Get to Know the Missouri Evening Primrose
Like a secret shared by a lover, one of the most beautiful blooms in my garden first reveals itself at night, and it remains on luminous display throughout the following morning all the way into the afternoon. This ethereal yellow flower floats in the darkness before dawn, and nods in the sunlight to the whims of a morning breeze. It’s a wonder of the hardy perennial world, but in more northerly climes, it remains somewhat enigmatic. So today, right here on The Renaissance Garden Guy, I’m giving you a full-on heads-up on the Missouri evening primrose.
So why am I writing about a spring-and-summer-blooming plant in the depths of winter here in hardiness zone 5B/6A? Couple reasons. First, in terms of northern-ish, cultivated ornamental gardens, the beautiful Missouri evening primrose, whose luminous flowers open at night and gleam all morning well into afternoon, is something of a nonentity, and I can’t wait to give it its due and proper. Second, right now is the perfect time to find this plant in relative abundance at many reputable online nurseries, and to get your order in for it. I planted mine during the second half of March back in 2021 and they’re flourishing beautifully. Late winter or very early spring is a great time to bed these large-flowered beauties.
That’s my rationale for the timing of this article, so now, let me lay the nuts and bolts of the Missouri evening primrose on you.
The Missouri Evening Primrose (Oenothera macrocarpa macrocarpa)
The Missouri Evening Primrose Rundown
This is a lovely little plant with beautiful big flowers. Its character is rugged and tough, its lifespan is considerable, its beauty is mystically yet brightly flaxen, and its blooming habits are intoxicatingly mysterious. Despite its intrinsic beauty, substantial longevity, and remarkable hardiness, this little plant remains relatively obscure in more northern climes – I’m amazed at the number of my fellow gardeners that are unfamiliar with it. So, I’m going to fill you in on everything I know about this beauty, based not only on my nearly four years of growing it in my garden, but on my anal research, as well. You’ll learn its taxonomy, nomenclature, and geography, you’ll see that it’s really not a true primrose at all, you’ll get a handle on the basics – from its characteristics to its care, and you’ll get my notes from the field. You’ll get photos of this little plant’s flowers and foliage, plus two really excellent product recs. And of course, you’ll get one of my (usually) half-assed “For Further Reading” bibliographies at the end, which will nevertheless give you some great resources for additional Missouri evening primrose study, and will assign credit for any firsthand research not conducted by me. By the time we’re done here, you’ll not only want to get some Missouri evening primroses of your very own to brighten up your garden, you’ll also know enough about these amazing plants to grow them successfully and to ensure that they continue to brighten up your garden for years to come.
Taxonomy, Nomenclature, and Habitat
First of all, the Missouri evening primrose is not a true primrose. It’s in the genus Oenothera within the plant family Onagraceae,¹ as opposed to true primroses (family Primulaceae, genus Primula).² True primroses and the Missouri evening primrose are not at all closely related. The MEP’s (Missouri evening primrose) family, Onagraceae (also known as the evening primrose family) contains approximately 650 different species included within 17 different genera.³ But the genus we’re concerned with today is Oenothera (the MEP’s) genus.⁴ Approximately 145 separate species make up this genus, but macrocarpa is the one to which the Missouri evening primrose belongs. And of the Oenethera macrocarpa’s five commonly accepted varieties (macrocarpa fremontii, macrocarpa incana, macrocarpa mexicana, macrocarpa oklahomensis, and macrocarpa macrocarpa), the one I’ll be discussing today is the one that grows in my garden (and is by far the most widely distributed of the five varieties),¹ Oenothera macrocarpa macrocarpa – the Missouri evening primrose. When you read or hear the term “Missouri evening primrose,” know that it’s Oenothera macrocarpa macrocarpa to which it’s referring (there’s gonna be a quiz on that spelling, gang, so get it memorized real good now, ya hear?).
