Question
I have had my cacti collection in a south window on the windowsill for 15 years & they did very well.  I watered them once a month.  I live in the NW.  A year ago we installed a forced-air gas furnace & vinyl windows.  I no longer have windowsills that are large enough for my cactus pots.  And the cacti were all getting so tall and/or leaning over so badly, that I threw them all out & bought 4 new cacti.  I put them on the dining room table right next to the south window.  The heat vent is right above them.  All four of them died within 6 months.  They slowly turned brown & rotted.  I don't know if I got a bunch of inferior cacti, or if the heat killed them, or if it was something else.  I presumed that overwatering would cause them to rot, but I continued to water them monthly, just like I did my old cacti for 15 years.  I thought the overhead heat might make them shrivel up, if anything.  Any suggestions on the best place to put cacti in the house, & how often to water them?  Thank you very much.

Answer
Dear Kathie,

While it is true that cacti need good air circulation, the air should be the of ambient temps, not heated air. I think that the heat helped kill them, but there are lots of questions, too. Is your soil porous enough? Often commercial mixes don't have enough drainage pamterial, so you might want to add pumice, perlite or small gravel to your mix.

Many cacti have a resting period in the winter, and watering them on a regular schedule doesn't do them any good. It's best to water them lightly only then. In the spring, depending on warmth conditions, you'd want to start watering again.

Additionally, while cacti need warmth to grow, they also need a period of cool at night.

I'd say that you have the right location for your plants, but perhaps your watering regimen can be altered to match that of the plant's normal growth cycle.

Please let me knwo if you have further questions.

Thank you,

Jeff