Cut Flower Updates: September 26, 2025

It's officially fall! Day lengths are shortening, and nights will be getting cooler. Depending on where you are in the region, a first frost may be around the corner or several weeks away. In this week's update, we'll cover a few fall tasks you may wish to add to this season's to-do list.

The first is cutting back peonies. Peony foliage can develop several diseases as the season progresses, some of which overwinter in plant debris (see this post from August for more information). To reduce the disease inoculum for next season, it's important to trim peony foliage and remove it from the field. You can begin this process in late summer, or whenever you start to observe disease symptoms, by trimming out and removing any diseased portion of the plant, leaving the healthy green foliage to photosynthesize for as long as possible.

In the fall, cut back the rest of the top growth. Trim stems down to about an inch or two above the soil line and compost the plant debris. Heavily diseased plant debris should be bagged and thrown away, buried, or placed far from flower fields to decompose. Spreading a few inches of mulch around the plants can help protect them over the winter.

Another early fall task to consider is providing frost protection for newly planted or tender plants. In Pennsylvania, our frost-free season usually comes to an end between October 13^th and 25^th. That means that within 2-4 weeks, your farm will likely see temperatures below 32°F, or sooner if your production area is in a cool microclimate (a hard frost, below 28°F for more than 4 hours, is probably still 4-6 weeks away). It’s a good time to consider some frost-protection measures, which could include shifting production to high tunnels or greenhouses, or constructing temporary structures like low tunnels.

To make a low tunnel, you need a framing material, a cover, and something to help hold the fabric on the frame. The frame is usually constructed of a series of 3 to 4-foot-tall hoops made of wire (9-gauge) or PVC tubing (0.5-0.75-inch). Floating row cover allows some sun and water to penetrate, and comes in different grades or thicknesses to allow for different levels of sun penetration and frost protection. The material is secured to the hoops with snaps or clips, and weighed down on the sides and ends with sandbags, bricks, or rocks. These structures can protect crops down to 24-28°F, depending on the grade of the row cover.

Lastly, as you start to remove spent crops from their beds, it’s a great time to add organic material back to the soil. Adding a 3-4-inch layer of compost can protect the soil during fall and winter and replace valuable organic matter and nutrients after the growing season.

To sign up for these Cut Flower Updates, you can enter your email and choose your preferences. When prompted about your areas of interest, select "Commercial Cut Flowers", which is under the Trees, Lawns, and Landscape heading. You'll get an email each Friday morning when the pest and disease update is available.