Question
I have a very large Mothering In-Laws Tongue, that I have had for over 10years. However, since the last time I re-potted I've noticed tiny flies living in the soil. Now I've seen worms in the pot. They are from tiny mm sized silver worms up to 6/7cm sized worms. I didn't use soil for in door plants only as i never have for the whole time I've had it. I know it's my fault but what are the flies/worms and how do I get rid of them with out killing the plant please.
Thank you for any help you can give

Answer
Hi Debbie,

The flies are probably fungus gnats and the worms are probably some type of centipede. Yes, they were introduced when you added non-sterilized garden soil.

Sansevierias do best when kept very potbound and rarely need repotting. I suggest that you undo the repotting that you did by removing the soil that you added. Most of the critters will be removed when you discard this added soil.

Then, put the slimmed down rootball back into a smaller pot that does not require the addition of any more soil. Next, allow the soil to dry out almost to the very bottom of the pot before adding any water. Sansevieria will withstand drought, but it will not survive soil that is kept constantly moist. The fungus gnats thrive in soil that stays moist. So by allowing the soil to dry deep into the pot in between watering, you will deprive the gnat larvae of the moisture they require.

A few of the centipedes may remain. They are harmless, but if they become a problem for you, then wait until the soil is very dry and then plunge the pot up to its rim into a tub filled with water and leave it for about 30 minutes. This flooding will cause the centipedes to rise to the top in search of air.

I have written an article on Sansevieria care that I will email for free to you (or anyone else) who sends a request to me at [email protected].

Please let me know if any of this is unclear or if you have any additional questions.

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Will Creed, Interior Landscaper
Horticultural Help, NYC

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