Don’t you just love to head out to a nursery on a beautiful April day? You buy a nice amount of your favorite flowers, then bring them home and plant them only to wonder why they are not growing! I used to do that, and got upset when they became a yummy dinner for the rabbits! Then I learned to consider the soil temperature before planting.

Spring is a great time for transplanting a plant from one location to another. Whether the move is from one place in your garden to another, from your garden to a friend’s, or from a nursery pot to your garden soil, it’s all the same to the plant. It’s a transplant.

It is just impossible to transplant any plant without a certain amount of root damage taking place. When digging, a good gardener will get as much of the root ball as possible, but some fine feeder roots will always be lost or damaged. This makes root development the first and most important mission of the plant in its new home. It needs those roots for taking in water and nourishment. The larger the canopy of the plant, the more water and nourishment will be demanded. Therefore, it makes sense to move the plant when the canopy is small, AND at a time when soil temperature is most ideal for root development.

So, when is that ideal time? For the average garden plant, that would be when there is ample water and nutrients available, and when the soil temperature is about 55 degrees. Please note there are many cool season plants (vegetable and ornamental) which can develop roots in soils as low as 45 degrees. However, 55 is a much safer general rule of thumb for all plants in general, most especially your annuals.

In early spring, we sometimes have a period of beautiful warm days with temperatures even into the 70’s. Don’t be fooled. That’s the air temperature! The soil temperature may still be something like 40 or below. That’s way too cold for a new plant to develop its root system.

Just like guessing at a child’s temperature to determine if he is sick is not a great idea, guessing at your soil’s temperature is equally iffy. The soil’s temperature should be taken at about 6 inches deep, or at the depth the new roots will find themselves. An inexpensive soil thermometer, which can be purchased at most garden supply stores or online, is an invaluable tool at this time of year.

The right thermometer will have the capacity of measuring down all the way to freezing. The dial will face up, and it should have a strong probe. It will look much like a meat thermometer but is geared to lower temperatures. If the soil is hard, think about using a screwdriver to make a hole for the thermometer to slide into easily to protect it from breaking. There is also such a thing as a compost thermometer which has a longer probe designed to reach the center of the compost pile. It will be geared to read temperatures as high as 220 degrees.

Clay content in the soil can affect the temperature. Many gardeners in Adams County are confronted with a high clay content in our soil. You may be surprised to know that clay soil is actually quite high in nutrients. The problem is that the clay particles are the smallest of soil particles, and they tend to stick together and interfere with the passage of air and water making it difficult for plants to grow. Clay soils also tend to stay cold for longer in the spring. You can remedy all this by adding organic materials. The organics will lighten the clay by enlarging the pores between the soil particles.

The easiest way to add organic material to your soil is by collecting all your garden waste in a pile and allowing it to decompose into compost. If you don’t like the idea of a big pile, get a bin. It is neater and more efficient.

Grass clippings mixed with chopped leaves can be used as an acceptably attractive mulch to help prevent weed seed germination. As it breaks down, it makes an excel-lent soil conditioner which will work to feed your soil.

Sudden change in air temperature is the most dangerous situation for our winter plants. Mulching with compost around plant roots in the fall will help moderate the soil temperature to keep it on a more even keel. This is especially important for any new transplants that may not yet have established a complete root system. The mulching will prevent them from being "heaved" up out of the ground.

Evergreen trees and shrubs have a much greater need for water in winter because their needles and leaves require a greater supply of moisture than a plant that has lost its leaves in the fall. Winter winds can be very drying and a newly planted evergreen may not be able to bring up enough moisture in winter to support itself. This is why ever-greens do much better when planted in the spring. Ornamental grasses are also better planted in the spring because spring is when their root system is developing most quickly.

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