How to prepare for pre-emergent Starthistle control

Published on
December 21, 2022

The attached picture shows mature, flowering Yellow Starthistle (YST), as these invasive weeds appear in BVS now and for the next couple of months.  The plants at this stage all in flower are too mature to be sprayed with an herbicide.  To be effective, the plant shouldn’t be more than 5 percent in flower.  The other option is to whack each plant off with a shovel at just below ground level (it is not necessary to get the roots out as the YST will only re-grow from seed if you cut is low), and carefully place it in a tarp to haul it off to the YST burn pit, adjacent to the green waste area.

I have ribboned this plant for a reason—to demonstrate an easy way to mark the plant to spray it in the winter.  (Brightly colored rolls of plastic ribbon are available at Home Depot.)  By identifying the YST now while you can readily see the plants or the outline of a large infestation, you will then be able to spray the area where these terrible, invasive weeds with the inch-long needles have gone to seed.  This is an option if you are unable to remove the plants now before they drop tens of thousands of seeds (the flowers) this summer.  However, it is a very effective option.

Star Thistle Killer is the homeowner’s version of the commercial spray, Transline.  It can be very effective as a pre-emergent.  This is an herbicide which, when sprayed within 30 days of enough rain to water the herbicide into the seed bed (about 2 inches), it will prevent the weed from germinating, from emerging—you are spraying it pre-emergent.

Star Thistle Killer is available for under $50 online or from Abate-A-Weed in Bakersfield by the quart.  As it is very concentrated,   so the cost is reasonable.   And whether you spray it in the winter (December, January) as a pre-emergent or before the YST gets too many flowers as a post-emergent, it is a great way to control this weed.

Laurie Rude Betts, 821-1904

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