Question
Hi,
My Zizi plant, which I've had for about a year and a half, has suddenly started to lose leaves and a few leaves are yellowing. Some of the stocks are also drooping. Is it time to re-pot? If so, what's the best way? Thank you!

Answer
Hi Stephanie,
   Unnecessary repotting is one of the main causes of plant failure so plants should not be repotted unless absolutely necessary. Plants need to be repotted when they become root bound and/or when the potting soil is spent of nutrients and the soil structure is broken down.
A few common signs that a plant is rootbound and needs repotting is an almost constant demand for water, slowed or stopped growth and roots growing out of the drainage holes in the bottom of the pot. When the rootbound plant is removed from the pot the rootball should be just a mass of roots with very little visible soil both in the rootball and in the bottom of the pot.
There are not really any good signs that a plant needs to be repotted because the structure of the soil is breaking down except maybe slowed growth but that is due to a lack of nutrients in the soil and can be fixed with fertilizer. Commercial potting soils are usually good for about 1-2 years. As a general rule small and medium sized plants should be repotted once a year in the spring and large plants should be repotted every 2 years. However large plants should have their soil changed once a year (in the spring). With a large spoon remove about 75% of the soil in the pot and replace it with fresh potting soil. Be sure to mix the fresh potting soil into the remaining soil at the bottom of the pot.
Also you should avoid repotting plants during the winter when most plants are in their dormant cycle (resting cycle).

There are several things that could be causing the leaf drop and yellowing leaves. Check to make sure there are no hot or cold drafts blowing on the plant. Changes in temperature can also cause leaf yellowing and leaf drop
Be careful not to overwater or underwater the plant. You should allow the top 1-2 inches of soil to dry between watering. Use distilled water to water the plant. That will prevent problems caused by fluoride, chlorine and mineral deposits commonly found in tap water.
Avoid over-fertilizing. In the winter during their dormant cycle, plants usually do not need to be fertilized. In the spring/summer during the active growth cycle it is better to fertilize lightly (half strength) frequently than to fertilize more heavily once a month.
Check the plant carefully for any sign of insects and/or mites. Some plants will drop leaves and have leaves turn yellow due to an insect presence.
Also check the roots for any sign of root rot. Roots should be pale, crisp and the tips of the roots should be a lighter color than the rest of the roots. If the roots are dark and mushy then the plant has root rot.

Keep in mind that some leaf yellowing and leaf drop is part of the normal aging process. Typically the older leaves toward the bottom of the plant are the ones that turn yellow and leaf drop is not excessive. Leaves that are lost due to normal aging will be replaced in the spring when the plant goes into an active growth cycle.

I hope this helps. If you have any questions or need additional information please don't hesitate to ask.
       Thanks
         Tracy