Mel's Tip #6

            Often the question is asked, “How is the best way to start new plants from a leaf cutting?” I personally have two favorite choices. The first, which I believe is the best choice, is to place the new leaf cutting into a 100%, non-compacted vermiculite rooting medium. Vermiculite allows the excess water to drain away easily, while holding sufficient amounts to sustain the healthy growth of the leaf cutting while it is developing roots and plantlets. Vermiculite also releases small amounts of potassium which helps the leaf to ward off pathogens and physiological stresses. The second is to place the leaf cutting in water. As a plant scientist I have a fascination with wanting to watch how the leaf petiole (stem) develops roots and plantlets.
            Either way works well and neither seems to have an advantage over the other when it comes to obtaining new plants from a leave cutting. You could make an argument there is less stress to the plantlets when transferring them from a vermiculite rooting medium into a potting mixture.

            In Tip #6 I mentioned “physiological stresses.” What are they?  This is where the plants die because of incorrect cultural practices by enthusiastic growers.
            There are many types of physiological stresses, such as: over or under watering, improper lighting, nutrient deficiencies, temperatures too high or too low, mechanical damage, petiole rot, ring spot (water spotting), drafts or any other type of stress which affects the health of an African violet.
            Poor cultural practices are responsible for the death of more African violets than any other single cause, including: fungi, insects, and other pathogens.

            To top water or to bottom water-that is the question?  And what is the answer? To me it usually depends on how many plants I have to water. If I only have a small number, say 8 to 10 plants, then I mostly top water them. When my collection contains several dozen and sometimes upwards to several hundred then bottom watering (wicks, mats, saucers) becomes a necessity. Using either method, the goal is to supply the water needed so the plants thrive and produce the beautiful flowers we all enjoy. (See Tip #9 for discussion on salts, as related to watering plants.)

            Salts. What is the source of them in potting mixtures? For the most part the salts come from two sources: fertilizers and water. There are also some salts in the ingredients used to form a potting mixture. However, the major source is the fertilizers you use to feed your Africa violets.
            The best way to control the salts in a potting mixture is to water from the top,  allowing the excess water to drain out the bottom of the pot. When doing this the excess water, called leachate, should be discarded as it is likely to be very high in salts. When watering from the bottom, regardless of the method use, it is important to periodically apply an excess amount of water from the top. This will flush the salts from the potting mixture. Again, discard this water.

E.M. from Amarillo, Texas asked the following question:

            I have a question for you on testing the pH of …. potting mixes. I don't care for the litmus paper type of tests. For me it's hard to be sure on the shades of color when they are close. So here's what I'm trying and I’d love your thoughts. Is this all wrong or have I hit upon a good thing?
            I use a digital pen to test the pH of my water and nutrient mix. The pen tells what's up...no guessing about shades of color. As long as you keep it calibrated, the readings should be fine. I take my mix and get it wet (using water with a pH = 7) then let it sit for a day. Unless I’m checking the soil in potted plant then I just go on. I'll water the plant or some mix until a get a little run off. I then test the run off with my pen. This seems to work or am I fooling myself and hoping it works. 
             
Mel’s response:
 
            pH is always an interesting topic. Most hobbyists do not pay close enough attention to it.
            The use of the digital pens to test the pH is okay. I believe they will be most accurate when being used to check liquids. Using pH neutral water (distilled) is correct for calibrating the digital pens and this same water should be used when soaking the potting mixture or collecting the leachate for testing. Sounds like you are on the right path. Good luck. Below is some info from my book African Violets: Gifts from Nature. Hope you find the info useful.

From African Violets: Gifts from Nature.