Why plants need moisture in the winter

This past week has brought us temperatures much colder than we've experienced in the last few years. 

How will our outdoor plants react? 

It's too early to make any predictions, but our plants have one fantastic thing going for all concerned. We did have good soil moisture around the roots of all our plants this past fall and so far this winter.

The No. 1 reason that our plants suffer winter damage is having those plants in dry soil.

That makes our plants even more vulnerable to cold damage, especially to our evergreens.

They need good moisture in their winter foliage to stay healthy and keep from drying out. It's also important to realize that all cold hardy plants produce their own anti-freeze, the amount produced varies with different plant varieties.

That is why plants are categorized by their hardiness in different weather zones. Our plants that are growing in the TriState have to be able to sustain low temperatures in the 5 to 10 degrees below zero or weather zones 5 and 6 according to the weather zones we live within. 

That's the very reason you don't walk down any streets locally that are lined with palm trees. 

If you selected plant varieties that are not cold hardy to zone 5 and 6, you and those plants are already in serious trouble.

Thank goodness that the vast majority of plants offered for sale in our little corner of the world are all cold hardy.

The biggest threat to our outdoor plants is a warm spell in late winter (February to early March) for a week or two and then the real cold weather returning. The warmer temperatures in late winter will tell our trees and shrubs to wake up and the return of the much colder weather will cause a lot of damage to those plants that start greening up for the spring. 

We can't do anything about that but file away this thought.  In all my years working with plants, I've seen some damaged, but mom nature has always risen to any weather condition and has done a very good job.

Plants have a plan for all seasons

Many plants need to avoid flowering in the autumn – even if conditions are favourable – otherwise they would perish in winter.

To flower in the spring they need to sense and then remember winter, a process known as vernalisation. But how do plants sense vital information such as temperatures to align flowering with the seasons?

Until now, many researchers thought that fluctuations in monthly, daily, hourly temperatures were detected by a small number of dedicated sensors.

But new research by the John Innes Centre reveals that plants combine the temperature sensitivity of multiple processes to distinguish between the seasons.

"At first glance this might seem like a surprising finding, however in hindsight, it is very reasonable and it is also more likely as a mechanism to evolve," comments Dr. Rea Antoniou-Kourounioti, first author of the study which appears in the journal Cell Systems.

"Biochemical reactions are naturally temperature sensitive, so the alternative, a few specialised sensors, would suggest that the temperature sensitivity of everything else must be ignored or compensated for. On the other hand, taking inputs from multiple pathways that were already responding to temperature, and evolving to use this combined information is less complicated and can lead to a more robust system," she explains.

The team from the labs of Professors Martin Howard and Caroline Dean developed a predictive mathematical model of temperature sensing for the key flowering regulator FLC in Arabidopsis.

This vernalisation model can be used in combination with climate models to predict how plants will change their flowering in future climates. In this study, the team collaborated with groups from Sweden to test the model on patterns of data from plants grown in field sites in Sweden and Norwich – and the model matched these well.

Arabidopsis is a relative of many crop species, such as broccoli and oilseed rape, so the work could be extended to help breeders develop climate-resilient varieties.

Future work will involve adjusting the model in crop species and integrating it into current crop prediction models for farmers and breeders.

The team will work with climate modellers to more accurately predict the temperatures that plants will actually experience in future.

Grant will help determine how plants interact with microbiomes

While many people know that the microbes in our guts are an important part of our health, many are unaware that microbes are just as important to our crops.

Different microbes can help plants acquire nutrients, fend off pests and disease, and produce higher yields, but we know very little about how these partnerships work. University of Georgia researchers are working to understand these partnerships so that they can be used to breed better, more sustainable crops.

A team of researchers at the University of Georgia College of Agricultural and Environmental Sciences has received a $1.35 million grant from the National Science Foundation to better understand how plants interact with their microbiomes.

"Just like people, plants host trillions of microbes that live on, around and inside them," said principal investigator Jason Wallace, a CAES professor of crop and soil sciences. "Some of these cause disease but many are beneficial, helping the plant thrive in harsh conditions, but we don't know how this interaction works.

"Learning how a plant's microbes make it more resilient could be an important key to developing more sustainable and stress-tolerant crops in the future."

