Fertilization and Aeration: Partners for Growth

I’ve said it before, but it bears repeating. Before you can have a healthy plant, it must have a healthy root system. Given this, there are a couple of things you can do this fall to strengthen the root systems of plants in your landscape: namely, core aeration and fertilization. These two processes used together can do much to insure your plants’ health and longevity. They can even help your plants recover from the last 3 years drought and flooding patterns; and especially this year’s significant drought.

Since the core aeration and fertilization focus on promoting well-being of root systems, fall is the ideal time to take on these projects. This is due to the fact that root systems continue to grow and recover long after top growth ceases for the season. Therefore, fertilization and core aeration at this time of year can do much to help root systems catch up and even get a head start on next year’s growing season.

Basically, core aeration allows air to enter the soil around the root system by taking plugs of soil out, allowing the roots to “breathe“. Fertilizer adds elements to the soil that become nutrients and are necessary for the plant’s life functions to run smoothly. Fertilization without good air circulation in the root zone is helpful, but the two improvements are best used together as complementary processes rather than individual components.

Core aeration can be the saving grace of many of your older trees or plants and it can also help rejuvenate a tired lawn. To obtain maximum benefits for trees, plugs should be removed anywhere from 18 to 36 inches apart depending on soil density. They should also be one to one and a half inches in diameter and about 10 to 14 inches deep. Do a circle of holes at the drip line and 2 more circles outside and inside that area also at 18-36” apart. Core aeration (also called vertical mulching) always helps improve a plant’s root zone.

Fertilization is the next logical step. If you are doing it yourself, a granular material is more convenient and it may break down over a longer period of time. Just use the recommended amount (see package directions) for the area of root zone you are going to fertilize and place the material in the core aeration holes. Pay close attention to the application rate because you will probably be putting only a small amount of fertilizer in each hole. To fill the holes to the top with fertilizer could very well burn the plant’s roots and create lawn problems.

For plants that are slightly frail or are already showing signs of stress, core aeration should be your first reaction. However, fertilization probably shouldn’t be your next step. Contrary to popular belief, fertilizer isn’t the only thing to pull a sickly plant back from the brink. In reality, fertilizing a frail plant may cause severe damage to the root system. Therefore, if a plant looks weak, go ahead with core aeration and follow up with mulch and watering and an appropriate amount and type of slow release fertilizer.

With these guidelines in mind, the combination of core aeration and fertilization could be just the boost your plants and trees (and even the lawn) may need.

If you have questions, please call your local nursery/garden center or arborist for details.