From the USPS on October 29, 2025:
Available in booklets of 20, this issuance offers the public an attractive stamp for mail use and pays homage to the sunflower, prized by both gardeners and pollinators as a dependable source of nectar and seeds for birds, bees and butterflies. Illustrator Nancy Stahl, who has created more than 40 stamp designs for the Postal Service, says she used as few colors as possible to enhance the brilliance of the sunflowers within the small frame of the stamp. Greg Breeding, an art director for USPS, designed the stamp using Stahl’s original digital art.
More details will be posted below the line, with the most recent information at the top.
Updated February 10th:
Here are the first-day postmarks for this issue: 
The Digital Color Postmark measures 2.99″ x 1.44″
There is no Pictorial Postmark for this issue, just the FDOI “killer bars.”
Updated February 5th:
Surprisingly, according to the Postal Bulletin, there will be a Digital Color Postmark for this issue.
On March 14, 2026, in Strongsville, OH, the United States Postal Service® will issue the Sunflowers stamp (Forever® priced at the First-Class Mail® rate), in one design, in a pressure-sensitive adhesive (PSA) double-sided booklet of 20 stamps (Item 685800). This stamp will go on sale nationwide March 14, 2026, and must not be sold or canceled before the first-day-of-issue.
This new stamp, available in a booklet of 20, highlights the beauty of sunflowers. The stamp is a stylized illustration of four sunflowers with blossoms rendered in gold and brown and leaves and stems in shades of green against a pale yellow background. Art director Greg Breeding designed the stamp with original art by Nancy Stahl.
Item 685800, Sunflowers (Forever Priced at the First-Class Mail Rate) Double-sided booklet of 20 Stamps
No automatic distribution.
How to Order the First-Day-of-Issue Postmark:
The first-day-of-issue postmark is a postmark notating the day a stamp is first authorized for use by the Postal Service™. Customers have 120 days to obtain the first-day-of-issue postmark by mail. All requests for first-day-of-issue postmarks (Traditional or Digital Color Postmark) must be sent to the following address with the choice of Traditional or Digital Color Postmark identified. All orders must be postmarked by July 14, 2026.
FDOI – Sunflowers Stamp
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900
Technical details are not yet available.
Updated December 12th:
This stamp will be issued Saturday, March 14, at the Garfield-Perry Stamp Show in Strongville, OH, a Cleveland suburb.
I assume it is the annual flower booklet. My favorite one in years.