Q: A tree care professional looked at my ailing tree and recommended removal. I’m not excited about that prospect. Do I go with what they suggest, or do I have any other options?
A: It’s always a good idea to have trees assessed by arborists certified by the International Society of Arboriculture. The ISA-certified arborists must pass an exam on multiple aspects of tree care and hazard assessment, plus maintain their credentials with ongoing education. The ISA provides a search tool on their website, treesaregood.org. As with medical care, getting a second or even third opinion, especially for major work or expensive treatments, is sensible. Some arborists work as employees of a tree-care company while others are independent consultants.
Diagnosing the main causes of tree decline is challenging, especially since symptom manifestation can be surprisingly delayed. Insect or disease presence tends to be secondary, as environmental stressors often start the spiral of decline with subtle or unseen impacts. Unfortunately, few trees experiencing notable dieback are salvageable, though some treatments might postpone the inevitable or cosmetically improve their appearance for a time. That said, depending on the nature and pace of the damage, they may yet live for decades, continuing to provide ecosystem services that are so needed in human-altered landscapes.
Landowners that have ailing or declining trees should consider leaving them standing (or minimally cut) if their eventual fall won’t endanger people or property. Obviously, heed an arborist’s warning if they deem a tree a hazard, especially if it affects someone else’s property. When feasible though, foregoing removal will not only spare you considerable cost, but also will greatly benefit wildlife that depends on rotting or dead wood. (Think of the cute flying squirrels!) With few exceptions, the insects or diseases contributing to decline or decay will not threaten nearby healthy trees.
You can still plan for the future and plant a site-appropriate species that will eventually grow up to take the original tree’s place among the canopy. Local natives are the most practical, and among them, oaks top the list for wildlife value. Maryland has nearly two dozen species of native oak alone, so there’s plenty to choose from.
Q: Why is soil pH important?
A: Soil acidity or alkalinity affects how plants absorb nutrients from the soil. pH stands for “potential of hydrogen,” because hydrogen ions participate in molecular changes that make a solution acidic or basic (alkaline). Pure water has a neutral pH of 7.0; acids are lower in number and bases are higher. The scale is not linear, so a one-point pH change (say, 6.5 to 5.5) actually has a tenfold change in acidity.
Most garden and landscape plants grow best in the 6.0-7.0 soil pH range. When soils have a very low or very high soil pH, some nutrients can become too available and cause toxicity symptoms in plants, or be relatively unavailable and cause deficiency symptoms.
But pH isn’t always easy to change, mainly because the chemical properties of the soil are inherent to the minerals it’s made from. Using results from a soil test, though, you can gradually adjust levels by periodically applying formulations of sulfur or lime. (See our “Soil Testing” page for more information.) Potting mixes, on the other hand, tend to be pH-balanced and buffered so changes don’t readily occur. This is a good thing, since drastic alterations in such a small soil volume will stress roots or alter the microbial community the plant relies on to boost root function.