The Missouri evening primrose is an herbaceous perennial found in the continental United States from Texas through the areas encompassing the Ozark Mountains,¹ north into Illinois, Indiana, and Michigan. It is often found growing naturally (growing wild) in these regions and in these habitats.¹’⁵’⁶ Evidently, this plant grows just as well in rocky, craggy terrain¹’⁵’⁶ as it does in fairly fertile soil, like the kind found in my own garden.
For a visual comparison of the Missouri evening primrose to true primroses (which grow in abundance in my garden), check out my RGG articles “5 Awesome Perennials You Can Plant Right Now” and “Beautiful Blue Garden Blooms.” There are some pretty good photos of, and info about, these beautiful little plants, which are nevertheless unrelated to the MEP. You can also find an overabundance of true primrose pics in the RGG “Precocious Bloomers” and “Spring” image galleries. The anatomical differences between these little plants and the MEP are clearly illustrated by those photos.
In Practice...
The basics.
Plant family – Onagraceae (includes such other genera as Fuschia [fuschias] and Epilobium [willowherbs], etc.). Height – 9″-12″. Spread – 12″-24″. Light – full sun to mostly sun. Bloom color – bright yellow. Bloom size – 4″-5″. Bloom time – May-August in zone 5B/6A. Foliage – perennial, deep green, lance-shaped leaves with light-colored veins, and herbaceous. Root system – deep-rooted with a long taproot. Hardiness – zones 4-8. Growth rate – medium growth rate, but fairly prolific naturalizers via self-sowing. Pollinators – bees, moths, and butterflies. Toxicity – non-toxic. Pest resistance – excellent insect, microbe, deer and rodent resistance.
Notes from the field.
I’ve gotta tell you, I really love my Missouri evening primroses. Aside from the fact that they’re (inexplicably) sort of unknown here on the Indiana/Michigan border, which lends them something of an air of mystery and exclusivity, they’ve got some other remarkable traits that I find particularly appealing.
Fairy tale-like blooming habits. You can read any number of articles from any number of sources about the Missouri evening primrose, and each one will offer a slightly varying time frame regarding its nightly/daily flowering habit. As far as my own small colony goes, the big yellow flowers of these plants open at night, and remain open fairly well into the afternoon. By late afternoon, the bloom is entirely spent. So, in terms of each bloom’s longevity, those large, almost surreal, nocturnally nascent flowers are good for about one day. At least in my experience, and in my garden. And these flowers ARE huge. The plant, which tends to grow in trailing, sprawling fashion, only gets to be about 24″ wide in spread. Tops. And at any given time, the flowers, which can be up to 5″ across, often appear in substantial multiples (I’ve counted as many as 9 or 10 per plant, blooming simultaneously, among the rich, green foliage). Once a flower is spent, what remains is a long-ish (about 2″-3″) seed pod.
There is really something transfixing about finding several of these yellow blooms, opened first to the moonlight of a warm summer night, then glistening with dew drops in the sunshine of the following morning. The flowers of the Missouri evening primrose are truly magical.
Pretty effective at self-sowing, but not aggressive in my garden. I started out with three plants, planted as bareroot specimens in mid March of 2021. They grew beautifully and, by their second year, dropped enough seeds to produce two or three more viable plants the next year. Aggressive spreading by my MEPs is kept in check by their proximity to taller, more vertically robust plants, which effectively mitigates the growth of their population. Because my colony grows among taller, extensively over-arching specimens like buddleia, echinacea, and potentilla, its population is confined in size to a relatively few (5 or 6) perennialized specimens.
Pest resistant. My own colony of Missouri evening primroses is impervious to attack by pests of any kind, as far as I can tell. Within the confines of my garden’s stockade fence, the only herbivorous predators are those of the burrowing variety: voles and chipmunks. My MEPs have remained entirely immune to the intermittent presence of these guys. As far as microbial or insect pests are concerned, I’ve seen absolutely zero evidence of infestation of, or damage to, my MEPs.
