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Common House Plant Diseases


If you have any experience with plants - outdoors or indoors - chances are you are very familiar with powdery mildew. It has the appearance of a fine white powder that attacks the surfaces of leaves.

When left untreated, the leaves and new growth will be contorted, and curled; it can even mean the end of the plant. Not a good thing - especially if you've spent a ton of money for a nice Mother's Day begonia or African violet.

Powdery mildew is a fungus. Usually the infection occurs by airborne spoors or from purchasing a plant that is already diseased. Examine new plants carefully -before you buy them. I know you've seen other customers in plant departments picking the plant up, pot and all, and peering underneath the leaves. (This is not a perversion - it's being a careful, responsible shopper!) Do the same thing. You don't want to take a chance on bringing a disease home from the store that has the potential of wiping out your entire collection of plants.

Powdery mildew will attack most plants, given the right conditions, even my precious jade plant which is almost fool-proof.

You can prevent infestation and treat infected plants by removing affected leaves and disposing of them - be sure to wash your hands thoroughly so that you don't transfer spores from your hands to other plants.

Since powdery mildew is a fungus (Oidium) it likes moist, humid environments. Either put your plants in a room that has good ventilation or invest in a small, unobtrusive table-top fan to circulate the air around your plants.


Do not over water your houseplants! Most do well if you allow the soil to become rather dry, then give them a good flooding.

I know this is true with the jade plant. Many people think it has to be routinely watered well because it is a succulent. Not so. Succulents store water in their leaves and too much H2O is a bad thing. I let mine dry out until you can almost see the leaves shrivel, then pour a quart of water into the plant. Hard to learn to do, but I call it "tough love".

My little kitten loves to hide in my jade plant!


As mentioned on another page, I have a gardenia plant with leaf tips that have turned yellow, then brown and are now in the process of shriveling up and falling off. This causes me to say that this web site really is a work in process. In researching information for this page, I have answered my own question about why my gardenia is falling apart.

There is a fungus among-us. Two of them, actually. Their names are Colletrotrichum and Gloeosporium. (Yeah, I'd say their momma didn't love them either to give them such silly names!) These fungi thrive in moist conditions. In my good intentions to provide the best possible environment for my gardenia, I provided it with a regular misting of fresh, room temperature water. Wrong!! You might consider wearing gloves, then pull of the affected leaves and get rid of them; try moving the plant to another environment with better circulation. I vow to never mist my gardenia again.


Depending on who you talk to, you'll get different answers to the same questions. In researching this information, I discovered that the above "rots" are attributed to more fungi - Rhizoctonia, Pythium, Botrytis, Sclerotinia, Alternaria and Phytophthora. (After you learn this, send in an application to Jeopardy!)

All of these fungi cause root, crown and stem rot in plants - outdoor and indoor. Infected plants share similar or the same symptoms and appearance. The plant will simply topple over and you'll see a ring of tissue which is brown or black - it's rotten. The roots are black or brown in color instead of a healthy white or pink.

The spoors (like powdery mildew) are airborne and are also transferred by moving of infected soil. It's important, when you see that you have the infestation, to dispose of the infected plant and its soil - then scrub the pot and allow it to thoroughly dry out before using it again.

Experts recommend that you sterilize your pots before adding also sterilized soil. (You can put clay pots in your oven - heat to a low temperature (180-200o) and leave in the oven for a half hour. Allow to cool in the oven before removing the pots.

Like all fungus, crown, root and stem rots are encouraged by warm, wet conditions. Be sure the pot and the potting mix provide good drainage. Avoid over watering - again, don't slobber all over your beloved plants - use a little tough love.