Jason Tartick and Kat Stickler are no longer accepting roses from each other ... with the two announcing they've ended their relationship after about six months.

The "Bachelorette" star and the influencer announced their split Saturday ... with JT taking to his Instagram Story to let everyone know they'd amicably parted ways.

Tartick says he falls in love quick ... and, sometimes it works out and sometimes it doesn't -- and, this time it just didn't.

That said, Jason makes it clear there's no hard feelings between the two ... adding he will "forever be grateful for her" and her daughter Mary-Katherine, 5.

Stickler echoes quite a bit of what Tartick says as well ... saying it just didn't work out in the end -- no hard feelings involved. She says she knows when you're in a public relationship, people want to see the conclusion whether happy or sad, and she will continue to speak on it in the future.

JT and KS first started seeing each other in April, it seems ... though it's hard to say exactly when it started 'cause they kept very hush-hush.

TMZ first obtained photos of the two on a dinner date together at the end of April ... with the two hitting a Tampa restaurant alongside Kat's kiddo.

The two looked real flirty during the dinner ... with Kat even feeding Jason a few bites of food. They went IG official in June.