Wallace's team is focusing on a grass called tall fescue, which has been grown for animal feed for over 70 years and covers 40 million acres across the U.S.

While breeding more water-efficient fescue has been a goal of plant breeders for decades, UGA geneticists are taking a new approach. They are investigating how the grass interacts with symbiotic fungi, which has been found to fortify it against heat and drought stress.

Some types of tall fescue have a fungus, Epichlo coenophiala, living inside them, which helps the plant survive drought, heat and disease. It also helps the grass fend off insects and predators.

Ironically, this partnership was discovered because the fungus usually produces toxic chemicals, ergot alkaloids, that make cattle sick. UGA was instrumental in breeding the first commercial varieties with toxin-free strains back in the 1990s.

Wallace's team will work with fescue that contains the fungus to understand how such a beneficial partnership works, including how the plant and fungus communicate with each other and how their interaction leads to higher stress tolerance in the plant.

The hope is that understanding this system will show how similarly strong, beneficial partnerships can be made in other crops to boost agricultural production and sustainability.

Wallace is partnering with Carolyn Young, an associate professor at the Noble Research Institute in Ardmore, Okla., to carry out this research.

To complete this work, Wallace, Young and their research teams will analyze thousands of fescue plants to find how the plant influences fungal growth and toxin production. They will also investigate how the plant forms relationships with new varieties of fungus, such as ones that do not produce toxins, and how the fungus helps the plant survive under heat stress that would normally kill it.

In addition to the work with fescue, Wallace and Young will assist middle and high school teachers in developing hands-on teaching projects related to these topics that they can implement in their own classrooms. This will give students a better understanding of plant-microbe partnerships and the ways that microbes impact the larger ecosystem.

The grant period will run from 2019 through 2022, but some parts of the project are already underway.

These plants bring all the birds to your yard

Like songbirds? Right, many people do. It's a different story when it comes to insects. Mention caterpillars, for instance, to most gardeners, and you'll have them squirming with horror. But backyard species like caterpillars and spiders actually play a crucial role in supporting our most beloved bird species. As a new study from University of Delaware postgraduate student Desirée Narango and coauthors demonstrates, native plant gardens are quite literally for the birds.

It's the largest comprehensive study to date of the effect of native plant species on a specific species of bird—the Carolina chickadee. It's also the biggest single piece of research to come out of years of fieldwork during Narango's PhD, she says, and it offers a tangible goal for conservation-minded individuals to work for in their own yard. That goal is a number: 70 percent.

By studying more than 160 yards, Narango found that suburban lawns with at least 70% native trees and shrubs were able to sustain breeding chickadees. Yards with less could sustain adults, but those adults weren't reproducing at replacement rate, meaning the population was falling.

Why are native plants important? When it comes to birds, it's because those plants have coevolved with local insect species—creepy crawlers that the birds themselves evolved to thrive on, says University of Maryland ecologist Karin Burghardt. Burghardt previously worked with Narango's coauthor, University of Delaware professor Doug Tallamy, but she was not involved with the current study.

"We think about birds [in human landscapes] as mostly needing birdseed," Burghardt says. But work over the past decade paints a different picture, one that points to the importance of insects for many. However, the vast majority of plant-eating insects are evolved to only eat a small number of native plants, which means that in gardens without the foliage of choice, they're not around.

For human gardeners, as well, introducing native plants and seeing the wildlife—from caterpillars and other insects to birds—they attract can be "a pretty rewarding process," Burghardt says. She recently bought a house, where she's in the process of redoing the garden with native species. Gardeners who do the same will quickly see results, she says, and know that they are providing homes for wildlife, from the crawly to the flappy.

Narango says that the 70 percent number that works for the chickadee is a baseline. "Almost all terrestrial songbirds require insects to raise their young," she says. The more insectivorous a bird, the higher percentage of native plants it seems to need for those insects to live on. The Washington, DC backyards she monitored were part of an existing citizen science project called Neighborhood Nestwatch.

Doing fieldwork is often no simple task, particularly in urban areas, says Tallamy. He's been working on the problem of backyards for more than a decade—Burghardt was his coauthor on some of the work that originally demonstrated the relationship between native plants and insects. Tracking hundreds of yards and birds "is not easy stuff," he says.

