Floxglove seedlings in the greenhouse
Happy Spring!
Much of my acre of cut flowers is started from seed, and looks a lot like the seeding you might have done or are getting ready to do at home. Here's a look at my seed starting process, and some tips and tricks for some of the more finicky ones - flowers are kind of known for being harder than vegetables.
Soil
You'll need a good quality potting mix and containers. I use MacEnroe light potting mix. You can use any good quality potting mix from a garden center, but I dont recommend soilless sterile mixes, as these don't have any nutrition that your growing seedlings will need right after germination. Happy Frog is another good one that some garden centers carry.
Fill your containers - you can use cell flats, pots, egg cartons, plastic clamshell food containers, etc. I use greenhouse supply plug trays with different sized cells for different rates of growth. A zinnia, for example, grows pretty fast, so these 128 cell trays (pictured) don't have large enough cells to accommodate their fast growing roots. Id use a 32, or your typical nursery flat plug size.
Gently fill and don't compress the potting mix. Your plant's roots will need all of those air spaces between particles to drink and breathe, so don't squeeze them out! be light and fluffy about it.
Seeds
Pay careful attention to whats recommended for the variety you want to sow. Cool loving varieties that enjoy a long mild Spring and thrive in, say, the Pacific Northwest, might not be suited to our hot NY Summers. Stock, ranunculus, iceland poppies, and godetia fall in this category for me. I have access to a greenhouse and can start things early enough to get them planted and mature before it heats up in May. Johnny's Selected Seeds has great growing information for many cut flower varieties on their site.
Some cool lovers that don't mind the heat as it comes on in late Spring are Bachelors Buttons, Scabiosa and Snapdragons.
Sow your seeds according to directions, 2-3 seeds per cell. Once they emerge and have true leaves, thin them - yes, pluck them out(!)- to one seedling per cell. You're doing them a favor since they don't like to be crowded and have to compete in a small space for water and nutrients, and they'll be much healthier plants.
Some flower seeds prefer to be pressed lightly in to the surface and kept evenly moist, and need light to germinate, which can take up to 14 days! Ammi, Queen Anne's Lace, Snapdragons and Feverfew fall in to this category. Plastic humidity domes or plastic wrap loosely covering the tray can help keep a moist environment that seeds appreciate while taking their sweet time to get around to it. I use a sprinkling of Vermiculite, available at some hardware and garden centers, to help keep the surface from drying out, and to limit algae growth from accidental overwatering.
Water
Now give em some moisture to encourage germination! Not all water is ideal though. Collect rain water if you can, as it's the gold standard chemically and energetically, as well as being neutral in charge. Stream, pond and well water are next best, though in 2021 the well water on my farm tested highly alkaline and I had to start treating it to adjust, since seedlings were suffering. I’ve since installed a rainwater catchment and storage cistern to correct this.
For surface sown seeds, water very gently from above, or better yet, set tray in another solid tray of water for a few minutes to wick up water from below (aka bottom watering), to avoid blowing your tiny seeds off the surface.
Light/Temp
I start my seedlings in a greenhouse setting where they are protected from cold and get ambient sunlight or bright light on cloudy days. You can set yours up under a grow light or hanging shop light with one warm and one cool tube, or set them in a very sunny spot, though they may also need supplemental light. Air movement is important for stem strength and avoiding allowing the soil to dry slightly between waterings, which most plants like. (though not while germinating!) You can set up a small fan to keep air moving through. Once you are past the threat of frost for your are, you can move them outside permanently, or before then, take them out on warm days and in at night, although they will need to be slowly acclimated to the sun over several days, an hour or two at a time so they don't get sun scalded. Warm days with lots of moving air can dry your plants out so keep a close eye on them.
Plant out
Since Im growing on a bigger scale, I sow many seeds in to strip trays until they have two pairs of leaves, and then 'prick' them out or transplant into plugs trays or pots, shown above, and grow them on for several weeks to allow them to size up before planting out. These snapdragons make good candidates for this method, as they take 12 weeks from seed to bloom, so have to be started in mid Feb for my mid June blooms.
Avoid planting out tender varieties like zinnia, sunflowers and cosmos until the threat of frost has passed in your zone, or unless you can give them some frost protection in a cold frame, or with floating row cover.
I begin with the majority of my annual plantings just before or around May 15th in my zone 5a/5b microclimate, knowing I have to keep my eye on the nighttime temps and possibly get some cover on if it's going to dip below freezing. Some plants like calendula and snaps don't mind cold, but need to be well hardened off, and no one wants to be frozen as a tiny seedling!
What to grow
Here are some of my favorite annual cut flower crops that I start from seed that are well suited to your home garden, according to difficulty.
EASY: Zinnia, Bachelor's Button, Scabiosa, Sunflower, Cosmos, Amaranthus, Cerinthe, Celosia, flowering Basils.
MEDIUM: Feverfew, Agrostemma, Snapdragon, Ammi, Aster, Coreopsis, Winged Ammobium.
TRICKY: Godetia, Foxglove, Lisianthus, Dianthus, Stock, Chantilly Snaps.
Prefers direct seeding: Nigella, Larkspur, Bells of Ireland, Breadseed Poppies (some types are Fall sown)
Resources
Hudson Valley Seed Company: Many of the cut flower seeds mentioned, floating row cover, seed starting supplies, tools, and lots of great resources including their blog.
Johnny Selected Seeds: large selection of cut flower seeds, detailed growing info for reference of each type of flower or vegetable. I consult this weekly!
Best of luck with your seeding! Get in touch with any questions or to let me know how yours are going! I'd love to hear what you're starting this Spring.
And if you don't have the time or supplies for seedlings and want a shortcut to a gorgeous Dahlia garden, my tuber shop is open mid-Feb through May! They’ll push up stem after stem from Aug-Oct.