Are the plants in the ground or in pots? Mixing peat moss into the soil will lower the pH pretty quickly. Adding garden sulfur is easier, but it takes several months for the pH to drop. I'd use sulfur, and make sure the plants are mulched with some kind of organic mulch, like compost or wood chips. As long as there is a lot of organic matter on top, the pH is not so critical to their survival, although they may not produce well until the pH is lower. You can find bags of sulfur at a lot of garden centers. I also see it at Home Depot and Lowes in the garden section with the garden fertilizers. Directions on the bag will tell you how much to use. Alex

I know blueberries will do well in most of that soil, but I REALLY want a nice little kitchen garden, although I wouldn't mind a nice blueberry bush. In a sense I do live in a caldera, at least in the summer (central AR summers are miserably hot and humid). My neighbors across the street are the only ones I've noticed who grow a garden, and theirs is primarily of ornamentals (roses, etc). The current naturally growing plants ("weeds" in laymen) are mostly clover and a bamboo screen that is very well established. I've read that bamboo thrives in acidic soil, and I suppose this explains why. Is it making it more acidic? Can I sheet mulch and just hope for the best? I really want to do a Three Sisters patch and grow lots of tomatoes. I've also read that wood ash can help increase soil pH. What are the most effective methods of applying these?

Those leaves look like they're suffering from iron chlorosis. The soil could be iron deficient, but iron chlorosis is often caused by alkalinity. I think it's far more likely that your potting soil is getting less acidic, not more acidic. Why do you think it's becoming more acidic? Have you had tests that show it, or is it because the leaves are turning yellow with green veins. If the former, I'll bet you're using a home test kit and I suspect it's not very accurate. If the latter, you've misdiagnosed alkaline conditions as acidic conditions. Get a small amount of fertilizer that says something like "for acid loving plants" or "rhododendron fertilizer" or "azalea fertilizer" (if it has some iron in it, that's even better). you probably want to get something that is water soluble/fast acting. If you're still thinking it's due to acidity, test it with one plant and see if it makes a difference. I really think you need to lower the pH of the soil, not raise it. One other thing to note is that you should make sure you're not over watering. Too much water can also cause chlorosis.

Won't hurt if you do. Give it a drink now, later in Fall, and early spring before blooms set. Water the plant well first, wait about half an hour or so, and then give it a drink of around 2 tablespoons AS mixed in 1 gallon water. I disolve the AS in a little hot water first and then finish filling up the gallon with cool water. There are many rules of thumb but few absolutes where hydrangeas are concerned. Every zone, every yard, every cultivar, and every caretaker will yield different results. ie; For as many folks that prune heavily and get no blooms the following year, there are others who say they have always cut them back almost to the ground and get loads of blooms, etc. etc....All I can tell you is that no plant has ever remained pink in my yard for more than one season (if that). So..if you're really itching for blue, do the AS thing until nature takes over, whenever that might be....yg