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Make the Most of Self-Sowers (Part 2)

Silene dioica 'Ray's Golden Campion' [©Nancy J. Ondra/]
Silene dioica ‘Ray’s Golden Campion’

Last month, I started discussing one of my favorite kinds of seeds: the self-sowers.  Though they have a reputation for being easy, self-sowers tend to make their own rules, sometimes needing specific germination conditions and benefiting from a little custom care to work to best advantage. Over the years, I’ve come up with some ways that work well for me and identified a bunch of self-sowers that have been happy to make Hayefield their home.

Getting Self-Sowers Started

It’s fascinating how plants that can so freely reproduce themselves can sometimes be uniquely challenging to get started in the first place. In my experience, it’s rarely as easy as buying a packet of seeds and sprinkling them where I want them to grow in the garden. Maybe the timing was wrong, maybe the site didn’t suit them, or maybe other plants provided too much competition.

When I hope to get a self-sower going here, I figure on a multi-year process. The first step is getting the seeds growing in a prime spot: either in one of my nursery beds or one of the raised beds in my vegetable garden, so they get the best soil, with no competition from perennial plants, in a spot where I can easily watch them. That way, I can see where and when the seeds form and gather them as soon as they are ready.

If all has gone well, I end the first season with more seeds than I started with. Unless I’m sure that some seeds dropped during the ripening and collecting process, I’ll leave a sprinkle of them in that spot to see when they germinate after being outdoors for the winter—a test of their self-sowing potential.

If I get a lot of seeds from the first harvest, I may try scattering some in other places for the next growing season. Usually, though, I sow a larger patch in a good spot the second year to bulk up the seed supply even more. By that second harvest, I usually have a generous supply of seed, and I have a pretty good handle on when the seeds like to germinate.

In the following year, I can start scattering seeds at the appropriate times: right after harvest, in fall, or in spring, depending on their needs.

Lychnis coronaria [©Nancy J. Ondra/]
Some biennials, for instance—such as forget-me-nots (Myosotis) and rose campion (Lychnis coronaria) [above]–flower relatively early, ripen their seed in early to midsummer, and can germinate in late summer or early fall, while the soil is still warm.
Silene dioica with Orlaya grandiflora [©Nancy J. Ondra/]
Some annuals, like giant collomia (Collomia grandiflora), larkspur (Consolida ambigua), kiss-me-over-the-garden-gate (Persicaria orientalis), lettuce poppy (Papaver somniferum), and white lace flower (Orlaya grandiflora) [above with Silene dioica] germinate best in cool conditions; these, I usually sow in fall, and they may start appearing in winter or wait until spring.
Amarathus 'Hopi Red Dye' [©Nancy J. Ondra/]
And then there are those seeds that can drop in fall and survive the winter outdoors but won’t germinate until the soil warms in spring. Amaranths (Amaranthus)–like ‘Hopi Red Dye’ above–celosias (Celosia), sulfur cosmos (Cosmos sulphureus), and flowering tobaccos (Nicotiana) are a few that come to mind. If I’m scatter-sowing these, I wait until May, usually, and look for seedlings in June. Self-sown seeds of those plants might show up sooner, if the weather warms earlier than usual.

That all sounds a bit complicated for seeds that are supposed to be “no-sow easy,” right? Well, keep in mind that my goal is to maximize seed production for sharing and selling as well as sowing. If you have a fairly young garden with lots of open bed space (which is optimal for self-sowers), you may have luck simply scattering a packet of something in spring and hoping for the best.

I’ve found some big advantages to my multi-stage approach, though. Growing a self-sower in a certain spot a couple years in a row creates a little “nursery” where I’m very likely to find seedlings. After a year or two, I get to know exactly what the seedlings look like at various stages, which is one of the most important parts of managing self-sowers. If you don’t recognize the seedlings, you’re likely to pull them out by accident when weeding. Or, you may leave too many, to the point where they get overcrowded or overenthusiastic in spreading.

Also, that “nursery” spot provides a reserve source of self-sown seedlings. If few or no volunteers show up in the garden, for some reason, or if I want to add a particular self-sower to a container planting, I can transplant my backup seedlings while they are still small (at the three- or four-leaf stage).

Nicotiana sylvestris seedlings [©Nancy J. Ondra/]
Keep in mind that self-sowers may need some thinning-out in spring so they don’t get overcrowded. This is after one pass through a patch of woodland tobacco (Nicotiana sylvestris) volunteers in late May. In mid June, I removed about two-thirds of these remainders to give each of those left plenty of room to fill out.

Some Favorite Self-Sowers

Ugh, trying to choose favorites among this big group of great plants is tough. Here’s a quick rundown of my own top ten, in no particular order: self-sowers that have become pretty much self-sustaining here at Hayefield without becoming problematic.

Silene dioica (red campion): I began with ‘Ray’s Golden Campion’, with bright pink spring flowers over bright yellow foliage. The seeds of any red campion are easy to start from a spring or summer sowing and transplant to the garden in late summer or early fall.

Silene dioica 'Ray's Golden Campion' seedlings [©Nancy J. Ondra/]
‘Ray’s Golden Campion’ doesn’t come completely true from seed, so I plant out only the yellow-leaved ones. (You can see how much more vigorous the green ones are!)
Silene dioica [©Nancy J. Ondra/]
For a few years after, I would remove any green-leaved volunteers that I noticed, but gradually, the yellow ones disappeared and only the green ones remained. The species plants of Silene dioica are really nice for no-bother, late-spring color, though, so I leave them in middle-to-back-border spots where they get covered up by taller perennials in summer and fall. Here, it’s with ‘Queen of Night’ tulip and the dark young foliage of ‘Erica’ Culver’s root (Veronicastrum virginicum) in mid-May.
Silene dioica [©Nancy J. Ondra/]
Here’s red campion (Silene dioica) with giant starflower (Ornithogalum magnum), a bulb that also self-sows here, in early June.

Bupleurum rotundifolium (thorough-wax, thorowax, or hare’s ear): This unusual annual produces circular clusters of greenish yellow flowers over blue-green leaves on upright, 1- to 3-foot tall stems.

Bupleurum rotundifolium [©Nancy J. Ondra/]
The beautiful perfoliate foliage of thorough-wax (Bupleurum rotundifolium)
Bupleurum rotundifolium [©Nancy J. Ondra/]
Spring-planted seeds of thorough-wax (Bupleurum rotundifolium) tend to bloom in mid- to late summer; in following years, the self-sown seedlings often begin in late spring to early summer. Both the flowers and developing seedheads are interesting additions to fresh bouquets.
Bupleurum rotundifolium [©Nancy J. Ondra/]
The developing seedheads of through-wax (Bupleurum rotundifolium) with ‘Prairie Sun’ rudbeckia (Rudbeckia hirta) and dill (Anethum graveolens), another excellent self-sower, in early July.

Verbena bonariensis (Brazilian vervain): The bobbles of purple flowers are a wonderful sight in later summer and fall, working beautifully with both bright and pastel palettes.

Verbena bonariensis [©Nancy J. Ondra/]
Brazilian vervain (Verbena bonariensis) nicely complements many late-summer and fall perennials, including ironweeds (Vernonia), golden lace (Patrinia scabiosifolia), orange coneflower (Rudbeckia fulgida), and ‘Lemon Queen’ perennial sunflower (Helianthus). The scene above was in mid August.

Brazilian vervain used to act only like an annual here but sometimes overwinters. It got almost too abundant for a bit, but now that I collect most of the seedheads in late September and October to save the seeds, I get just a manageable amount of volunteers. (By the way, thorough deadheading works as a way to control other self-sowers that are tipping toward over-abundance. If you are starting to see too many seedlings, try that for a year or two, until fewer volunteers appear, then let them self-sow again.)

Cuphea (cupheas): ‘Firefly’ cuphea came to me years ago as a gift, and it was gift that keeps on giving.

