April 15, 2016

How to grow primroses that return year to year

Primula elatior (this one grown by primrose expert Amy Olmsted in Vermont) as dug from the garden for a primrose exhibition, proves how resilient primroses can be in the spring, as all tolerate being dug and potted for a few days and brought indoors, only later to be returned to the garden often after dividing them (this is usually what most growers do).

I've struggled with growing primroses, and I suspect that I am not alone. Sure, I could buy pre-grown plants in the late winter and spring, and set them into containers and into garden displays, but they rarely or never returned. I wrote it all off for years as something not that I was doing wrong, but that my lack of wintering over primroses was because of our climate. USDA Zone 5, New England, and my neighbors and friends gardens all reinforced this theory - none of them ever had primrose borders or plants that wintered over. But all of that changed, once I joined the American Primrose Society, and started visiting gardens in New England that not only had primroses in the spring, but also found some with loads of primroses. Clearly, there is a lot to learn here.

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I think many of us get into our head this image of what primroses should look like in the garden, but few of us ever achieve this vision. Primroses, or those plants in genus Primula, can be challenging. Like most plant family's, there are those which are easier, and those which are more challenging. Yet it's pretty clear that few gardeners, even somewhat accomplished ones, seem to be able to master growing them. But why?

Here we are in April, and Primrose plants are beginning to appear on the shelves at the garden centers, and once again, I am tempted to buy some ( and, I now will, since I have learned more about this genus than I knew ten years ago), and this fact has me thinking - how many of you have tried growing primroses and failed? I can't cover the entire genus of primula in one post, but I can focus on 5 of the easiest to grow in the garden. They are worth growing, if you have the right spot for them, but there are some things I would avoid if you want them to survive for a few years.

Primroses in container displays? I use them this way too, but I treat them as disposable plants if I do so. The only option is to only allow them to provide their color for a couple of weeks, and then re-set them into the garden.

a. Don't plant primroses in containers. Temporary displays of potted blooming plants is essentially flower arranging with plants, so know that these sort of temporary container arrangements aren't  expected to live longer than a month or so, so if you are doing this with primroses - fine, but if you want plants to return year to year, I would set plants into the ground with as much care as you would take in planting a hydrangea.

Each species of primula has a special place in my garden where they will grow best. On the left, above, are planted a border of Primula veris, which enjoys the light shade under the pleached hornneam hedge and no competition from any other perennial. In this way, I can allow them to bloom and age graceful through the summer, as their foliage matures enduring flowers for next year.

b. Find the right spot in your garden for primroses. It may seem obvious but success depends on the basics, like learning how to identify the ideal growing conditions for the particular species you are planting.  Take an analysis of your garden, you'll want to find places that might be perfect for primroses. So although a wet, partially shady border or a stream would be perfect for Primula japonica, or many of the candelabra summer blooming species, I am limiting this post to the early spring garden primroses -  those which bloom in March, April and May.  Mostly, it all depends on where you live (Portland, Oregon?  Yay, Atlanta? Boo.).

These young Primula x Polyanthus seedlings from Barnhaven Primroses enjoy growing under our apple trees.

The rest of us are left with finding that  proverbial 'perfect spot', the place with damp,woodsy soil that either freezes solid and thaws once in the spring, or we find a nice spot near a foundation, or even in the open veg garden in a raised bed where the soil is rich and humusy but remains somewhat friable and soft for much of the winter. I have great luck raising the woodland species in the open garden, but I have the best luck with those planted in the vegetable garden, in raised beds which helps them survive the winter a bit better. This is how I grow my polyanthus types.