Got time for an interesting story about the Missouri evening primrose’s deer resistance qualities? Here you go. It’s short…
My house is located in the forest. And in this forest their exists a large population of whitetail deer. Since the biggest part of my ornamental garden lies safely within the confines of its fence, the deer are not an issue there. But anything growing beyond the fence is fair game (please click here to read my RGG article “How to Protect Your Ornamental Plants from Deer”). One summer, I evidently (and inadvertently) deposited some Missouri evening primrose seeds just outside my main garden’s fence, because the following summer, there was an MEP growing beautifully, in unprotected fashion, squarely in deer territory. This plant grew and flowered for an entire summer, surrounded by deer hoofprints, with no evidence of assault of any kind. It was ultimately relocated, deep taproot and all, to a fellow gardener’s fenced yard. Happy ending. My point here is that it was never touched by the ubiquitous deer for an entire growing season. Deer-proof? I think so.
Suggestions for planting the Missouri evening primrose.
Plant your Missouri evening primroses as soon as you get them. I’ve only very rarely seen these plants offered for sale as potted specimens in bricks and mortar nurseries. With online nurseries, it’s a different story. If you order them online from a reputable nursery, you’ll either get them in bareroot form, or as small, potted individuals (typically in 4″ or 5″ pots). They’ll send them to you at the appropriate planting time for your location. In my zone of 5B/6A, my bareroot MEPs arrived slightly past the midpoint of March (bareroots will usually ship earlier in the season), and I planted them almost immediately after I got them. They evidently rooted very well because they grew and flowered successfully during their first spring and summer. Admittedly, they were at their biggest, best, and most floriferous during their third year in my garden’s ground.
Soil. Although several reliable sources state that MEPs grow well in craggy, “thin” soil,¹’⁵’⁶ in my garden the critical soil requirement is good drainage. My garden’s top 18″-48″ of good soil exists on top of a substrate of sand (my home is located in an area on the shores of Lake Michigan). This implies excellent drainage. And although the pH of my garden’s soil typically lies in the slightly acidic range (5.8 – 6.9), there are spots in my garden where the pH drifts into slightly alkaline territory (7.0-7.5). My colony of MEPs is situated in an area within its planting bed where the soil pH varies from slightly acidic to slightly alkaline, and all individual members are thriving equally well. My own observations tell me that as long as their soil is well-drained (almost any ornamental perennial plant – including MEPs – will die if its roots are continuously stewing in soggy, non-draining mud) and its pH falls somewhere within the slightly acidic to slightly alkaline range, Missouri evening primroses will flourish beautifully.
Fertilizing. From an entirely practical standpoint, this is unecessary for this plant. Remember that these plants naturally occur in rocky, mountainous regions with no access to any minerals and/or nutrients beyond those that they derive from their existing growing media. As I wrote in my RGG article of a couple of years back, “Stupid-proof Your New Garden: 5 Huge No-nos,” it’s really easy to over-fertilize a plant. I know this for a fact. I’ve done it more than once. And with the Missouri evening primrose, which doesn’t need any real soil enrichment to speak of, any attempt to load it up with extra food will result in killing it with kindness and rendering it a shriveled, scorched carcass. In my garden, my MEP colony grows in a bed with a number of plants that do receive comparatively regular feedings of my organic fertilizer(s) of choice. As a result of this, it’s probable that the soil in which my MEP colony grows receives at least some ambient amendment/enrichment from the feedings that the neighboring plants receive. So what I do is this: I feed my Missouri evening primroses directly only once a year, in spring, at approximately 1/2 to 2/3 of the manufacturer’s normal recommended feeding amount. This is a system that works beautifully for my MEP colony. And in case you don’t already know what I feed them, you’ll get the info in the product rec section below.
Water. Please, not too much!!! These plants are extremely drought tolerant. Their deep taproots (I witnessed these in action firsthand when I dug up my beyond-the-fence straggler of a year or two ago) get them almost all of the water they require from deep in the ground. Water them only moderately. Water them more vigorously in fast-draining soils, and more sparingly in soils that hold water. If you want to wipe out your Missouri evening primroses, water the hell out of them, and when you’re done, water them some more. Almost nothing will kill them faster.
Pruning and/or deadheading.
