An Iowa Garden

Spring in the garden often brings with it a stiff neck; stiff from constantly turning this way and that to look at yet another woodland plant turned out in full flowering finery. However, even with all the peacocks like daffodils and rhododendrons blooming, the spring plants that I love best are the modest little primroses; plants often so small that they would fit in a teacup with room to spare. Here in Iowa, it is either too hot, too cold, or both, for most kinds of primroses, but visitors to our garden often express surprise at the variety that we do grow. When I first started growing primroses, learning the right cultural techniques was certainly a challenge, but a bigger challenge was figuring out which primroses stood a fighting chance of ever surviving here... going by the listed zone hardiness is pretty useless, as zone 5 Maine is a far cry from the zone 5 prairies of Iowa, with our winters that are sometimes relatively snowless, so that temperatures can vary by sixty degrees over a few days, with freeze-thaw cycles that would pop a bowling ball out of the ground. Our summers can be so hot and muggy, that the very air seems to throb from all the air conditioners whining away on July nights. Well, if you can't go by the listed zone hardiness then, the question became how to find primroses I could grow, without just buying one of everything and seeing what survived (a technique I have used somewhat in the past). There is a large group of hardy to semi-hardy primroses that are often called garden primroses, and this group is where I've had my best success. This however, brought me face to face with the most convoluted, sometimes misleading naming system I've ever seen. I've gradually caught on to some of it, and this is what I've learned (if any of this is wrong, correct me; if it's confusing, join the club):
Garden primroses primarily are from the section vernales of the genus Primula. This section includes the three common primroses of the English countryside: Primula elatior (the oxlip), veris (the cowslip), and vulgaris (the common primrose). Also in this section is P. juliae, native from northern Italy to the Caucasus, not introduced to the horticulture trade until 1900, but which rapidly became very important in hybridizing with the other members of vernales. Certainly other species and hybrids of primroses are grown in our garden, like sieboldii, cortusoides, and kisoana, but the section vernales has given us what most people think of when they think of primroses for the garden: some of these garden primroses are species, but most are hybrids between the different members of vernales (sometimes very complex hybrids), and here's where the confusing part begins... for some odd reason, some of these hybrids are labelled with the name of a species, even though they are hybrids, some are labelled with a name that would seem to be that of a species, but it isn't, and some are labelled as if they were a specific hybrid , when they are instead only a similar cross (sometimes faintly similar at that). Most of the hybrids are between one or more of the English species and P. juliae. The latter is a very early flowering, small plant, with flowers in the purple range. It grows in drier, less temperate areas than England, so is more tolerant of temperature extremes and drought. Juliae brings these qualities to its crosses in some measure, depending on how much juliae blood there is in these sometimes very complex hybrids, which may be crossed back and forth many times. So juliae gives hardiness, early flowering, drought tolerance, and the purple spectrum to flowers. Its hardiness may be partly on the basis of its small, very thick, crinkled leaves, which contrast to the thinner, lettuce-like leaves of the English vernales, which flop about in our summer heat, and shrivel in the afternoon sun. Vulgaris, elatior, and veris are all yellow-flowered (sometimes white). The purple of juliae is dominant to the yellow of vulgaris, so these crosses tend towards pink-purple. The yellow of elatior is dominant to juliae's purple, so these crosses tend towards yellow-pink; then many hybrids are recrossed, giving all the colors of the rainbow. Primula vulgaris is a species, but hybrids, often complex hybrids, that resemble it are often called P. vulgaris, rather than (properly) Primula x vulgaris. In addition, P. vulgaris and juliae have their flowers on short individual stalks; this is called acaulis or acauloid. Sometimes therefore hybrid primroses that show this flower form are called Primula acaulis, as if they were a species. Elatior and veris have their flowers in umbels (clumps of flowers on longer stalks); this is called polyanthus and hybrids with this same flower form are therefore sometimes labelled Primula polyanthus, again seeming to be a species, but just in fact a description of flower form. To further confuse you, the Brits often just divide their garden primroses into primroses and polyanthus; the former being any acaulis hybrid, and the latter of course being any with the polyanthus form. Hybrids of juliae with the other vernales members are very popular because of the good traits that I mentioned which are given to these crosses, but it all depends on how much juliae ends up being in some of these complex crosses. You will frequently see hybrids that have a fair amount of juliae in them, and thus resemble the species to some extent (small plants, smaller crinkled leaves) labelled as Primula juliae or Primula juliana, rather than more properly Primula x juliae or Primula x juliana, or just julianas. Wanda was one of the first crosses made in England between vulgaris and juliae; it is a small plant with dark magenta flowers, so has a lot of juliae in it. However, there is also the Wanda strain; other hybrids from these same early crosses, some of which also have a lot of juliae and are very hardy, but some of which may be more complex, less hardy crosses, but which are all too often also called Wanda, rather than Wanda strain. In addition, over the years the original plants have been further crossed, with less and less juliae in them, the plants getting larger and larger, and less and less hardy, yet they are still called Wandas, or even worse, Wanda. People complain about Wanda not being hardy, but what Wanda are they talking about? The original Wanda is very hardy; I grew it for years in a zone north of here with no protection, then dug it up and moved it here, so have grown the same plant for twenty years. These Wanda stepchildren would be better called julianas; at least they resemble juliae... the juliana nameplate however has been very stretched. A Japanese firm took over the breeding of the Pacific Giant strain of hybrid primroses, that resemble some type of large cabbage, and their hybrids are very popular flowering pot plants in spring in Japan, and this type is often called Julian there. The main trait it still has from juliae is early flowering. The original Wandas started out being very hardy plants; crosses basically between vulgaris and juliae, thus relatively small plants, tight growing, with dark flowers. They often show a very attractive red tinge to their tightly crinkled foliage. Finally, there are the pruhonicas, which were also early juliae x vulgaris hybrids, bred in Pruhonica, Germany, so called pruhonicas, or unfortunately often Primula pruhonica, rather than Primula x pruhonica or better yet, just pruhonica. These are little jewels, which seem to have retained more of the juliae; very small plants, with purplish flowers, tight leaves, and very hardy.
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