Chlorosis prevention

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ritamax

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Chlorosis prevention
« on: October 17, 2012, 09:01:47 PM »
I have been figuring out how to prevent chlorosis of those few plants in my garden which don't tolerate alkalinity well, such as Grevillea Robyn Gordon (which has survived the hot summer and the irrigation sprinklers and is flowering well) and Hibiscus syriacus, which is showing pale yellowish green leaves with green veins. No wonder, the soil and the tap water (pH 7,9) are both alkaline and saline in our region. I read, that it is very difficult to get the pH down permanently, but as all the other plants are doing fine, my concern is to get the pH down just for the grevillea and the hibiscus. I am not sure how to proceed at this time of the year. Could I use chelated iron as a foliar feed and add sulfur or ammonium sulfate in the soil? There are some phosphor-free fertilizers available, but that would be only in the spring, as they are rich in nitrogen.
Hobbygardener (MGS member) with a rooftop garden in Basel and a garden on heavy clay with sand 600m from seaside in Costa Blanca South (precipitation 300mm), learning to garden waterwise

Jill S

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Re: Chlorosis prevention
« Reply #1 on: October 17, 2012, 10:33:02 PM »
Sequestered iron and sulphur should both have some effect, you can use the iron watered around the plants as well. If you can get hold of some pine needles a good layer of those used as a mulch will also eventually help. If there is any way you can remove some of the lime from the tap water, if you use that on the plants during the summer, then that would also be beneficial. Rain water would be a better bet if you can collect enough during winter to use on your lime haters in the summer.

Making an acid soil more limey is a doddle compared to the rather thankless task of doing the opposite, but it should be possible to keep a few plants comfortable, if not there's always pots.
 
Member of RHS and MGS. Gardens in Surrey, UK and, whenever I get the chance, on Paros, Greece where the learning curve is not the only thing that's steep.

David Dickinson

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Re: Chlorosis prevention
« Reply #2 on: October 18, 2012, 01:41:55 AM »
I started a theme a few weeks ago asking if anybody uses vinegar in their water to get the alkalinity down. There were a few replies and I have been adding vinegar to the water I use on my balcony for the last couple of weeks. Their is a bit of information on the internet on this with varied opinions.

I spoke to a nursery owner on this topic a couple of weeks ago and he told me that some professionals add 400 ml of Nitric Acid to 1,000 lt of alkaline water to get to an average value of ph6.5.

I have just bought some Leucadendrons - Nitric Acid seems a bit drastic but I am going to try with the vinegar for a while yet so wish me luck :)
I have a small garden in Rome, Italy. Some open soil, some concrete, some paved. Temperatures in winter occasionally down to 0C. Summer temperatures up to 40C in the shade. There are never watering restrictions but, of course, there is little natural water for much of June, July and August.

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ritamax

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Re: Chlorosis prevention
« Reply #3 on: October 18, 2012, 11:48:14 AM »
Thanks for the replies!
First concerning the conifer needles. We have a lot of pines growing on our street and a large cypress hedge of our own, so I have needles for mulching, which is a great idea. But whether it has an impact on acidity of the soil, seems to be very controversial. Older sources claim it would be, but there is some research, that the acidity would decrease rapidly.
http://wood.uwex.edu/2010/11/18/pine-needles-cause/
http://davesgarden.com/guides/articles/view/2702/#b
I found an excellent article of Linda Chalker-Scott on foliar feeds. I will try the iron as a first remedy. Fixing the soil pH is important in the long run, but for just 2 plants it is manageable. Of course there is the option of sphagnum peat, which is soil acidifying (one can acidify water as well leaving peat in a stocking in a can of water for a day), but ecologically peat is not a good option.
http://www.puyallup.wsu.edu/~linda%20chalker-scott/Horticultural%20Myths_files/Myths/Foliar%20feeding.pdf
There is unfortunately no way I can figure out reducing the lime in the tap water for the whole irrigation system, but I will be able to cut down the irrigation as soon as the plants become established (most of the plants are less than 1 year old). We have mostly 6 months of drought and the annual rain fall of about 300mm comes down on 3-5 days in a year. I haven't figured out how to conserve such a daily amount as it can come to 127mm rainfall on one day, as it happened this September. I am an absentee gardener, so managing the rain water is a complicated issue in an arid climate.
For potted plants the vinegar trick is useful. I am using a special water softener from a garden center for my orchids indoors, as it is easier to calculate. But it is more expensive than vinegar. 
Hobbygardener (MGS member) with a rooftop garden in Basel and a garden on heavy clay with sand 600m from seaside in Costa Blanca South (precipitation 300mm), learning to garden waterwise

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greengrass

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Re: Chlorosis prevention
« Reply #4 on: June 24, 2013, 03:17:43 PM »
Hi,
A mulch of pine needles around the base of the plants will do the trick.