Houseplants Clean Indoor Air

Houseplants Clean Indoor Air

Lois Hole

As winter time nears, doors and windows of most homes are well sealed and tightly shut against the cold outdoors. Along with the cold, however, we are also keeping out fresh air. With so much more time spent indoors, the quality of the air within is more of a concern in the fall and winter.

Many homeowners are surprised when they realize the number of air-pollutants that are commonly found in most of our homes. New or newly-renovated houses especially, with their freshly painted walls and bran new carpeting, can have a high level of potentially harmful pollutants.

It is, however, fairly easy to compensate for that fact by simply filling your home with attractive houseplants. Studied by NASA have found that certain houseplants actually “clean” the air of harmful chemicals, such as benzene trichloroethylene and formaldehyde.

Benzene is a petroleum distillate commonly used as a solvent, and is found in gasoline, inks, oils, paint, plastic and rubber. It is also used in the manufacturing of detergents, pharmaceuticals and dyes.

Trichloroethylene is a commercial product used in some printing inks, paints, varnishes, adhesives and dry cleaning. Formaldehyde is found in virtually all indoor environments. Sources include foam insulation, particle board, pressed wood products, furniture and carpeting. It can also be found in grocery bags, waxed paper, facial tissue and paper towels.

Many common houseplants combat these pollutants. For a bright light situation, choose an attractive flowering plant. Both Pot Mums (Chrysanthemum) and Gerbera Daisies (Transvaal daisy) bloom in a variety of colours to brighten rooms as well as purify indoor air.

The Bamboo Palm (Chamaedorea siefritzii), English Ivy, Fig Tree (Ficus benjamina) and several types of Dracaena (Dracaena massangcana, Dracaena marginata, Dracaena ‘Janet Craig’, and Dracaena warneckei) are helpful, handsome plants that do best in a medium to bright diffused light.

Low light areas will support Chinese Evergreen (Aglaonema modestum), Peace Lily (Spathiphyllm ‘Mauna Loa’) and Mother-In-Law’s Tongue or Snake Plant (Sansevieria laurentii). The snake plant is one of the easiest houseplants to grow.

In almost any location, grow Spider Plants. These houseplants have green or variegated leaves and do well in bring or low light situations. The “spiders” that form on trailing stems can be repotted or simply plunked into a jar of water; they will grow for years- even with no soil.

The Cold Equation - Why Plants Die Over the Winter

The Cold Equation – Why Plants Die Over the Winter

By Jim Hole

By the time spring arrives, our gardens have endured a very long and arduous season. Months of sub-zero temperatures can take their toll on even the most stoic gardeners, but at least people spend most of their time on the warm side of the living-room window. Garden plants have little choice but to endure what winter throws their way. They must persevere or die.

Cooling Passions

What is it that allows a tulip bulb to survive extreme cold while a croton is damaged when temperatures drop to just a few degrees above freezing? The secret lies in water management. Plants have a love/hate relationship with water. During the growing season, plants are very enamoured with water, absorbing vast quantities of it to maintain vigour and encourage new growth. But during the winter, the love affair cools. Plants naturally retain some water within their cells. However, the water trapped in these cells is a recipe for disaster—when temperatures drop, it freezes and forms ice crystals. The expanding crystals burst cell walls, allowing the vital contents of the cell to leak out. The cell dies, and when this happens to enough cells, the plant perishes.

Coping Mechanisms

Plants that are native to areas with cold winters have several coping strategies to avoid the ice crystal problem:

  • One simple and obvious adaptation is the movement of the water out of the cells. Some plants transfer the moisture into the space between the cells rather than letting it lie within the cells and the cells do not burst.

  • Certain plants adapt by increasing the sugar or salt content within their cells. Water with higher levels of sugars or salts won’t freeze as readily as clear water —the higher the salt and sugar content, the greater the resistance to freezing. Ironically, plants may also suffer winter injury if their cells do not have enough water. Instead of freezing and bursting, these cells shrivel up and die from dehydration.

Running Hot and Cold

The water content issue isn’t the only factor involved in determining whether or not plants survive the winter. Sometimes, they are simply caught off guard. If temperatures drop rapidly following a warm spell, the plants do not have enough time to prepare for freezing temperatures.

Often, it is not low temperatures that kill plants, but rapid temperature fluctuations. It is much easier for a plant to adjust to gradual rather than brisk temperature changes and the ideal situation is for temperatures to cool slowly in the fall, remain moderately cold all winter, and then gradually warm in the spring. Of course, Mother Nature is rarely this benevolent. We’re all familiar with wildly fluctuating temperatures throughout fall and winter, and these conditions really test a plant’s hardiness.

Combating Winter’s Bite

There are ways to alleviate the winter weather woes:


  • Take steps to protect your more vulnerable garden inhabitants. Mulches of peat moss and compost can stabilize root zone temperatures of perennials, while wind and sunscreen fabrics can be staked up to protect sensitive fruit trees.

