Thursday, November 16, 2006

Alkaline Autumn

IMG_2661, originally uploaded by kath66.

It has taken me six years to figure out why the previous owner of our house stockpiled chelated iron. I actually didn't even figure it out myself. It was through a fantastic email I received after searching for answers to problems with my previously beautiful Grevillia 'redhooks'. I put the Grevillia in the ground about a year ago, and am trying to train it more as a tree with one leader, than as a bush, mainly because I don't have room to accomodate what I'm told is the tree's mature 15-foot width. It was coming along very nicely, but recently the growth in the middle of the plant has turned yellow, the tips of each leaf turning brown. The tree continues to grow, but obviously, there is something wrong.

The friendly response I received, within an hour(!!) from Jo at the Australia Native plants nursersy diagnosed my problem as alkaline soil, which is evidently a big problem this time of year in N. California, and being new to the subject I am hypothesizing that it has to do somehow with lack of rain. This leads to chlorosis, which is lack of chlorophyl I think, thus turning the leaves yellow. What distinguishes chlorotic leaves from overwatered leaves (I've had both) is the chlorotic leaves have green veins and yellow around them, as if you've give a yellow leave a sip of green water. I've noticed this most distincly in my citrus trees, but since Jo mentioned it, and I took a good look at all my plants, can honestly say that almost all of them have some symptoms, including the Cestrum, Abuitlon, and even the sword-leaved Clivia that I thought were getting sun-burned.

Jo's email recommended I give the Grevillia some iron chelate, for the short term, even pouring a diluted mixture over the leaves. Then dig some sulfer into the soil to combat the problem over the long term, followed by a long soak. I dutifully followed the prescription for every plant in the garden, and am waiting to hopefully see the leaves green up again.

No comments: