Have you tried this variety?
Sweetheart Primroses

So unique, this special primrose took Japenese breeders over 30 years to develop and is classified under the new name of Primula polyanthus rosaceous "Sweetheart".

You'll love Sweetheart's rose-like looks . The petals overlap each other and form rosebud shapes as they open, plus many are highly ruffled or have picotee edges. And good news for green thumbs in the wet Northwest climate... Sweetheart's flower petals are thicker and hold up better in poor weather than standard primrose varieties. So Sweetheart will maintain its beautiful looks for a considerable time.

Several vivid colors are available , and these colors last... A long bloom time, with many buds forming are a trademark feature of the "Sweethearts". Vigorous against cold, they will grace your garden for many years in the Northwest. Clumps will form with the ultimate plant size being larger than standard primrose varieties. Reports of older plants reaching sizes of 8-12" across are fairly common.

Slightly fragrant, and truly elegant, the Sweetheart series offers many beautiful looks for brightening your indoor home as potted plants , which you can then plant outdoors later.

Come look for Sweetheart Primroses at your Fred Meyer Garden Center today. You'll really like 'em!

While much of the information in these tips is applicable in several gardening zones/climates, some of the plants and timing suggested are best suited to the Northwest, generally in the mild/wet growing regions found along the I-5 corridor. You should make appropriate adjustments or consult local gardening experts in regions whose climates differ from this area of the Northwest.