Cuphea 'Firefly' [©Nancy J. Ondra/]
Cuphea ‘Firefly’ self-sows politely into the few open spaces I have in the front garden, popping up in early June and producing cute red flowers from late June or early July until frost.
Cuphea 'Firefly' [©Nancy J. Ondra/]
Cuphea ‘Firefly’ with a sprawled bit of ‘Isla Gold’ tansy (Tanacetum vulgare) in early September
Cuphea viscosissima [©Nancy J. Ondra/]
Though not as bright as ‘Firefly’, blue waxweed (Cuphea viscosissima) is another favorite of mine, with deep purple flowers over an equally long period.

Both ‘Firefly’ and blue waxweed usually germinate all right with warm-sowing in spring, but they seem to like alternating temperatures (warm days and cooler nights), so if you have trouble getting them going from indoor-sown seeds, try setting the pots outside to sprout. In following years, that will happen naturally to the dropped seeds and they will appear when conditions are right.

Talinum paniculatum ‘Kingwood Gold’ (jewels of Opar, fameflower): Though technically a succulent “subshrub” that can reach 5 feet tall, jewels of Opar is easy to grow as a self-sowing annual to about 2 feet tall.

Talinum paniculatum 'Kingwood Gold' [©Nancy J. Ondra/]
Regular jewels of Opar (Talinum paniculatum) has fleshy green foliage topped with clouds of tiny pink blooms that mature into coppery seedpods. ‘Kingwood Gold’ is different in that the foliage is greenish yellow to bright yellow.
Talinum paniculatum 'Kingwood Gold' [©Nancy J. Ondra/]
This self-sown seedling of ‘Kingwood Gold’ jewels of Opar (Talinum paniculatum) put itself in a perfect spot with other succulents, including blue Spanish stonecrop (Sedum hispanicum), green Orostachys malacophylla var. aggregata, and pink Echeveria ‘Perle von Nurnberg’.
Talinum paniculatum 'Kingwood Gold' [©Nancy J. Ondra/]
Here at Hayefield, in PA, ‘Kingwood Gold’ jewels of Opar (Talinum paniculatum) stays in the 1- to 2-foot-tall range, probably because its self-sown seedlings don’t start showing up until later June or even July. In the Deep South, one of the places the species is native to, and hardy in, it can get much taller and bushier.

Lychnis coronaria (rose campion): In leaf, rose campion looks rather like lamb’s ears (Stachys byzantina), with furry, silver-gray foliage. Come the second spring, though—and possibly for another year or two after that—the rosettes send up woolly-branching stems topped with brilliant magenta, flat-faced blooms in early summer.

Lychnis coronaria [©Nancy J. Ondra/]
You don’t often see this old-fashioned favorite for sale these days, but it’s easy to start rose campion (Lychnis coronaria) from seed in spring or summer to enjoy the following year, and self-sown offspring will keep the show going for years to come.

Oenothera glazioviana (magic primrose, large-flowered evening primrose): I’ve been growing this one for many years and still cannot tell its nondescript first-year rosettes apart from the very common O. biennis that shows up uninvited in my garden. The difference is obvious in the second or third year, though! That’s when the “magic” part happens, with upright, 3- to 5-foot-tall stems that produce a series of long, tapered reddish buds. Starting in midsummer, a few buds pop open each evening, right at dusk. Visiting the plants right before I go in for the evening is part of my routine for a good 6 to 8 weeks.

Oenothera glazioviana [©Nancy J. Ondra/]
You quickly learn how to tell which buds are getting ready to open, and as you stand there, you can see the sepals start to split, and then the petals spiral open, all in a period of just a few minutes.
Oenothera glazioviana [©Nancy J. Ondra/]
The large, yellow blooms of magic primrose (Oenothera glazioviana) have a wonderful scent: just like the Coppertone suntan lotion of decades ago, if you’re old enough to remember back that far.
Oenothera glazioviana [©Nancy J. Ondra/]
Here at Hayefield, magic primrose (Oenothera glazioviana) generally starts flowering in late June and continues through much of August. (Above is an early July scene.)

