Overwintering Perennials: Plan Ahead To Fungicide Drench And Cover

Perennials in hoop houseCommercial horticulture has seen a tremendous amount of change in the past decade, and the perennial market has not been left behind. Demand for perennials has increased as consumers educate themselves and seek out new and improved varieties.

Overwintering perennials can become an important profit center. Fall planting makes better use of available labor for many growers.


When To Transplant Perennials For Overwintering

Perennial transplanting time depends on labor, greenhouse space and the availability of plant material. Transplanting perennials from 50 or 70 cells can be done in August. In the North, smaller plugs should be planted as early as July. Depending on your area, finish planting no later than early to mid- October to allow the plants time to establish good root systems. The further north that your operation is located, the earlier this needs to be accomplished. Growers in southern climates have a larger window in which to get their perennials planted and bulked up for winter.

Protect Perennials Against Disease

The onset of cold weather causes top growth to die back. Cleaning up and pruning is important at this time to prevent diseases such as botrytis from occurring. A preventative, broad-spectrum fungicide drench can be applied at this time to lend extra protection for the roots. Banrot and Hurricane are broad-spectrum fungicides that contain two active ingredients. Tank mixes can also be used. Combine Terrazole L, Segway or Subdue Maxx with Affirm, Cleary’s 3336 or Medallion to protect against the major root and crown diseases.

Think About Indoor Climate

Perennials can be overwintered in an unheated house with a poly film cover or covered outside by December with an overwinter protection blanket. Avoiding heat build-up on sunny winter days is important. Greenhouses with roll-up sides are ideal to maintain cool temperatures if outside temperatures rise above freezing during the winter months. White poly and/or positive ventilation can also be used to keep day temps cool.

Inside production should begin by heating the greenhouse to 50°F, if needed, until all of the perennials are established. Slowly lower the temperature to 35°F and maintain that temperature throughout the winter. Keep the perennials cool even when they start growing in the spring. This is to avoid unwanted stretch and premature blooming that would cause lost sales opportunities.

Outdoor Production Is Subject To The Natural Elements

Once cold weather arrives, cover perennials with an overwintering protection fabric or place them in a hoop house covered with white plastic. Rodent baits are imperative no matter which method you choose. Once the outside temperatures begin to rise and new growth appears, ventilate the hoop house or uncover the beds to promote air circulation so that new growth doesn’t stretch or become soft.