Throughout this post I will provide links to the necessary supplies, so if you can’t find them locally you can order them online from the fine folks at Johnny’s Selected Seeds.
Before you go crazy sowing seeds in late winter and early spring, it’s important to know just how early you can start—if in doubt, ask your local Master Gardener group or staff at a trusted nursery for the expected last frost date. Fast-growing annuals that bloom in summer (such as cosmos, sunflowers, and zinnias) shouldn’t be started more than 4 to 6 weeks before the last spring frost, otherwise they’ll get too big for their growing container and have soft, weak foliage and overgrown roots by the time you can plant them out into the garden.
On the other hand, slow-growing plants like perennials can take a couple of weeks to germinate, so sow them indoors 10 to 12 weeks before the last spring frost date. Once you know your last frost date, check the back of each seed packet or catalog description for days-to-harvest to figure out how soon you can start them indoors.
If you’re reusing old pots or trays, be sure to wash them thoroughly with a 10-percent bleach-water solution to kill any lingering disease-causing pathogens.
For vines, pumpkins, and sweet peas, I use 4-inch (10-cm) pots; for sweet peas, I also love root trainers (long, skinny growing containers that give vigorous roots room to develop).
Be sure to check the ingredients and avoid any products that contain synthetic fertilizers or bark, since young plants can be burned or stunted by either. Seed-starting mix is fine and suited to tiny seeds. For varieties that have larger seeds and will be started in bigger pots, like vines and squash, use a high-quality potting soil.
But if you really get hooked on flower growing, you’ll outgrow these spaces fast. For more consistent results, invest in a heat mat specially designed for seed starting.
The first few years I grew flowers, I started all of my seeds in the basement, on shelves, under lights. For very little money, you can pick up a few shop lights that are available at just about any hardware store. Hang them from some inexpensive chains, and you’re in business. Suspend the lights a few inches above your seedlings and put them on a timer, making sure to give plants about 14 to 16 hours of light a day.
As the plants get taller, be sure to keep raising the lights so they are 2 to 3 inches (5 to 7 cm) above the tallest plant.
Direct seeding can be done by hand, but if you have more than a few tiny rows to do, use a walk-behind seeder, like the Earthway, to make this chore a snap. This handy tool digs a furrow, drops the seeds into it, and covers them all with soil while you walk at a normal pace. With it, you can direct seed a 25-foot (7.6 m) row in less than 30 seconds.
One of my goals here on the site is to provide you with the best information to help you grow great flowers, and I hope dispel the notion that success is only possible for professionals. You can do it!
In addition to the tips included in this post, I want to make sure you know about the following resources:
- My first book, Floret Farm’s Cut Flower Garden: Grow, Harvest & Arrange Stunning Seasonal Blooms has detailed seed starting tips and tricks.
- In the Floret Resources section, I have created a little Starting Seeds 101 tutorial and photo essay (be sure to click the arrows to advance the images) with some of the basics.
- Here on the blog, you’ll find a post that shares more tips plus detailed do’s and don’ts of seed starting.
- In the Floret Shop, I’ve included sowing and growing instructions for dozens of my favorite flowers.
Please share any tips or tricks that you use when it comes to seed starting in the comments below. Please note: If you submit a comment and it doesn’t show up right away, sit tight; we have a spam filter that requires we approve most comments before they are published.
Lastly, if you find this information helpful, I would love it if you would share it with your friends.
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