that we can give.
And if you do want to protect it from fungal problems, how would you spray the entire tree? Their height and volume would be difficult for even a local arborist to treat.
We often create problems for oaks by wanting to be near them. We build next to them, we put lawns under them, and we dig utility lines under them. Oak tree roots are not as deep as most people think. Have you ever seen an oak that has blown over? Their roots are incredibly shallow.
If you locate a new home, or create a circle drive, or do anything that disturbs the topsoil, you are effectively removing the roots that beloved tree depends upon.
Don’t forget buried utility lines or even that recently installed underground sprinkler system. That trench cuts the feeder roots. To add insult to injury, homeowners often cut the roots for an irrigation system and then smother the remaining roots with a turfgrass sod.
With the natural and human induced stresses, water management under oaks is most important to their long-term health. Thus, when we irrigate, we’ve got to irrigate both the tree and the adjacent landscape.
Turf is commonly irrigated twice a week which is not even necessary for turf except in cases of the coarsest sands. For the grass alone, apply one inch of water once a week when we get dry.
Now one inch per week would also be enough for your trees but if you will put out two inches every third or fourth watering, it will encourage deeper root on your trees.
The absolute minimum for oaks, during the growing season when it is not raining, is a single, two-inch application of water once a month. Again, this is only minimum possible when turf is not used.
Optimally, oaks should receive two inches of water once every ten days throughout the summer in the absence of rain. If you have turf under your trees, apply one inch of water per week for the turf and then apply an extra inch every third watering to reach the deeper roots of the trees.
But what if drought stress, construction, or other factors caused the tree to be in poor health? First make sure that it won’t be hazard if or when limbs fall off or the tree falls over.
After you are sure that an old tree won’t be a hazard, realize that you are the caretaker of an aged tree. Pamper it with water when we get dry. Don’t try and push it with extra fertilizer. Remove competing vegetation if that fits into your landscape plan. Above all don’t disturb the roots at all.
I’ve known folks who have collected and planted acorns to perpetuate the tree on other family or important sites. I’ve known some families that make something to remember the tree by out of the wood once it is harvested.
Looking forward, start thinking about what a suitable replacement might be in your landscape. Another tree perhaps? That tree had its heritage, it’s time you start a new one.