Rocks in plant pots do not improve drainage

Credit: Djenabou Diallo

Credit: Djenabou Diallo

Q: Please settle a bet. Should rocks be put in a houseplant pot to help with drainage? Annie Bresee, Decatur

A: Which side did you take? I sometimes say that folks who put rocks in their pots to improve drainage have rocks in their head. The reason may not be obvious, but it is based on soil physics. Imagine the way water moves in a pot. When you water a potted plant, the moisture initially soaks lower and lower through the soil. Eventually some drains out of the bottom. Much, however, stays in the soil at the bottom of the pot. The soil there becomes saturated with water. But soil above that area is only moist and roots thrive.

As you know, roots suffocate and die when they are surrounded by water-filled soil because the roots can’t breathe. When rocks are placed in the bottom of a pot and then covered with soil, there is less soil in the pot above the saturation zone in which the roots of your plant can grow. When you add rocks to the bottom of a pot, the result is a higher proportion of harmful, waterlogged soil.

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Q: I found lots of small bugs with long noses in my birdseed. Any idea what they are? Glynn Stepp, email

A: Could be granary weevils, rice weevils or maize weevils. These insects are commonly called “snout weevils.” They probably got into your seed at the processing factory. The larvae bore into seed and make themselves at home. You won’t know you have them until the larvae hatch into the adult weevils you are seeing. Weevils are harmless to humans. They do not bite or sting, but the birdseed should be fed to the birds promptly. Weevils commonly move from birdseed into any beans stored in the home pantry, so never store birdseed indoors. Buy smaller bags of seed in the future so it will be used up before the weevils hatch.

Q: I found two huge grubs in a potted plant. Each one is the length of my index finger and about as big around. The dirt started to undulate when I watered it. George Cohick, Meriwether County

A: I think you’ve found two formerly happy Hercules beetle grubs. They are commonly found in compost piles. I’m guessing that somehow the eggs survived processing at the potting soil plant. They hatched and grew into the monsters you found. These two would normally pupate and emerge as big Hercules beetles. Good thing they don’t have teeth … they might be awful grumpy after being awakened by cold water going down their necks.

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Email Walter at Listen to his occasional garden comments on “Green and Growing with Ashley Frasca” Saturday mornings on 95.5 WSB. Visit his website,, or join his Facebook page at for his latest tips.