Cyp. californicum - leaf blacking

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Abgeschickt von Barry Tattersall am 05 Oktober, 2001 um 18:25:19

I have been growing several seed grown plants of C. californicum for a number of years. I acquired them about six years ago, un-weaned and straight from the flask. From the first season they have all suffered the same fate – from a fairly early part of the year (June-ish) the lower leaves start to turn black (not the same necrotic condition which occurs when they have been over fertilised!). The affected (infected?) leaves have the appearance, apart from the colour, of being still fresh and able to function. This appearance remains for a further 3 or 4 weeks but then the affected leaves finally die! The problem starts from the base of the leaf, where it joins the stem; discoloration moves along the areas between the veins until the whole leaf is covered. At the moment (5th October) the largest plant, which has (or had) a total of 6 leaves, only has 2 functional leaves left.

I have tried a variety of different growing media, mostly organic mixes, although I have also tried a Seramis style mix, all with the same results. In desperation, I even tried to mimic the conditions in which it grows in California – Serpentine grit; even this produced the same results!

Could it be heat related? They are grown in plastic pots plunged to the rim in moist sand in an open frame. The frame receives sunlight from about 2 o’clock when the plants are in active growth. However, they are also receive 50% (sometimes 75%) shading.

I have not seen this problem in any other species of Cypripedium.