HI Diana, We have a couple places locally that do soil testing. ASM Lab (217) 356-5756 on North Mattis and Illini FS 1509 East University Ave Urbana, Il 61802 217-384-8308. home kits are available. I generally recommend a lab test it at least periodically to get a more accurate reading. keep in mind pH changes are relatively slow and be sure the hydrangea you have is one that can change flower color. the white ones generally do not change. hope this helps. Sandy