Jerusalem is a very alkaline area. For me this presents interesting challenges, I have always worked in acidic areas. The plants in the JBG are different to what I’m used to. The problems encountered with alkalinity, I’ve seen mostly only in books.
One of the major issues in the nursery is salt in the water. The garden is irrigated with mains drinking water, but this still has around 600ppm salt. The place its most visible is on the nursery misters. A white residue builds up on all the misting heads within a day of cleaning. Failure to clean them every few weeks results in clogging. To clean the misting units they are disassembled and soaked in vinegar for 24hours, we have spare units for rotation.
I think the salt is more prominent on the misters because they constantly dry out. Our propagation benches are not isolated in a tent, I wonder if a tent with higher humidity would reduce drying and therefore residue build up.
A while ago I found a specimen of Quercus insignis on the floor near the propagation benches. Sitting within range of the misters it had suffered pretty bad salt damage. I have since moved it into the other greenhouse which has RO water. Now the plant has formed new leaf growth it shows a nice comparison between healthy and salt damaged leaves. The photos are below.
The PH of the water is around 7.5. Part of me always wishes we had RO water throughout the nursery, but then I think realistically and remember is it needs RO water it probably can’t manage in the garden! The best way to overcome alkalinity issues is with good plant selection, this is really the way to deal with most issues.