Growing Giant Zinnias
Though we mainly sell Dahlia tubers, our biggest crop for our local customers is actually Giant Zinnias! These lovely workhorses of the flower world are one of the lowest cost, most productive, and easy-growing choices for any cut flower garden.
We make the distinction “giant” not because we have some secret to growing bigger blooms, but because there are many different varieties out there, including one called “giant” zinnias. That’s the only kind we’ll grow. Regular zinnias are pretty to look at, but not much good for cut flowers since they’re so small. At Sunset View, we go big or go home!
Floret Flowers’ guide to growing Zinnias
If you’ve read any of our other guides, you may have noticed we’re happy to say when someone else has already done a great job explaining something.
When it comes to Zinnias, Erin Benzakein’s guide to growing Zinnias is one of the best out there. We learned a lot from her and she has taught many other people besides. Start there.
The Sunset View Farm Method
Just as we've learned something from many different people, we know there's something you can take from our process and that will work for you, too, so we'll also include our own method for growing Zinnias. We start our zinnias indoors in seedling trays to get a jump on the growing season, which is approximately mid-May to mid-October here in Northern NJ (zone 6a). However, we’ve grown zinnias from seed in the field and they generally do very well, though the natural growing season is shorter. We’ve had success growing a few hundred to thousands of plants with this method.
In March we start sifting well-aged organic compost by the wheelbarrow, using our own piles at the farm. (Our compost is 100% plant-based) Sifting is not strictly necessary, but if there’s one thing farmer Andy loves, it’s well-sifted compost. Or maybe he just enjoys playing with the mechanical dirt trommel he made out of fencing wire and bicycle rims. Either way, the result is soft, black, beautiful dirt that’s a joy to work with. You don’t need to use 100% organic compost, but make sure you don’t use clay soil. The sticky clay can make removing plugs from the seed cells very difficult come planting time.
We then fill 6-cell planting trays by hand from a wheelbarrow. We drop the seeds, one per cell, on the surface of the soil, then sprinkle just a little more soil over the top. Zinnias do not like to be buried deep.
The planted trays are stacked in crates where they can be moved to shelves in our growlight room. Grow lights may not be necessary, depending how many seeds you’re starting. A windowsill or two might do it for a home gardener.
The seeds are watered gently daily or as needed, and are ready for planting outdoors when the sprouts are about the size of a dime. You don’t want to wait much longer or the seedlings will get rootbound inside their containers.
Shortly before the last frost date, we’ll till the field plots in 60’ x 5’ rows until the soil is so soft you’ll sink in if you step on it. Then landscape fabric (with holes that we pre-burn using a torch and a metal template) is rolled out in overlapping rows and stapled down.
Like all clever farmers, we’re essentially lazy people with an unfortunately strenuous job - so when it comes to planting time, we like to invite all our friends over for “Zinnia Madness” to help us plant several thousand seedlings in one day or even one morning, all for the cost of a hearty lunch on the porch. Over the years, we’ve somehow convinced dozens of people that farm labor is fun, for a day at least. We’ve almost even convinced ourselves! Anyway, the event is always a blast and we’ve never had to hire labor for planting in ten years of growing flowers on a small agricultural scale. It’s important to note that we also always have a harvest party in early October, where everyone involved in planting gets a chance to come and enjoy the bounty of the flower fields in full bloom. The workman deserves his wages!
To plant zinnias from seed cells, it’s important to let the seedlings dry out just enough that the soil separates easily from the cells. This could take a day or two, but otherwise, it’s a nightmare removing the plugs, and you’ll wind up destroying many of your plastic cells and your seedlings. A handheld “plug ejector” can be purchased or made at home to help this along. But a seedling plug with just the right moisture content will almost fall out of the cells. It's as satisfying as popping bubble wrap. Maybe more so.
The ejected plugs are then popped right into the soft-tilled ground and patted gently down.
Depending on your climate, you may need to water zinnias regularly. In zone 6b, we have almost never watered ours, but others will need to. Drip irrigation lines help in field settings. But for a small garden plot, a hose or a watering can will do fine. Be gentle when watering the seedlings. Giant Zinnias are hardy when grown, but seedlings are fragile and can be easily washed away by heavy watering.
The next step after planting is pinching. When the plants are 8-12 inches tall, cut off the top 3-4 inches of the stem right above a set of leaves. This encourages the plant to send out multiple stems, which will give you a greater volume of flowers over the growing season.
After pinching, there’s not too much to do. Zinnias take about 60-75 days to reach full maturity. And once that happens, it’ll all be worth it!