Photo by George Hodan

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Do you notice more details in your garden in the winter when you’re not distracted by green leaves and showy blossoms? Here are some explanations for those unusual winter sightings:

Q: It’s February. Why are brown leaves still hanging from some trees?

A: You are observing marcescence, the term used to describe leaf retention. The dried leaves of certain hardwood trees hold fast, sometimes all winter long.

Marcescence is most common with certain trees, such as species of oak, American beech, witch hazel, hornbeam and ironwood. In addition to the stubborn oak leaves in my yard, I most notice the tobacco-colored beech leaves throughout the winter.

For most deciduous trees preparing to shed their leaves in fall, cells between the twig and the end of the leaf stem release enzymes and form an abscission layer that unglues the leaf, allowing it to fall free.

Scientists are not sure why some trees routinely have marcescent leaves. A study in Denmark found that deer preferred bare twigs to marcescent twigs. Some people speculate that retained leaves conceal buds hiding them from browsers such as deer.

The other reason trees might hold onto their leaves relates to a process called nutrient cycling. Leaves that fall in the autumn decay as leaf litter on the forest floor, leaching nutrients for all surrounding plants.

By holding onto their leaves, small understory trees with smaller root systems retain and recycle their nutrients for themselves only.

Sometimes, early hard frosts or freezes, such as ours last fall, may interrupt the abscission process, increasing the occurrence of marcescent leaves. This year, my Japanese maples and even my crape myrtles have held dead leaves for an abnormally long time.

Q: Is something wrong with my rhododendron? Its leaves are curling.

A: Your rhododendron is fine. Leaf droop, or thermotropism, is related to the temperature. As early as 1933, Japanese scientist Y. Fukuda studied the leaf-curling patterns of rhododendron, making an important observation that its leaves could be kept from curling when covered by snow, which insulated them from cold air temperatures.

Based on these observations, Fukuda concluded that the thermotropic leaf movements were correlated with leaf, rather than air, temperature. The drooping of rhododendron leaves protects them from membrane damage due to cold temperatures. Additionally, it prevents more damage to cellular membranes during daily rethawing in the early morning.

Q: My neighbor’s roses are blooming now! How can that be?

A: More than likely, the flowers you see in shades of white, pink or red are not roses, but camellias. Virginia marks the northern range for camellias to thrive outdoors.

Sasanqua camellias begin to bloom in fall and are often completed by Christmas, just in time for the earliest Japanese camellias to begin blooming.

Two lovely cultivars of Camellia sasanqua are the white-blooming ‘Setsugekka’ and the popular ‘Yuletide,’ with its bright red flowers decorated by bright yellow stamens.

Camellia japonica is often called the Rose of Winter or Rose of the South. Grown all over the world where conditions are right, most of them are upright, dense bushes growing between five and ten feet tall.

They usually flower between January and March, but some cultivars flower earlier or later than that. What you might imagine are roses painted on Chinese porcelain or in Victorian still lifes are probably camellias.

Q: Who is digging up my perennials?

A: Deer, squirrels and other mammals are my first suspects. However, they usually eat or, at least nibble on, what they uproot.

If a perennial appears to pushing out of the soil but is not eaten, there may be another reason: the weather. Frost heaving is the culprit.

Wide temperature fluctuations, with repeated cycles of freezing and thawing, cause the water in the soil to expand and contract. These repeated movements push and turn plants and their roots.

The result is that the crown is elevated above the soil, and the roots are exposed. This leaves the plant vulnerable to cold temperatures and drying winds, which may damage, stunt or kill the plant.

Although you can’t control the weather, you can reduce the dangers of frost heaving. Make sure that your planting beds are well-drained, that you plant early in the fall, and that you mulch with an organic material no more than four inches deep.

Enjoy being observant to the sights in your winter landscape.

Lela Martin is a Master Gardener with the Chesterfield County office of the Virginia Cooperative Extension.