Expert: Sarracenia Northwest - 8/9/2011

Question
Is algae growth harmful to carnivorous plants?  We're using rainwater collected from the roof here in east central Indiana to water Venus', Drosera, and small Pitchers being grown in 4" plastic pots outdoors in peat moss.  In full sun, the water trays and sides of pots all quickly turn green and slimey with algae,  as well as giving off bad smell, and trays become infested with mosquito larvae.  Moved them all out of direct sun (into shade from roof overhang), and algae growth slows down, but still end up cleaning out and changing water about every three days.  Can, or should, anything be done?  Thanks!

Answer
Hi Christine,

I'm afraid algae just comes with the territory with growing carnivorous plants since most are watered on the tray system.  It doesn't harm the plants, it just looks bad.  It tends to become less of a problem after much of the organics leaches out of the peat moss.  Using dark trays rather than white helps some.  It gives the algae less light.  You can control the mosquito larvae with mosquito dunks, small doughnut-type rings laced with a bacteria that only kills mosquito larvae.  We've used them for years, and they are totally safe for plants, and don't seem to harm other types of insects.

I would avoid moving your plants into the shade.  Your carnivorous plants will not be very happy with you if they are in the shade; they need full sun.

In the future, if you want to avoid the whole tray issue altogether, you can pot your plants in very large pots, and top water them.  With a large container the media holds enough water to not need the water trays.  However, you need to water them daily during hot weather.

Good Growing!

Jeff Dallas
Sarracenia Northwest
http://www.cobraplant.com