The only mulch I use with most of my primula species is shredded leaves and pine duff. This is how most grow in nature.

c. Mulch primroses carefully. Spring blooming garden primroses (excluding the alpine sorts that I am am not including in this post, as they require more exacting conditions) generally prefer woodland-type soil, humus rich and on the moist side.  Writing about soil is a science, but generally speaking, a top dressing of compost (leaf mould or composted, shredded leaves) is best when it comes to mulching primroses that I mention in this post. If you must use shredded bark mulch (and honestly, I do on some of my beds), be careful to remove it from the crowns.

b. Buy really great plants.  Again, a bit of a vague and somewhat subjective statement,  but simplified, there are those primroses sold at nurseries that are intended for temporary displays, and those intended for garden use. I've struggled with helping you identify the two, but there are some broad assumptions to make. First, think back to those little pots of low growing primroses that we all see sold in markets just after New Years day. You know, rosettes of leaves and flowers low and tight - - if your nursery is selling plants that look like these and they are not labeled as Primula vulgaris? Then be wary. If your nursery has some with  taller stems, and slightly less showy flowers? Or if they look as if they were kept through the winter in a hoop house? I would buy them.

Look at the list below as well, for any of these species names listed on a plant label will help you in choosing a primrose, and once you are home? Research the variety and see if it was intended as commercial potted plant use, or for the garden. I know it's confusing, but after a while, they will all make sense.

Look for: P. x polyanthus which have been wintered over in hoop houses in half or 1 gallon pots, or those from a good nursery such as the newer selections seen right now  being distributed by Monrovia Nurseries, Plant Delight's Nursery or White Flower Farm, for example.

The Drumstick Primrose, P. denticulata does well in my garden. Each year I start a few flats from seed, as it isn't terribly long lived, lasting in the garden for about 5-6 years. If I had a moister location, I think they would do even better.

Also look for these:
    Primula veris
    Primula x Polyanthus (named strains are best)
    P. vulgaris (the true species is great in the garden)
    P. denticulata

Avoid buying the primroses that you see at the supermarket or at the florist, the ones that look like rosettes or african violets.

Cost will factor in here as well. $2.99 means that the plant was grown en-masse for disposable display, but $6.99 or $12.99 probably means that it's a selection that is proven.

Primula vulgaris does very well in my garden, where it is often the first flower of spring. Slowly emerging often like this.

I have to add this - plan on getting frustrated when it comes to learning about primroses. My best advice is to start mastering one, and then move onto another. The names of even just the species can drive one batty. So don't worry if it begins to get confusing.

For eample, I know that this isn't cool, but check out this exact quote I copied from another gardening blog which will remain un-identified. To make matters worse, it included an image of an Oenothera, or 'Evening Primrose - not a primula, at all.

Primroses, like Polyanthus come from the Primula genus. They are often confused, but a few things separate Primroses to Polyanthus. Primroses, like Polyanthus are closely related to the cowslip, but are also known to be linked to the oxlip too. Primroses are actually two different types of flowers which look superficially almost identical. One type is called ‘pin-eyed’ (female) and the other, ‘thrum-eyed’ (male). The two different types of flowers are produced on separate plants.

In case you are wondering, 'Primrose' is a common name. Best to use the genus Primula, to be clear. Primula x Polyanthus is a cross, which most conclude was created between the two wild species of P. vulgaris and P. veris. The terms 'Pin' and 'Thrum' refers not to the sex of the flower, but to the length of the stigma, which Darwin noticed extended beyond the anthers on some flowers (pins) and was recessed deep in the flower tube in others, below the anthers. Weird, but true. Fussy Victorians who exhibited primula had strong thoughts about the 'purity' and aesthetics of such craziness nature could create. As for Cowslips? To most people they mean 'primroses'. To the English speaking in Western Europe, it's a lovely common name for Primula veris, so common in English hedgerows at one time. Then again, Oxlips could mean the same thing to people, yet to primula folk, Oxlips refer to Primula elation. Best to avoid all common names if you want to be accurate.

Gold Lace Polyanthus primroses can often still be found at good garden centers.  This one happens to be a 'Pin' flowered one. Can you see why?

These polyanthus types all grown by American Primrose Society member Judith Sellers in upstate New York, are being relocated to another garden. We helped her dig her collection a few years ago, and it proved to me just how resilient most early garden primroses are. Look at the stems on these. It plants have a stem, is a good tip for beginners when they are buying polyanthus types that night be good for the garden. 

