Tidewater Gardening - December 2007

December Gardening Duties


K. Marc Teffeau

     With all the holiday activities during December, Christmas parties, family get-togethers, shopping, gift wrapping, baking, decorating the house, etc., we are fortunate that there is not much to do outside gardening-wise. After all, who would have time for gardening with all the other competing holiday activities? However, no matter how busy you are, there are some things that you should attend to in the plant area.
      You will need to pay some attention to your house plants. House plants with large leaves and smooth foliage such as philodendrons, dracaena and rubber plant benefit if their leaves are washed with a damp cloth to remove dust.
      In winter, reduced light and temperature means reduced or no growth of house plants so don’t fertilize this month. Plants will still require watering but be careful not to over-water as this will cause the roots to rot. Continued drying out of the soil (as evidenced by the soil pulling away from the pot) also damages the roots. Without adequate water, plants will wilt and may die. A common complaint growing rubber plants indoors is yellowing leaves and dead spots on the edges. This is usually caused by over-watering.
      As a rule, flowering plants need more water than foliage plants of the same size. To gauge when a plant needs to be watered, check the soil. It will become lighter in color and drier as the soil mass dries out. Stick your finger in the soil about two inches deep (to the second joint of your finger). If the soil is wet at this depth, don’t water. Otherwise, add water until it comes through the drainage hole in the bottom of the pot. After an hour, discard whatever water is left in the saucer underneath the pot.
      You can also water plants from the bottom, ensuring that the roots get proper moisture. Place the pot in a pan or saucer filled with water. Or dip it in a pail of water to just below the rim of the pot. Once the water reaches the top, remove the pot, let it drain, then place it back on its saucer.
Protect houseplants from winter chill by moving them away from windows at night. Or you can place a newspaper between the pots and glass panes to protect your plants. If your house is dry, provide your plants with extra humidity by grouping plants together or by placing the pots on trays of moistened pebbles. Rotate pots to make sure plants get enough light without getting leggy.
      An exception to the pot rotation in December is the Christmas Cactus. Don’t rotate your holiday cactus when watering as you do with other indoor tropical plants. Doing this after the flower buds have set will cause the buds to bend toward the light, thus severing and causing them to drop off. If you water in the sink, simply draw a line on the pot which is closets to the window and place back in the same location, in the same position.
Outside in the landscape, don’t be concerned if certain evergreen trees and shrubs begin to show some yellowing a leaf drop on the interior of the branches. This is a common occurrence on pines, arborvitae, junipers, yews and spruce. These evergreens must renew their foliage as part of their normal life cycle. Some pine species will experience needle loss every fifteen to eighteen months, while hollies drop leaves at about four year intervals. Yellowing of leaves and needles that occur to the whole plant is cause for concern and is most likely a watering problem, either too much or too little. Since we are still in a moisture deficient situation resulting from the summer drought and fairly dry fall, it is still important to do a deep, thorough watering. Be careful not to overdo it, especially if your soil type is a heavy, poorly drained clay soil.
      Tie evergreens such as yews, juniper and arborvitae in a spiral fashion with rope or twine to compress the shrub’s size and reduce damage from snow or ice. Erect snow deflectors over shrubs under the drip line of your home and other buildings to protect them against avalanches off the roof. Where snow drifts, plan to plant a windbreak next spring. Experiment with a movable barrier to decide the best angle and position for the planting.
Mums and pansies tend to be easily heaved out of the ground during weather freezes and thaws, causing root damage. Place discarded Christmas tree branches over flower beds to prevent this from happening. You can also use those branches to mulch beds of bulbs. Mulch your perennial borders after the ground freezes to a depth of two or three inches. Applying mulch too early increases the chance of harboring destructive field mice that are still on the lookout for comfortable winter quarters.
      We usually have a few mild days in December. I remember one year cutting broccoli from the garden on Christmas day. Mild winter days can cause a problem with some plants in the landscape because of the drastic change between the day and nighttime temperatures. A sharp temperature change between day and night may freeze the water within the trunk of a tree, causing it to explode or split open. This is called frost cracking.
      If not severe, cracks caused by frost cracking seem to close when warm weather arrives, although the wood fibers within may not grow back together. This is also sometimes called southwest injury because it is commonly found on the southwest side of shade trees where warm afternoon sun creates further extremes in the day to night temperatures. Particularly susceptible are many cultivars of evergreen azaleas. In most cases plants close over the cracks adequately, with no treatment necessary.
      Wrapping trunks with burlap strips or commercial tree wrap, painting white, or even shading with a board may prevent bark splitting. All of these methods reflect sunlight and reduce the buildup of heat during the day, thus reducing the temperature fluctuations that cause splitting.
      Any wraps should be removed after one season to prevent insect or moisture damage. The sun can also prematurely stimulate the opening of flowers or leaf buds in the spring. Freezing night temperatures might kill these buds. Bud injury due to the cold temperatures of winter also occurs in the dormant state on more tender trees and shrubs. Flowering shrubs may lose their flower buds, although their leaf buds usually survive.
Even with good management, injury to young growth or insufficiently hardened tissues may still occur as a result of unusual weather patterns. Little can be done to prevent injury in these instances.
      Root injury may occur in containers or planters, or balled and burlapped (B&B) stock, which has been left exposed during the winter. Lethal root temperatures can start as 28° on some species. Containerized or B&B plants should be placed in protected areas, sunk into the ground, grouped together or heavily mulched to avoid low temperature injury to roots.
      Happy holidays and Happy Gardening!!