Perrenials in planters

Thank you for the question. For the best planting success in a free standing planter, flowering annuals or even vegetables or herbs would be preferred. Annuals are plants you plant new every year. The type of annuals are completely a personal choice. Just be sure to read the tags and choose plants that do well in part sun. Here is a link to an Illinois Extension article listing annuals that would work just as well in Minnesota: http://web.extension.illinois.edu/cook/downloads/9219.pdf Be sure to pay most attention to the part sun selections.

This being said, you could try planting some perennials and mulching as you suggest, but be sure to keep the perennials about 12 inches away from the sides of the plantar for best chance of avoiding freeze/thaw heaving and extreme low temperatures and water well before winter. They still probably won't make it, unfortunately. Encasing the planter completely in black plastic wouldn't be advisable because roots wood probably rot and you risk encouraging development of soil borne diseases. Perennials in free standing pots or beds need protection because their root system is basically above ground in a container. This poses problems because the root system is now subject to extreme cold injury.

If these same perennials were planted in the ground, the roots would have the benefit of the soil to help insulate and protect the roots from potential cold injury that can kill roots leading to a good number of the plants not coming back in the spring. Above ground, that protective root insulation disappears making the roots vulnerable to extreme winter temperatures.

Thank you for contacting Extension