Zinnias are a favorite annual flower that will produce blooms throughout the summer that look beautiful, attract pollinators, and make excellent cut flowers. However, this lush growth and heavy flower production can lead to one issue: the plants become top-heavy and topple over.
In addition to being frustrating to see your prized plants stretched out along the ground, bending and broken stems don’t make for good cut flowers.
Using netting, staking plants, and dense spacing can help prevent zinnia flowers from falling over. You can also prioritize growing strong-stemmed or shorter varieties that are more resistant to falling over to ensure tall and straight plant growth.
Some of these strategies come straight from flower farmers who grow zinnias and other cut flowers for a living, so that’s about as close as it gets to a guarantee for perfect advice!
1. Stake your zinnia plants
Staking tall zinnias helps to protect them from strong winds and rain. This method is especially helpful if you live in an area where you experience frequent summer storms accompanied by high winds that could knock down the tall plants.
When I lived in South Carolina, we would get storms almost weekly that would beat down my garden, and staking was a life-saver.
Use one 3-4 feet tall stake per plant or a tomato cage. Place the stake in the soil when the zinnia is about 6-weeks old. Loosely tie the plant stem to the stake and continue to add more ties as the plant grows taller.
Bonus: You’ll see birds perching on the stakes to scope out the garden, looking for bugs to eat.
2. Use horticultural netting
Netting is another support option and is ideal when growing a large crop of zinnias. This is the preferred method of flower farmers for many types of flowers.
Horticultural floral netting is spread over the top of all the plants when they’re young, and they grow up through the net to produce their lovely blooms. The netting is anchored into place by stakes around the perimeter of the flower bed and will help keep the zinnias standing tall.
3. Implement dense plant spacing
Dense spacing allows the plants to support each other. Instead of planting the zinnias 10-12 inches apart, space them 4-6 inches apart. A thick stand of flowers won’t get blown over as easily, and rain-soaked plants are more likely to stay upright when they can lean against each other.
The dense spacing support system can work well, but there are a couple of drawbacks, especially if you live in a humid climate.
Air can not circulate between the plants, making them more susceptible to powdery mildew. Also, the dense spacing can cause the plant to become stunted and produce smaller blooms if they aren’t in an area with full sun.
Spacing for cut flowers is a little different than for landscaping, so get the details here: How To Space Annuals For Cut Flower Production (With Chart).
4. Grow zinnias in a sheltered location
Grow against a wall so the wall will provide them with protection from the elements and support. Select a wall to an outdoor structure that is in the sun most of the day. Prepare the soil along the length of the wall and 2-feet out from the wall.
Plant a row of zinnias, placing the seeds about 4-inches away from the wall, and the overhang will keep them protected.
5. Go easy on the fertilizer
Don’t over-fertilize your zinnias, or the foliage will become too heavy for the thin stems to support. Plant food, organic or synthetic, will promote top growth. The weight of the extra leaf growth and increased blooms will cause the plant to flop over.
Plus, too much fertilizer can promote stem and leaf growth at the expense of bloom production. When growing for cut flowers, the blooms are the most important part of the plant!
5. Grow in full sun for strong growth
Grow your flowers in full sun so the plants will be strong and healthy. Zinnias need at least eight hours of sun each day to produce an abundance of blooms. The more sun they get, the better they will perform.
For more on why full sun is ideal for zinnias, check out this article: Can Zinnias Grow In Partial Shade? (Yes, But Not Optimally)
6. Pinch the plants to promote lateral branching
You can encourage your zinnias to grow out and up to make them stronger and get even more blooms. The shorter, bushier plant will also be less prone to flop over.
To pinch zinnias, cut the top stems when the plants are young and between 8-12 inches tall. Use a pair of sharp pruners to snip off the top 3-4 inches from the plant. Cut just above a set of leaves.
This will signal the plant to send up multiple stems from below the cut, increasing the lateral growth. The main stem will become stronger, and each plant will produce more flowers.
There are a few ways to cut zinnias for the best growth, which you can learn about here: 3 Ways To Cut Zinnias To Keep Them Blooming.
7. Choose shorter varieties
Shorter varieties of zinnias are less likely to fall over in a rain or wind storm.
Dwarf varieties of zinnias will grow to a mature height of 6-12 inches and rarely have a problem with becoming top heavy and falling over. Flower sizes will vary depending on the dwarf variety planted. Some are loaded with smaller blooms, while other dwarf varieties produce large blooms.
The Queen series grows tall and upright and produces large flowers in several colors. Double blooms sit atop sturdy stems in rose, orange, peach, and lime shades.
The zinnia plants will reach a mature height of 2 1/2 – 3 1/2 feet and produce blooms all summer. Ideal for cut flowers, the more you cut the blooms, the more the plant will produce.
The Oklahoma series offers medium-sized plants that produce mid-sized single and double blooms. The plant has sturdy stems and is reliable for flower production throughout the summer.
The flowers are long-lasting after cutting, so they make perfect cut flowers. Bloom colors include yellow, red, white, purple, and pink. I have the salmon variety in my garden this year.
This variety is very resistant to powdery mildew and requires minimal maintenance. Regular deadheading will promote an abundance of colorful blooms, and the plant will reach a mature height of 2 1/2 feet.
Jazzy series produces colorful petite double and semi-double blooms on strong stems. The petite beauties typically do not need to be staked and rarely succumb to high winds or heavy rains.
The plant will reach a mature height of 1 1/2-2 feet tall and produce an abundance of 2-inch blooms.
The compact plants produce a multitude of blooms in earthy shades of brown, gold, yellow, burgundy, red, and bi-color. The Jazzy series makes excellent border plants and are ideal for cut flowers.
This is a great variety to grow in pots if you need to grow your zinnias in containers.
8. Choose strong-stemmed varieties favored by flower farmers
To make the most money and have an excellent product, flower farmers need to grow strong-stemmed varieties. We can take a hint from them and choose the same varieties for our home gardens.
Benary’s Giant are vigorous growers that will produce blooms all summer. This variety holds up well in summer rain and heat and thrives in all USDA growing zones.
This variety will reach a mature height of 4-5 feet and produce huge blooms six inches across.
Bloom colors include vibrant red, orange, rose, coral, lime, burgundy, purple, pink, white, salmon, and golden yellow.
State Fair is also a vigorously growing plant and heavy bloom producer. The plants will reach a mature height of 4-5 feet and produce blooms that are 5-inches across.
State Fair zinnias are hardy, strong-stemmed, and able to withstand summer rainstorms and winds very well.
The blooms range in scarlet, gold, purple, orange, pink, red, and yellow colors. They make excellent cut flowers, and the plants will produce them all summer.