Drippin’ Gardening: Fall is Tree Time

I love gardening. I enjoy the fresh air, physical activity, mental stimulation, constant change and more. Autumn is a great time to become re-inspired to get outside and do some important maintenance in the garden and to plant new trees and shrubs. Big dividends in spring are the added reward, not to mention how wonderful it feels to be outside in cooler weather!

One of my favorite parts about gardening is that I’m always learning. Fortunately, I learned something recently that changed my approach to when I fertilize established trees and shrubs.

For most of my gardening life, trees and shrubs that needed a nutrient boost got their annual fertilizer application in early spring, right before active growth began for the year. This timing has been the generally accepted practice by experts everywhere for years. And although early spring is a good time, new research indicates there is an even better time.

Contrary to traditional wisdom, many experts now consider late fall to be the ideal time for applying fertilizers. We now know plants utilize nutrients throughout the year in different ways.

In the past, the most common reason against fertilizing in the fall was the fear that plants and trees would put on new growth if unseasonably warm weather returned, only to be burned or damaged by imminently colder temperatures.

They key is to understand the difference between early fall and late fall timing. If you fertilize in late summer or early fall, when temperatures are still warm, and plants are still actively growing, it is likely new growth could occur and damage to tender new foliage could be the result.

The rationale for late fall fertilization makes sense when you understand why. At this time, deciduous trees and shrubs have lost their foliage for the year and active growth of plants and trees has slowed. Rather than put on new foliage growth, the roots of established trees or shrubs take the nutrients from the soil and apply them to important health-promoting functions, such as disease resistance and root development. The excess nutrients are stored in the roots and become immediately available when needed for new growth in spring. But when is late fall? We had snow last December but the trees I planted just before that “blizzard” were gorgeous come spring!

However, keep in mind, not all established plants and trees are candidates for a regular fertilization program. I suggest a soil test be obtained through our local county extension office. Taking a soil sample is easy and inexpensive. Simply gather up a representative soil sample from around the area where your trees and shrubs are growing, fill in the form and send it to the lab.

The report you get back will let you know what nutrients may be lacking in your soil for optimum growth. The report will also suggest the proper type and amount of nutrients to add.

A common mistake is to assume fertilizer should always be added, and if a little is good, more is better. Nothing could be further from the truth. Excess nutrients are wasted and can end up contaminating the soil, and the environment beyond. In fact, one of the largest contributors to polluted downstream waterways is excessive fertilizer application wasted by well-intentioned homeowners.

In light of this new research you may be wondering if you should amend a hole when planting a new tree in your yard. Current research indicates the planting hole should not be amended unless amending the entire area. This may come as a surprise to you, as it did to me, as I was always taught that it was critical to amend the soil when planting any tree or shrub.

Fall is the best time to plant most trees and shrubs. The cool air and warm soil temperatures are the perfect combination for establishment. The cooler air is kind to plants and especially to ones that have just lost a major portion of their roots from being dug up. In addition, soil temperatures are still warm, creating an excellent environment for the production of new root growth.

Another benefit to fall transplanting is that most plants and trees are entering a period of dormancy. Rather than continuing to transfer energy into new foliage and aboveground growth, plants are now are transferring energy into their roots and storing nutrients and resources for the cool months ahead.

By spring, the result should be a well-established root system and a plant that can handle the upcoming demands of summer. Here are a few additional tips to ensure the success of all your fall transplants.

When transplanting, my great grandmother always advised that I “dig a ten-dollar hole for a one-dollar plant.” She wasn’t wrong. It’s not always easy but is always worth it. Make the planting hole two to three times wider than the current root ball but don’t make the hole any deeper than the plant was growing in its previous environment. Remember that – wider, not deeper.

As I mentioned above, and I know that this is contrary to traditional planting methods, the latest research-based data indicates that you should not amend the hole with additional organic material. This is because roots growing in amended soil rarely venture into the harder native soil. The roots become spoiled so to speak and tend to stay only within the modified area. The long-term affect is a smaller root system, reduced growth, and a weaker plant that is susceptible to illness and disease.

Instead, simply break up the existing soil, remove the rocks and backfill. Studies show plant roots simply growing in the native soil actually do better at expanding beyond the original hole.

Place transplants in their new environment at or slightly above the surrounding soil level. Newly disturbed soil has a tendency to settle and plants growing below grade can easily succumb to root rot or disease. It is better to plant a tree or shrub slightly high and allow the area to drain than for a plant to sit in a bowl and collect excess water.

Next, lightly tamp or handpack the soil around the plant roots to ensure good soil to root contact. A critical step at this stage is to water well. Not only does it provide needed moisture, but the water helps eliminate air pockets that could otherwise result in dead roots or worse.

The final step is to mulch with 3-4 inches of organic matter such as shredded leaves, ground bark or straw. Mulch helps retain moisture and keeps soil temperatures moderate. Winter conditions can be very dry so water throughout the winter if soil conditions needed. Roots are still growing, and soil moisture is essential for proper establishment.

Autumn is inspiring and the perfect time to relocate plants you thought about moving over the summer. It’s easier on you and the plants and you’ll be rewarded for your efforts next spring and beyond. The time is now so what are you waiting for?