The Ornamental Garden in December

  • By Pat Chadwick
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  • December 2017 - Vol. 3 No. 12
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The winter solstice in December brings with it the shortest days of the year and freezing temperatures. While that sounds like a downer, it also means the gardening season is officially over.  For the gardener, it’s time to reflect on the successes–and perhaps even failures–of this year’s garden and possibly start planning for next year’s garden.  Without weeds to pull, flowers to deadhead, or bugs and pathogens to fend off, we turn to our houseplants to satisfy the itch to garden.

Heavy December frost on ‘Gulf Stream’ Nandina foliage




Overwintering plants indoors doesn’t have to be all that challenging.  You don’t have to be a “houseplant whisperer” to keep them healthy and vigorous. It’s simply a matter of understanding their requirements for water, humidity, temperature, and light.  If you ignore these essentials, you’ll find that it’s quite easy to kill a houseplant.  Let me count the ways:

  1. Overwatering (also known euphemistically as “killing with kindness”). This is considered perhaps the most effective way to kill a houseplant.  Overly saturated soil prevents the plant from taking up oxygen at the root level. Symptoms of overwatering include wilting and yellowing of the foliage.   The proper way to water a houseplant is to give it enough water so that it drains from the bottom of the pot.  Otherwise, salts in the water may build up in the soil, which will eventually harm the plant.  Unless your plant is one that prefers consistently moist soil, like an African violet, allow the soil to dry out somewhat between waterings.
  2. Lack of humidity. The flip side of overwatering is not having enough moisture in the air.  Once we turn the heat on in our homes, the humidity in the air drops to well below 50%, which is the moisture level that most plants need to stay healthy.  Browning of the leaf margins or tips generally indicates that the air is too dry.  To remedy this problem, place the houseplant in a bathroom or kitchen where steam from showers or from boiling water will raise the humidity level in the room.  Or, if you have a humidifier, try to position it near your houseplants.  Another solution is to fill a pebble tray with water and set the pots on top of the pebbles so that they are not actually touching the water.
  3. Exposure to direct heat. Avoid placing houseplants near a vent or other source of direct heat.  Hot air blowing on a plant can severely dehydrate it.  A plant that is overheated will appear very limp.
  4. Exposure to cold air. If your house is not well insulated or sealed against cold drafts, your plant can suffer from exposure to the cold temperatures.  You’ll have the same problem if you place a tender tropical plant near a door that is opened frequently.
  5. Direct contact with a window. Although most houseplants need as much light as possible, don’t let them have direct contact with a frosty window.  Otherwise, the foliage touching the glass may freeze.
  6. Not enough light. Plants that aren’t getting enough light will let you know by looking pale rather than a healthy green color. New growth will look tall and leggy or spindly rather than robust, and the new leaves may appear smaller than normal.  To solve the problem, move the plant to a brighter spot, preferably to a south or west-facing window.   Remember to give the plant a quarter turn about once a week so that it grows evenly and doesn’t lean or stretch toward the light.
  7. Pest problems. It may be wintry outside but that doesn’t mean you can assume plant pests are not an issue.  Pests such as white fly, spider mites, aphids, mealy bugs and scale can multiply very quickly on plants.  It pays to inspect your plants frequently for unwanted hitchhikers and deal with them promptly.


One the best things about December is the chance to celebrate winter holidays and that means decorating the house with greenery. For many households, a favorite family activity is selecting and decorating a Christmas tree.  You may have noticed that Christmas tree lots appeared around town before Thanksgiving, which makes one wonder just how fresh those trees could possibly be.  For information on selecting and maintaining a cut Christmas tree, see Nancy Bolton’s excellent article on Holiday Decorating with Fresh Greenery, which appeared in the December 2015 issue of The Garden Shed.   Her article includes a table comparing the four most popular Christmas trees – Fraser Fir, White Pine, Scotch Pine, and Norway Spruce.  If you’re not sure which is which, here’s how to tell the difference:

  • Fir – If the branches bear their needles individually rather than in groups and if the needles feel flat to the touch, the tree is most likely a fir.
  • Pine – If the needles occur on the twigs in groups of two, three, or five, it’s a pine.
  • Spruce – if the needles have four sides and roll easily between your fingers, it’s a spruce.

