Garden Q&A: Several factors control African violet blooms
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Q. My son gave me a lovely African violet for Mother's Day last year. It flowered well through the summer, but it is not blooming as well now. What can I do to get it to bloom again?
A. Most modern African violets (Saintpaulia spp.) bloom throughout the year without much effort on the grower's part. However, there are a number of cultural issues that discourage them from blooming.
Too little light is one; African violets prefer bright, indirect sun. Too little sun causes them to stretch for the light and produce few or no flowers. Too much sun can burn the leaves. An east-facing window is ideal, especially with a sheer curtain to block the sun's harshest rays.
They also need eight hours of darkness every night. Although they need sufficient light to produce a flowering hormone known as florigen, florigen does not trigger blooming until it gets dark. If you grow African violets under lights, be sure not to run them more than 16 hours a day.
How you water can be a factor, too. African violets prefer to stay evenly moist -- ideally the soil feels like a well wrung-out sponge. They do not like to dry out completely in between waterings, nor do they like to be sopping wet all the time. Too much water can lead to root rot, and roots start to die in soil that is too dry much of the time. Either way, plants with reduced roots systems often sacrifice flowering to survive.
Your fertilization practices can also impact how well African violets bloom. Unlike plants that grow outdoors, houseplants are totally dependent on the grower to apply sufficient nutrients without overdoing it. The small pots these plants are typically grown in do not maintain a large reserve of nutrients. If you do not fertilize them on a regular basis, they may not have the necessary nutrients to spend on flowers.
On the other hand, too much fertilizer with high nitrogen content can lead to lush foliage at the expense of flowers.
You can purchase fertilizers formulated specifically for African violets. You should always use a balanced fertilizer that contains all of the major plant nutrients: nitrogen (N), phosphorus (P) and potassium (K). Nitrogen is important for the growth and development of leaves and stems. Phosphorus is important for healthy roots and flowering. Potassium is required for the accumulation and movement of carbohydrates throughout the plant.
These major nutrients are represented on the fertilizer label by numbers known as the analysis. Typically, fertilizers for flowering plants contain more phosphorous than nitrogen, perhaps an analysis of 8-14-9.
The African Violet Society of America recommends choosing a fertilizer that does not use urea as the nitrogen source because it can burn their roots. You can determine if a fertilizer contains urea by looking at the guaranteed analysis on the label. Be sure to follow label directions of the fertilizer you choose -- more is never better when it comes to fertilizing.
Finally, if you have recently repotted your African violet into a larger pot, the pot may be too big. African violets prefer to be root-bound to bloom well. It is good practice to periodically repot houseplants because the soil should be refreshed periodically.
You can often repot the plant into the same pot after cleaning it well, using fresh potting mix. As a rule of thumb, pots should be no larger than one-third the size of the diameter of the plant.
First Published January 26, 2013 12:00 am