Protecting Plants from Winter Injury

By Bruce Wenning

 

Trees and shrubs, whether native or naturalized to our region (zone 6; -10 to 0F), can succumb to cold temperature injury if the natural dormancy or hardening-off process is incomplete. Mild fall and winter temperatures, where day and night temperatures do not go below 35 F for extended periods of time, contribute to incomplete plant dormancy.

When woody plants in this condition are subjected to a sudden large drop in temperature, injury or even death of plants or plant parts can occur. This phenomenon is usually called winter kill. You can limit the damage or even prevent this from happening if you take protective action now.

This is how plants protect themselves from freezing. Generally, from late August to mid- December light levels and air temperatures gradually decrease, inducing hormonal changes in plant cells to enable them to adapt to the oncoming freezing winter temperatures. Plant growth slows down considerably and the cells of different plant parts reduce their water content by osmotic pressure; water inside the cell travels to the outside of the cell and between all cells. The cellular contents left inside cells become more concentrated allowing the reduction of ice crystal formation (supercooling).

This supercooling process protects plants from being killed at freezing temperatures. Water outside of cells freeze, but contents inside the cell, including traces of remaining water, do not freeze. This remarkable environmental adaptation ensures that plant cells won't burst from ice crystal formation.

Sometimes certain plant species, both woody and herbaceous, contain specific plant pathogenic bacteria in their cells that act as ice nuclei for ice crystal formation. For example, the bacterial plant pathogen, Pseudomonas syringae, is a gram-negative, rod-shaped bacterium that kills infected plant tissues. The black-brown colored twig tips of Japanese red maple that you see in spring may be a direct result of this bacterial-induced cold injury.

Winter winds also cause winter injury to plants. The action of drying, cold wind on evergreen foliage draws water out of the leaf stomates faster than the plant can replace water from the roots. Newly transplanted trees and shrubs, young seedlings, broad-leaved evergreens (such as rhododendrons, boxwoods, mountain laurels, and hollies) are especially vulnerable. Even the needle-leaved evergreens such as pines, hemlocks, spruce and firs can be affected. The cold wind dries out leaf tissues and partially or completely kills them. Rhododendron and boxwood leaves in spring may show leaf margin browning or completely brown leaves.

Here’s how to protect your trees and shrubs from cold and drying.

1.    Water the roots of all woody plants until the first hard freeze, one inch per week.

2.    After the soil freezes, mulch the roots of small trees, shrubs, and newly planted and transplanted trees and shrubs with salt marsh hay or leaves. Apply at least three to four inches of mulch around the roots. This will moderate the freezing and thawing action (frost heaving) in the root zone and help to conserve soil moisture.

3.    Wrap evergreens with burlap. This will help reduce the wind speed on the foliage. Better yet, put four wooden stakes around each small tree and shrub that you want to protect and tie burlap to the stakes forming a "room". Fill this room or enclosure to the top with leaves. The protected plant should be a minimum of six inches from the burlap.

4.    If you don't want to wrap your plants you can apply anti-desiccant or anti-transpirant products to the evergreen foliage, particularly for plants in exposed sites and new plantings. According to Brian Hanson, Plant Health Care Manager, Cedar Lawn Tree Service, these compounds are primarily used on the foliage of evergreens, especially the broadleaf evergreens, to reduce transpiration water loss that naturally occurs through the stomata in plant tissues. A possible side benefit for some plants is better foliage color retention. Hanson suggests several applications in late fall and winter depending on weather conditions. Unfortunately, these products provide only limited protection from cold temperature injury.

Bruce Wenning is on the Board of Directors of the Ecological Landscaping Association.  www.ecolandscaping.org.

 

Read More...

Summary only...

Surveying Newton’s Nature

By Patricia G. Goldman

 

“I first came to Newton with preconceived ideas regarding the quality of urban-centered conservation areas…I did not really think that I would find much of interest…how terribly wrong I was.  Newton’s conservation areas are rich in beauty and wildlife,” said consultant John Richardson in his 1996 report to the Board of Aldermen. 

Ten years later, a group of volunteers from the non-profit Newton Conservators have been out walking once a week to document the current status of Newton’s natural open spaces.  They are carefully noting every type of tree, shrub, fern, wildflower, and wildlife they encounter.  They are particularly noting invasive species that may be crowding out native plants. And they are noting where illegal dumping may be endangering these environments.

Where Richardson looked closely at seven areas, the Conservators have tackled over 30 sites, as part of their mission to preserve and maintain open spaces in Newton for public use and enjoyment.