In late fall, when everything in my garden, including my Missouri evening primroses, is brown and dessicated, I cut my MEPs down to the ground. Throughout the blooming season, I never deadhead my MEPs. I like the seed pods to develop and drop. The somewhat “natural” ecosystem that’s evolved in my garden at large, and in the MEP colony’s planting bed specifically, may potentially allow for the growth and development of a new addition or two to my Missouri evening primrose population. On an interesting note, I have a gardener friend in a neighboring state who swears that deadheading spent MEP blooms results in a more floriferous plant. Since I’ve not tried it firsthand, I can neither endorse nor refute this claim. If any of you RGG readers/subscribers have an opinion or experience regarding this claim, I’d love to hear about it. Fill out a “Contact Me” form or leave a comment in the “Comments” section at the end of this article.
Companion planting. Since Missouri evening primroses require a great deal of sunlight throughout the day, it’s best to not plant them in spots where taller, more robust plants will overpower them and prevent them from receiving enough sunlight. As I’ve mentioned, it’s the presence of taller neighboring plants which has prevented my own colony of MEPs from spreading in aggressive, unchecked fashion. That’s not to say that they can’t grow near taller plants when they’re receiving enough sunlight and air circulation. In my garden, the perfect companions for my Missouri evening primroses seem to be my perennial violas (‘Northern Lights’), and modest-sized echinacea (‘Prima Saffron’). The color scheme of the blooms in this arrangement is beautifully complementary, and the plants do not overpower each other. The violas don’t require quite as much sun as do the MEPs and echinacea, but keeping a thicker layer of mulch around each viola’s base allows them to retain moisture and deal with the sunnier conditions reqired by the MEPs and echinacea.
Product Recommendations
Below you’ll find two excellent, tried and true products that I use extensively in my own garden. They’re the only product recs of this article. As always, I’ll only recommend products that I use and love. These are both major winners.
I am a huge fan of Espoma’s line of organic fertilizers. Plant-tone is the one I use for the majority of the plants in my garden, including my Missouri evening primroses. It’s got an N-P-K ratio of 5-3-3 and is a great all-purpose organic fertilizer. It works perfectly for an incredibly wide variety of ornamental plants. Again, Espoma Organic Plant-tone is the food that a huge number of my plants get. They love it, and it shows. You can order this product here, directly from Amazon, by clicking the #advertisement link.
I bought this Luster Leaf Rapitest 4-way soil analysis meter in February of 2022 and have used it successfully time and time again since then to test for soil fertility and pH levels. It also measures sunlight and soil moisture levels. It’s fast, easy to use, convenient, and accurate. By using this device, I’ve been able to determine the necessity of appropriate fertilizer applications and pH amending to the soil of a large number of the plants in my garden. Order it here, directly from Amazon, by clicking the #advertisement link. Note that this unit doesn’t test for iron levels in soil. Also note that I really love this little meter!
Bibliography/”For Further Reading” List
Below is the list of works I used to assist me in writing this article. Some of these citations are in (extremely) relaxed format, but all appropriately assign credit where it’s due. Each entry is included here as a direct link to the actual work, which you can click if you’d like to read it. The list of cited works/links is as follows:
1. “Oenothera macrocarpa.” Wikipedia, p. 1.
3. “Onagraceae.” Wikipedia, p.1.
4. “Oenothera.” Wikipedia, p.1.
5. “Oenothera macrocarpa.” Missouri Botanical Garden Plant Finder, p.1.
6. “Missouri Evening Primrose.” Missouri Department of Coservation Field Guide, p. 1.
And We’re Done!
Well, my dear readers and subscribers, you’ve now got everything I know about the beautiful and somewhat mysterious Missouri evening primrose. These little plants mesmerize and transport all who grow them – including yours truly – with their beautiful nodding flowers and their mystical, almost diffident, blooming habits. In your own gardens, they’ll gaze steadfastly moonward while you sleep, and, having overcome their shyness by morning, greet you happily with their beaming, bright faces in the sunshine.
Cheers, and Happy Gardening!
