A recent trend is to use perennials in container gardens. As one who might get above average grades in plant growing and very low grades in design and conventional marketing I view this as assigning the plant to death row with little hope for reprieve.

Let's begin with the requirements for a plant to survive in a pot for more than one season, or more specifically the winter. Unlike in the ground a pot will track air temperature and be significantly effected by the absorption from the sun.

Research would suggest that the plants soil ball might easily exceed 75 degrees on a sunny winter afternoon and fall to the air temperature overnight. Swings of 60 to 80 degrees are very possible. When does that happen in our normal growing season?

To survive our zone six winters in a pot a plant must be rated as zone four. I think that's minus 20, which reflects winter conditions in the upper Midwest. Most conifers are on the short list of zone 4 plants we see in our greenhouses or garden centers.

The designers will tell you that the perennials in containers will do double duty. Their saving solution is to breakup the container in the fall and plant its perennial components in the ground. My guess is that by September 1, the container plants are either stressed or they are one of the highlights of your garden. If they are a highlight most of us would delay ripping the container apart until frost in late October or even November. By then we are pushing the desireable window for fall planting.

This concept of a double duty reprieve is sound but I doubt if it happens successfully very often.

A second chance to save the perennials is to dig a hole and bury the container so the plants it contain will think they are planted in the ground. This would work but would be more effort than most of us will undertake.

The third option is to move the container to an inside location that is cool with low light after the plants have entered dormancy. They may need to be watered several times over winter but keep them on the dry side. My guess is that a temperature between 25 and 35 degrees would give the best results.

Unless you are featuring foliage I see little merit using perennials with short blooming periods in containers when the greenhouses or garden centers are full of annuals that will bloom their hearts out from purchase to frost with the same care.

Given our limited selection of zone 4 plants building containers around perennials is not the best idea horticulturally. If you have no problem turning a perennial into a non-perennial go ahead. I frequently kill plants unintentionally but hate to see them assigned to death row from the start.