Expert: Christopher Littrell - 8/16/2007

Question
Hello.  I have been growing pitcher plants/venus flytraps in Seattle for about a year now.  Until very recently, all were doing quite well (full sun, in trays of water, in growing media that is composed of peat/pearlite...).  I saw a display at a local garden center (small, local owner, not a mega-chain) that interested me.  Several carnivorous plants (pitchers, butterworts, flytraps) were potted in a small vessel (closed bottom) with a drain hole about 1/2 way up the side.  This vessel was 'planted' into a larger pot (drain on the bottom) filled with normal potting soil into which several sedum were planted.  The idea is that the high-water carnivores can be watered directly, the drain hole in their pot allows a fair amount of water to remain (but drain below the root-level) and the drought-loving sedum get the overflow (I can send a picture if this lengthy description makes no sense).

So since the change (about 3 months ago) I have noticed several of the larger pitchers getting brown spots -- both mature pitchers and new growth (before opening -- so I doubt it is 'indigestion').  Strangely, some of the smaller pitchers are doing fine.  1 flytrap is thriving, while 2 are struggling.  I water daily to every-other-day (soil is always moist to touch) with tapwater (our water is pretty soft, and the sundews and asian pitcher pots I have indoors are doing fine on this water).  

Any information on the lack-of-thriving would be appreciated!

Answer
Hello Cary,

From your description, it is older and younger leaves on the older plants that are suffering while younger, smaller plants seem fine for now.

Your description of the pot is of concern to me. The idea sounds nice, but the regular potting soil in the secondary pot and the stagnant water left in the bottom of the carnivorous plant pot sound like the culprits to me. What might be occurring is backwash from the potting soil filled pot washing fertilized material into the carnivorous plant pot, altering the peat/perlite Ph and sickening the plants that have roots deep enough to get a dose of it. The half drained pot also collects water in the bottom, so that water can go stagnant and encourage bacterial growth. The larger plants can send rather long roots out, so it is not surprising that they would be the first affected by stagnant water either. You also indicated that the carnivorous plant pot is quite small, enhancing the problem of stagnation and backwash of fertilized water.

I would suggest a good change of soil and separate pot for the carnivores with good bottom drainage and a large tray of water under it. Sarracenias (from your description you have Asian Pitcher plants growing separately and Sarracenias with the Flytraps) will enjoy more water than Flytraps, so you can keep the bottom of their pot up to half submerged and top water to encourage movement of water and reduced bacterial buildup. The Flytraps can go in a pot with a tray that provides up to a quarter of their pot bottom with water and top watered as well. In general, they all would do well in a 5 inch pot for now. Bottom drained pots are better for flushing out impurities than that half drained pot you described. The half drained pot would suffer from almost the same level of stagnation as a terrarium set up.

You also mentioned that you have had the plants for about a year. Did they go through dormancy this last winter? If not, they might begin to weaken and die back after a few months of forced growth past their dormancy. Some can survive this treatment, but most will succumb and die off, basically becoming an annual. Venus Flytraps and Sarracenias are North American plants that need a temperate climate and dormant period for about 3 months in winter. It sounds like you have the tropicals indoors, Asian Pitchers and some sundews, which do not require dormancy, which is fine.

So long as your tap water is soft, less than 50-100ppm at the most, and does not contain much actual salt as a softener, it should be fine, particularly if your indoors sundews are doing well in it. Just change out the plants peat every year to freshen up their potting mix and revitalize their roots.

I hope your plants recover,

Christopher