Saturday, March 9, 2013

Growing African Violets, part 5 - Repotting

Some growers recommend repotting African violets with fresh soil twice a year.  As I’ve told you before, I am an essentially lazy gardener, so that almost never happens at my house.  Instead, I watch carefully for evidence that the violet is becoming root bound, e.g. failure to thrive, or visible roots growing around the sides of the pot or through the drainage hole.  Sometimes that is twice a year, but generally I really only have to repot my African violets once a year.  Contrary to what you might have heard, African violets do not like to be root bound.  They do, however, like to grow in the right shape and size pot.

Azalea pot
The pot your African violet is going to appreciate most will be relatively shallow, with a height that is roughly three-fourths the size of the diameter of the pot’s opening.  Most planters are roughly the same height as the diameter, which is not the preferred style for violets.  Roots of African violets grow out from the center more than they grow down.  If you plant your violet in a pot that is as deep as it is wide, the roots will fill the diameter but will not get down to the lower part of the potting soil.  That means there won’t be any roots in that bottom one-fourth of the planter to drink up the excess moisture.  The bottom potting soil will stay soggy, interfere with the aeration the roots receive, and foster the growth of Root Rot or other fungal or bacterial diseases.  And yes, I know – many of the pots marketed as “African violet pots” are the same depth as the diameter – another reason I am not a huge fan of them.  Pots marketed as “Azalea Pots” do have the correct dimensions for African violets.

There is an easy method to determine the appropriate size pot for your African violet.  The size of the pot should be about one-third the diameter of the leaves.   For example, if the diameter of the leaves is 12 inches, your violet will be happiest in a 4 inch diameter pot that is 3 inches deep.  If you don’t want to do any measuring and your violet is already in a pot, increasing your pot size by one inch each time you replant is a good rule of thumb.

Whether you plant your violet in a clay pot or plastic pot is really up to you.  I prefer porous clay because I have fewer disease problems related to the soil retaining too much moisture.    I also prefer the look of clay to plastic.  The downside of clay pots is that they tend to accumulate fertilizer salts more quickly than non-porous plastic, but this is easily remedied by occasional leaching.  Clay is heavier than plastic, but that generally isn’t an issue with the size pot needed for an African violet.

Regardless of the type of pot you use, it must be disinfected before planting African violets.   Unsterilized pots can harbor nematodes and other microorganisms that are especially deadly to African violets.  Disinfecting is simple – just soak the pot in a solution of one part bleach to 9 parts water for a half hour or so, then rinse with clear water before use.

The type of potting soil you use is very important.  African violets have very tender roots which are easily crushed by heavy potting mixes.  A good African violet potting soil contains no soil at all.  It is almost all sphagnum peat moss.  It may contain some perlite but by far the largest component should be peat moss.  As we learned with fertilizer, just because the manufacturer says it is for African violets doesn’t necessarily mean it is so.  Look at the ingredients on the potting mix bag and choose one that has only peat moss and maybe perlite listed.  No bark and no soil.  You may see calcium carbonate or some type of lime listed in the ingredients, also.  Peat moss has a relatively low pH (high acid content) and African violets prefer a more neutral environment so the calcium carbonate or lime is added to lessen the acidity of the mix.

Even if you just opened a brand new bag of potting mix, you should sterilize the soil before planting.  We talked in an earlier blog about how to accomplish this.

African violets and their tender roots can be easily damaged during the transplanting process if proper care is not taken.  I prefer to transplant my violets when the potting mix is on the dry side and then water after the planting is completed.  There are times, though, when you need to moisten the root ball to get it out of the pot.  Either way works fine. 

The easiest way to transplant is to take your new pot, which is approximately one inch larger than your old pot and measure the difference in depth of the two pots.  Place potting mix to the depth of that difference in the bottom of the new pot, e.g. if the new pot is ¾ inch deeper than the old pot, place ¾ inch potting soil in the bottom of the new pot.  I also like to cover the drainage hole with a coffee filter disc to allow drainage but keep the soil from sifting out through the opening.  A tissue or paper towel also works for this.  Loosely pack the new soil. 

Remove the violet from the old pot by making a “V” with your fingers and gently sliding them under the leaves, sliding the stem of the violet into the crook of the “V”.  Turn the pot upside down and gently shake the violet loose.  If it won’t release, you can use a blunt object like a pencil to very gently push on the root ball through the drainage hole.  Do not push the object up into the soil, though, as that will damage the roots.  If you are still unable to loosen the root ball, try soaking the soil, and if that doesn’t work, as a last resort, take a sharp knife and run it between the soil and the edge of the pot.  This is a last resort because it almost guaranteed to cause root damage.

Set the violet and intact root ball aside and place the old, now empty pot inside the new pot, centering it.  Pack potting mix in between the inner edge of the new pot and the outer edge of the old pot, to approximately ½ inch below the edge of the new pot’s rim.  After it is packed, remove the old pot.  The potting mix should stay in place along the side of the new pot and you can slip the root ball right into the new pot and just gently settle the soil in around it.  The top of the soil should be approximately 1/2 to 3/4 inch below the rim of the pot.  Do not tease the African violet roots to loosen them - simply place the root ball into the new pot in the exact same condition in which you removed it from the old pot.  Place your newly potted violet in a saucer of water and allow it to absorb whatever water it needs, then move it to its home.

If you had to disrupt the root ball during the repotting process, you may need to place the plant in a humidity cocoon for the first week after transplanting.  If you were able to easily remove the root ball from the old pot and it stayed intact during the transplanting process, this probably isn’t necessary but it certainly won’t hurt anything if you wish to do it.

If your potting mix remains chronically soggy even though your pot drains well, your violet may be in too large a pot and it isn’t able to establish a cohesive root ball.  In this case, you would transplant it into a pot one or more sizes smaller than its current pot.  Use the pot that is ¼ the diameter of the leaves to find the correct size.  Brush off the excess potting mix and pat the root ball into the soil of the new pot.  There is a lot of disruption to the roots during this process, so you will need to place the plant into a humidity cocoon for a week after transplanting when this method is used.

"Gooseneck" on African violet
Another situation that might require you to repot your African violet is you find yourself with an African violet with a long skinny “neck” that is bare of leaves on the lower part and has an “umbrella” of leaves at the top of the neck.  Most of us don’t really like the look of a violet that grows in this fashion, and all new growth for violets occurs at the crown so there is no hope it will “grow out” of its bare neck.  But we don’t need to throw it away.  We can “pot down” that gooseneck and make our violet look perfectly normal again.

Potting down is a very easy and successful process.  To do this, you remove your violet from its pot and clean the pot well, including sterilizing because it is sometimes a disease process that causes the lower leaves to drop, leaving the elongated neck.  You are going to repot your violet in the same pot (unless you want to move it to a different pot of the same size as the old one).

Once you’ve removed the plant and its root ball from the pot, starting from the bottom of the root ball, trim away a section of the rootball that is equal to the length of the neck which you are going to immerse in the potting mix.  When you return the violet to the pot, the bottom of the root ball should be roughly ½ inch from the bottom of the pot and the neck should be covered with soil, with the lowest leaves now resting on the rim of the pot.  Add potting mix up to the level where leaves start from the main stem and press the potting mix firmly around the neck and root ball.  Place the pot in a watering tray, allow it to absorb as much water as it can and let excess water drain away.  Place the repotted plant in a humidity cocoon for one week, remove it and resume normal care.

Tomorrow we’ll cover some common pests and diseases that attack African violets.

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