Tips for End-of-the-Season Perennial Care – Wholesale Grower

By Esther Langley, CGG, CCNP, General Manager, Britton Nursery

Britton Nursery overwinters 100,000 plants in cold frames each year. As fall comes, the staff of the wholesale grower in Colorado Springs has to balance keeping the plants full and flourishing to meet the needs of late-season customers and cutting them back to prepare them for their winter naps.

The staff stops potting by mid-September, allowing a few more weeks when the plants are still looking good for people still wanting to buy plants. But, as October begins, the focus turns to cutting plants back.

“There’s a tension between trying to maintain the beauty as long as possible but recognizing the plants can’t be like that when they are put away for the winter. You have to take the makeup off before they go to sleep,” said Esther Langley, CGG, CCNP, Britton’s General Manager. “If the plants have too much foliage going into the winter, they won’t fit under blankets well, and they take longer to clean up in the spring.”

While retail customers generally stop coming in to buy plants in August and September, the occasional landscaper with a late season job does show up wanting full blooms and foliage. A customer came in last year wanting flowering perennials for an outdoor wedding in October, and it was a challenge to supply the late-season request.

Landscapers are more likely to continue to buy into late summer and early fall, as their commercial customers hire them for projects before the snow falls. “If they have the choice between a cut-back plant and a lush full plant, often to satisfy their customers’ desire to see full plants in the landscape, they will take the lush full plant even if it needs more work in the fall,” Langley said.

Britton’s staff encourages late-season buyers to mulch and water well, so the plants have a better chance of making it through the winter so soon after planting. Landscapers should also be reminding their customers with late-season projects to continue to water well after installation; otherwise, when spring comes and the plants haven’t survived so well, their customers will be calling them up complaining.

The landscapers might be better off convincing those customers who may not be consistent in their winter-watering to wait and plant in the spring. Not only will they prevent plant deaths over the winter due to insufficient care, but the overwintered plants they get from Britton will be just as tough, hardy, and bigger and even better looking the next spring.

“We want to encourage the plants to follow the pattern of what the weather is doing by slowing down as they go into winter. Because we work only with perennials, we understand that these guys need to rest, like starting a bedtime routine when the nights get colder,” she explained.

Repot, Water & Cut Back

Throughout the summer and as fall sets in, Langley and her crew shift all of the smaller plants up to either #1 pots or F25 flats (two and a quarter inch pots), so they can overwinter comfortably with enough resources — insulating soil and nourishing water — in each pot.

“The F25s are the biggest plugs we move into our gallon pots. It’s nice in the spring when we put an F25 plug into a gallon container, because it finishes faster than the smaller plugs,” she said.

In September and October, the staff starts watering less so roots can continue to grow. The days and nights are cooler so plants dry out less, plus as plants are cut back, there is not as much plant material that needs water.

“October 1 is the green light to cut most plants back,” she said, “though a lot of times, it’s easier to cut plants back after they’ve gone through a freeze. We are trying to cool them down and ready them for bed.”

The timing of cutting back each plant, whether they’re in gallons or flats, varies. And she admits, it can be “quite a challenge” deciding how much to cut back. “It’s about really understanding the different plant personalities, as we do the dance of our fall preparations,” she added.

Some plants don’t like to be cut back early because of what they still need to pull out of their stems. Some become more vulnerable to pests and diseases if cut back too much or too late, and it’s not practical to be checking under every blanket for fungus or weevils every week from December to early March.

“We’ve just recently discovered some plants need to have some regrowth. Most are fine as long as the cut doesn’t get to too close to the crown and we don’t have a cold hard freeze,” she said. “If they are cut off too late without a chance for some regrowth, those scars where the leaf was cut off become a weak point and more susceptible to be taken down by fungus over the winter.”

The final step before overwintering is to saturate the plants with water — usually around Thanksgiving. Britton’s staff tries to water right before temperatures drop. Then the freeze turns the plants into “popsicles” with moist, firm root balls, which preserves plant health like being stored in a freezer.

“We’ve learned if we water too close to blanketing, we have a fungus issue. You want the tops dry but roots saturated before putting blankets on,” she said. “The whole preparation for overwintering has been a long learning process but we’ve had many breakthroughs, and now have healthy, hardy stock waiting for us when the blankets come off in the spring.”

Esther Langley