Make the Most of Self-Sowers (Part 2)

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

• Amaranthus ‘Elephant Head’, Amaranthus ‘Hopi Red Dye’
• Bupleurum rotundifolium
• Cuphea ‘Firefly’, Cuphea viscosissima
• Lychnis coronaria
• Nicotiana mutabilis, Nicotiana sylvestris
• Oenothera glazioviana
• Talinum paniculatum ‘Kingwood Gold’
• Tinantia erecta
• Verbena bonariensis

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 15^th. Stay well, all, and I will see you then.