PlantFiles: Yellow Starthistle, Golden Starthistle, Yellow Cockspur, St. Barnaby's Thistle Centaurea solstitialis
It's time to read and vote for your favorite article in the 2013 Write-Off Contest! The four finalist's articles are featured in the May 13 newsletter and can be found through this link. Hurry! Voting ends May 18.
Height: 36-48 in. (90-120 cm) 4-6 ft. (1.2-1.8 m) 6-8 ft. (1.8-2.4 m)
Spacing: 36-48 in. (90-120 cm)
Hardiness: Not Applicable
Sun Exposure: Full Sun
Danger: Parts of plant are poisonous if ingested Plant has spines or sharp edges; use extreme caution when handling
Bloom Color: Gold (Yellow-Orange)
Bloom Time: Mid Summer Late Summer/Early Fall Mid Fall
Other details: May be a noxious weed or invasive This plant is attractive to bees, butterflies and/or birds Average Water Needs; Water regularly; do not overwater Self-sows freely; deadhead if you do not want volunteer seedlings next season
Soil pH requirements: 6.1 to 6.5 (mildly acidic) 6.6 to 7.5 (neutral) 7.6 to 7.8 (mildly alkaline) 7.9 to 8.5 (alkaline)
Propagation Methods: From seed; direct sow outdoors in fall From seed; winter sow in vented containers, coldframe or unheated greenhouse From seed; stratify if sowing indoors From seed; direct sow after last frost
Seed Collecting: Allow seedheads to dry on plants; remove and collect seeds Properly cleaned, seed can be successfully stored
On Apr 1, 2007, Joan from Belfield, ND (Zone 4a) wrote:
This plant is listed on the North Dakota invasive/troublesome list and this information is being distributed in a guide developed by the ND Weed Control Association and other agencies.
Winter annual or biennial, up to 3 feet tall
Single yellow flowers on the end of branches
Flower heads have long, straw-colored spine-like bracts arranged star-like
Small stiff hairs give plants a grayish look
Spreads by seed only
May germinate in fall as a rosette (dandelion-like) and resume growth in the following spring
First introduced in North Dakota via contaminated grass seed. All known areas have been eradicated
If ingested, causes lethal neurological disorder in horses known as chewing disease
Actually a knapweed, not a thistle
Produces a toxin that inhibits other plant growth (allelopathic)
Most abundant noxious weed in California (infests over 14 million acres)
I can't believe this showed up on a gardening site. A particularly obnoxious weed with little ornamental value. A severe problem in much of California, and hard to manage. Infests thousands of acres of rangeland; seems to suppress native vegetation. Seeds profusely; seeds will survive for years in the soil. The foliage grows very slow at first; while other plants are growing leaves, this one grows a long tap root straight down. By the the time most wildland foliage in my native foothills have browned-up in summer, the star thistle begins to bolt upward, gathering moisture from deep inside the soil. Toxic to horses. Nothing positive to say about this nasty plant.
On Jan 24, 2003, Terry from Murfreesboro, TN (Zone 7a) wrote:
A serious noxious weed, especially in the Northwest (U.S.) This thistle contains compouonds that produces chewing disease in horses, a permanent and fatal disease (the toxic effects build up over time when animals are allowed to graze infestested pastures.)
On the other hand, high quality honey is produced by bees foraging on these plants.
Gardeners are not encouraged to cultivate this plant.