Every autumn, tree and shrub owners are faced with the title decision. Some “experts” advise not fertilizing and others advise fertilizing. The reason most often cited for not fertilizing is that it may cause the plant to put on new growth that won’t have an opportunity to harden off in preparation for winter. That doesn’t apply to woody plants, at least not in our area. Winter preparation is also the reason others recommend fall fertilization, and I belong to that group. Here’s why.
Fertilizer is spread around the base of plants, but its purpose isn’t to feed plants. Its purpose is to replenish soil nutrients. If you’re one of the few residential property owners whose soil is rich in organic matter and teaming with microbes, you probably don’t have to worry about fertilizing. Otherwise, the only way to replenish depleted soil nutrients is with fertilizer and organic matter. The soil cannot replenish nutrients by itself.
If you’re not sure whether you need fertilizer, we can test the soil. Your plants have probably used most of the nutrients replenished during spring fertilization. They were needed for the plants’ intense spring and summer food making process. Although it’s autumn already, the plans still need to make a lot of food before all the leaves fall. Like animals that hibernate for the winter, deciduous plants have to binge, so they have enough energy stored to sustain them through the winter and to break their buds to flower and leaf out next spring. Even after the leaves fall, the roots remain active until the ground freezes.
In the fall, the plant is working extra hard to make enough food to sustain itself now and pack enough away in the roots to keep it alive through the winter and get the food-making and reproduction system going again in the spring.
Nutrients from the soil aid in the process of photosynthesis, which is the plant’s food-making process that takes place in the leaves. The comparison between plant and animal needs that I find most easy to understand is comparing fertilizer to the vitamin supplements that many of us take. Some of the minerals (nutrients) that plants need is the same as those that we need.
Plants need three major nutrients – nitrogen, phosphorous and potassium – and trace nutrients zinc, copper, selenium, chromium, cobalt, iodine, manganese, molybdenum, calcium, magnesium and sulfur. Check these against the label on your multi vitamins and you’ll see that many are the same.
If you apply fertilizer, it’ll, no doubt, be granular, in which case, you’ll have to water the area thoroughly. Fertilizer only works when it’s dissolved or suspended in water. The roots then absorb the fertilizer laced water and send it up the plant. After the photosynthetic process has taken place, the food is distributed throughout the plant. Any food that’s left is stored in the roots until needed. If we fertilize your plants, we place it directly in the ground, near the roots, in liquid form. You don’t have to water the area and the roots can begin absorbing it and putting it to work right away. Fall fertilizer can be applied until the ground freezes but the sooner it’s applied, the sooner it can go to work helping your plants get ready for winter.