March 19, 2020

Learning More About Growing Annual Poppies, and My New Book

Annual poppies are not easy to grow, at least not for most people. Oriental poppies? Much easier, as they are a long lived perenial.  notoriously fussy about root disturbance, and like many wildflowers, they will always grow best if direct seeded exactly where they are to grow, and then thinned to leave a good amount of distance between plants (a foot is best). If you can keep root disturbance to a minimum, that checks off the first box. Beyond that, temperature and light will need to be controlled. Clearly these are not easy plants to grow to perfection, but if you care and want gorgeous poppies in your garden (and who doesn't?) it might be worth it to try a few methods.

In this post I am only addressing cultural techniques for two species of poppies: The Shirley Poppy (Papaver rheas) and the Bread Seed Poppy (P. somniferum).  The genus Papaveraceae includes hundreds of species, many of which require special treatment which may add to the confusion out there, but for these two species which should be more commonly grown in our gardens, the methods often found on-line and in literature seems to be unnecessarily complex and incorrect.

You may be saying to yourself "What's all the fuss about? I just sprinkle seed on the snow in spring and have wonderful poppies every year.". To that specific statement, I respond with "great for you!" The truth is, that method just doesn't work for me many years, and, when it does, it often doesn't produce the best plants.  

Here is what I wanted to know. 

• Where did that 'sowing on snow' advice come from?

• Does poppy seed need light to germinate like everyone says?

• Does poppy seed need a cold period to 'stratify'?

•What is the ideal germination temperature for both Shirley Poppies and Breadseed/Opium Poppies?

• Can one start these poppy seeds indoors instead of direct seeding?

The answers I found were staggering in that it was the polar opposite of what I have found most everywhere on-line, in consumer-facing gardening books and on most blogs and social media posts. I'm not nailing anyone here - even I have gotten this wrong in the past, and even in my new book where I started to share some of my personal methods that are different, I get a few things wrong.

Many of use research on-line today, and hey - you can do it yourself too. Just Google "how to sow annual poppies" and see what you will find. Most sources advise that one first chill the seed for varying lengths of time, sometimes first mixing the seed with peat moss, damp sand or soil then chilling in the fridge, then sow direct (usually sprinkling on a late snow) and then thinning the seedlings.'

If you are in a hurry, here is what I discovered:

• Where did that 'sowing on snow' advice come from? It started in the late 1900's in England but the assumption is that wintered-over poppy seeds could fall on snow and still sow. It's not necessary for germination and doesn't offer any special treatment other than helping seed distribute.

• Does poppy seed need light to germinate like everyone says?

Not necessarily. Some species do, yet most prefer to germinate just under the surface of soil and this includes both P. rhoeas the Shirley Poppy and P. somniferum, which germinates better with a thin layer of soil or medium covering the seed. Many poppy species do require light, however.

• Does poppy seed need a cold period to 'stratify'?

No. Most studies indicate that especially with P. somniferum, both of these species germinate best using seed that was stored dry and germinated at 70° F.

•What is the ideal germination temperature for both Shirley Poppies and Breadseed/Opium Poppies? 70° F.

• Can one start these poppy seeds indoors instead of direct seeding? Yes,  if one can provide the high light intensity and if they use individual pots with one plant in each (thinning to one plant). Transplant with great care not to disturb roots while plant is still small.

Here are the details....
These P. somniferum poppies in my garden last year were transplanted from plants started early in a cool greenhouse.

I referenced my 'go-to' seed starting source, an out of print book titled 'Seed Germination Theory and Practice' one often shared amongst plant geeks as a photocopied document that was first published in the 1990s (and sold often at North American Rock Garden Society auctions and book sales). I think since the book is rather heavy on data points and science, with no photos that it seemed unmarketable to the masses (as in: no one in the public cares about the stratification requirements of an Anemonopsis species). Still - it is a useful book. IF YOU WANT IT, it can often be found on Amazon as in here.) And maybe on Ebay? The author Norman C. Deno tested many challenging genera and species, and what he discovered about Papaver somniferum is nearly exact to what I found in a couple of journal articles outlining studies in germination. 

All conclude that P. somniferum germinates highest at 70°F That's right, 70°.

