Yellow Star Thistle

Since arriving here we have had the chance to meet and talk with a few of the beekeepers that we will be working with all year. We talked about many things including their bees, their operations, and the weather. The one reoccurring theme with all of them was talk of yellow star thistle. The yellow star thistle in and around the Chico area has started to bloom, exciting bees and beekeepers alike.

Centaurea solstitialis

Yellow Star Thistle can bloom anytime between May and September depending on region and climate.

All of the beekeepers we talked to agreed that yellow star thistle is an excellent source of nectar. What some of them didn’t agree on is when the plant produces its nectar. I had one beekeeper tell me that nectar production was time dependant. He explained that the plant does not begin to produce nectar until late in the bloom. I had another beekeeper tell me that nectar production is temperature dependent. His observation was that the plants will only produce nectar when it is very hot, explaining that there is a specific temperature range in the low 100’s that motivates the flowers to produce. So which beekeeper observation was correct? Was it temperature or time dependent, neither, or both?
This weekend in Upper Bidwell Park I came across a feral bee colony that had nested in the cavity of a dead tree (see video below). It was late in the afternoon and the bees were very active. As I stood there watching foragers and drones move in and out of the entrance I began to wonder what sparked the high level of activity. The obvious answer was the yellow star thistle. It was growing rampantly along the side of the road and had over-taken most of the meadows in the surrounding area. Then I remembered what the beekeepers told me about yellow star thistle. Nectar, from what I was told, was either time or temperature dependent, none of which seemed to come in to play at this moment.

It was about 80 degrees that afternoon and the star thistle had just started to bloom (about a week ago I noticed my first yellow flowers). From what I gathered it was neither the right time for a nectar flow (early in the bloom) nor the right temperature (

Written By: Michael Andree

Michael Andree has written 43 post in this blog.

Based out of the Butte County Cooperative Extension in Oroville, CA I am a member of the “Bee Team” created by the Bee Informed Partnership as a tool to help bridge the gap between scientists and beekeepers. The team works directly with bee breeders in the field and has been coined as those with their “boots on the ground”. We assemble field and lab data through hive inspections, surveys, and sample collection. The data and samples we accumulate are processed by the Bee Research Lab in Beltsville, MD where reports for beekeepers are generated. Our most essential duty is to report results to beekeepers empowering them to make more informed management decisions.