Fertilizer and Variegation

Question:  I purchased ‘Rob’s Whippoorwill’, which originally had variegation on the outermost ring of leaves, but it has now started to turn all green.  I feed all of my violets with ‘Miracle-Gro African Violet Food’ (7-7-7 formula), every time I water, 10 drops per quart.  Am I feeding too heavily for a variegate?  Do they require more or less light than the average violet?  This is my first try with variegates, and I’m not happy with the results.  Am I doing something wrong?

Answer:  Not necessarily.  To begin with, ‘Rob’s Whippoorwill’ is a Champion (or crown) variegated variety that can easily lose its variegation with age.  In this case, it’s probably the variety, not you, that’s the source of your frustration.  In explaining further, we’re about to say a few things that will fly in the face of conventional wisdom.

Beyond the habits of the variety itself, our personal experience tells us that the single, most important, factor in determining the amount of variegation is temperature.  Variegation is always greater when plants are grown in a cooler environment.  Variegates can be sensitive to overfeeding, especially since heavily variegated varieties seem more likely to show signs of fertilizer burn on leaf margins and tips.  It’s also true that, because of the lesser amount of chlorophyll in their leaves, they grow slower and process relatively less food than do all-green varieties.  Still, feeding them significantly less, or feeding them low-nitrogen fertilizers, won’t necessarily produce heavier variegation–it just means that the green portions of the foliage will be a lighter shade of green.  We feed our variegates the same balanced fertilizer as all of our other violets, since our goal is a plant whose leaves have green portions that are dark green, and whose variegated portions are bright white (or yellow, beige, etc.).  Conventional wisdom also says that variegates require less light.  We suppose, in theory, that they do.  But in practice, we’ve grown them precisely the same as all of our other violets with no noticeable difference.

If you really want to grow heavily variegated varieties, simply grow them in as cool an environment as possible.  By cool, we mean night temperatures as low as 60-65f degrees, and day temperatures less than 70-75f degrees.  For those varieties whose foliage tends to turn green with age even when grown in moderate temperatures, here’s a trick we use for growing showplants.  Remove all but the center row or two of foliage, and remove all but a third of the root system.  By “starting over” these all-green variegates, the new growth (assuming, again, that your conditions aren’t too warm) should be variegated, at least long enough to show.  For those not growing for show, is it really that important?  After all, are the blooms on an all-green “variegated” plant any less pretty than those on a non-variegated variety?

Saucer Watering

Question:  I saw another grower soak his violet in a saucer full of water.  The violets seem to grow well.  I do the same, but rot my violets.  Why?

Answer:  What works for one won’t necessarily work well for another.  Unless every aspect of each grower’s environment is identical, the results may not be.  In this case, we suspect that your soil is different from that used by the other grower.  If the soil is light and porous enough, containing plenty of perlite or coarse vemiculite, it can be kept wetter than a soil containing little of these materials.  To give an example, a violet could be grown “hydroponically” in nothing but drainage material (like clay pebbles) without risk of rotting.

Your friend might also be more careful in how much water is poured into the saucer.  In addition, it is a good practice to check on the plants after having given them enough time to absorb the water, emptying the saucers of any unused water.  From experience, most growers who saucer-water have a sense for just how much water the plant can use, so that very little excess water will be left in the saucers.

Urea in Fertilizer


Question:  I’m a bit confused about the use of urea, and wonder if you can help me.  I was told sometime agao that we should not use any fertilizer with urea listed in the ingredients.  I’ve used fertilizers containing urea in my garden and it looked great!  Should I use my old fertilizer or toss it?

Answer:  There seems to be plenty of opinions on the subject, and it seems that the prevailing opinion of the violet hobby is the one you were given.  Still, urea has been an ingredient in fertilizers for years, and may successful growers us it.  For tha matter, we use it (4% or the 15% total nitrogen in our fertilizer), apparently without ill effect.  So what gives?

Let’s outline some important points.  To begin, don’t get distracted by “organic” and “synthetic”–though produced differently, chemically, they are identical.  Urea is just one particular form of nitrogen, an essential element needed for plant growth.  Nitrogen (N, the first number in you fertilizer formula) is the most essential element in any fertilizer.  Without it, your plant essentially starves.  it must have it.

