"What's Up With My Boxwood?" - Late Winter Edition

Author: Holly Scoggins, Program Manager

Many of us experienced a relatively warm late fall and early winter. Late December in my own Southwest Virginia garden (Zone 6b, 2100’ elevation) saw some perennials emerging that had no business even peeping until early spring, plus a bit of new growth on some evergreens. Then blammo! Temperatures dropped dramatically, winds increased, snow and ice became the norm for January, and the first half of February hasn’t been much better. What an excellent time to review a few common winter issues for boxwood! Note that as with most things Buxus, susceptibility to abiotic or biotic issues is usually species- or cultivar-specific.  Start with cultivars that are cold-hardy in your geographic region – check tags and other resources as to USDA cold hardiness zone.  Here are a few of those frequently asked questions.

FAQ #1: What’s up with the cream/tan/straw-colored foliage at the tips of branches?

New growth can be susceptible to cold damage, resulting in bleached or desiccated foliage.

Chances are this was new growth that hadn’t had the chance to harden off. The same damage can occur on fresh growth in spring that gets hit by a late freeze. Gradual acclimatization to cold (and then to warm) is ideal but doesn’t always happen. And as with many woody plants, don’t encourage late-season growth. Fertilizer applications and pruning in late summer and early fall can stimulate fresh foliage that is susceptible to damage. Be sure landscape or nursery plants are well-watered going into an extreme cold spell to limit desiccation. While this bleached foliage is unattractive, rarely is the health of the plant compromised. Simply snip off damaged foliage and twig tips in spring.

FAQ #2 Should I remove the ice and/or snow weighing down the branches?

Buxus sempervirens branches can bend under the weight of significant snowfall. 

Nothing insulates and protects hardy plants better than a nice blanket of snow.  However, rarely is the snow deep enough to completely cover shrubs. The weight of snow and ice over exterior branches can cause them to snap or split.  The chance for damage is exacerbated by whacking at the wintery build-up with a broom or shovel – a too-common practice. Let it melt naturally if possible.  If additional snow and/or ice is expected to the point of concern for breakage under the load, remove by gently shaking or brushing with gloved hands. 

FAQ #3:  Why is my boxwood foliage bronze/orange in winter? 

Bronzing happens!

“Bronzing” is the boxwood term for the appearance of purple-to-orange anthocyanin pigments that can occur in winter. The discoloration can affect one side, the whole plant, or just the tips. Bronzing is much more likely to occur on boxwood planted in full sun, especially with southwestern exposure. The pigment change is not harmful to the plant, as the foliage greens up in the spring – but you may consider a shadier or more appropriate site for that specimen. Again, susceptibility to bronzing is a bit cultivar-specific. If the aesthetics of bronzing are an issue and your boxwood will be sited in full sun, pick a cultivar shown to be less prone to the condition.

For a list of cultivars and much more information on winter care of boxwood – visit the NewGen® Boxwood site https://www.NewGen®boxwood.com/boxwood-care#winter

Tips and Tricks for Growing Cleaner Plants

Creating a phytosanitary plan doesn’t have to be a daunting endeavor. There are many simple steps you can take to grow cleaner plants. Saunders Brothers has worked with many researchers and Extension agents to establish protocol to help prevent the introduction and spread of Boxwood Blight at their nurseries. Although this plan was designed with Boxwood Blight in mind, these practices will help growers produce cleaner, more successful plants.

Foot mats/baths:

Foot baths are located at every walkway leading to the Saunders Brothers office.

One of the first and easiest steps to take is the inclusion of foot mats/baths for sterilizing shoes of anyone entering a growing area. These can be placed in greenhouses, worker common areas, and near offices. Having foot baths as a first line of defense minimizes the introduction of new pathogens to your growing area. Saunders Brothers uses foot mats at the entrance to all of their office and worker areas. Saunders Brothers uses Zerotol® 2.0, but a 10% bleach solution is also effective.

Disposable pant/boot covers:

Crews in the field nursery wear disposable suits when they are working on larger plants.

Crews wear rubber boots that can be easily cleaned and disposable pants when moving between growing areas.

An example of plastic pant and boot covers in the field.

Disposable pants and boots serve as a physical barrier between one’s clothing and the plants they are working in. If there are any spores or pests on the clothing, it is less likely they will migrate to the plants. Saunders Brothers employees wear disposable, plastic pant and boot covers while working in boxwood houses. Boxwood Blight spores can stick to tools and clothing moving from location to location, so instead of worrying about having fresh clothes, disposable pant/boot covers are the perfect solution.

This is also a great tool for landscapers that may visit many sites in a day. Instead of having to change or sterilize clothing, wearing disposable pant and boot covers greatly reduces disease or pest movement from site to site.

Sterilizing tools/equipment:

Pruning crews as Saunders clean their tools with alcohol between each house.

Even large equipment like digging machines are cleaned with sterilant between fields.

Sterilizing tools and equipment is an easy, practical step to take towards growing cleaner plants. It is a good practice to carry around a spray bottle of isopropyl alcohol. Research shows that a 50% isopropyl alcohol solution is effective at killing most plant diseases. Alcohol spray can be used to clean any handheld tools such as pruners, shovels, or trimmers. Other options of sterilants are a 10% bleach solution or Lysol® spray. Many researchers also recommend hydrogen dioxide products such as Zerotol® 2.0. Make sure to always check labels before you use any products. Most of these products are very user-friendly and are labeled to clean tools, equipment, or even surfaces.

Dragging a hose through a bed of infected plants and then moving it through a healthy bed could spread diseases. Taking an extra minute to spray the hose down with a sterilant could avoid a bigger cleanup in the future.

Cleaning Stations/Sectioned growing areas:

Cleaning stations in the field nursery.

Cleaning station in the container nursery.

This tip takes a bit more planning than some of the other suggestions, but might have the biggest pay off if you ever run into a disease or pest problem. Saunders Brothers has set up both their field and container nurseries in sections. In the container nursery, boxwood are grown in specific locations separated by roadways. In the field nursery, areas are sectioned based on geography. Each section has a cleaning station that all employees must visit at they enter and exit. Cleaning stations are stocked with:

• Disposable pant/boot covers

• Trashcan

• Boot bath and brush

• 70% Isopropyl alcohol spray/liquid hand sanitizer.

• High pressure water hose (field)

Crews using a cleaning station to rinse off their shoes and equipment.

Upon entering and exiting the area each employee must:

Entering:

• wear rubber boots, easily washed boots, or disposable boot covers

• step in boot bath/wash boots

• put on disposable pant covers

Exiting:

• remove and trash disposable pant covers or spray pants

• step in boot bath/wash boots

• wash hands/ use hand sanitizer

• rinse off tools, then spray with alcohol

This is an example of the sectioned boxwood production areas are at the containers nursery at Saunders Brothers.

The perks of setting up these sectioned areas is that in the event of an infection, you can quarantine one area, and continue production from the other locations. Consequently, each time a person or a crew enters a new area, they are cleaning off any potential pests or diseases.

Establishing cleaner growing protocol doesn’t have to be a daunting task. Taking some steps early on in production can help set you and your plants up for success while combating common pests and diseases. Consider these tips and find what works for you.