An Iowa Garden

Primroses are generally thought of as being rather delicate in the garden, and most of the species are, in fact, difficult to impossible to grow in the open garden in the midwest... if our winters don't get them, our summers do. There are, though a number of species and groups of hybrids that are quite reliable, asking only decent, loose soil, some afternoon shade, and reasonable moisture (so I'm talking about plain old shady spots in the garden, not artificial bogs or cool stream banks). I do grow other types of primroses in my garden than are on today's list; some seem quite hardy but I haven't grown them long enough to feel comfortable recommending them, some of them haven't made up their minds whether they want to continue growing here, some look pathetic enough that I secretly wish they would give up, and then there are a number that seem to be doing very well, but they either have a reputation for being short-lived, or just a reputation as being a little more finicky, so they're not currently in my hardy list. I would stress that my hardy list would be different even in different parts of the midwest; there are many more primroses that I could grow well if I lived, for example, in Minnesota, where summer nights are cooler.
Pictured above is Primula kisoana, which is almost a weed here; it is unusual in that it spreads by underground runners, reminding me somewhat of a strawberry patch, with its hairy, slightly scalloped leaves. It is a toughie; it likes to spread out into the bark chip paths, where I can just pull up plants anytime I want, and pot them up or transplant them; they will grow anywhere for me... with their very hairy leaves, they seem the most drought and heat-resistant of any I grow, not wilting even in hot sun or dry wind, that would turn other primroses to mush. Primula sieboldii is often called the beginner's primrose, with its special advantage being that the foliage goes dormant in the late summer, so it is more resistant to heat and drought (though even dormant primroses don't want to be baked). In Japan, this primrose is keenly collected and grown, as there are numerous named clones, some quite pricey; I suppose one could come up with a dozen or so varieties in this country without too much trouble. I might like a close relative of sieblodii a tiny bit better: Primula cortusoides... it is a little smaller and perhaps a little more delicate, but I like it because its foliage grows in a better clump than sieboldii (which tends to run about). The common species primroses of England: vulgaris, elatior, and veris, also are pretty reliable, as are the hybrid complexes between these three species, and those crossed with the species Primula juliae, which all are sold under a variety of labels: vulgaris (should be called "x vulgaris"), polyanthus, acaulis, juliae (should be "x juliae" or juliana), and such names as Pacific Giants, Danova, Wanda, etc. There is a lot of variation in hardiness in this whole group, and a major topic in itself would be just sorting out the confusing names and parentage (which I about half understand but will nevertheless tackle sometime in this blog). Primula denticulata is the last member of my list, and probably the most delicate of the bunch; it really would like a little cooler, moister summer than we can provide; it persists, but multiplies fairly slowly, and occasionally disappears. The beauty of its flowers makes up for its shortcomings.
There are other primroses that likely will eventually join this list: saxatilis, polyneura, yuparensis, rosea, and hopefully many others, but I could be happy and have quite a primrose garden just with these hardiest of the hardy.