Not Really Yellow, Not A Giant, Not A Hyssop!

By Hubert Ling

Yellow giant hyssop, Agastache nepetoides, has small but numerous flowers which are not a pure yellow. The 1/3 inch flowers are greenish-pale yellow and are crowded on narrow spikes from 2-16 inches long and ¾ inch wide. However only a few flowers are fully opened at any one time.

The flowers contain both male and female parts and provide insects with both pollen and nectar. In fact, yellow giant hyssop is generally grown because it is such a pollinator magnet; it is recognized in Canada as one of the top 20 plants for encouraging pollinators.

This plant attracts bumblebees, halictid bees, honeybees, bee flies, beetles, butterflies, hummingbirds, and wasps, but don’t expect the flowers to look buttercup yellow. The plants look best when several are massed together. The plants begin to bloom in August and blooming may extend until frost. Small birds enjoy the seeds.

The genus name comes from the Greek “agan” which means “very much (like)” plus “stachys”, Greek for “ear of wheat” which refers to the flower heads. The species name is from Nepeta which is the genus name for catnip since the plant has a superficial resemblance to catnip.

In addition, yellow giant hyssop, is large but not a giant native plant; certain species of wild lettuce and Turk’s cap lily, et cetera, can, under ideal conditions, reach 11 feet high in a single season. So yellow giant hyssop is just a big, unusual mint at three to five feet tall with a maximum of seven feet. Compared with true hyssops however, yellow hyssop could be considered a giant. Almost everything about yellow hyssop is reasonably large: the basal leaves can reach 6 inches in width, the stems are wide and tall, and the branched flower spikes can stretch out over more than a foot. Also yellow giant hyssop is not a hyssop. The true hyssop, Hyssopus officinalis, is a native of Europe and the Middle East. In the Bible the hyssop is associated with purification and cleansing. It is 2 feet tall with small purple flowers similar in general appearance to our much taller yellow giant hyssop. Both plants are in the mint family although the foliage of yellow giant hyssop is not fragrant as many mints are, such as the true hyssop.

Yellow giant hyssop is widely distributed in Eastern North America from Canada to Georgia and west to Nebraska. However, it is uncommon in several states and is considered rare in

WI, VT, NY, and in NJ it is listed as S2 (imperiled). At one time it was widespread in NJ, but currently it is restricted to a few sites in three or four counties.

Yellow giant hyssop is easy to raise and is considered a perennial. However, unless conditions are just right it often fades away in three or four years. If happy it can produce a system of rhizomes and establish a colony. Give the plant a lot of room to spread. The plant grows best in light shade to full sun in a moist, rich, light soil. It tolerates fairly dry conditions as well as very wet soil. It also tolerates sandy or clay soil, frost, deer, and rabbits.

Propagation is generally done from seed which should be sown in the fall or given a moist cool treatment for 60 days in the refrigerator (cold stratification) before sowing. Seedlings may not bloom until the third year. The plants have no serious pests and are easy to grow.

The flower stalks may be utilized as cut flowers, but they are not spectacular since only a small number of flowers are in bloom at any one time. This characteristic however, makes the plant a great pollinator plant because it is a reliable source of pollen and nectar, as subsequent rings of flowers mature over many days generally from the bottom upwards. Our native-American people group, the Iroquois, used the crushed plant as a remedy for poison ivy and other skin irritations.

If you want to impress the pollinators and your friends, consider a patch of yellow giant hyssop.

Editor’s Note: Hubert Ling is Horticultural Co-Chair of the Native Plant Society of New Jersey. He can be reached at milhubling@ verizon.net.

Atlantic County

Phone: 609-625-0056

Bergen County

Phone: 201-336-6780

Burlington County

Phone: 609-265-5050

Camden County

Phone: 856 216 7130

Cape May County

Phone: 609-465-5115

Cumberland County

Phone: 856-451-2800

Essex County

Phone: 973-228-2210

Gloucester County

Phone: 856-224-8040

Hudson County

Phone: 201-915-1399

Hunterdon County

Phone: 908-788-1339

Mercer County

Phone: 609-989-6830

Middlesex County Phone: 732-398-5260

Monmouth County Phone: 732-431-7260

Morris County

Phone: 973-285-8300

Ocean County Phone:732-349-1246

Passaic County Phone: 973-305-5740

Salem County

Phone: 856-769-0090

Somerset County Phone: 908-526-6293

Sussex County Phone: 973-948-3040

Union County

Phone: 908-654-9854

Warren County Phone: 908-475-6505