Date: Fri, 26 Jun 1998 15:26:58 +0200 From: strega@split.it (Tassara) To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2163$foo@default> Subject: interesting observation about south african winter growing sundews
Dear Filippo,
>I've another question for you about D.cistiflora dormancy. The small
>plants which I sowed this winter have now reached the size of about one
>cm. in diameter. Temperatures are getting here very high (40 deg.C a
>couple of days ago in the terrarium where sundews live), but the plants
>are still actively growing. Last year I kept two seedlings of
>D.cistiflora standing in water during all the summer: they stopped then
>growing, but never lost their leaves; they started growing again in the
>autumn and in the midlle of spring they died back. The same thing
>happened to my D.trinervia plants (another winter growing species from
>South Africa): the first summer they didn't go dormant, but the second
>summer they did so promptly. Have you ever noted such a feature in
>your plants?
I have noted this in some instances though I've never given it too much
thought. Its possible that as seedlings the plants will continue growing
if conditions are right. The fact that the plants stop growing in the
hottest part of the year may be due to the increased photoperiod rather
than the heat, though the latter may well still be a contributing
factor. I know that a long photoperiod in the mid summer can stop
tropical species growth (e.g. Nepenthes). Whether the South African
species are likely to be effected I'm not so sure. Anyway your summer
photoperiod is almost certainly not such a contributing factor as ours
(mid summer days will be something in the region of 17 hours daylight).
Whatever the reason it is almost certainly no bad thing when the
seedlings continue in growth in this way since they will use the extra
growing period to continue to increase in size, making their eventual
reappearance in the autumn more likely.
>Maybe it is a way to try to increase their size before the new growing
>season begins.
Agreed - see above.
>How do you keep the soil during summer? Slightly moist or bone dry (I mean,
>coming back from a three months cruise, would I find my plants still living?)
I let the soil dry out totally. To see the pots after a few months of
dormancy you would not believe that anything could still be alive.
I will experiment this year with watering the South African species
earlier this year to see if I can get them in growth sooner. This might
be the key to getting my plants to flower. I am certain that unlike the
Australian tuberous species the roots of D. cistiflora and D. pauciflora
are only stimuilated to start growing again when the soil is re-wetted.
As you may be aware the tuberous species will start growing, virtually
at a preset time so they are in active growth by the time the winter
rains arrive. Occasionally I am surprised to find a tuberous Drosera
appearing above the soil before I have even started to water them. I've
never found this with the South African species.
Regards,
-- Phil Wilson
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