Classic, splashy, big, summer flowers, zinnias are a mainstay of many summer gardens. They provide loads of flowers from early summer through fall that last well in the vase. Easy to grow and they come in a wide range of colors.
Butterflies love these! They’re said to be deer-resistant though I’ve never tested that.
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The most classic varieties produce flowers that are 4-6 inches wide. Usually double flowered so that the center shows just a bit.
The plants grow to 3 ½ – 4 ½ ft. tall, with sturdy branches, needing no support and holding up well to rain and overhead irrigation, and to heat.
These are easy to grow. They take 75-90 days to bloom from planting so it’s best to start seeds early in cell flats. Or if your season is very long, plant directly in the garden bed.
Cell flats are best way to start them because they air prune the roots. It’s important to not allow roots to become root bound and to avoid transplant shock, or any other stress while growing these because the double-flowered varieties, which are what you want, can cause the plants to produce single blooms for a while after the stress event. The single flowers are not very pretty at all and not nice in arrangements—BUT the singles are great for pollinators giving good access to the pollen and nectar.
Many sources say to succession sow these in order to keep a long supply of flowers, but I never do this. They are such a good cut-and-come-again flower with their strong branching and long harvest, I like to keep it simple and grow a handful of zinnias to mix with my other flowers.
Space them at 9-12” apart. They like good garden soil and full sun. Plant them out when the soil is warm as you would for tomatoes.
As in sunflowers, pinch the lead stem to a lower node will encourage more branching and more flowers. If you’re anxious for the flowers, pinch a few of them and leave the rest to bloom early. Deadhead any unharvested flowers to keep them coming.
In my opinion, zinnias are a bit coarse and garish, but I know I’m in the minority here. They are colorful and splashy so I understand the enthusiasm for them. I get so disappointed when my zinnias turn out single flowers all summer, but sometimes they’ll work in bouquets.
Benary’s Giant Series offers good doubles in a fantastic mix of colors. These are all I grow, since I’m not that fond of zinnias.
There are also cactus-flowered ones with quilled petals, bi-colored ones, crested scabiosa-type zinnias, green flowers, and then a plethora of dwarf zinnias and others good for flower beds and landscapes.
How many plants
If you have other flowers, 5-10 plants will give you plenty.
My go-to source of zinnia seed is Johnny’s Seed. They have a great selection of Benary’s Giant Series colors, as well as many other varieties. But all seed companies at your local nursery offer good varieties.