FAQ - Fertilizer


Question: What is the best fertilizer to use on African violets?

Answer: There are a number of good fertilizers that will work well, especially those that are labeled for African violets. Our growers prefer either a balanced fertilizer (e.g. a 20-20-20 formulation) or one that has a higher phosphorus count (e.g. 15-30-15). The latter is believed to improve flowering. Fertilizers also contain many trace elements, but these are not always listed on the package. Occasionally a grower may find that the local water supplies also contain some of the same trace elements which can lead to problems with toxicity. It is often wise to ask others in your area which fertilizer works best for them. If you grow in cold conditions or have problems with acid pH, you may prefer a fertilizer that does not use urea as a source, as this can lead to a condition called ammonium toxicity which spots the leaves. Some growers like to rotate and use different fertilizers during the year, using balanced formulas during times when more growth is desired and high phosphorus formulas when preparing for show.  

Question: Is it okay to use a fertilizer with urea? I use fluorescent light and average 24 degrees (centigrade).

Answer: Urea-based fertilizer should not cause problems for you if 24 C is your usual temperature for growing. The exception to that would be if your soil pH were quite acid. Even then, the symptoms of ammonium toxicity (the result of using urea-based fertilizers in cold or acid conditions) are generally seen on the leaves or in the root system. Happy Growing! Joyce Stork

Question: The only peat moss I have found in bags also has fertilizer in it. Can I still use fertilizer in the water every time I water or will this be too much? 2)The fertilizer I have is 12-14-12 and says to use 1/2 tsp per gallon of water. Should I dilute it even more then? 3)I haven't found any peat moss without fertilizer unless you can use the kind you buy in bales that you would use in the garden. If you use this kind I thought I read somewhere about having to sterilize it. Is this true and how would I go about it?

Answer: 1)If you have no choice except for the fertilizer-charged potting mix, then you do not want to fertilize for about three months. This is why we dislike charged mixes... you really don't know at what point you should begin fertilizing. 2)If the fertilizer recommends this rate for once a month fertilizing, and you are going to use it weekly, you should dilute it to no more than an 1/8 tsp per gallon. If this is their recommendation for weekly watering, I would still dilute to 1/4 tsp and then watch. If you see fading vigor then a bit more might be good. However if you see yellow spots or edges around the perimeter of the older leaves, you are over-fertilizing and need to cut back the rate of feeding. 3)If you choose a bale that has no tears or cuts, the peat should be safe to use. Rather than sterilize the potting mix, the goal is only to pasteurize it which is done by heating the damp mix to 180 degrees and holding that temperature for thirty minutes. Sterilizing it (at a higher temp) would destroy the beneficial bacteria that enable the roots to absorb nutrients.

Question: I was told to water my African violets with warm tea. What does this do and is it okay? What brand name fertilizers are okay to use on these plants, as mine have great foliage but are not blooming although I have them in a window with north light.

Answer: There isn't anything obvious in tea that would be beneficial for African violets, although some teas might help amend the pH or provide some nutrient that the African violets need in tiny quantities. I would be very careful about using "warm" tea, since it is not good for a plant to have a sudden change in the temperature around the roots... a change of more than ten degrees (either colder or hotter) can result in spotting on the leaves because of root damage. There are a number of good African violet fertilizers including Miracle Gro and Schultz's. Look for a brand that has either a balanced formula (20-20-20) or a higher phosphorus number (15-30-15) which encourages more flowers. Use this according to package directions, erring on the side of using less rather than more than recommended. In a north window, you may not be getting enough light to the plants to get them into good bloom. The ideal window seems to be an east-facing one in which the plant receives bright morning sun. On the north side, the window must be fairly large and the African violet must be sitting so that it almost touches the glass. Having a building nearby that reflects light into the window can also really enhance the quality of the light. If you suspect inadequate light, you may need to supplement it with a little artificial fluorescent light for up to twelve hours a day. For more blooming tips find the article “Blooming Secrets” on the AVSA web site. Happy Growing! Joyce Stork


Question: The first time I repotted my African violets, I lost some plants due to shock, I believe. How can I prevent root shock? Will extra Superthrive help?

Answer: Many growers do use Superthrive with good results, but I would not recommend using more than the package suggests. I find that I rarely have shock if using a light porous potting mix (equal parts of sphagnum peat moss, perlite, and vermiculite) and if the plants are enclosed in a clear container or bag (set away from direct sunlight) for about one month after transplanting. Happy Growing! Joyce Stork

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