No snow.
No cold.
No surface sowing.
No 'Light needed to germinate'

What remains the same is that both poppies resent being transplanted and that both prefer poor soil (so no fertilizer).

Yet, they can be transplanted if one is able to slide a root ball out of a pot and set it into the ground without breaking it. I should add that seedlings like these are best raised in a greenhouse, or outdoors like on a deck or on a porch in the brightest of light - so not everyone is going to be able to grow individual plants from seed in pots. A light unit indoors most likely wont produce light bright enough.

Yet, if you have a sunny porch, or want to try starting a few trays of individual pots outdoors in April or May if you live in the North, it's worth a try.

Some flower farmers have discovered this already as they often sow P. somniferum in plug trays along with P. rhoeas and carefully transplant plugs into growing beds with a minimum of root damage. It's kind of a secret few home growers know about. Of course, this does require a greenhouse and some heating mats, but the idea - the idea can be hacked to work on a glassed in porch, or in a garage with some artificial lights. Natural bright sunlight is best as poppies will stretch out, but it does mean that you could grow wonderful poppy plants by sowing individual seeds in =plug trays, keeping them at 70 and then moving them outdoors as soon as possible.

What about sowing outdoors on snow or direct on soil in March or April?

This method works to, in fact, it still may be the ideal method, but it does have a few problems. Sowing on snow works where you want a more natural look, but it won't work if you use mulch and it is challenging to do in areas where you are growing other plants - such as in a perennial border. It works much better if you have a place dedicated to just poppies, which makes it easier to see the tiny seedlings that you will need to thin so that plants are about 8 inches apart from each other, and so you can weed effectively. I still grow poppies this was in a few places, and direct sowing works well when I sow a row or band in the vegetable garden as it's easy to see the seedlings.

As early 20th century seed catalog like this Sutton's one from 1910 often featured Shirley Poppies. Few flowers are as old-fashioned as these poppies are. Methods such as 'sowing on snow' began appearing around 1900 in garden texts, and quickly caught on as an approved method mostly in northern Europe, but also in North America - the truth is, there is little to no scientific data to back-up this method. Does it work? Sure, for some, but sowing a bit later in soil will work just as well.

Do know though that there is no benefit that comes from the cold, or from the snow. Seeds sown direct outdoors still won't germinate until day time temps tip near 70 degrees (although seedlings are cold-tolerant can handle very light frosts) my point here is that the seeds don't need a cold period. The texts all state that in particular P. somniferum, 70° is the ideal germination temperature when using seed that was in dry storage at room temperature. 

The Shirley Poppy is more variable but seed still germinated in much the same way but the length of time is slightly longer. Even in my home greenhouse, the seed germinated - covered or not covered at 15 days without bottom heat with night temps at 45° F but seed on heat mats (70° F) both covered (1/8") or not germinated at 4 days nearly at 90%. Light doesn't affect germination.

 In areas where hot, summer temperatures arrive in late June along with high humidity, direct sowing early is still the best way to grow poppies, it's often not practical to wait until a 70° Day to sow, the seeds sown early are just fine waiting.

Papaver somniferum in my garden that was started from seed in individual pots then set out once the weather became mild in late May.  These were still three feet tall and covered with bees.

Some books have it right, and I started with the classics like Christopher Grey-Wilson's book 'Poppies - The Poppy Family in the Wild and in Cultivation' (1993, Timber Press), now out of print, but you can find it at online booksellers. A useful book even though some species may have been reclassified.  Grey-Wilson's book is nearly a monograph with excellent details about the natural history and botany of most plants in Papaveraceae, but shorter bits about specific poppies, particularly only a few pages on P. rhoeas. Readers should factor in that this book was written in the United Kingdom so the cultural bit lean more towards what works in a mild-winter climate (sow in late summer or autumn) a method that won't work where the ground freezes deep and solid such as in a Zone 5 garden, or where spring freezes are variable. 

I cant live without Shirley Poppies, but every year is different. I've found that direct-sowing seed works best with these smaller poppies, but I keep trying new methods of started early under glass, now trying plug trays. 

