Tall, bright, and blonde (sometimes redhead or brunette), the sunflower is not just another pretty face. The flower world may be rooted in good looks and pollinator appeal, but this plant earns its most industrious living by working to clean the soil — an exceptional talent that belies its cheery beauty.
Helianthus annus, our native sunflower, is well-known:
- For its edible qualities, producing delicious seeds loved by people and birds (see Squirrely Behavior, eSS&SC Fall 2010);
- As a versatile cooking oil extractable from the seeds (see Yellow, the Color of Happiness, eSS&SC Winter 2017);
- For its tasty, protein-rich young shoots, served by chefs and home cooks (see Mega Friends, Mighty Microgreens, eSS&SC Spring 2016 about a local farm growing “sunnies”).
But who knew, sunflowers can also get the lead out?
Soil contaminated by heavy metals, like lead, is common in both urban and suburban areas from lead paint, lead fuel, and coal ash left behind from the past century. Performing a simple soil test can tell a home gardener if their own garden beds hold such toxins. According to Tracy Allen, Soil Lab supervisor at the UMass Soil lab, “We process an average of 18,000 Routine Soil Tests annually. In addition to pH testing and nutrient analysis, as well as lime and fertilizer recommendations, the Routine Soil test includes a lead screening. That means we measure extractable or ‘plant-available’ lead.” The cost of the soil test is a small price to pay for a lot of very useful information about your unique soil profile! (See note).
Because heavy metals don’t leach out of soil or dissipate on their own, they must be capped, physically removed, or slurped up by accumulating plants, like sunflowers (or mustard, violets, foxglove, clover, or chives) before the soil is safe for growing food. Very important to note: these and other hyper-accumulating plants must then be harvested and removed for proper disposal (preferably bagged for hazardous waste collection), and never, ever be composted back into the soil cycle.
Although sunflowers have successfully been used to help clean up the Chernobyl nuclear zone in Russia and are currently being researched as a tool for home landscape phyto-remediation (the use of plants to clean up air, soil, and water pollutants), mostly they are a joy to grow and to set on the table in a sturdy vase. This summer, be sure to gather up a big, bright bunch from your local grower for a burst of indoor sunshine. Let these magical flowers remind us that plants are prodigious sources for food, a reward of color and beauty, and notably, some even manage to help clean up the messes we humans too often leave behind.
Test Your Soil
Note: It’s a truly simple action to collect a small amount of soil from the garden, label it in a baggie, and send it off (with $15) to UMass Soil and Plant Nutrient Testing Lab for testing.
UMass Soil and Plant Nutrient Testing Lab
Paige Laboratory 203
161 Holdsworth Way
Amherst, MA 01003
Barbara Anglin gardens in a yard full of lead-contaminated soil by growing veggies and herbs in raised beds; keeping native lawn grass well established to lessen soil dust; and composting to build up topsoil depth and health. In late summer, a sturdy vase is reserved for lead-free sunflowers from her Web of Life CSA share.