1. The Polyanthus Group - Think ' primrose', and most likely, this is what you are thinking of, but  Polyanthus  is still a catch all name (thank you Victorians!), and confusing. Somewhat simplified, these can include both  those 'disposable' primroses one sees in the supermarkets (those deep purple, yellow, pink and white ones) but they also include some of the best for the garden. There were once some very good garden strains available in the 1930's and 40's, but many have been lost. Only the most serious of gardeners have searched out sources for the really great ones (Barnhaven, to begin with), but I highly recommend trying some if you can find them.

If you are interested, you can begin ordering some from  Barnhaven Primroses, which moved to France from the UK, (and before that, from Oregon  where they lead the entire early 20th century primrose craze) - Even though the property has changed hands a few times, their original strains are some of the best, and worth ordering. They ship both seeds and plants to the US, but you can find some very good polyanthus type here in the US if you look.

Judith Sellers' amazing collection of Polyanthus as seen ten years ago in upstate New York when we visited her, show just how beautiful a bed of just primroses can be in May. Now, remind yourself why commercial growers rarely carry the good garden varieties? Maybe it's time to bring them back.

Some promising news here - I think some plant breeders and commercial distributors are experimenting with newer strains.  I see that Monrovia has introduced some named strains (look for them now- I've seen double varieties at Lowes in the US, and I would try then if I liked double primroses.

Then there is this other tip that I mentioned earlier  - look for those small mom and pop nurseries that had a few polyanthus types which they may have wintered over in a hoop house or a cold frame along with their early perennials. These large clumps of polyanthus are more likely to survive your winter as they have more established root systems, and you can be assured that they have already survived a year in a pot.

Polyanthus types on display at the New England Primula Society annual show ( it's going to be held again at Tower Hill Botanic Garden the weekend of May 1).

Polyanthus types with stems fell out of favor when the practise of raising perennials from plugs or liners came along. Plant breeders focused on shorter plants for indoor display rather than longer stemmed plants for outdoor vigor in the garden. I fear the primrose is dangerously at risk of becoming lost to gardeners in our world of commercial horticulture which has seemed to push the more hands-on care that primroses tend to need. I mean, how many nurseries do you know who actually start their own plants from seed? Annie's Annuals and a handful of others, perhaps. Everyone else brings in their stock from liner growers, and plus growers. It's all a numbers game.

I should mention a particular strain of polyanthus types known as the gold lace strains.  - a historical type often seen with maroon or nearly black-red flowers edged with golden yellow, a Victorian favorite that primrose enthusiasts can get very particular about, but they also make somewhat good perennial garden plants. By 'perennial' I mean that they will last a few years without disturbance but will require dividing, as no primrose is long lived.

Primula veris, the cowslip (or is is Oxlip?) in its pure wild species form, blooms like crazy each year under our hornbeams. It enjoys this light, open woodland condition with little competition aside from spring blooming bulbs.

2. Look for the  easier species like Primula veris, P. vulgaris,  and P. elatior  - I lumped these three species together just because at the primrose society shows, they are looked at as the 'easier ones'. Beginners plants, if you will when compared to the really fussy types like auricula.  So, somehow, in my mind, I group these together in the EASY and YELLOW bucket. they all bloom at the same time.  Think - 'wildflowers', and plant them in woodsier conditions.

Few primroses are as easy as P. veris, which happens to come in a few selections as well as the pure species which can have tiny flower on longer stems.  Easiest species from seed actually, but again, you may want to cheat with pre-chilled seed. It can sometimes be found at garden centers, while P. elation might be more difficult to find, I think it is the showiest of the clan, with wider flowers, and larger displays.

Primula vulgaris, the species as found in the wild, makes a hardy long lived plant. 

There are some named strains of P. veris, most are pale yellow but there are a few new red and orange strains such as "coronation' and ' Sunset Strain', and then other forms with more open flowers. Also, look for double selections like  ('Katy McSparron', and a weird hose-in-hose form (a flower that look as if you stacked them one on top of another such as that seen in the variety 'Lady Agatha'.).

Primula denticulate as second-year seedlings, bloom in a bed which I mulch with shredded leaves and pine needles.

3. Drumstick Primroses -  Primula denticulata 
This may be my favorite, but I really didn't master growing them until 10 years ago. I craved this species so much ever since seeing white selections at White Flower Farm in CT. in the 1980's. It seemed so magical, but I could never get it to winter over, which seemed crazy, as this is a species native to the Himalaya.