In this case, each participating yard got a nestbox, and homeowners monitored the box from the first week of April through June to see if chickadees moved in for their breeding season. Narango and her field technicians also visited the yards of neighboring houses to see if chickadees that were feeding in the backyards they studied were actually nesting close by but not in the yard itself.

Their results show something that hasn't been seen before: a comprehensive study of the effect of non-native species of plants, higher up the food chain, Tallamy says. It takes a story he's been working on for a long time and stretches it "to the next trophic level," he says, by looking at the birds who eat the insects.

"These simple choices on what people are planting can really have profound consequences on the birds that are living in these yards," Narango says. Those consequences stretch beyond nesting birds and to the migratory birds that pass through on their long journey from the tropics to Canada's boreal forests each year. They might only stop in a yard for a week, but they're looking for high-calorie, high-protein food to sustain their next great hop—just like the nesting birds that need extra to raise young. If they can't find food on their stop, that week "could be the most important week of their life."

The new study does a "meticulous" job of defining what insects can do for birds, says Burghardt, but it's important to remember they're more than just food. "I think that they have value in and of themselves," she says. They're part of a web of life evolved long before we started bringing non-native plants to our gardens. They also have the potential to enrich gardens, says Nancy Vehrs, president of the Virginia Native Plant Society. "There's more to a garden than just the plants," she says.

Successfully transplanting landscape plants takes forethought, preparation

McDONOUGH — If you want to rearrange your landscaping, the best time to do so is quickly approaching, though it's not easy lifting.

Nurseries use tree spades to dig large trees from a field-grown nursery. Unfortunately, this is not the kind of equipment a home landscaper can rent for a weekend project.

The roots of trees and shrubs normally grow beyond the amount of soil a home gardener can move. To keep most of the roots within a small area, plants should be root-pruned in the spring or fall before transplanting. Root pruning is the process of severing the roots of an established plant that is going to be transplanted to encourage growth of new feeder roots along the root ball.

Plants moved in the fall (October or November) should be root-pruned in March. Those moved in spring (March) should be root-pruned in October. Root-prune after the leaves have fallen from deciduous plants in the fall or before buds break in the spring.

To root-prune, mark a circle the size of the desired ball around the tree or shrub. Next, dig a trench just outside the circle. Cleanly cut larger roots and backfill the trench with the available soil. Water the area to settle disturbed soil and provide adequate moisture.

Roots within the pruned area grow many new fibrous roots, and form a strong root system within a confined area. If not root-pruned, larger plants may die from transplant shock because of root loss.

Shrubs less than 3 feet tall and deciduous trees less than an inch in trunk diameter (measured 6 inches above the ground) may be moved bare root. "Bare root" means most or all of the soil is removed from the roots.

Bare-root plants are easier to handle than those with a ball of soil around the roots. Bare-root plants should be planted while dormant. It is best to immediately replant. If not, keep the roots moist in peat moss or wrapped in plastic or wet papers until you are ready to plant.

To move trees with soil attached to the roots, trim the root ball to the proper size and shape with a spade. Keep the back side of the spade toward the plant, round off the trimmed ball at the top and taper it inward toward the base.

Avoid loosening the soil around the roots by cutting the large roots with hand or lopping shears and the small roots with a sharp spade. Next, undercut at an angle of about 45 degrees to loosen the root ball from the soil and sever remaining roots.

Prepare the new site before transplanting a tree or shrub. Have the soil tested and follow recommendations. Don't use fertilizer that contains nitrogen for the first year after transplanting.

Dig the new hole 50 percent wider than the soil ball to loosen the surrounding soil and ensure good root establishment. The root system should be at the same depth it was before it was moved.

Research has shown that adding soil amendments to the planting hole will not provide any benefits to newly planted trees or shrubs. Most studies show amendments can create drainage issues and cause poor root establishment.

When moving the plant to its new home, lift trees and shrubs by the root ball. Never carry a tree by the stem. This can damage underlying bark tissues. Place the plant in the hole and backfill with existing native soil.

Maintain constant moisture, not saturation, of the root ball. Add 2 to 3 inches of mulch to help conserve moisture, moderate temperature extremes and reduce weeds. Keep mulch away from the trunk of the plant.