General advice seems to be similar everywhere  (just Google it, and see for yourself). That 'sprinkle seeds on the snow' advice, or 'sprinkle seeds in late winter or early spring and thin-out seedlings.'. Not bad advice, as it works - but not always (just in case you have tried these methods and have failed). You are not alone.

Sowing in a greenhouse or under bright lights is possible if one sows seed individually into plug trays or single pots.

While there are some unconventional methods that you might want to try - sowing annual poppies in cells under glass, using individual seeds in a 4-inch pot, or setting out pots of thinly sown seed on a porch or deck, or under lights and then setting the entire rootball early out into the garden - these methods also work, but again, only if you are careful with light, watering and with thinning out all but one plant per pot (never transplanting the thinnings as they will fail). All are tricky to master, but if one can master a pre-start method, the results are extraordinary.

The wild version of P. rhoeas is all red with black spots, but selections that first appeared in the 1880's changed how one viewed this common weed of European wheat and cornfields. Selections like this one named 'Mother of Pearl' have mostly pastel shades, and while many are advised to cull-out the red ones to keep the strain pure, how could one not want this?

In a search to find out more, I began trying all methods last year, and some of my results are surprising me. I will add here that I still sow direct, but always sow a few in individual pots and cells just in case one method doesn't work. No method is easy, and I think it's safe to say that one isn't any easier than the other unless you are having luck with direct sowing early (if you live in the north, or in autumn if you live in a mild climate).

Use a precisions seeder like this (it will take some practice to master! But it makes all the difference in the world with truly small seeds that you often cannot sprinkle especially in pots or plug trays.You can. find one here at Gardener's Supply, or Google for other sources.

My Tests

As a test, for two years now I've been sowing seed outdoors. For the past 6 years, I usually sow both on snow and with direct-sowing methods on raked, drained and workable soil outside in March.

To back things up I also so seeds in deep cells under glass (individually sown seeds). These I've tried pre-treating a number of ways, chilling the seed packets, mixing seed with damp sand and then chilling for 2-4 weeks in the fridge, and then sowing dry seed straight from the seed packet in the greenhouse.  To keep this short, all of these methods have proven to be unreliable. Some flats I kept in a cold frame to expose them to freezing temperatures, others I just kept under glass.

These tiny poppy seedlngs (P. somniferum) emerged in just 4 days last week. They were set on a heat mat set to 70° F with a thermostat, and the seed was covered with 1/8" soil. Surface sown seeds in another tray germinated four days later. Do notice that even in a glass greenhouse these seedlings are slightly stretched out compared to seedlings that emerge outdoors. I try to move these outdoors most every day once the weather begins to warm above freezing to keep them from etiolating.

This year, I began using heating mats set to 70° using both chilled seed, and seed straight from the packet as it came in the mail - and to my shock, I'd say 85% germination in about 4 days for the seed that was covered with a 1/8 inch of soil, and 6 days for seed surface sown. This has proven itself over and over with both P. somniferum and P. rhoeas with 8 flats of plug trays and four flats of 4-inch pots.

I thin the seedlings out to single plants just as they are forming their first true leaves, and will relocate them to a cold frame or set pots outdoors if daytime temperatures are over 40° to keep plants stocky and strong as my daytime temperatures in the greenhouse can get too hot with the spring sun - I like to keep air temps below 80° to slow down growth, as plants will need to be set outdoors in early May and plants need to be stocky enough with withstand wind and should still be in their rosette stage (not forming a stem and certainly not a flower bud).

Papaver somniferum 'Lauren's Grape' still in rosette form were individually sown and germinated warm, on heat mats, but grown cool near 55° are ready to be set out into the garden.

Last year my Greenhouse plug trays were split into two groups, one group that I kept under glass at 40° F and three other flats that I first kept outdoors in a cold frame. The Greenhouse flats germinated after a month, but irregularly, and about 1/3 survived. The flats in the cold frame never germinated, I suspect that the temperature differential was too much (hot days, freezing nights). Direct sown seeds grew well, but a few self-sown seeds from previous years were virtually gigantic. I did have one tray of seedlings that were individually sown into 4 inch pots that I acquired from my favorite source of hard-to-find annuals Bunker Farm Plants in Vermont, and her rosettes were nearly 5 inches across, grown from early sown seed in an unheated hoop house with seeds germinated on a heat mat.