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Thank you for this really great article! Now I’m hooked.
I need to go to Flower World – or call them – and see if they carry this plant. I hope that since it’s related to fuchsias – which do grow here in Washington state – I can grow it here also [zone 9 as I recall that we live in].
Blessings to you. Stay well.
Thank you so much for reading the article, Annie, and for your kind comments and kind interest. The plant is definitely hardy up to zone 8, but I’ve seen some claims that it’s hardy all the way to zone 10 (a claim of which I’m skeptical). Washington State encompasses 6 different hardiness zones, the highest, which is 9, runs along the westernmost edge of the state, along the coast. I’m not sure how this plant would do in that zone. If you happen to be in zone 8 or lower, it’s a slam dunk. You may try looking at Springhill Nursery or High Country Gardens. I got my MEPs from both of those places. You can google them and check their websites for availability. Unbelievably, a local bricks and mortar nursery here in Michigan had a large selection of good-sized potted MEPs a few weeks back, but I’m certain they’ve sold out by now. I wish you luck in your search for your own colony of Missouri evening primroses, and I hope that your hardiness zone up there in Washington will accommodate them. Thanks once again, Annie – your kindness and your interest are truly appreciated.
It’s beautiful! Oh, how I wish I could have this in my Florida garden.
Thank you for reading the article, GG, and thank you for leaving your thoughts here. It really is a beautiful little plant – those flowers are just wonderful. You may want to refer back to the article to see the other 4 varieties of O. macrocarpa. I believe some of them may thrive in your warmer zone. They’re all beautiful, and they share the same flowering habits as O macrocarpa macrocarpa (the MEP). Maybe one or two of those varieties will grow in your Florida garden. Please do let me know what you discover. Best of luck, and thanks again!
How do I live in the Northeast and not have these gems in my garden?! I’m sold! Do you recommend an online nursery where I can order MEP?
Thank you for reading the article, Jill – much appreciated! It’s really amazing how this beautiful little plant has stayed under the radar in northern regions. It’s so hardy and so beautiful – I’m flabbergasted. In any case, Jill, and in answer to your question, yes I do. I’ve actually purchased MEPs from Springhill Nursery in bareroot form, and from High Country Gardens in 5″ pots. Since you’ve not tried these before, I’d go with High Country’s 5-inchers. You’ll get established plants with substantial foliage that will yield blooms for you in their first spring/summer in your garden. Plus, you’ll get them a bit later than when the bareroots would arrive, so you’ll be planting in milder weather. I’m so glad to know that you love these wonderful plants, and that you’ll have a colony of your very own “dancing in the moonlight!”
I love their vibrant yellow color and the size of their flowers. They seem mysterious in the way they open at night. What a cool plant! Thanks for sharing their story.
I totally agree with you, Kevin. Those flowers – their size, beauty, and mystery make them unbeatable for planting in an ornamental perennial garden. I love mine! Thanks for reading the article, Kevin, and for commenting. It’s much appreciated.
A gorgeous plant! And I love flowers in the garden that I’m not tempted to put in a vase lol. However the foliage, now that’s a different story, and may find its way into one of my arrangements!
Thanks for giving this one a read, Cathy, and thank you for commenting. Yep, it’s a real beauty. The disproportionately huge flowers on this sprawling little green plant are stunning. And the foliage really is fascinating. I love your idea of using that foliage in your arrangements. Great idea – I’d never thought of that! If you do, share some pictures here – I’ll put them up on the site! Thanks again, Cathy!
Great information and well written prose . Unfamiliar plant that is worth pursuing.
Thank you for the kind words, Rick. I’m glad you enjoyed the article. I’m really surprised at the level of unfamiliarity I’ve been encountering since I first introduced this plant to my Midwest garden. Its hardiness makes it amenable to a wide range of continental U.S. geographies, yet many gardeners I’ve spoken to – especially in the northern reaches of its hardiness potential – know nothing about it. I’m very pleased with the performance of my own MEP colony, and I heartily recommend giving this plant a try. Thanks once again, Rick.