Plants need the correct pH level which controls how well the plants utilize the nutrients available in your soil. All plants have a pH preference, so it is important to know the pH level of your soil. You can then choose plants with the same pH preferences, avoid those that will not do well in your soil, or know how to go about supplying their special growing needs. By testing your soil, you determine its exact condition so that you can fertilize and/or adjust pH more accurately, effectively and economically. 1 color comparator for pH. 10 test capsules Complete instructions for adjusting soil pH pH preference list for over 450 plants Additional discounts apply for this item when purchased as Bulk.