When people think of container gardening, they often envision pots of petunias or geraniums. However, woody ornamentals can be a great choice for decorative pots in outdoor areas, and bring to life the typical adage “thriller, spiller, filler” in a more distinctive way.
Flowering shrubs add height, texture and, of course, color to container designs. Here are some tips for successful container gardening with flowering shrubs:
• Choose the right size container. The following chart shows suggested sizes for decorative containers based on the size of the shrub.
• Fill the entire container with potting soil—don’t add rocks or other materials to the bottom of the container. It won’t help drainage, and will give the plant less room for its roots to grow.
• If you want to prevent soil from washing out the drainage holes, place a small scrap of newspaper or a coffee filter over the holes.
• Don’t forget to water, even in winter. Plants in containers will need more water than plants in the ground. An automatic watering system can help and is a great enhancement for professional projects.
Incorporating containers for all-season interest
Speaking of winter, shrubs are a good way to add winter interest to a patio or deck. They should be fine overwintering in a container as long as they are a zone hardier than where you’re planting. For example, if your project is in a USDA Zone 4, a plant rated to USDA Zone 3 should be okay above ground for the winter. Watch out for winter wind, though; evergreens in particular can struggle in exposed locations over winter.
[Related: Cold-hardy color for Colorado landscapes]
Good options for container designs are dwarf Hydrangea paniculata like Bobo, rose of Sharon (columnar Purple Pillar is ideal) and shrub roses. Containers are an effective way to incorporate a tender shrub like Buddleia into a cold-climate garden; while butterfly bush won’t be hardy in USDA Zone 4, a dwarf variety like one of the Pugster Buddleia will look nice in a patio planter and provide plenty of fragrance and butterfly appeal all summer long.
Cold-hardy flowering shrubs in a good-sized container can be kept for two or three seasons and then transplanted into the permanent landscape. You’ll know it’s time to plant it in the garden when it becomes difficult to keep the plant watered or it’s tipping over.