Container planting can be a pleasurable, yet difficult undertaking if you want to have your plants survive in the containers over the harsh Winter season. And I know how nice it is to have color on your porch, patios or balcony space especially if you don’t have access to a yard for planting. There are some simple rules to follow and certain plants that will survive the containers over others. For the most part it comes down to your watering habits, wind protection, and the root ball size compared to the container size. The biggest threat for overwintering a container plant is the root ball freezing and unfreezing and the plant’s drying out since there is no excess moisture from the earth.
An important tip to remember is you must always be watering correctly, be sure to water the plant on a regular basis throughout the season and continue watering 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. If there is a thaw during the Winter season, you may need to water. Start testing the soil for moisture in late Winter and early Spring and do not hesitate to water in late March or early April if the soil feels dry and is pale in color. The last watering of the season and watering when the soil thaws, are critical to the success of your container plants. You also need to keep in mind the drying winds of Winter, it is important to protect the foliage of Evergreens, especially the broad-leaf. You can move the pot to a more sheltered area and use an anti-transpirant spray (such as Wilt-Stop) to hold the moisture in the plant.
You should try to maintain the root ball size at half the size of the container (if possible) to prevent the freezing and unfreezing of the roots. We do sometimes recommend putting bubble wrap around the interior of the pot, followed by the soil and plant, just as a little extra insulation for the root ball. At some point, usually after a couple years depending on the plant, the plants should be taken out, root pruned, and reset in fresh soil. They will most certainly decline without this maintenance. No plant stays the same, just because its container stays the same.
Here are some recommendations for plants that make great container plants:
DWARF MUGO PINE (Pinus mugo var. Pumilio) — Zone 2-8 prefers Full Sun- A slow-growing dwarf conifer with dark green needles and dense foliage, reaches 3-5′ x 4-8′. Prefers loamy, well-drained soils. Prune and feed in the Spring before new growth appears.
JAPANESE BOXWOOD (Buxus microphylla var. japonica) — Zone 6-9 prefers Full Sun to Part Shade- Can grow 6-8′ x 8-10′ prefers evenly moist, well-drained loams. Rabbit and Deer resistant.
GREEN MOUNTAIN BOXWOOD (Buxus x ‘Green Mountain’) — Zone 4-9 prefers Full sun to Part shade retains dark green foliage throughout the winter and grows into more of a pyramidal shape then the usual meatball shape. Living in a container will keep it smaller than its normal 5-foot height and 3-foot width. Place out of reach from strong winds and if possible periodically rotate pot to expose all sides to the sun to avoid bare spots.
BLUE STAR JUNIPER (Juniperus squamata) — Zones 4–9 prefers Full Sun but can handle part shade, slow-growing and low-growing with steel blue needles. Reaches 3′ x 3-4′ the branches arch elegantly over the rim of a pot. It doesn’t like humid conditions.
ANDROMEDA ( Pieris japonica) — Zones 6–8 grows in Full sun or Full Shade evergreen foliage provides interest in all seasons, the spring growth of varying colors from glossy red to salmon pink to creamy white are spectacular followed by white bell shaped fragrant flowers. In winter, the flower buds are showy—usually dark red, with some opening to shades of pink. The graceful branches of this shrub drape naturally over the edges of pots. Protect it from winter’s harsh winds and strong sun.
EMERALD GREEN ARBORVITAE (Thuja occidentalis ‘Emerald Green’) — Zones 4–8 grows in Full Sun to part shade provides excellent year-round interest with a rich green color. An upright, narrow habit makes the ideal vertical accent that many containers need and is excellent when combined with other plants. A container will keep it well under its natural size of 15 feet high and 4 feet wide.
GOLDEN SWORD YUCCA (Yucca filamentosa) — Zones 4–11 Prefers Sun but can tolerate light shade. Prefers dry conditions. The creamy white and yellow sword-like leaves combine easily with so many plants. It grows 2 to 3 feet high and wide. In summer they bloom white, fragrant flowers on 3- to 6-foot-tall stems. In late winter, the foliage may get a little flat, but it will perk up again in spring. Pull off the old foliage to maintain a tidy appearance.
REDTWIG DOGWOODS (Cornus alba) — Zone 2-8 prefers Full Sun to Part shade. A deciduous shrub with fantastic Autumn color followed by bright red stems throughout the Winter makes a perfect upright feature in a container for all seasons.
GOLDTHREAD CYPRESS (Chamaecyparis filifera) — Zone 4-9 Prefers Full Sun to part shade. An evergreen shrub with golden-green color and feathery draped habit. Makes an excellent accent in a container. Prune it in fall to help keep its shape.
DWARF ALBERTA SPRUCE (Picea glauca ‘Conica’) — Zone 2-8 Full Sun to Part Sun An evergreen tree with a dense, pyramidal habit. Can make an excellent dwarf topiary. Makes a great accent in the formal garden.
DWARF HYDRANGEA — Sun to Shade. There are a variety of dwarf hydrangeas that make a great container plant. With bright colorful flowers throughout the growing season. The flowers make excellent cut or beautiful dried flowers that can be brought indoors.
ROSE — Full Sun. Make a colorful focal point or accent in the container garden.
There are also a variety of perennials that thrive in the Container garden: including Heuchera, Creeping Jenny, and Sedums. Having perennials come back year after year is worth the effort and research.
Having a Container garden flourish at your home is always a pleasure just remember to water and fertilize!
