Roots and Shoots: Lemon or Lime Soil?

By Pamela Doan

For Christmas this year, I gave my friends and family soil test kits. (Note: Doing this will get you labeled as a “garden nerd.”) When I checked in on them recently, no one had used their kits yet, which I can’t understand at all, because it’s just a really cool and fun thing to do, now that high school chemistry is a thing of the past. I’ll give them until the end of the month before I start suggesting they don’t really care about their plants if they haven’t tested their soil yet.

Getting to know the balance of your soil is like solving a crossword puzzle with a chemistry set. The first clue is to observe what’s currently growing in the area that you test and how healthy it looks. Yellow leaves on your plants? Maybe the soil is too alkaline. Lots of moss? Could be acidic. Those are your first clues, but you need to fill in the blanks to get the full picture.

If you’re lucky enough to have a garden nerd friend who has given you a soil test kit, you’re ready to create the right environment for your plant to get lots to eat. Every plant has its own unique requirements for vitality. If you want blueberries, make sure the site where you plant the bushes is acidic. Azaleas and rhododendrons also thrive in moderately acidic soil, around 4.5-5.5. A vegetable garden generally produces best in the range of 6.0-7.0, and this is true for most plants.

Soil test kit from Cornell Cooperative Extension Photo by P. Doan

Soil test kit from Cornell Cooperative Extension
Photo by P. Doan

This range is neutral and allows your plants to get the most nutrients from the soil. The pH scale is 0-14 with 0-6 roughly in the acidic range, 6-7 being neutral, and 7-14 in the alkaline range. As the numbers get bigger from 0-6, the soil becomes more neutral, then gets more alkaline from 7.5 and up. I can’t ever remember which is acidic and which is alkaline since I never took chemistry in high school, so I think of lemons on the acidic side and lime (as in limestone) on the alkaline side. All the rest of you liberal arts students can feel free to use that system, as well.

Climate, geography, topography and construction are a few of the factors that affect the pH balance of the soil. I’ve tested soil all around my yard because as I mentioned, it’s fun, and I’ve discovered that each site is different. The pH can vary widely. Don’t assume that just because the soil next to your house comes in at 4.8 that the site you choose for your garden 30 feet away will be the same; check both spots and save yourself a lot of time and energy in maintenance and growth. For example, there’s a slope on the west side of my house where the soil is 5.4, and we’ll call that lemony, yet 30 feet away where the vegetable garden grows the soil pH is a perfectly neutral 6.8 (not limey or lemony).

If your soil is too acidic or alkaline, there are lots of things you can do to balance it again. Acidic soil can be amended with lime, wood ash and organic matter, like shredded leaves and compost. Follow the instructions carefully on the lime for the proper application. Alkaline soil can be adjusted with sulfur. Know that soil always reverts to its parent material eventually and you’ll need to monitor your soil, testing every two to three years and adjusting accordingly. Making it a regular practice to add organic matter annually keeps your soil in good shape, too.

Soil test kits can be found at landscape centers. Make sure that your kit has two reactive agents for best results. Take the sample from a depth of 6 inches, not the surface, and clean out any debris like pebbles or twigs. The Cornell Cooperative Exchange in Putnam County offers pH soil tests for home gardeners for a very reasonable $10. Check out the form online for instructions about how to take a sample at, under “Hort Forms to Download.”

On Saturday, May 18, the Master Gardeners of Putnam County hold their annual plant sale and will be doing free soil pH testing. I can’t imagine a better way to start building your own reputation as a garden nerd — spending Saturday morning at a plant sale getting your soil tested. See you there, fellow nerds.

Garden questions? Send them here: [email protected].

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