It seems frustratingly difficult to find soil test kits around here. There are several companies that will do soil tests for you, but it's pricey. The one place I did find where I could get a
soil test kit (10 tests for $55 + postage) is unfortunately out of stock and has been for weeks!
So back in late September/early October I tried an experiment. 'Going Home' had mild chlorotic markings, similar to a number of other Irises, but was conveniently isolated in a pot. I had already done some research as to the possible nutrient deficiencies and came to the conclusion it was either phosphorous or potassium (and I was leaning towards the latter). So I added a little bit potash to the pot containing 'Going Home'.
After cleaning up around the Irises in the garden today, I realised that whilst 'Honey Pie' (the worst one) and its neighbours haven't improved with the warmer weather (in fact, its neighbours are starting to show more symptoms!), 'Going Home' was almost clean. My next step is to try adding a bit of potash around 'Honey Pie' and co to see if it improves whilst I wait for the soil test kits become available again.
