Primula is such a large genus that it has numerous sections, and under those section headings, often numerous species. Primula has more species and untold hybrids from so many sections I could never hope to grow them all in my lifetime. Thus the "what if I could only grow one" filter to make me select only the best for my garden.
So many of the primula we are familiar with from photos in magazine articles and books, illustrate the large species and hybrids growing beside ponds and streams. Quite a few of those idyllic scenes are from English gardens. English gardening climate is quite different from our gardens here in the mid-west. If you are fortunate enough to have a babbling brook remaining wet all year with an overhead canopy of shrub and trees foliage providing bright shade, then lucky you.
If your garden is like mine, there is ample spring moisture from natural rainfall, but no brook or pond. Come July and August our temperatures will rise, the rains will drop off into a drought and the shrubs and trees of my woodland garden suck up the remaining moisture. Not the most agreeable of environments for plants needing that extra sip.
Fortunately for us mid-west gardeners, there is Primula sieboldii, the Japanese woodland primula. Here is a primula that blooms in late April through the month of May.
This species of primula will bloom, set seed and complete its cycle for the year by July. As the temperatures go up and the moisture levels go down, the Japanese woodland primula goes dormant. The plant disappears from above ground to sleep through the tough times, returning next spring.
In my garden the Japanese woodland primula is planted in soil with compost or rotted hardwood mulch. I do mulch with chopped leaves each fall, allowing them to decompose over the primula roots and help to maintain the moisture levels. I give them as much light as I can without placing them in full or afternoon sun. That is the only care I give my plants for them to grow into nice colonies over time. At this time I have 3 colonies growing in my garden and would like to add another this spring.
Foliage on primula sieboldii reaches about eight to ten inches in height. To me, the leaves have the appearance of crinkly bib lettuce. Of all primula this species is probably the most variable in bloom. Color can be pure white, pink, red, lilac, or lavender, sometimes with a different color on the reverse side of the petals. Bloom form can be flat, bowl or cup. The five petals can be rounded, notched, or a combination of both. Petals can also be prominently fringed. There are many named forms to collect. To get an exact form one must either do root cuttings or division. The seed does not come true.
I do not believe there is a "bad" or "unattractive" Japanese woodland primula. Most of the plants in my garden are colonies of unnamed seedlings I happened to enjoy and saved them back for my garden.
If you have been hesitant about trying primula in your shade garden, here is your opportunity for success with the genus.