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weed seed cluster orange

The Washington state noxious weed law requires landowners to control orange hawkweed as a regulated Class B noxious weed in King County. However, because of the challenge of control and the sensitivity of the habitats where it grows, the noxious weed program began offering in-house control of orange hawkweed in the Skykomish area in 2005 and in Alpental and other Snoqualmie Pass and North Bend areas in 2007. In addition, a cooperative and coordinated effort to control orange hawkweed on the ski slopes of Snoqualmie Pass began in earnest in 2010.

Controlling orange hawkweed is much harder than it would seem. Physical removal rarely succeeds in the shallow, hard soils we often find it in. The fragments of roots and stolons quickly regrow. Even if you do remove all the roots, the seed bank helps re-populate areas before other plants can re-establish. Smothering hawkweed with heavy layers of mulch should work, but it has to be carefully maintained to avoid plants growing out of the mulched area. And mulch isn’t very practical on mountain slopes! Even chemical control is difficult. The plants are well-defended with their hairy leaves and stems. Did I mention how devilish this plant is!

Orange hawkweed flowers form in tight, flat-topped clusters on the top of the stem. Photo by Minwook Park.

Orange hawkweed leaves grow close to the ground, preventing other plants from encroaching. Photo by Sasha Shaw

Orange hawkweed has invaded into the mountain areas of the Cascades such as here on the Skykomish River. Photo by Sasha Shaw.

The flowers start to open in late May to mid June and continue to bloom through the summer. If plants are mowed they can re-flower later in the summer. When plants begin to flower, also look for new stolons covered with fuzzy white hairs. Each plant produces 4 to 8 leafy stolons that can extend up to 1 foot and form the next generation of plants.

Orange hawkweed leaves are simple, strap-shaped and not lobed or toothed on the edges. New leaves are very hairy and older leaves have some hairs on them. Photo by Frances Lucero.

Grow Butterfly Weed: All of our perennial butterfly weeds attract bees and hummingbirds, are important nectar sources for a wide range of butterflies, most notably the Monarch. To promote Monarch butterfly caterpillars, Asclepias incarnata is the host most preferred. Plants are deer and rabbit resistant. Learn more about monarch butterflies and butterfly weed.

We guarantee all the seeds we sell for one full year from the date of purchase. If you are unsatisfied with any seeds purchased from Swallowtail Garden Seeds, we will issue a refund. For customers in the U.S., we can send one-time replacement packets or issue a refund.

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Large 6 in. clusters of vibrant-orange flowers on 3 ft. tall plants. Blooms attract swarms of butterflies in summer. Winter hardy to zone 3. Seeds occasionally require chilling, instructions included. Germination uneven over a period of 21-90 days.

Plant Butterfly Weed Seeds: Full sun. Asclepias incarnata (Milkmaid and Soulmate) thrive in moist, even wet soils, will adapt to average garden water. Asclepias tuberosa (Orange and Gay Butterflies) tolerate heat and drought, need only occasional water once established, will happily accept average moisture with good drainage.

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