Tinantia erecta (widow’s tears): Most of my favorite self-sowers thrive with plenty of sun, but this uncommon annual prefers my shadier sites. Widow’s tears grows anywhere from 2 to 4 feet tall, with rich green leaves and succulent stems topped with clusters of pink blooms from mid- or late summer to frost.

Tinantia erecta [©Nancy J. Ondra/]
The blooms of widow’s tears (Tinantia erecta) open in the morning and usually disappear by midday; for that reason, it’s not the most eye-catching of annuals. But I consider it worth growing just for the lush foliage and think of the blooms as a nice bonus.
Tinantia erecta [©Nancy J. Ondra/]
The newly opened flowers of widow’s tears (Tinantia erecta) are somewhat nodding. After they close, the pedicels turn upward. Look for the small, dark seeds to form in the upright “cups.”
Tinantia erecta [©Nancy J. Ondra/]
It can be a bit challenging to get widow’s tears (Tinantia erecta) started at first, but once you get a plant growing in your garden, it’s dependable as a self-sower (at least, it has been for me).

Amaranthus (amaranths): These sun-loving annuals are terrific for adding height to summer and fall gardens. The seeds sprout readily in warm conditions and grow quickly.

Amaranthus 'Hopi Red Dye' [©Nancy J. Ondra/]
‘Hopi Red Dye’ amaranth is a gorgeous strain that is deep red throughout: in its stout stems, its abundant leaves, and its plumy seedheads. Transplanted seedlings can be on the short side, reaching just 3 to 4 feet tall, but self-sown seedlings can reach to 6 feet or even taller—perfect for pairing with sunflowers (Helianthus), castor beans (Ricinus communis), and other back-of-the-border annuals and perennials. (Or front-of-the-border companions, if you choose to let them come up there!)
Amaranthus 'Elephant Head' [©Nancy J. Ondra/]
‘Elephant Head’ is another amaranth I adore, with big, dense heads that typically produce a stout spike in the center. If the main stalk starts leaning, the heads can indeed look something like an elephant’s head; when they stay upright, the effect can be more like the vegetative equivalent of a rude hand gesture.
Amaranthus 'Elephant Head' [©Nancy J. Ondra/]
If needed, you can keep the tall, upright amaranths (Amaranthus) shorter and bushier by pinching out the main stem tip when it’s nearly the ultimate height you’d like. This ‘Elephant Head’ volunteer made itself at home right in front of my shed one year. I couldn’t bear to pull it out but pinched it to keep it from getting too tall; otherwise, it would likely have gotten knocked over by the wind in this exposed spot.

Nicotiana (flowering tobaccos): Like the amaranths, flowering tobaccos have tiny seeds that can grow into sizeable plants in just a few months.

Nicotiana sylvestris [©Nancy J. Ondra/]
I’ve had woodland tobacco (Nicotiana sylvestris) reach nearly 6 feet in good years, which put its nodding, fragrant, white blooms right close to nose level. In other years, and other spots, it’s more like 3 to 4 feet tall.
Nicotiana tabacum 'Variegatum' [©Nancy J. Ondra/]
Variegated tobacco (Nicotiana tabacum ‘Variegata’) got nearly 5 feet tall for me last year, but its pink flowers are secondary to the brightly splashed foliage. Be aware that you’ll get lots of solid-green seedlings if you let this one self-sow, and be prepared to remove them in favor of the few variegates.
Nicotiana mutabilis [©Nancy J. Ondra/]
N. mutabilis is another tall growing flowering tobacco, but it has a more branching, airy habit. Its white flowers turn pink as they age.

A brief commercial message: I have seeds available for some of the self-sowers I mentioned here, if you’re interested. Click on the names to see their listings in my Hayefield shop. I have others there too, mostly in the Annuals and Edibles category.

Well, that’s it for my seed-focused posts—for a while, at least. I plan to get back to doing Garden Bloggers’ Bloom Day posts on April 15th. Stay well, all, and I will see you then.

