Urban Living- Choosing Containers for Growing Trees and Shrubs

Garden containers allow trees and shrubs to be grown effectively by urban dwellers living in small spaces. Trees and shrubs will thrive in containers and planters if their basic needs are met. Homeowners and apartment dwellers alike, who have small outdoor spaces, can enjoy growing their favorite trees or shrubs. You will find facts and information on sizes of containers, how to plant your tree or shrub in containers, making your soil mixes for containers, fertilizing plants in containers, and how to root-prune container plants.

For a young tree or a small shrub, such as a gardenia, suitable outdoor plant containers should be  14” to 16” in height and diameter. Because soil insulates, that amount of soil is usually enough to keep roots from freezing as far north as Zones 6 and 7. You will find that there are many different containers for sale. Containers will vary in price according to the size, type of material, and design of the container itself.

"Garden Containers"

Garden containers for small spaces

A larger plant, such as a dwarf flowering crabapple, will do well for years in an 18” to 20” container. A tub that size holds enough soil to protect the roots in most winters as far north as Zones 4 and 5. A larger plant could start in a 14 to 16” tub but will eventually require a big tub, perhaps 30” high and and 24” in diameter.

*Additional Help:  Step-by-step directions for planting in containers can be found to assist you in having success with your plants.

Urban Living for Gardeners

Urban living in apartments or condos can be a little discouraging if you enjoy plants and gardening. Sometimes the amount of outdoor space you have is either non-existant or very small. By using various sizes of containers, you can plant your favorite type of tree or flowering shrub to enjoy. They do well on patios or outdoor terraces, or in between buildings.

Choose bright colors for your containers if you want to  liven the area up. If you prefer a more subtle colors, choose tones that will work well with your outdoor surfaces. Earth tones work well outdoors and will blend in with most surfaces. If  you are planting a flowering shrub, you may want to choose a container with colors that will harmonize or contrast the color of the blooms. You will also find many types of containers for sale. Your options are almost limitless. Containers can be found at home stores, discount stores, or online for convenient shipping.

Using Large Tubs as Containers

Larger tubs will allow for more root development, which helps the plant grow bigger. A large tub also makes maintenance easier because it will need watering only once or twice a week, even during the summer. During hot, dry, windy periods, smaller containers must be watered daily, even when the soil is a very good organic mix.

"Plant containers"

Whiskey barrels make great plant containers

Soil Mixes for Containers

You will be able to find commercial soilless mixes that are often used in containers because they are lightweight and easy to move. Yet a fertile semi-soiless mix provides a better diet for the plants.

Make Your own Soil Mix

You can mix your own soil by thoroughly combining the following ingredients:

  • 1 part good topsoil
  • 1 part horticulture perlite
  • 1 part coarse peat moss
  • For every 7” of planter height, add 1 cup of dehydrated cow manure and 1/3 cup of slow-release 5-10-5 fertilizer.
  • Mix in horticultural polymers

Horticultural polymers help keep the soil humid. A horticultural polymer is a jellylike granule that hold many times its weight in water and releases moisture as soils dry out. Mix it in thoroughly with the soil.

"Trees in Containers"

Trees are easy to grow in containers

Before planting, soak the container mixture two or three times until water runs out the bottom of the container. After planting, top the soil with a 2-3” layer of mulch to minimize moisture loss and keep the mix from blowing around.

Tip- Frequent watering leaches nutrients from the soil, so compensate by giving the plants light applications of a water-soluble fertilizer.


Citrus tree grown in container

Fertilizing Container Plants

If you did not apply a slow-release fertilizer at the time of planting, scatter the fertilizer over the soil surface. Apply a dilute solution (about 1 teaspoon of 20-20-20 per gallon of water) of a balanced soluble fertilizer once a week or a far more dilute solution every time you water. Every year, topdress the container soil with 2-3” of improved soil or compost.

Root-Pruning Container Plants

Container plants can become rootbound. This means that there is too much root material relative to the container and soil mix. Root-pruning every two or three years keeps a plant growing well and helps retard its growth without impairing its form. Root pruning should be done in late winter before growth begins.

With a small tub, remove the mulching material and tip the tub onto its side before slipping the rootball out. Disentangle the roots wound around the rootball, prune them back, and then cut away the roots growing straight down the sides of the rootball.

Next, add fertile soil to the tub, slide the rootball back inside, and set the tub upright. Push fresh soil down around the sides, and add 2 or 3” to the top of the rootball before replacing the mulch. Water thoroughly. If the tub and plant are too big to turn the tub on its side, use a hand pruning saw to sever all roots growing around the outside of the rootball.

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