Guest Author - Jessica Carson
Make sure your container is adequate and ensure your potting soil will be right for your tree, as the container and soil will be your tree’s home for many years to come.
CHOOSING YOUR CONTAINER
- CONTAINER VOLUME
Your container should be large enough for your tree when it reaches its full-containerized height. Once you plant your tree, unless it is a very slow growing type, it will soon be too big for you to easily transplant again and re-potting can be injurious to the root system.
Select a container that holds at least 2 gallons of soil for every foot of eventual tree height. For example, a half wine barrel tub is about 25 gallons and would be good for a 12 1/2 foot or shorter tree.
If your container isn’t measured in gallons (and most aren’t) the conversion is
1 US gallon = 231 cubic inches = 3785.4 cubic cm.
Volume Calculation
For a square or rectangular shaped container, measure the inside width (W), length (L) and depth (D) in inches or cm and multiply together – W x L x D = volume. (Note: remember to subtract 1 to 2 inches or 3 to 5 centimeters from the measured depth, as you won’t fill the soil completely to the top)
For a round container, estimate the average diameter (d) of the container (the distance straight across the center of the circle) and measure the depth (D). To calculate the volume, multiply the diameter by itself (d x d), divide by 4, and then multiply by 3.14. Take the resulting number and multiple by the container depth (less a few inches or cm as you won’t fill the soil completely to the top) and you have the volume. The mathematical formula is ((d x d)/4) x 3.14 x D where d is the diameter and D is the depth to which you will fill the soil in the container.
Once you have calculated your total volume in inches or cm, divide by the number of cubic inches (231) or cubic centimeters (3785.4) in a US gallon to get the number of gallons your container will hold.
- CONTAINER DRAINAGE
Make sure your container has good drainage. Overly wet soil is a leading cause of death in container grown trees, so I can’t emphasize this enough. Choose a container which drains well with several large drain holes, and being made of a porous material such as wood or terra cotta clay is an added plus, though not necessary. Elevating your container on a trivet, pot feet, or rolling stand will also help ensure your container will drain well.
POTTING SOIL FOR CONTAINER TREES
The potting soil used for planting your tree is also very important. It must be loose enough to allow for good drainage and for the small hair-like roots of the tree to penetrate. By putting a tree in a container you are asking it to grow in an unnatural manner, so the soil needs are special.
Most potting mixes are too heavy for a container tree and will need to be amended with sand and vermiculite or perlite to help it drain properly. Choose a good-quality potting mix with a pH of 6.5 to 7.5 (7.0 – pH neutral – is ideal). Avoid mixes that contain sedge peat as the fine particles will clog up your soil and inhibit drainage.
Make a mixture of 1 part potting soil, 1 part vermiculite or perlite, and 1 part sand, crushed granite, or hardened clay pellets. Vermiculite or perlite is widely available from nurseries and some hardware and landscape supply stores. Sand is also widely available – be sure to use a course sand. Crushed granite can be purchased from feed supply stores as poultry grit – be sure it is crushed granite and not crushed shells or dolomite, as these will effect the pH of your soil. You can also use Turface, Soilmaster or Terra Green hardened clay pellets, which are available from landscape supply, sod farms and lawn maintenance stores.
You can prepare your mixture before planting and store in a large heavy-duty bag or garbage can, or mix small amounts in a bucket or wheel barrow as you plant. Make sure all materials are well mixed so your soil materials will be evenly distributed when you plant your tree.
Fruit Trees
