Hardy Plants in Year-Round Containers

Hardy Plants in Year-Round Containers

For those with limited space who want to have an attractive garden year-round on a deck or balcony, plant only the hardiest small trees and shrubs in containers. The trick is to use the right plants, the right size and type of planter, the appropriate soil, regular watering and proper placement of plants.

Choosing Containers

For plants you’ll be over-wintering you need containers that can handle freezing and thawing. Most ceramic or clay pots will probably crack, as will inexpensive plastics.

Rot and moisture-resistant wood is ideal. It can be left as is to weather naturally or stained to suit your colour schemes.

half barrel summer flowers

Half whisky barrels are also ideal. They are large, relatively inexpensive and can also be stained or painted.

Concrete planters are tough and durable but heavy in larger sizes and are not always easy to move.

•Thick, high-grade plastic pots come in all shapes and sizes. Some are even coloured to look exactly like terra-cotta.

Cast iron is very elegant and sturdy but can rust and leave a stain on any surface they touch. They can be treated with rust proof paint.

In all cases, your containers need at least one drainage hole at the bottom to allow excess moisture to escape and some form of insulation (Styrofoam works nicely).

Planting Small Trees

• In a half-barrel or equivalent size you can plant dwarf standard trees like Weeping Peashrub, Dwarf Lilac, and Russian Olive.

• A flattened fruit tree, called an “espalier,” that’s grafted with 2 or more varieties for cross-pollination, is very attractive against a bare wall in a container that’s at least 75 cm (2.5′) high and wide.

espalier brick wall

Evergreens

• Your evergreens, especially broadleaf, should be planted in a sheltered area to protect them from the cold winter winds. If not, affix strong casters to the bottom of a large wooden planter so that your containerized evergreens can be moved against a wall out of the wind.

Topiaries, Upright Cedars, Junipers, and Dwarf Alberta Spruce all make definite vertical statements in a half barrel or similarly sized pot. They can be under planted with annuals, perennials, an evergreen groundcover, or a draping evergreen like Dwarf Japanese Garden Junipers.

• Medium size evergreens such as spreading Junipers for sun, Mugho Pine, various Globe Cedars and the Dwarf Alberta Spruce can be potted up on their own or in combination with other plant material.

Yuccas may survive but broadleaf evergreens such as Euonymus, Oregon Grape, Holly, Japanese Pieris, and Mountain-laurel burn very easily over a long, cold winter.

Boxwood is slow-growing, and can be tried in weatherproof planters that are a minimum of 40 cm (16″) deep and wide. For large rectangular containers Green Mound Boxwood can be used at the edge as a formal hedge.

Vines

• If planting vines, provide a means of support like a trellis, obelisk, or tripod upon which a vine can climb.

• Try the hardy Dropmore Scarlet Honeysuckle in either sunny or shady areas.

Shrubs

• Proportion is the key to using shrubs.

• You must have large built-in planters so the shrub will look balanced once it has matured.

• Smaller, deciduous shrubs can work well and will not be burned by the winter wind. Dwarf Lilac, Potentilla and dwarf Spirea will flower beautifully.

Roses

• Plant smaller, hardy Shrub Roses, such as the Rugosa Rose, the Explorer or Parkland Rose.

• Prepare roses for winter as you would any rose planted in the garden by hilling them with firmly packed soil and/or by using a rose collar.

Perennials

• Experiment with perennials.

empty terra cotta pot

• Keep in mind that plants in planters that are less than 40 cm (16″) tall or wide do not have a good chance of survival.

• Choose larger planters in which you can establish several perennials.

Overwintering

• Continue watering containers all through the fall.

• In late November, water one last time so the soil freezes up with lots of moisture in the event of a mid-winter thaw.

• Keep in mind of the wind and move pots to protect the foliage of evergreens if necessary.

• Start testing the soil for moisture in late winter and early spring.

• Do not hesitate to water in late March or early April if the soil feels dry to the touch and is pale in colour.

• The last watering of the season and watering through April are critical to the success of your container plants.

Maintenance

• Hardy plants often cover more than half of the soil surface so you cannot count on nature providing any moisture for your containers.

• Ensure you provide enough moisture, especially through the periods of high temperatures as summer wind will rapidly dry your plants.

• Use a moisture meter if you are uncertain how often you should water. Nutrients in a small soil system will deplete quickly and leach due to frequent watering.

• Fertilize approximately every 2 weeks from April to August with water-soluble Evergreen & Shrub Food, 30-10-10 or All-Purpose, 20-20-20.

• For flowering plants use Flower Food, 15-30-15.

• If new growth is scarce, flowering reduced, roots growing out the drainage holes at the bottom, or the plant is lifting itself out of its container, you may need to transplant into a larger container.

• Transplanting is best done when the plant is still dormant in early spring.

• Prune plants as required and keep an eye for insects and disease so you can control them.

Planting Tips

• Your containers need drainage holes. A power drill can easily go through wood or plastic.

• Place porous black landscape fabric or very fine mesh over the holes so soil doesn’t wash out.

• Put 2.5 cm – 5 cm (1″ – 2″) of gravel on top of the landscape fabric so roots don’t sit in wet soil.

• Use only Enriched Potting Mix, specially blended for planters.

• Follow the planting instructions and backfill the sides to within 2.5 cm (1″) of the top.