African violets can bloom any time of the year. They are indoor plants, and as such, are not under the constraints that other plants are to bloom seasonally. Some growers say their violets actually can bloom 12 months of the year; in other words, all the time. I, myself have found that after blooming for six to eight weeks my violets need to take a "rest" period of one to three months.
But, usually my violets are in bloom twice a year, sometimes three, and at six to eight weeks at a time that sums up to about five to six good months of blooms, not too shabby! They are especially lovely when blooming during the cold of winter, when their deep green foliage and bright colorful blooms are in contrast to the white snow or the gray landscape, outside the window. One thing that will contribute to violets’ potential to bloom year-round is to fertilize them every time they are watered. That, along with enough sunlight, humidity and warmth is the best recipe for African violets.
It is not uncommon for violets to "sport". In other words, your white violet puts up a purple blossom, or pink blossom or some other color. When the hybridizer created your particular variety, they cross pollinated two violets, more than likely, one of them was purple. So your violet has reverted back to one of its parents. Will it go completely purple? That’s a good possibility. Why? Well some are just more "unstable" than others. I would guess the plant you bought was probably an Optimara violet.
Optimara violets are grown by a huge commercial grower in Nashville, Tenn. It was started by the Holtkamp family when they were in Germany. Eventually they came to this country and the family has carried on with violets for years and years. They are the biggest or at least one of the biggest commercial violet hybridizers and growers in the nation.
They produce plants for the home grower that uses window light. Folks like me that have ten lighted plant stands and a big room grow for show, I do grow Optimara violets, some of their plants make great show plants. However, when I do get one, I figure it has at least a 50% chance of sporting to a different color.
That makes it not blooming true so I couldn’t show it under the name that was given because the plant would not match the description they gave to the African Violet Society of America to register it. Complicated I know but that’s the rules and since I’m also an African Violet judge, I have to know those rules.
When a violet sports to a different color, it doesn’t mean you have done anything wrong. Although environment can be a factor, it is more likely that the plant is just not stable. Sometimes you get pretty interesting color combinations from the plant that sports. Sometimes it will change colors and never go back to the original color. In fact, all the plants that I have grown that sported never went back to the original color. You never know what you’ll wind up with sometimes.
As for repotting. If it has been over six months since you acquired the plant or since you have repotted, it would be a good idea to repot. But repotting into a pot that is too large will cause the roots to stay too soggy and your plant will not thrive. Violets like "tight feet" and they don’t like soggy roots. So overpotting and overwatering is a no,no. The general rule is the pot should be 1/3 the size of the plant. For example: If your plant is 12 inches across from leaf tip to leaf tip, then it should be in a four inch pot. The soil you use is important also.
Most of the soils labled for African Violets is junk! Way too heavy for violets. So I would try to find a very light soil. Sunshine makes a good one, Optimara makes a good one. You can use one labeled for violets but be sure to add at least 50% or more perlite to the mix. That makes it lighter. You can usually find everything you need at Wal-Mart or a good nursery might have what you need. Most good violet soils are 1/3 peat moss, 1/3 perlite and 1/3 vermiculite. But you should be able to find a "ready made" one.
The most important factor in getting African Violets to bloom is light-Insufficient light is probably the most common reason for failure of African violets to flower. They need at least six to eight hours per day in order to flower. South or west windows will give you the best light this time of the year. You can also use artificial lighting.
They do best in daytime temperatures of 70 to 90 and nighttime temps of 65-70. They also like high humidity, which you can offer by placing the pot into a pebble tray-fill a small tray with pebbles and place the pot into this tray. Keep filled with water, this will create humidity around the plant. Never mist an African Violet or any plant with ‘hairy’ leaves.
Allow the soil to become dry to the touch between waterings. Pour water until it is coming out of the drain holes. Try not to splash water onto the leaves. Add a 20-20-20 fertilizer at least once a month. I believe it is Miracle Grow that makes one just for African Violets.