Posted on 10 Comments

10 thoughts on “Make the Most of Self-Sowers (Part 2)

  1. Lovely post, Nan! Nice to finally know that the tiny but vigorous succulent spreading in my garden path is Spanish Stonecrop. Happy early spring!

    Glad I could help, Ginny. That’s a really charming little sedum. Happy spring to you too. Enjoy being in your garden!

  2. I love your posts, and can always learn something. Your photography is outstanding, as is your flower placement. Keep up the good work in educating us.

    Thank you so much, Judy. I appreciate you visiting today. Hope you get to enjoy some time in your garden!

  3. I planted a campion similar to the one in the first photo last year and loved it. I just transplanted it to a new spot last week. I am not good at all with seeds. I think I am too impatient but also, I tend to forget they are there and end up planting something on top of them.

    Hi Phillip! I wouldn’t be surprised if you find seedlings from last year’s flowers, so you may have lots more you can transplant without ever intentionally starting the seeds. Enjoy!

  4. I did not know that Ornithogalum magnum was a self-sower. It never even crossed my mind! I will have to keep my eye out for seedlings.

    For the first few years, I deadheaded mine, being concerned that it might spread as freely as O. umbellatum. I forgot for a few years and finally started seeing volunteers–not anywhere near the seedlings the other species can make, but enough to now have a nice-sized patch in one spot.

  5. As always, I loved your post and learning some of your favorite self sowers! I too love my rose campion but have not grown the other campions. There is a wild white campion net Lake Ariel, PA where we go sometimes but I have been unsuccessful in transplanting.
    Can’t wait for your blooms day posts!
    Stay well
    All the best
    Jean Spangenberg

    Ooh, I wonder if it is Pennsylvania catchfly (Silene caroliniana ssp. pensylvanica)? Or, it might be the more common Silene latifolia. Pretty either way. Thanks for stopping by today, Jean!

  6. Thank you for putting a bright spot in my day in the midst of ominous news about the spread of the new virus. Good to know that the plant world gives us such self-propogating beauty that does not threaten health and life.

    I am so happy to hear from you today, and with such a lovely thought. Thank *you*, and stay well.

  7. Some self sowers become weeds! White violets got into the lawn many years ago, and no one can get rid of them. Alyssum has been there since 1978, but I really like it anyway. You know though, I have never gotten silene to do well. I can’t figure that one out.

    Hey there, Tony. Yes, that’s always a possibility–any plant that is well adapted to a particular site could do that, I suppose. Maybe it’s too hot where you are for the silene?

  8. This is very helpful. I’m obsessed with self-sowing seeds. I’m also obsessed with natives. Can you note which, if any of your plants are native? I think the Oenethera might be the only one?

    Hey there, Molly. It depends where you want them to be native to. Cuphea viscosissima is another self-sower native to some part of the US; Tinantia erecta to parts of the Deep South.

  9. I’ve enjoyed your reseeding posts, and it’s always nice to find out about a few new plants which you need ;)
    After years of trying, there are finally a few lettuce poppy seedlings coming up on their own. Now I just need to convince the orlaya that it should do the same… although I’ve seen your masses and don’t know if I’ll regret saying that some day.
    Take care, it should be an interesting year to say the least.

    Good to hear from you today, Frank; thanks for checking in. Yes, it’s a fine line with the Orlaya, as well as many other self-sowers. Right now, it feels like anything green and growing and vigorous is welcome. Whatever happens, I hope your garden provides a source of peace and happiness for you.

  10. Thank you for all the effort you put into your posts. I soak them all up!! I ordered the Elephant Head seeds from your Etsy site. They will go in the middle of a new garden bed that can be seen from both sides. I’m wondering what you would put around them to keep them ….. more rude and less pachyderm-ish

    Hi Shelley! Your seeds are on their way to you; thanks so much! I’ve noticed that the heads look most elephantine when the stems lean. So, whatever you can do to keep the stems growing straight will contribute to the…um, “rude” look.

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