When designing summer, autumn, or winter containers be sure to follow the thrillers, fillers, and spillers rule for maximum effect. The “thriller” is the center, tallest plant. The spillers go around the perimeter of the pot; choose ones that sprawl “spill” over the edges. The fillers go in between the thrillers and the spillers to fill in the bare spots.

Annuals or Perennials?

Most people choose annuals over perennials for their summer containers. That’s because annuals bloom all summer until frost kills them off. Perennials, on the other hand, bloom for two weeks on average, if you’re lucky. You can use a combination of both for your thrillers, fillers, and spillers. For example, perennial ornamental grasses make an awesome, inexpensive (dig a clump up from your garden) “thriller” (center) for containers.

Sun or Shade?

When designing your container, be sure to take its intended location into consideration. Some plants (both annuals and perennials) like full sun, others full shade, with others somewhere in between. Don’t try to combine these different requirements in the same container. If you do, some will thrive, and others will fizzle.

You can probably tell from these pictures that coleus and hibiscus are my favourite annuals for shade and sun containers respectively….

Fertilizer

Containers of annuals can be fertilized weekly right up until frost. This practice will keep the annuals looking cheerful as long as possible. Perennials need less fertilizer, especially those in garden beds when monthly is ideal up until August (in zone 4/5).

Deadheading and Pinching

Deadheading, or removing spent blossoms, helps to keep your containers looking nice all season. For annuals and perennials with flowers on stalks, remove the stalk right back to the first set of leaves after the flower has passed its peak. This practice often encourages repeat blooming. Others just need the faded flowers picked off.

Pinching the center of annuals and perennials encourages them to get bushier instead of leggy.

Frost Warnings

While annuals will be affected by frost, most perennials will not. Some annuals tolerate a light frost, others not so much. Of course, the first frost date varies across the globe, sometimes year to year within the same area.

In other words, frost is unpredictable.

Perennials can overwinter in your containers if you choose plants two zones hardier than what is normally hardy in your area. Otherwise, you can stick them in the ground to overwinter, to use again the following spring.

You can extend the season on both ends by heeding frost warnings in your weather forecast. In the spring I tend to start my containers early to ensure I get the annuals I want. If a frost warning is issued, I move the containers into my garage, off the (cold) cement floor, for the night in question. The same technique can be used in the fall when a sporadic early frost is in the forecast.

Once frost has set in for several days, you are fighting a lost cause. It’s then time to switch your concentration to fall or winter containers. Use the same thrillers, fillers, and spillers technique to create unique designs…