When Planting Natives, Get the Soil Tested for Proper pH Levels

Apr 12, 2019
Photo by: David Biggy The Rutgers Soil Testing Laboratory has a simple kit gardeners can use to find out the fertility and pH results of the soil in a particular area before the development of a native plant garden or landscape.

So maybe you have a clear space in your yard, or you’re planning to clear one, and this spring you’re staring at the possibility of re-creating and developing a new garden landscape utilizing native plants. That’s a great idea, actually, since native flowers, shrubs and trees are less prone to disease, insect damage and deterioration from our local environmental factors, such as wind and salt spray. In fact, there are plenty of options for planting within the Barnegat Bay watershed, in which Southern Ocean County is situated – from sweetspire to butterfly weed to American beachgrass, and dozens of others.

However, before you start digging holes and inserting plants – even before going to any nearby garden center to select plants to bring home – there’s one crucial bit of information you must know.

“Native plant gardens and landscapes are awesome, and along the coast in Ocean County they’re the best option,” said Susan Servidio, horticulturist and Rutgers Master Gardener coordinator at the Rutgers University Cooperative Extension of Ocean County in Toms River. “But if you don’t know what your soil consists of, you might get native plants that won’t thrive in that type of soil and you’ll waste a lot of time and money on a garden or landscape that will never reach its full potential. That’s why it’s important to get your soil tested.”

Soil testing may sound tedious and far too intricate for most home or rental owners, but if part of your plan is to grow a bunch of bee balm, and the soil is dry and sandy, the plant may grow for a season or two but won’t thrive – if it even lasts – beyond that, meaning the benefits of that particular native plant will be minimal or lost entirely.

“The key to native planting is your foundation, and that means the soil,” Servidio said. “It’s important to match the plant to the soil, and the best way to know what to plant in a particular space is to know your soil. It sounds like a chore, but it’s really not, and getting a soil test done can mean the difference between a native plant garden barely surviving and thriving into a beautiful, beneficial ecosystem.”

In general, a soil test can provide information about many things regarding the soil in your yard. Chemical and elemental factors of all kinds can be determined with an extensive soil test. But when it comes to basic development of a native plant garden or landscape, the biggest factor is the pH level of the soil.

For the more scientific minds among Southern Ocean County gardeners, the SUNY College of Environmental Science and Forestry defines soil pH as the negative logarithm of the hydrogen ion concentration. But for the average person, that simply means a soil test can determine the acidity or alkalinity level of the soil in a particular area. The pH scale runs from 0 to 14, and the lower the number on the scale the more acidity is in the soil, with 7 being a neutral state. The higher side of the scale indicates higher alkalinity.

Now, for the purpose of developing a native plant garden or landscape, Servidio says a higher acidity level is best – meaning the lower side of neutral, 7.

“Our soils in Ocean County are naturally acidic,” she said. “So if you’re planting natives, they will mostly thrive in soil with a pH of between 4.8 and 5.8. In contrast, 6.8 is 10 times higher in lime content, which is less acidic, and most natives won’t thrive in that kind of soil.”

Of course, the average gardener probably doesn’t have the equipment or know-how to conduct a proper soil test, and that’s where the Rutgers Soil Testing Laboratory can help. As part of the New Jersey Agricultural Experiment Stations, Rutgers’ soil-testing lab is staffed with soil experts and researchers who are fully equipped to do such tests.

Yes, there’s a fee for those who want to utilize the service, but it’s well worth it compared to how much a homeowner may spend on plants that won’t thrive, or fertilizer to try to help them thrive. Remember, natives will require a lot less fertilizing, watering and maintenance than non-native plants.

“The soil test gives you a baseline of where to start, so that you know ahead of time whether you have to make any adjustments to your soil before you start planting,” Servidio said. “If your soil is extremely acidic and you have to add lime to the soil, it can take six months for that lime to make a difference to your soil. And if your soil isn’t acidic enough for natives, it’s good to know that before you put any in the ground.”

Soil-testing kits are available at any Rutgers Cooperative Extension – most counties in New Jersey have a Cooperative Extension office – and the fee for a basic soil fertility test is $20. Once you extract a soil sample, enclose it in the kit package and send it to the Rutgers Soil Testing Lab in New Brunswick; you will receive a report in the mail detailing your soil’s composition as well as planting recommendations.

Conveniently, there is a do-it-yourself version outlined on the soil testing lab’s website at njaes.rutgers.edu/soil-testing-lab as well. Just make sure to download the necessary forms and follow all instructions carefully.

“The most important factor about your soil sample is to get a correct one by following the instructions in the kit,” Servidio said. “You’re not just getting one scoop of soil from the top of your garden space, or a scoop from one spot in it. You want to get at least six samples from different parts of your space to generate a good sampling. When you dig for your samples, you should dig a hole 6 to 8 inches deep to get it, and then take a slice of soil from the hole and put each slice in a clean bucket.”

For best results, prior to sending in your sample, mix the soil in the bucket and let it sit for a day or two to dry out – you have to pay the postage for the sample you’re going to send to the Rutgers lab, so you want it to weigh as little possible. Then, take a cup to two cups of the soil in the bucket, dump it into the kit’s plastic bag, tie it up and insert it into the kit’s cloth pouch for mailing. Each kit has soil sampling instructions as well as a questionnaire that must be filled out and returned with the sample.

When filling out the questionnaire, it’s important to know a few things about the space in which you intend to plant, particularly how much sunlight it gets and how well the area drains. If you’re not sure of the drainage, you may have to do a percolation test by digging holes in various spots and filling them with water to see how long it takes for the water to subside.

“With drainage, it’s important to know how quickly the water runs through the soil,” Servidio said. “There may be too much clay or compacted soil underneath the surface, and that will create very slow drainage, as compared to extremely sandy soil, which tends to drain very fast. Again, it comes down to matching the plant to the space. Some natives thrive in very wet soil while others will barely survive in it.”

Once you send in your sample, test results generally take a couple of weeks. If there’s something in the report you don’t understand, contact the Cooperative Extension office and somebody can help explain it.

For those who may not want a full-scale fertility report about their soil, the Cooperative Extension office also offers a simpler service that  tests soil only for its pH level. In that case, gardeners can take a soil sample – follow the same guidelines outlined earlier –  and bring about a cup of that soil in a small bag to the Cooperative Extension office, pay a $5 fee and get the sample pH-tested there.

“We can do a simple pH test here and mail the results to you,” Servidio said. “For a lot of people with existing gardens, knowing the pH level is good for determining whether to add anything to the soil. For many people, that’s sufficient. But if you’re about to redo an entire garden or plant in a cleared area, it’s better to get the more extensive test so you know exactly what you’re dealing with and how that can affect your native plants.”

For more information about soil testing and the Cooperative Extension’s full list of services, visit ocean.njaes.rutgers.edu/garden. For another excellent resource for gardeners who want to maintain healthy soil for native plants, visit the Ocean County Soil Conservation District’s “Top Healthy Soil Resources” page at soildistrict.org/healthy-soil-resources/to-10-resources.

— David Biggy

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