Four years after the city of Portland replaced all of the hybrid tea roses at the Karl Switzer Rose Circle at Deering Oaks with lower-maintenance varieties, the experiment has shown that some roses – often considered a notoriously fussy plant – can thrive on neglect: no fertilizer, no pesticides and no watering.

“These roses survived last year’s drought, and that says something” about how resilient the plants are, Portland City Arborist Jeff Tarling said as he and John Shannon, horticulture supervisor for the city, gave me a tour of the circle earlier this month.

The Rose Circle was designed in 1927 as a bed of mixed flowering plants, but under Switzer, parks superintendent from 1939 to 1972, it morphed into just roses.

For years, the rose circle served as a test bed for the American Rose Society, which selected All-America Rose Selections as the best introductions of the year. But those hybrid tea roses required a lot of care, Tarling said. They had to be fertilized and watered, and often treated with insecticides and fungicides. Then, each year, the roses had to be cut back, mounded with nearly 12 yards of soil to cover each rose’s bud graft (where the flowering part of the plant is connected to the root stock), and then mulched with straw. With only two full-time and two part-time workers tending all of the city’s plantings, including the 52 planters with thousands of tulips downtown each spring and annuals after the tulips go by, the rose circle had become too labor intensive.

After consulting with Peter Kukielski, then curator of the Peggy Rockefeller Rose Garden at the New York Botanical Garden (he now lives in Portland), the city arranged to have the Rose Circle become a test garden for the Earth-Kind Rose program run by Texas A&M University; it’s the only Northeastern test garden, in fact. As the name implies, Earth-Kind roses are intended to be kind to the Earth, conserving water and reducing the use of chemicals. The test runs for four years, so the lab work, so to speak, will be over at the end of this growing season, but the university still must analyze and publish the results.

The city received three specimens each of 21 different rose varieties and was required to follow specific rules for planting. The site for each plant was randomly selected. Watering was allowed the first year (using a sprinkler system donated by the producers of “The Preacher’s Wife” when that move was filmed in Portland), but no watering is allowed after that. Pruning is also off-limits. City gardeners were allowed to add compost to the rose bed before the planting was done, and add mulch after the planting was complete; they can replenish the mulch as needed each spring. Other than that, though, it has been plant ’em and forget ’em.

Some roses have been done better than others, which is what any trial garden is designed to show. Some have died. Others have grown and bloomed profusely.

While peak bloom for the rose garden is late June, several of the bushes still had plenty of blooms when I visited on Aug. 1, and Shannon said another flush of blossoms often comes in late August and early September. Under the rules of the study, the roses in the circle may not be deadheaded. But Mainers growing Earth-Kind roses at home could deadhead, which would encourage blossoms to continue through much of the summer.

“Once the hips form, it tells the plant to shut down,” Shannon said.

Tarling and Shannon say they will contact the Earth-Kind next year officials to see where the test goes from here. They expect the city will be sent roses to replace the ones that have died, but say the changes could be more extensive.

Tarling and Shannon would not say which of the roses are performing best in the study. Just by looking at them, though, Shannon thought one of the Home Run series (the label had gone missing, so we didn’t know its exact name) and Ruby Ice were doing especially well. Two different colors of the popular Knock Out series had some blooms in early August. One called Apricot Drift, which my wife Nancy and I have in our garden and is so low that it acts almost like a ground cover, also had an extended bloom time.

Once the results are analyzed, they’ll be posted to the Earth-Kind website, so Mainers will be able to check which roses can excel in Maine with little care. If you visit the website now, it’ll tell you which varieties already have the Earth-Kind seal of approval.

If I were to add roses to our garden, those would be the ones I’d choose.

TOM ATWELL is a freelance writer living and gardening in Cape Elizabeth. He can be contacted at 767-2297 or at: tomatwell@me.com.