Lowenfels: Take care of indoor plants, and they'll take care of you

Jeff Lowenfels

OK, let's talk a little about houseplants. For far too long there has been a series of myths about how indoor-grown plants are different from their outdoor brethren. Since these plants are what gets us through the winter, it is important to dispel the misinformation.

First, I am always amused when readers inquire about potting soil for indoor plants. The fact of the matter is that houseplants are no different than outdoor plants. If you read "Teaming with Nutrients" (my Christmas-giftable book published by Timber Press) then you know all plants "eat" and "grow" the same way. They all need the same basic soil, one that is rich in organic matter, full of microorganisms and drains well.

By the same token, indoor plants need mulch just as much as their outdoor counterparts. If you let it, the soil food web will maintain your plants with a microbial population that keeps building and maintaining the soil structure. This is crucial to a plant's existence, indoors or out. Shredded landscape bark and leaves do great things for indoor plants, which are almost always perennials.

Next, what about feeding indoor plants? Wonders of wonders, again they are just like your outdoor fare. This means you should feed them with organic fertilizers just as you do with outdoor plants. How often? I suppose you should have your potting soil tested and feed accordingly, but this is probably not practical if you have a number of plants. So, my suggestion is feed indoor plants once or twice a year. "Band" some food just below existing roots when repotting indoor plants and use am organic liquid for existing plants. Remember, over-fertilizing a plant will kill it. In general, under-fertilizing a plant will not.

It is possible to maintain your plants with compost and compost tea applications. Add some compost to the potting soil and apply a 1/4 inch layer onto the soil of indoor houseplants every September and May.

What about mycorrhizal fungi? You got it! Plants are plants indoors or out and over 90 percent rely on these fungi to get food. Whenever you repot an indoor plant you can dust the roots with a bit of mycorrhizal fungi. This will help the plants access phosphorous and other nutrients in the potting soil.

Lights? I have been through the rift about the need for lights enough times to not have to repeat it. Once you have lights, you can grow almost any kind of plant available. If you don't have lights, stick with things like philodendrons, pathos, sanseveria and aglaonma. You can usually find these at the nurseries, which remain open during the winter months. Supermarkets and box store garden centers usually sell them, too. Remember that these are all tropical plants and you must take care when bringing them home in our subtropical weather.

Finally, I recently received a post about plants which clean the air. I have always been a bit skeptical about these kinds of articles because the original NASA studies included fans, which circulated the air to be cleaned through the soil. If you've read "Teaming With Microbes" (another shameless promotion for Christmas), then you know these microbes have some ability to clean the air as well. Still, I am told that additional studies have been done and that suggest plants clear the air of such things as formaldehyde and benzene, and other byproducts of cleaners, paints and even furniture, rugs and toilet paper.

Aloe vera is one such plant. While it does enjoy sun, it certainly isn't easy to grow the succulent with which most Alaskans are familiar. By the same token, mother in law's tongue, Sansevieria trifasciata, is a great air cleaner which doesn't need much light at all.

Golden pothos does so well in low light that it will maintain its green leaves for quite some time, even when it's left in total darkness. They along with Dracaenas will handle xylene, trichloroethylene and formaldehyde, just in case you have gasoline or varnish fumes about the house. Ficus benjamina is not bad at clearing the same chemicals, too.

Perhaps the best at removing volatiles from the air is what's commonly called a "Peace Lily," Spathiphyllum. According to NASA, this plant removes formaldehyde, benzene in tricholroethylene as well as toluene and xylene. Better yet, they don't need a lot of light and will actually produce blooms under fairly dark conditions.

In sum, it's time to pay some attention to your house plants. Do it like they were outdoors.

Jeff's Alaska garden calendar for the week of Dec. 5

Lowenfels speaks: Come hear me speak Thursday night at Grant Hall: go to www.alaskabg.org under events for tickets and further information. I'm pretty sure you'll enjoy this "Ted- like talk," a fund raiser for Alaska Pacific University and the Alaska Botanical Garden. $15 for members of APU President's Forum, ABG and students, $20 for members of the public, $30 for parties of two.


By Jeff Lowenfels
Daily News correspondent