8/8/2024 - By Dr. Aaron Palmateer

When it comes to commercial horticulture, nursery winter prep for growers can be vastly different for outdoor nursery production depending on your geographic location. For example, temps rarely drop below 60 in south Florida, but they can remain below freezing all winter long in northern locations, such as Minneapolis, MN.

One of the nice things about wintertime is that the mild and drier environmental conditions are less favorable for most pests and pathogens; thus, pest and disease pressure is generally lower when compared to the warmer and wetter months of the year. Read on to learn the proper timing for winter prep, as well as your best solutions with Harrell's Bio-MAX® products.

Nursery Winter Prep for Growers is All About Timing

Most containerized plants and woody nursery stock require more than one production season and need protection from the cold. Believe it or not, roots are often more sensitive to cold temperatures than above-ground shoots, and plant roots growing in containers are more susceptible to cold damage than those growing in the ground.

Root development, cold hardy tolerance, fertilization, irrigation/soil moisture, and temperature fluctuations are important factors for overwintering plants. But it's all about timing when it comes to successful winterization in the nursery.

One thing for certain is that a rapid change in temperature can be much more severe than a gradual change. For example, plants being shipped from the south that get stuck somewhere in transit due to a winter storm or flight delay will have less chance of surviving than plants acclimating to colder temperatures over time. Whether plants are transitioning into dormancy to withstand freezing temps or temps are just cooling down, production practices must address these environmental changes.

Growers Trust POLYON® for Nursery Winter Prep

When temperatures cool down, and photoperiods become shorter, plant growth slows down. This includes the need for food and water.

As they work on winter prep,  growers need to account for adequate nutrition as nutritionally balanced plants will have the greatest success withstanding winter conditions. One of the easiest ways to time this correctly is the use of controlled-release fertilizer. The release can be predicted for POLYON® fertilizer ornamental blends using Harrell’s proprietary CustoGraph® software. Based on laboratory-determined release characteristics of POLYON® fertilizer and historical weather data for a given location, the CustoGraph® will provide an accurate description of week-to-week and month-to-month nutrient release so that adequate fertility is ensured through the growing season.

Depending on the location, a spring application of POLYON® fertilizer (for example, an 8-9 month or 5-6 – month period) will have released coming into fall with EC levels low enough not to cause winter injury. Irrigation events need to be monitored closely as providing too much water in the fall can lead to a late flush of growth, that can be damaged by a frost, but keeping plants too dry is not good either.

Proper Control of Water Sources During Nursery Winter Prep

Roots need water to properly function, and when transitioning into colder temperatures, plant available water is necessary for roots to store essential carbohydrates and nutrients. Even if plants are protected by a covering such as plastic, they still need water, especially before a long hard freeze where water cannot be readily absorbed. Freezing water gives off heat and can provide protection to the plant. Therefore, many nurseries have overhead irrigation that can be used for frost protection.

Plant Growth & Development Fundamentals During Nursery Winter Prep

The geographic location where a plant species originated does affect winter hardiness, and generally, plant species that originated from southern regions will acclimate more slowly and develop less hardiness than northern species. It’s also important to address light. The intensity and duration of light affect acclimation and plants growing under shade will acclimate more slowly than in sun.

Regardless of your location, winter preparations need to address the fundamentals for proper plant growth and development including adequate food, water and light. Be sure to choose the appropriate winter protection techniques for your location and those that address the plant species in production.

Nursery Winter Prep with Harrell’s-BioMAX® Products

The Harrell's Bio-MAX® product line serves to promote stress tolerance, photosynthesis, and root development. Adding BioMAX products to your fall application schedule is a good way to also target stress remediation with applications made preventatively going into winter, and then again in the spring. Here are a few recommendations that would be an easy addition to your existing plan:

Reach Out to Your Harrell's Rep

If you have any questions about products or are looking for any tips to help you prepare nursery plants for winter, your Harrell's rep is here to help.