  • Finally, give your plants a good soaking a couple of weeks prior to freeze-up. This will ensure that plants strike the right balance between too much and too little moisture. Ultimately, plant survival over the winter is part skill and part luck. Don’t be immobilized by the fear of losing a plant. Take a chance and plant a few of the more tender perennials and trees. A great deal of satisfaction in the garden comes when a gamble turns into a success.

Winter, Your Best Ally for Managing Insect Pests

Winter, Your Best Ally for Managing Insect Pests

By Dr. Ken Fry

Have you ever thought how fortunate we are to live in a climate that has a cold winter season (yes, cool and rainy on the west coast counts as winter)? Beyond the obvious recreational benefits such as hockey, skiing, tobogganing and snowball fights, a cold winter protects us from many insects and insect-borne diseases that thrive in the warmer tropics. Who would have thought cold is good.

The freezing cold of winter prevents a great many insects from surviving year-round in Canada, but not all perish in the cold. Many insects have adapted their life history to allow them to survive during the cold and dark. Have you ever considered where insects go during the winter? The majority spend the winter safely tucked away out of the elements in a resting state called diapause. Shorter days and lengthening nights or increasingly colder temperatures trigger insects into preparing for winter.

Insects overwinter in any of the life stages, egg, immature, pupa or adult, depending on species and preferred habitat. An example of an insect that spends the winter in the egg stage is the aphid. Aphids typically reproduce asexually, the females essentially producing clones  during the summer. But come fall, in response to the changing season, males are produced that mate with the females resulting in the production of eggs for the winter. The eggs are laid on the stems of woody perennials. For example, the woolly elm aphid, Eriosoma americanum (Riley), overwinters in the egg stage in cracks and crevices in the bark of white elm trees. Overwintering eggs are destroyed by treating the host tree in early spring with horticultural oil to smother the eggs.


The forest tent caterpillar, Malacosoma disstria Hübner, also overwinters in the egg stage. In the fall the adult moth lays her eggs in a foam-covered ring around small branches of its preferred host, trembling aspen. As a child I was pressed into service every spring by my father to search for egg bands and remove them by hand. This is still the best method of control for this pest.

Some insects choose to overwinter as an immature (i.e. larva or nymph). Wood-boring beetles, including the poplar borer, Saperda calcarata Say, and bronze birch borer, Agrilus anxius Gory, spend the winter under the bark in feeding galleries. The poplar borer can spend up to three years feeding before pupating and emerging as an adult. To combat this stage you have to prune off the infested limb in late fall or early spring before the adult emerges in spring or
early summer.

Two of three species of birch leaf miner overwinter as a larva as well but not in or on the host plant. Instead, these insects drop out of the leaf and burrow a short distance into the soil and spin a silken cell to spend the winter protected under an insulating blanket of snow. The third species overwinters inside the leaf mine. One option to reduce the number of leaf miners emerging is to turn over the soil at the base of the tree in the fall to expose the larvae to the harsh conditions of winter. To get the third species, you should remove mined leaves
that remain on the tree over winter.

Turning over the soil or putting down a landscape fabric to prevent burrowing can also be used against a common garden pest, root maggots, Delia species, and an ornamental tree pest, the yellow-headed spruce sawfly, Pikonema alaskensis (Rohwer). These insect pests burrow into the soil to change into a pupa, a non-feeding stage where they metamorphose from larva to
adult. Many insects feed on insect pupae in the fall and early spring so encouraging beneficial insects in your yard and garden will help to reduce this stage of pest as well.

There are many other insects that overwinter as adults, including the ash bark beetle, Hylesinus species, Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), and many species of flea beetle. Pruning is the best defense against the ash bark beetle. The CPB burrows very deep so it is likely out of reach and should be dealt with in the spring when it lays its eggs. Flea beetles
commonly burrow into the leaf litter near the garden. They are commonly widespread and therefore difficult to manage effectively by taking action on the overwintering stage.

With a little effort in fall or spring you can reduce the number of pests emerging from their winter slumber. The fewer pests that begin the season, the fewer eggs are laid, the fewer offspring there are to attack your plants and therefore the less impact they will have on your garden and yard.

I See That Poinsettia Is Painted Green and I Want It Painted Red (and White, and Pink).

We mentioned last week how many indoor plants need extra, artificial light to survive Edmonton's dark winters (by the way, if you haven't picked up your full spectrum grow lights yet for your indoor plants, what are you waiting for? Come visit us today!)

One exception to this rule is our poinsettias, grown right here at Hole's Greenhouses. Like any other plant, they do need lots of light to grow and to get bigger.

But if you want your poinsettias to bloom, they must be exposed to at least 12 hours of continuous, uninterrupted darkness each day for 8 to 10 weeks.

We've been subjecting our poinsettias to 12 hour "black-outs" since late-September and they are now changing colour! Check them out!

You can order your Hole's poinsettia online or come visit us in store to browse from our selection of over 60 different poinsettia varieties.