Nitrogen can be supplied to plants in a number of forms, the most common being urea, ammonium, or nitrate (these should appear on your fertilizer label).  The crux of the matter is this: your plant can only use nitrogen in its nitrate form.  As ureas, it must first be broken down into ammonium (carbonate) then further converted into nitrate.  This is the basis for the “no urea” argument–since urea is not directly usable by the plant, why have it?  Wouldn’t a fertilizer containing only ammonium and/or nitrate forms of nitrogen be better?  If so, why is there any urea in fertilizer?  This is where the answer gets messy.

The simple answer is economics.  Urea is cheap, and fertilizers using it can be produced chapely and sold inexpensively.  But can it still be useful?  Yes, and it has been for many growers, for many years.  The secret is in making is possible for urea to be broken down into ammonium, then the usable nitrate form, of nitrogen.  This requires the work of microorganisms in the soil, which can oxidize the urea and ammonium forms.  In the “old” days, when growers commonly used compost, manure, or the like, in the soil mixes for their indoor plants, this was never an issue (though “sterilizing” these mixes undid some of this).  These mixes had plenty of bacteria (as well as other less desirable things, like nematodes and mealy bugs).  Modern “soilless” (peat based) mixes, though, contain no actual topsoil, compost, or manure.  Because of this, many growers believe they lack the microorganisms necessary to break down urea into usable nitrogen.  Unused, excess urea leads to an accumulation of “salts” in the soil mix, attracting water away from the plant’s roots and causing “fertilizer burn”, visible as brown leaf edges and plant centers.

Solutions?  First, good watering habits and occasional leaching (cleansing) of the soil with clear, unfertilized, water.  This will help prevent the build-up of excess fertilizer salts.  Use fertilizers at their recommended dilutions, keeping in mind your frequency of watering and the growth needs of your plants.  Can you still use urea-based fertilizers and soilles mixes?  Yes.  Even soilless mixes do contain some of the necessary bacteria to break down urea.  Soil conditioners ar available to add more, if you’d like.  Better, many of today’s soilless, peat-based, mixes do have these microorganisms–check the label (look for terms such as mycorrhize).  Good culture means more than just your choice of fertilizers.

Chlorine in Water

Question:  I am concerned about Cloramines in water.  I’ve heard that these cannot be boiled away and, over time, will cause toxicity in the plant and damage the leaves.  I use tap water that I boil and let sit at room temperature.  The other alternative I could personally use is collecting rain water and straining that as well as boiling it–I do have a rain barrel.

Answer:  We’ll begin this answer like we do many others–if what you’re doing now is working, don’t change it and don’t worry about it.  For my first 20 years growing violets, I used municipal water out of the tap (yes, they added chloramines), with little consequence.  For the next 20, we’ve used well water (with no additives).  Given the choice, I’d return to municipal water in heartbeat!

This is not to say that chloramine is of no concern–just not greater than any number of others faced by the grower.  Chloramine is a chemical compound (or ammonia and chlorine) added in low concentrations as a disinfectant to municipal water, as an alternative to “free” chlorine.  It has been used by municipal water systems for many decades.  Its used is becoming more widespread, wince it is more stable than chlorine and does not dissipate from the water before reaching users.  Precisely because it does not easily dissipate, it is likely to remain in the water when used on your plants.  Unlike chlorine, you cannot “age” your water, leaving it out in open containers for a day or two, until the chlorine has left the water.  Chloramine also cannot be removed fro the water by boiling, distilling, or reverse-osmosis filtration.  According to the EPA, the best means of removing chloramine is by use of an activated carbon system–a quality, granulated, activated filter and allowing sufficient contact time with the water being treated.  The best of those multistage systems can remove nearly all of the chloramines (as well as most other contaminants).

After all of this “scary” stuff, why not be concerned?  First, unless your municipal water authority is negligent and using chloramines above recommended levels, it should be harmless for both you and your plants.  Second, to the extent that you might be concerned about cumulative effects on your plants, this is only an issue if other good cultural practices are absent.  One of these is regular repotting of your plants.  Violets, and most other plants, should be repotted at least once per year, better every six months.  By refreshing soil regularly, you will be removing much of the contaminants in the soil, such as chloramines, fertilizer salts, and the like.  If you’re using a constant-watering system, like wicking or self-watering pots, regular refreshing of the soil is a must, since the soil is not “cleansed” as it would be with top watering.

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