Winter Miracles
by Melissa Martin, Texas Discovery Gardens

    For some of us, even the thought of cold weather can send us inside for jackets and hot chocolate. But for many of the plants and critters that call Texas home, it takes more than a few nippy evenings to slow them down. A wide variety of plants, birds, insects and mammals keep quite active during what passes for winter in Texas, since we don't have three feet of snow and subfreezing temperatures - for the most part!

     Long after most deciduous plants have lost their leaves, many native Texas trees and shrubs produce bright, shiny berries. Beautyberry, Rusty Blackhaw Viburnum and native hollies are quite showy this time of year. One such holly, Possumhaw or Ilex decidua, produces reddish orange berries that are especially striking when everything else around them is lifeless and brown.

    Many herbaceous plants - such as the Texas bluebonnet - bloom in the spring, produce seeds in the summer and die in the fall. The seeds sprout and overwinter close to the ground as tiny rosettes. This allows the plant have a "head start" and grow quickly as soon as the days begin to lengthen and get warmer. During the winter, the rosettes provide fresh green food for insects and other animals when there is nothing larger to eat.

     There are several different strategies that animals can take to outlast Old Man Winter. One of these is migration. Some birds migrate to Texas in the winter due to the abundance of food commonly available here. Others continue on to Mexico, Central and South America. They stop at fields and ponds in Texas to feast along the way.

    Scientists have found that birds can navigate by using the sun, landmarks such as mountains, river valleys and coastlines or, at night, even the stars! They seem to have internal navigation aides that help them gauge the angles of the sun or stars to the horizon. They also seem to somehow sense the earth's magnetic field, which flows north to south.

    Another famous migrant is the Monarch butterfly. Monarchs come through Texas in the early spring, nectaring, mating and laying eggs on various milkweed species as they travel northward to Canada. It might take 2-3 generations of Monarch to reach Canada by summer as they only live about six weeks. Sometime in August, probably due to the change in day length and temperature, the Monarchs start their trek southward.

     These migrating Monarchs arrive in Texas in late September or early October. While here, the Monarchs will feed and gain the weight they need to survive the winter. These Monarchs will continue to the Oyamel Fir forests in central Mexico where they will congregate in the millions, hanging from the tree branches and wedged in bark crevices.

     There it is cool enough for them to stay in a semi-dormant state that conserves their energy, but not so cold as to harm them. They stay in this semi-dormant state for up to four months, only occasionally drinking water from puddles and nectar from flowers. In late February, they start their journey north.

     The Monarchs that migrate from Canada to Mexico live about nine months - from late summer until the following spring. When these Monarchs return to our part of the country in March, they lay eggs here and die. Their offspring continue the migration north.

     One of the many mysteries that remains to be solved is - how do the Monarchs that migrate south find their way to those exact overwintering sites in Mexico in spite of the fact that none of them has ever been there before?

     Other insects survive the winter as eggs, larvae or pupae. Some insects in these life stages hide under leaf litter, rocks, decomposing logs or a shallow layer of soil. This insulates them from the cold.

    Others, such as dragonflies, stoneflies and mayflies remain active in frigid water - even under ice! They feed and grow during the winter and emerge as adults early in the spring.

    Some insects overwinter in galls. Round galls form on a plant when an insect lays its eggs under the surface of a branch or leaf. The gall keeps the egg and larvae warm and protected during cold weather. In the spring, the adult insect will emerge from the gall.

     Insects that overwinter as pupae have the added protection of a thick outer cuticle or cocoon to help keep them warm. No wonder we use the old saying - "Snug as a bug in a rug!"

     Some insects, such as ladybird beetles (ladybugs), hibernate during winter. They find a protected spot such as a hollow tree, cave or even inside buildings. They often are seen emerging in mass from a ceiling fixture or under the eave of a roof on a warm day in spring.

    The Mourning Cloak butterfly hibernates in trees or sheltered areas around streams. They sometimes are seen gliding through shafts of sunlight on the occasional warm winter day.

    Honeybees can remain semi-active during the winter in hives by eating stored reserves of honey and generating body heat by congregating closely and fanning their wings.

     Some insects survive freezing weather by producing glycol. Glycol is similar to the antifreeze we use in our cars. This chemical also has been found in frogs and toads. Some toads can survive being almost completely frozen solid.

    Small arthropods, such as ants and spider mites, are able to survive freezing temperatures because they are composed of less water than larger insects, such as grasshoppers. It has also been found that insects with an empty gut - or those who overwinter in a non-feeding lifestage such as egg or pupae - can survive lower temperatures. Food in the gut attracts water that can freeze and cause permanent cell damage.

    So on a sunny day this winter, take a walk in the woods or go for a stroll in your garden. Look for rosettes and galls. Check the leaf litter. You might find that the "dead of winter" is full of life!

About Texas Discovery Gardens

     A year-round urban oasis at Fair Park in Dallas, Texas Discovery Gardens is a delightful, refreshing destination for local residents and out-of-town visitors. The first certified organic public garden in the state, Texas Discovery Gardens showcases beautiful native and adapted plants that are grown using sustainable methods that conserve water and help to protect the environment.

     Educational programs and exhibits at the gardens emphasize that when it comes to environmental issues, the most positive impact can be made by starting in our own backyards - literally. By including native and adapted plants in gardens and landscaping, urban residents can add beauty, conserve priceless resources and provide vital habitat for butterflies and other native Texas wildlife.

     Texas Discovery Gardens is a 501(c)(3) nonprofit organization that is funded in part by the Dallas Park and Recreation Department.

     For more information, please call 214-428-7476 or visit the website at www.texasdiscoverygardens.org.