If you want to do further research on Christmas trees, check out Virginia Cooperative Extension Publication 420-641, Selection and Care of Christmas Trees.   The National Christmas Tree Association website ( is another good source for learning about the characteristics of conifers commonly used for Christmas trees.    Also, the National Gardening Association website ( has descriptions of the top 10 most common Christmas trees.


Just because the past few winters here in Virginia have yielded minor snow accumulations, don’t assume we’ll have the same mild weather (translation:  little or no snow) this season.  It wasn’t that many years ago (2010, actually) that the northeast and mid-Atlantic regions received two heavy snow storms (dubbed “snowmageddon”) back-to-back, producing more than 3 feet of snow in Virginia.

Should we experience heavy snow or ice storms this season, take some precautions to prevent damage to your evergreen landscape plants. Species with multiple leaders are susceptible to snow and ice damage. The branches of Leyland Cypresses in particular are bad about splaying under a heavy snow load, and the damage is generally permanent.  Other evergreens that might also be damaged include arborvitae, upright junipers, yews, magnolias, boxwoods, and some hollies.  There are a couple of ways to minimize damage.  By loosely encircling the outside of the plant with jute twine, narrow rope or strips of cloth, individual branches can’t catch and hold much snow.  Another technique is to tie the main leaders together, high up on the side of the shrub.   The bindings may be left in place once the snow melts or left in place until new growth begins in spring.

Clemson Cooperative Extension’s Publication on Protecting Evergreens from Ice Damage recommends preventing the problem in the first place by selecting evergreens with a single trunk or leader.  Species with multiple leaders should be pruned to a single trunk or leader when the tree is young.


Before the first snow flies and you lose all memory of how well your garden did this year, take a walk through your garden (preferably on a mild winter’s day) and take notes on what did well and what didn’t.  Before you forget where the spring flowering bulbs are planted, make a marker of some sort – it doesn’t have to be fancy – and stick it in the soil so that you’ll be able to find the bulbs next spring. This is a good time to make a list of plants that need to be divided, donated to a plant sale, shared with friends, or simply put out of their misery.

This is also a good time of year to inventory your seeds – the ones you collected and the packaged ones that are left over from previous years.  I find it handy to organize seeds by year.  Just write the year the seeds were packaged for sale in the upper corner so that you can instantly see how old the seeds are.  If you have a lot of leftover seeds, you might want to make a database of the seeds and the year they were packaged.  This system helps you keep track of what you have and may prevent you from buying duplicates you don’t need.   Then, next spring, before you start planting, do a seed viability test to see if the older seeds are still any good or whether they need to be tossed.


Do you ever wonder where insects go once the weather turns cold? It turns out that they have a variety of strategies for surviving cold weather.  Monarch butterflies, for example, migrate to warmer climates.  Wooly bear caterpillars overwinter in the larval state under leaf litter.  Japanese beetle larvae burrow deeper into the soil to escape the cold.  Some insects, such as dragonflies and mayflies, overwinter as nymphs in streams or ponds. Yet others, such as praying mantids, overwinter as eggs.  Certain moths overwinter as pupae and then emerge as adults in the spring.    Lady beetles, wasps, and some butterflies, such as the Mourning Cloak, simply hibernate.  For an interesting and colorful article on insect strategies to survive winter weather, see the University of Minnesota’s publication on Tough Buggers.


Now that gardening season is over for the year, keep in touch with your inner gardener by learning a few fun facts about plant names. For example, approximately 200 plants have the word “wort” in their names.  This word, which is derived from the Old English “wyrt,” originally meant plant, herb, or root and was applied to the names of plants believed to have healing properties.   For example:

  • Lungwort (Pulmonaria), which has spotted leaves, was believed to cure lung diseases.
  • Liverwort got its name from the shape of its leaves, which resemble a lobed liver.
  • Spiderwort (Tradescantia) may have been used to treat spider bites.
  • Barrenwort (Epimedium) was believed to prevent pregnancies.
  • St. John’s Wort (Hypericum) was thought to ease symptoms of depression.










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