7 Things You Should Know About Zinnia Blooms

red and pink zinnia flowers

Zinnia blooms are a beautiful addition to any garden and are easy to care for. Here are seven things you should know about zinnia blooms before you plant them in your garden so you can enjoy their beauty all season long.

1. How long do zinnias take to bloom from seed?

Zinnias need 60-90 days to bloom from seed, also known as the days to maturity. As long as you plant the seeds in warm soil or seed trays, they will germinate in 7-10 days, quickly grow to maturity, and produce flowers.

Some shorter varieties, such as Thumbelina, will bloom more quickly than the larger varieties, such as Benarys Giant. The range of bloom time and size is one of the reasons why zinnias are such a popular annual flower to grow from seed. They are relatively fast growers and produce an abundance of blooms all summer long.

2. When do zinnias bloom?

Zinnias bloom in the summer, usually starting in July following an April sowing. You can start seeds indoors 4-6 weeks before the last spring frost to get blooms a few weeks earlier in the spring. Zinnias will continue to bloom all summer until the first fall frost.

zinnia seedlings in soil blocks
Zinnias are easy to start from seed and can help you get blooms just a little sooner than direct sowing.

If you want to maximize your zinnia bloom time, here’s a complete guide on starting seeds indoors: Germinate Zinnia Seeds Indoors: Tips and Tricks For Success. It’s an easy process, and considering the reward is earlier blooms, it’s totally worth it!

3. How many times does a zinnia bloom?

Zinnias will bloom multiple times throughout the summer because they are what’s known as cut and come again flowers. Every time you cut a flower from the plant, more will appear in its place. You can expect to harvest at least a dozen flowers from each zinnia flower.

I joke about how zinnias and other cut and come again flowers are like the everlasting gobstoppers of the flower world, and each time I see a new set of buds on my zinnia plants, I’m reminded of how true this statement is.

Here are some of my other favorite cut and come again flowers that will fill your garden and counter-top bouquets all summer: 10 Cut And Come Again Flowers That Are Easy To Grow. Along with zinnias, cosmos and black eyed Susans are my favorites.

4. What do zinnias need to bloom?

Zinnias need full sun and well-drained soil to bloom their best. A minimum of eight hours of sun daily will produce the most robust and productive plants. Zinnias are less picky about soil than sunlight, so although they appreciate rich soil, they will tolerate poor to average dirt.

You can fertilize zinnias throughout the season, which is a good way to keep them producing flowers all summer. I like Dr. Earth’s Bud and Bloom Booster or FoxFarm’s Flower and Fruit Fertilizer. Both have higher ratios of phosphorous, which promote flower production. Adding compost to the soil before planting is an excellent long-term solution, as it helps build soil health as well as provides nutrients for the flowers.

5. Do zinnias bloom all summer?

Zinnias will reliably bloom all summer as long as the weather stays warm. If you live in an area with long summers, this usually means that zinnia plants will produce flowers until September or later. Once the first frost arrives and temperatures drop to the 30s, the zinnia plants are done for the season as they won’t survive a frost.

purple and red zinnia flowers
Two or three succession sowings will guarantee zinnia blooms all summer.

You can help guarantee months of zinnia flowers by making 2-3 plantings instead of just one. This process is called succession sowing and can help you enjoy a longer blooming season. Flower farmer Floret mentions that she likes to succession sow zinnias three times from late spring to early summer to ensure she constantly has blooms.

If your first planting starts to slow down or falls victim to powdery mildew, then you have two fresh plantings to replace it, avoiding a flower gap.

6. How can I encourage my zinnias to bloom?

You can help promote bloom production with regular fertilization. Zinnias are heavy feeders and need plenty of nutrients to produce an abundance of flowers. Look for a fertilizer with higher levels of phosphorous and potassium, which help with bud development and leads to more flowers. 

Another way to encourage flower production with zinnias is to make sure you’re deadheading them through the blooming season. Deadheading means removing spent flowers from the plant. Like many other annual flowers, zinnias will produce fewer flowers if allowed to go to seed.

If you want to learn more about deadheading and how it can help your flowers perform their best, check out this post: Should You Deadhead Cut Flowers, Too?

7. What do I do when zinnias stop blooming?

Once your zinnia plants have stopped blooming, you can replant if there’s enough time left in the summer. If the season ends soon, you can leave the plant in the garden to produce seeds and self-sow, or you can remove the plant, compost it, or throw it away. 

Leave the zinnia plant in the garden through the winter if you can. Doing so will help you get new zinnia seedlings popping up next spring without you having to plant them. The seeds will also provide a snack for birds in the fall, and the tall stems make for excellent perches as they feed.

Leaving plant material in the garden can also provide shelter for overwintering beneficial insects like ladybugs and ground bees. They nest in the leaves, stems, and underbrush of gardens, so if you want pollinators and beneficial insects in your garden next year (who doesn’t?), try leaving a few dead plants in the garden over the winter.

Read more about what to do with annual flowers in this article: Annuals At The End Of The Season: Birds, Bugs, Or Compost.

Zinnias for the win

You’ve got all you need to have a productive zinnia season. If you’re unsure if it’s too late to plant zinnias, let this article help you out: Plant Another Round Of Zinnias (It’s Not Too Late). Now go out and enjoy these beautiful flowers!

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