I avoided growing P. denticulata for years until I saw how this cool -growing plant can handle being dug up for exhibitions for a few days, and then returned to the garden. I guess it wasn't as fussy as I had believed. Just site it well, not in the perennial border, but somewhere where it can be looked after without too much competition near bu.

The trick for me, was to raise my P. denticulata from seed. Again, pre-chilled seed ( or regular fresh seed, sown in December and left outdoors all winter), which provided me with literally hundreds of strong growing seedlings by June, which I just set out into the dampest part of the garden. The following spring, I have hundreds of plants in bloom. This is also a short lived primrose, so I sow plants every other year, although my garden plants live for about 5 years before petering out. I don't dig and divide this species, but I do know some folks who have wetter areas in their garden where they do form large clumps. My site for P. denticulata is open shade, with dampish soil in the early summer, and they seem to do fine.

My seed raised Primula x polyanthus from Barnhaven Primroses are set out into raised beds in my vegetable garden. This allows me to keep an eye on them, and they enjoy the lack of competition from weeds and other perennials.

In the end, I will share with you  where I grow my primroses.

My polyanthus primroses  are set out near or in my raised beds in the vegetable garden, with a few planted on a  sunny side of our boxwood hedges under some espaliered apple trees.

My P. veris are planted along a walk under a row of pleached hornbeams. The leaves naturally mulch them, and they enjoy the shade which becomes rather dark by mid-June. They are interplanted with small, spring bulbs like muscari.

My P. denticulata are set out in a damper spot, which is not really wet, but which is shady for half the day, under a canopy of birch trees where I also grow columbine, and hellebores.

Primula vulgaris in mid April

Primula vulgaris is planted under deciduous shrubs, I keep a few colonies under Enkianthus where they get a light mulch of leaves, and no competition from other plants for the rest of the summer in part shade.

My seed-raised P. denticulate ready to be set out in late spring. They will start blooming next spring, and continue for at least 5 years.

Look for all of these plants now, in April and May at garden centers, but if you want to try some from seed, you must sow them in the fall or winter  -  since most species require a chilling period, you may find ordering pre-chilled seeds from Jelitto Seeds in Germany ( I highly recommend them).  This would be your easiest choice. I order seed every December, and start them in the greenhouse. Plants are ready to set out in late spring, and all bloom in the following spring.

Primula denticulata in my open bed behind the house in May last year.

In no way do I want to mislead you that primroses are indeed 'easy' from seed however, but like anything, do each step properly, and things should work - like following a difficult recipe.Try to get fresh seed, and have the proper conditions to raise them from seed. I have not tried raising mine completely indoors, so my greenhouse may make things easier for me. But honestly, I just sow the seeds on the surface, set the pots on a bench, and they germinate - what can I say?


  1. Anonymous2:02 PM

    dear matt
    thanks for the colorful garden and greenhouse pix.
    i am continually torn between having an attractive garden and having my poultry out free ranging. the hens are curious and discerning--anything new, or special, is promptly flung far and wide by their scratching.
    are you suggesting dividing primroses now? (mine are mostly purchased Pacific Giants.)
    all best,
    ~ 02568

    1. 02588 - I would wait to divide your Polyanthus as they are probably a little too large right now. Mosts here will be divided just after the blooms fade.

  2. Anonymous8:58 AM

    What a helpful post, I'm thrilled to have found it!
    Glad to hear I'm not the only one who was confused by all the species and common names and odd pin and thrum terms which come with the primula family. I've been dabbling in the family but never even considered trying the p. denticulate. It's on the list now!
    Thanks for the photos of beds full of primrose, they're inspiring.

  3. Very helpful, thanks!

  4. Very interesting post. By the way from my personal experience with primroses I've found that they are particularly desired by snails and slugs. So I've found it to be very useful if you have some sort of artificial garden pond nearby which will inevitably attract some toads(if you don't mind that), which will take care of all the other unwanted visitors. I have no idea why primroses are so delicious to the slugs though. Anyway keep the good work, thanks

    Irvine Herb


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