Alkaline soils are not a result of a deficiency, they are a product of parent rock and somewhat of climate.

You'll want to apply a chelated iron to correct the iron deficiency in your hydrangea.

Dan

Dan, agreed the plant is chloritic, but doesn't ph impact the ability of a plant to take up the iron? In this case, isn't a dose of agricultural sulphur possibly called for as well?

Chelated iron, Mary, can still deliver iron in higher pH soils (the chelation makes Fe available).

Surely the underlying pH should be addressed, but out here it takes a lot of soil amendment to do that - best prior to planting. When I lived in CA you could guarantee the iron chelates would start selling in summer when folks' gardenias started yellowing...

Dan

I think the OP was trying to ask if the 'pale leaves and dark green veins on a hydrangea' is the result of an Fe or Mg deficiency. It could be either or neither. There are a lot of things that can cause interveinal chlorosis. The effects of high pH, Fe, Mg, N, Z, Cu, Mn, Mo ..... deficiencies are others. Too much P in the soil, a high level of solubles (over-fertilizing), soil too wet/compacted, cold soils + organic sources of N or urea-based fertilizers, herbicide injury .....

If the pH is high enough that deficiencies of the minors are occurring, then steps to lower it are probably a good idea. Adding organic matter might be enough. W/o a soil test it's going to be difficult to nail it unless it can be corrected in a shotgun approach by adding whatever fertilizer you deem appropriate.

If you do decide an Fe chelate is appropriate, please consider Sprint 138 ..... expensive, but worth it - formulated for high pH applications.

Al

Thanks Dan -- that's useful to know. We who garden in the tending-to-acidic soils of the mid-atlantic don't have the experience you westerners have with this subject!

Al is fortunate to live out East, where alkaline soils are generally localized and copious rainfall ensures lots of OM breakdown for woodland garden cultivars. Here in the PedOCal region, we are not so fortunate and there are many plants easterners try to grow out here that suffer. The ~first thing we reach for on the shelf for these poor plants is the iron chelate, which is a "relatively" safe addition to correct chlorosis for many plants-gardens. Definitely the OP's beds need lots of OM tilled in and compost from the pile should be spread when it is ready, and some sulfur may not hurt either.

Dan