“We wanted to do something outdoors, hands-on to preserve these places,” says Beth Schroeder, co-chair of this land management committee with Cris Criscitiello.  “We didn’t even know where all these open spaces were until we met with Martha Horne of the Newton Planning Department.  My interest came from enjoying my own garden, doing landscape design for clients, and wanting to know more about which plants are native to this area.”

Says Criscitiello, a retired physician, “We initially intended a survey of what’s growing in the different conservation habitats in Newton, in the wetlands and elevated hillsides, the sunny areas and shady areas.  We wanted people to have a good time walking around and really seeing things.”

Florrie Funk, a member of the committee notes that “it’s hard to appreciate what’s here if all you do is look around and see green stuff.  If you can identify trees and shrubs, it becomes more exciting and you’re more likely to be interested in protecting good native plants.”

Funk is particularly interested in identifying and preventing the spread of invasive species.  Plants like Japanese knotweed, goutweed, garlic mustard, purple loosestrife and Oriental bittersweet tend to crowd out native plants.  Even though some invasives may be attractive plants, they are tending to endanger rare and beautiful native species, such as gentians and cardinal flowers. 

The volunteer group has a fern expert, bird experts, people particularly interested in wildflowers and mushrooms, even a research botanist who is an expert in plant classifications.  They are waiting for their vernal pool expert to have time to help identify amphibians.  When an expert cannot immediately identify something, they turn to their Field Guides and even take photos to match up on internet sites.

The group intends to keep up their weekly survey trips all winter long.  “Even in the snow and ice, we can identify trees and bushes by their structure, the shape of their leaf buds and whether the leaves grow opposite each other or in an alternating pattern,” says Schroeder.

Thus far the group has produced extensive spreadsheets with checkmarks indicating every time any of hundreds of species has been found in each of the 30 Newton conservation sites. “This document establishes a baseline of existing species, which allows us to detect changes over time,” Schroeder notes.

“As we get the information we compare it with the 1996 Richardson report,” says Criscitiello.  “We would also like to track the species during different seasons and make all the information available for educational purposes on our website (NewtonConservators.org), at the library, in the Newton Planning Department, and in an episode of the Environmental Show on NewTV.”

 “We could use an insect expert in our group,” he says.  Funk adds that it would also be nice to have someone who knows grasses and sedges.  “To identify sedges, you have to look at the seeds under a microscope,” she notes.

Has the group identified anything surprising thus far?  “We have found over twenty types of ferns, Jack-in-the-pulpit, pink lady’s slipper, trout lily, bloodroot, trillium and huge sassafras trees,” says Schroeder.  “There are a lot of things you wouldn’t see unless you look carefully.  Our group has located many of the plants listed in Richardson’s 1996 report and quite a few new ones.”

Read More...

Summary only...

Doing the right thing with lovely lumber

By Eric Olson

 

The idea of paying a bit more for products that help us live healthier lives is no longer foreign to most people.  As proof we need only look to the growing interest in fresh, locally produced fruits and vegetables and the rise in sales of organic milk.  Some people take the next step and choose products that do not yield personal benefits so directly, but do favor producers over middlemen (Fair Trade coffee) or are considered better for the environment (recycled paper).  How about wood used in furniture and construction?  Are there ways to encourage logging companies to minimize harm to both local and tropical forests?

Roberta Durschlag of Waban asked just this question recently when she and her husband, Mark, set out to remodel their back porch.  They hoped to use a beautiful tropical wood called Honduran Mahogany but hoped not to support companies that are cutting forests willy nilly.  So they did some research and found that there is indeed such a thing as “sustainably harvested” wood.  In a sustainable logging operation, trees must be cut and processed in such a way that a forest’s soils, wildlife, waterways, and other essential features are only temporarily disturbed by selective cutting and carefully constructed logging trails.  Trees are big plants, of course, so any logging operation results in some damage.  But by inviting foresters and ecologists from the Forest Stewardship Council and other groups to observe a logging operation, companies can prove that they are following best-practice rules.  For this whole notion to work, of course, homeowners and businesses must then favor these firms with their purchasing decisions.

Consulting the Green Decade Coalition/Newton,  Ms Durschlag learned several dealers of certified wood in this region, but it turned out that only one – Sterritt Lumber of Watertown – was willing to deal with a residential customer.  Though it cost significantly more than standard lumber, the Durschlags chose the certified product.  Knowing that their wood came from a certified forest should lend it a special glow as they enjoy their porch for years to come.

The Green Decade Coalition/Newton would like to hear similar good news stories from other local buyers and sellers of certified lumber.  info@greendecade.org.

Eric Olson, PhD, Adjunct Professor of Ecology in the Sustainable International Development Program at the Heller School, Brandeis University, is Chair of the Energy Committee of the Green Decade Coalition. 

Read More...

Summary only...