Is Fertilizing Houseplants Necessary?
Plus, putting beans to work in your garden to improve your soil this fall and winter. A deeper dive into Episode 146 of the Garden Basics with Farmer Fred podcast.
On Episode 146 of the Garden Basics with Farmer Fred podcast, we delved into two topics related to fall garden chores: Master Gardener and Interior Landscape specialist Lori Ann Asmus on houseplant fertilization and watering during the cool months; and, college horticulture professor (retired) Debbie Flower discusses getting the best performance from nitrogen-fixing legume seeds when preparing to plant a cover crop, such as fava beans (this was a scenic bypass from the original question of a listener who wondered why she had no bean production in her garden this year, despite having healthy looking pole bean plants).
Fertilizing House Plants: Yes or No? It Depends.
Fluoridated Tap Water vs Your Houseplants
One question that came up with Lori Ann Asmus, owner of Emerald City Interior Landscape Services, was the danger to your plants of using fluoridated tap water. Here’s part of our transcript conversation on that. The full transcript is available on the Garden Basics home site.
All right, fluoride in water, tap water. Should I be using municipal tap water to water my houseplants? Or should I start buying gallons of distilled water?
Lori Ann Asmus
If you don't have too many houseplants just make sure that you leach out the soil on a fairly regular basis. Because what happens with fluoride, it builds up in the plant tissues, as well as in the soil. And so the spotting and the tissue dieback that you get is basically from the fluoride building up in the tissue of the plant and the plant can't get rid of it, it doesn't break it down. It doesn't get rid of it, it just interferes with all the normal processes of the plant. And that's why you get those that spotting, especially on older foliage, and on an older plant. Fluoride is a problem. There's a couple things you can do about it. One is you can lower the pH. Even lowering the pH from seven, which is neutral, to like 6.8 or 6.5 will limit the fluoride uptake which is really important. Reverse Osmosis. if you decide that you want to do something with the water that you already have, will take out about 60% of the fluoride. The other thing that you can do is you can increase calcium. You can actually add calcium. Small amounts of calcium will also limit fluoride uptake. It binds with the fluoride. So there's some things that you can do.
Using distilled water really depends on how many plants you have and how committed you are. Now, distilled water is really not necessarily the best answer because you don't have any minerals. You don't have anything in that. I don't generally recommend distilled water unless it's a very tender plant, something that you're going to take and enter it into competition at the fair or something like that. Or you're going to enter an orchid or a bromeliad or something that's very tender that you're trying to take really good care of. But if you've got as many plants as I do, you're not going to go buy 10 gallons of distilled water every week, that's not going to happen.
Can you boil the water?
Lori Ann Asmus
No. In fact, leaving the water sit out like what you do for a chlorine abatement just concentrates it (the fluoride). It is a heavy element and so it's not going to off-gas like the chlorine will. It just concentrates it, so that's not going to help. Boiling is not going to help.
Is there a water you recommend buying?
Lori Ann Asmus
Even just a spring water that you know what's in there. If you go and buy spring water, you want to make sure you know what's in it, because you don't want to be fertilizing with something that's...
Have you looked at a spring water label lately? It just says, "bottled at the purest source."
Lori Ann Asmus
You have to look it up online. Yeah. And hope that it's true.
What about if I get the Brita water pitcher out from the refrigerator and use that water that's been filtered? Is that a better choice?
Lori Ann Asmus
You know, I don't know the answer to that.
Okay. Fair enough. I know it takes chlorine out, but I'm not sure what it does about fluoride, for example.
So, does the Brita water filter eliminate fluoride from tap water? Here’s a rather cryptic mention at the Brita website:
Note, Brita® filters keep a healthy level of fluoride, a water additive that promotes strong teeth
The website, fluoridealert.org, is more succinct about the water filters than can, and can’t, filter out fluoride:
Water Filters: One way of avoiding the fluoride from tap water is to purchase a water filter. Not all water filters, however, remove fluoride. The three types of filters that can remove fluoride are reverse osmosis, deionizers (which use ion-exchange resins), and activated alumina. Each of these filters should be able to remove about 90% of the fluoride. By contrast, “activated carbon” filters (e.g., Brita & Pur) do not remove fluoride.
On another houseplant fertilization note, Lori Ann Asmus says fall and winter is NOT fertilization time:
When using a houseplant fertilizer in spring and summer, Lori Ann Asmus explained it should be a low dosage fertilizer, where the nitrogen-phosphorus-potassium content listed on the label is in single digits. And she has definite favorites in her day job of taking care of houseplants in commercial buildings.
Why Inoculate Beans Before Planting?
Our favorite retired college horticulture professor Debbie Flower (I love her brain!) explained to us in another segment on Episode 146 why you want to treat your bean seeds with a bacterium inoculant before planting: free fertilizer for your plants and soil!
Here’s a link to more information from Colorado State University on using inoculants on legumes that are nitrogen-fixing plants.
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