Single, Breadseed poppies are beloved by many bees for their pollen, but not for nectar as they do not produce any.

Sowing in a greenhouse is possible, but a more mindful approach to sowing outdoors works even better. Dry sand will help you dilute your seed, and some chicken wire may help deter curious critters - like dogs (necessary in our garden!).

I had heard of some local flower farms raising poppies the same way, so I purchased a heating mat or a germination chamber mat from Johnny's Seeds and found that even seed sown in March germinated. While there are a few plants that require low, then warm temperatures, most common flowers and vegetables will germinate best at 70°. Some, (even those often listed as being 'cold-weather crops like cabbage, broccoli, and other brassicas) will germinate even better at higher temperatures, but much slower rates at lower temps. Then there are the real freaks like Gomphrenia which scientists have found will germinate best if exposed first to hot temps near 100° for a couple of days although 90° will often get good results.

Mix seed packet of either P rhoeas (Shirley Poppies) or P. somniferum (like 'Lauren's Grape) in a bowl, and mix well. This just helps disperse the seed so that you wont have as much waste. One of the biggest errors one can make is to not thin young plants (I get it - it's hard to pull and toss a precious poppy) but know that if you leave 8 inches between each seedling your results will be much better.

Dig, till or pitchfork your soil to loosen it up and then rake to make it evener. Leaving some furrows will help the seed fall into nooks and crannies, which is OK as some coverage of the seed helps.

Sift the sand/seed mixture over the prepared area. Now, the 'prepared area' could be in the border where there is a bare spot, or in the veg garden - as where I often grow mine, which makes weeding and thinning easier. Never mulch, and remove old mulch as seed will need contact with the soil. Also, poppies enjoy low soil fertility so no fertilizer is needed.

This isnt neccessaryl but since we have 'diggy'Irish terriers, I pin down a protective wire covering over the bed. It also helps remind me where I sowed the seed as a month or so may pass until the weather warms up enough for the seedlings to emerge, and often weeds will germinate first.

Last year it took 2 months for seedlings to emerge, but it was a very cold spring.

Look carefully after a few weeks for poppy seedlings (and keep watered if a dry spell arrives). This seedling will be very tiny so get your glasses on. Each cotyledon is about 1/8 inch long. These are too thickly sown, but I will wait to remove all but one plant every 8 inches to a foot apart later.

Both species will seem to grow slow at first, but will suddenly take off once the weather become warmer. This is a bed that I should have thinned but I didn't. Shirley poppies can grow well closer together, but P. somniferum really does better with lost of room between plants. I'vd read in many old books to pinch plants back at this stage, but I have never done it myself, have you? I've read that some P. somniferum can become very bushy and tall if pinched back - I'll try it this year.

My direct-sown Shirley Poppies always like the walk to my greenhouse where I plant them in some raised bed in the veg garden. They bloom in my Massachusetts garden between mid-June and the Fourth of July or just until the weather turns hot and humid. After that, they are pulled and vegetables are planted.

A double lavender-grey Shirley poppy from my garden a few years ago. 

Coral and White picotee forms are very pretty.

An all white strain called 'The Bride'  seems less pretty in the garden.

These P. somniferum  'Lauren's Grape' were buzzing with bees in my garden last July. All were started early in individual pots and set out in mid-May.

P. somniferum like this white peony form can self-seed if you allow the seed to dry in the capsule. I've found that in my garden if I cut the seed to dry indoors and sprinkle in the garden in late fall or early spring, I get a better germination rate as a naturally dried seed that falls in late July or early August often germinates in late summer, and small poppy plants cannot survive out winters.

If you want to learn more, order my brand
 new book just published here on Amazon and where most books are sold!

Here are a few spreads to share with you! If you do order it, I would appreciate any revew you could write (or just rank it) on Amazon. It's important data for us authors as it tells publishers that it's worth offering another book deal.


1 comment :

  1. Anonymous11:40 PM

    thanks for this post! poppies make me squee!
    congrats on your new book! i've ordered a copy and can't wait to read it. best wishes.


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