How to Grow Zinnias
Zinnias are one of the easiest flowers to grow, as they grow quickly and bloom heavily. Available in a brilliant rainbow of colors, these happy blooms are a must-grow for any flower lover. As one of the easiest cut flowers to cultivate, they are a perfect first crop for beginning growers and are reliable, prolific producers for most flower farms. Keep reading to learn how to grow zinnias and some tips on how to use them in your cut flower bouquets.
Zinnias are annuals, so they’ll grow for one season and produce seeds, but the original plant will not come back in subsequent years. They have bright, solitary, daisy-like flowerheads on a single, erect stem, which makes them great for use as a cutting flower.
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Types of Zinnias
The most popular zinnia species is Zinnia elegans, which has been bred to produce a great number of unique varieties.
There are three main kinds of zinnia flowers: single, semidouble, or double. The distinction between these forms comes from the number of rows of petals and whether or not the center of the flower is visible:
- Single-flowered zinnias have a single row of petals and a visible center.
- Double-flowered zinnias have numerous rows of petals and their centers are not visible.
- Semidouble-flowered zinnias are somewhere in-between, with numerous rows of petals but visible centers.
In addition to these forms, zinnia flowers come in a number of shapes, including “beehive,” “button,” and “cactus.” The plants themselves also come in different heights: taller varieties are best for the background of a garden bed, while shorter varieties work well along a border. There’s really a zinnia for every garden!
When to Plant-
Zinnias resent cold weather and prefer to be planted after things have warmed up a bit. Many gardeners in warmer parts of the world are able to successfully direct seed their zinnias straight into the field. We start ours inside about 4 weeks before the last frost.
If you decide to start Zinnias inside make sure the transplants are only a few weeks old (3-4 weeks) when you move them outside. Larger, older transplants tend to be “root bound” and will be permanently stunted in their growth and vigor
Zinnias will grow in a minimum daytime temperature of about 60°F (16°C), though a range of 74–84°F (23–28°C) is preferred.
Sow a round of seeds every week or so for several weeks to extend the flowering period.
Where to plant-
Choosing a location that gets full sun is essential.
Good air circulation will help to prevent foliar diseases such as powdery mildew later in the season.
Zinnias are adaptable to most soil conditions, but the ideal soil will be rich in organic matter and well-drained.
Soil pH should be between 5.5 and 7.5.
If soil is amended with compost, the flowers will grow more quickly.
In the last few years, plant breeders have been introducing new types of Zinnias that are designed specifically for cut flower use. You can now find Zinnias in not only bright, bold colors, but also muted and dusky pastels. Zinnias also come in a variety of flower sizes, ranging from the large “dahlia flowered” types, to cute little button like blooms. When choosing Zinnia seeds, be sure to choose varieties that will grow to at least 18” tall.
Here are some of my favorite Zinnia’s to Grow for Cut Flowers
“Benary’s Giant” series (come in various colors)
“Uproar Rose” (expensive seed, but worth it for the disease resistance)
“Queen Red Lime”
“Queen Lime Orange”
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How to Plant Zinnias from Seed-
Once the planting beds have been prepared, we lay down four lines of drip irrigation, roughly a foot (30.5 cm) apart, then the beds are covered with a layer of pre-burned landscape fabric to control weeds. Plants are spaced 9 inches (23 cm) apart.
If given good soil and a steady supply of water, zinnias can get huge and require some type of support. We use a layer of Hortonova netting stretched horizontally about 12 inches (30.5 cm) above the ground. Netting is held in place by steaks. Any type of stake, wooden or metal, will work just fine. As the plants grow, they push up through the grid of netting and get the support they need.
When we first started growing zinnias this closely together I was worried that they would be plagued by disease, but since they are grown in such rich soil, this hasn’t been a problem. We succession sow zinnias every 2 to 3 weeks in order to have a steady stream of these beautiful blooms all summer long.
How to Care for Zinnias-
Maintain moderate soil moisture and fertilize lightly to maximize growth and blooms.
The secret to getting the longest stems from your zinnias is pinching them when they are young. Here’s how it’s done: When plants are between 8 to 12 inches (20 to 30.5 cm) tall, take sharp pruners and snip the top 3 to 4 inches (7.6 to 10.2 cm) off the plant, just above a set of leaves. This signals the plant to send up multiple stems from below where the cut was made, resulting in more abundant flower production as well as longer stem length.
If you are not regularly harvesting your zinnias, be sure to deadhead any spent blooms to help focus the plant’s energy into producing new flowers and not going to seed.
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Zinnias should be harvested when they are fully open. They will not continue to open after being cut.
Zinnias need to be picked when they are fully ripe, otherwise they won’t last in the vase. To tell whether a zinnia is ready to harvest, use the “wiggle test.” Simply grab the stem about 8 inches (20 cm) down from the flower head and gently shake it. If the stem is droopy or bends, it is not ready to cut. If the stem is stiff and remains erect, it is ready to harvest.
As with all cut flowers, be sure to cut deeply into the plant between 2 sets of leaves, cutting stems at least 18” long. Deep cuts signal the plants to produce MORE flowers to replace the one you just cut.
Allow them to rest in a clean bucket in a cool, dark spot, like a basement. Zinnias are a “dirty flower” that will muck up the vase water unbelievably fast. Dirty water breeds bacteria, the enemy of cut flowers. Bacteria significantly reduce vase life. To combat this, it’s important to use commercial flower food (easily found on Amazon) or add 1-2 drops of bleach to the bucket or vase. Just a few drops, not an entire teaspoon. Too much bleach will actually bleach the color from the flowers!
Do not put them in the cooler since the flowers are very cold-sensitive.
Zinnias are annuals and will die with the first hard frost of fall. If you want them to reseed, let the last flowers of the season mature fully and scatter their seeds.
Zinnias are one of the easiest cut flowers to cultivate, they are a perfect first crop for beginning growers and are reliable, prolific producers for most flower farms. Do you grow zinnias or plan to add them to your garden this coming season? If so, what are your favorite varieties, or what varieties do you plan on trying this year?
Lastly, if you find this information is helpful, I would love it if you would share it with your friends.
Do you want to learn more about cut flower? Check out our Cut Flowers Page.