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Need to clear the air? There is an air-cleaning houseplant for every kind of home

  • Author: Jeff Lowenfels
  • Updated: November 16, 2017
  • Published November 16, 2017

Aloe brevifolia succulent and snake plant. (Getty Images)

A few houseplant comments this week, as it is that time of year, isn't it? What would we do without our indoor plants to keep us out of trouble?

First, have you noticed that every single horticultural news aggregator out there has a story this week on "NASA houseplants" to grow for cleansing the indoor air. (And here I go!). NASA, I am assuming, is probably starving for publicity in this era of all things Trump.

You probably know the story by now, as it has been around for almost 20 years. NASA did its first study to find plants that might help clean the air in a space station setting while releasing oxygen and using carbon dioxide (which is what plants do). Turns out some plants had a significant impact and, and in some cases, totally cleared the air of benzene, formaldehyde and trichloroethylene (whatever that is).

Others picked up the work and came up with plants that also removed other toxic chemicals, such as xylene, toluene and ammonia. One study showed that the right plants can remove 80 percent of formaldehyde in a room in just four hours.

From my perspective, the most important and interesting discovery made was that growing plants in soil increased their "power" to clean the air, especially when it comes to removing benzene. The original studies were done using hydroponics. Turns out the microbes in the soil do a lot of the work to clean the air. Ah, "Teaming With Microbes." I could have told them.

Anyhow, the current recommendation is that growing one of these proven plants for every 100 square feet helps clear the air. So the question is, what plants do the trick? You can do an internet search for a complete list. What is really neat is that, because of the intended use in a low-light situation, the plants studied and shown to be effective include palms, spider plants, English ivy, Peace lilies, aloe vera, snake plants, philodendrons, dracaenas, ficus and even Dendrobium and Phalaenopsis orchids.

Surely there is an air-cleaning plant or two that will grow under your specific conditions. And all are readily available from several local sources.

Which holiday cactus is it? 

The other horticultural subject I expect to see covered extensively in the aggregated internet press this month is the annual discussion of so called "holiday cacti" — more specifically, Thanksgiving cactus (Schlumbergera truncate) and Christmas cactus (Schlumbergera bridgesii) and less specifically (due to the time of year), Easter cactus (Rhipsalidopsis gaertneri).

I always get questions regarding how to tell the difference between these plants. The silly answer is to wait until you see during which holiday it blooms. The proper answer is that the Thanksgiving variety has serrated, tooth-like "leaf" tips. In addition, the flower's anthers that produce pollen are yellow. Christmas cacti have smooth tips and a dark purple-brown color. These plants require 14 hours or so of light to bloom well.

Easter cacti bloom as the light increases, so are not confused with the earlier holiday cacti.

The loyal Alaskan reader knows that all three of these plants are light- and temperature-sensitive. Leave them by a window with natural light and they will automatically do their thing. Grow them at 65 to 68 degrees, their ideal temperature when in flower, and they should stay in bloom for six or seven weeks, provided you don't over-water. Wait until the surface of the soil is dry before you do.

You will find so-called holiday cacti (they are not cacti, but rather Epiphilliums) for sale at most plant outlets in Alaska this time of year. They are really easy to grow and really do produce flowers "on demand" every year at the same time.

Finally — I have to do it! — the end of the cursed Daylight Savings Time is the signal that you need to once and for all get those plant lights out. We are losing a handful of minutes of light every day now, and you know our dark winter period is heading this way, and fast.

I used to suggest that all one need do is go and get a simple shop flourescent fixture and a timer. I am amending that advice this year. You should go to at least one so-called "indoor grow" shop. With the advent of legal cannabis, there should be one relatively near you.

Why visit one of these stores? Because there are so many new kinds of lighting systems that go so far beyond the shop fixture that there will surely be one that fits your needs and budget. The new light bulbs are super efficient, and since you live in a place where you not only need lights for your indoor needs during the long winter, but also to start seeds for the summer, it makes sense to get a good system and to do it now. If you don't see something you like, you can always go back to that shop fixture.

Jeff's garden calendar

Bird feeders: It is mid November and should be safe to fill yours now. Place them so they are high enough to keep them from the moose, which is not something you think about in other places. Sunflower seeds are what the birds want.

Learn to make ice candles and luminaries: 12-1:30 p.m. Saturday, Dec. 15, at the Alaska Botanical Garden, $40 for members and $45 for non-members, limited space, call 907-770-3692 or

Drafts: No plant likes a draft. Many will drop leaves. Either block your drafts or move plants away.

Read my books: "Teaming With Microbes," "Teaming With Nutrients" and "Teaming With Fungi"!

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