Our current weather conditions demand that we rethink some of our fall chores. Fall lawn and tree fertilization should come later this year then normal because of the drought conditions. An application of high nitrogen now would only burn up what little green grass you may have and force trees to work more then they should under stressful conditions.
Even if you irrigate the lawn and water is not an issue you still want to hold off because our lawns also share space with the roots of our trees and shrubs and will have access to the applied nitrogen. Irrigation systems are designed to deliver water shallowly to our lawns so the moderate to severe drought conditions across the state means that the subsoil for larger trees is still at a deficit. This deficit has likely initiated dormancy a bit earlier then normal but we want to be certain trees and shrubs have shut down up top before we apply any stimulus.
Nitrogen is a stimulus and is best used by the lawn and woody plant material if it can be absorbed and used to establish stronger root systems. If the plant is still actively growing it will be used up to push new growth and this is not helpful in the fall if you are a plant struggling to survive under drought conditions.
Our drought conditions have been made worse, too, by the Hurricane Ike winds from Sept. 14. Extension Horticulturist Donna Michael said it best, “plants experienced a month long drought in the matter of 8 hours” as wind gusts literally sucked all the moisture from our plant; and whatever may have been left in the soil.
October is typically the driest month of the year so for newly planted trees (within the last three years) water deeply every week; water what ever else you can that looks excessively dry and vulnerable. And, do not fertilize because you will potentially encourage new grow before true dormancy takes place. Several good hard freezes are needed to trigger real dormancy.
Forego any fertilization when it comes to newly planted trees; water is the best medicine. For the lawn and the rest of your woody plant material a slow release formulation of nitrogen or some corn gluten (for the organic gardener) can be applied later; plants can also be mulched with composted manure for easy to digest nutrients throughout the winter. To be safe this year, my guess is that “later” will be after Thanksgiving.
Nitrogen is an extremely important nutrient for plants and it is also the nutrient that leaches out of the soil the fastest but we need to know how and when to use it. This is why I fundamentally prefer using compost and organic mulching materials over synthetic forms of nitrogen and aggregate mulch. If we annually apply a layer of compost and use bark mulch we continue to add to the organic matter that becomes available to our plants in the form of nitrogen as material naturally breaks down. This type of nitrogen release is slow and easy for our plants and available year round without stimulated too much growth at the wrong time.
So, for now, hold off on any major fertilization project. Wait for true dormancy and for quenching rains to return, instead.