When To Plant Zinnia Seeds - Method, Zone, & Bloom Time Tips

Wondering when to plant your zinnia seeds? It’s so easy to grow zinnias – as long as you choose the right time for planting! Zinnias love warmer weather and tend to struggle if they’re planted too soon.

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Yellow zinnia, what zones can you frow them in?

In this straightforward guide, we’ll go over the best times for planting zinnias based on your planting method (indoor, seedlings, direct sowing, or potted zinnias), grow zone, and ideal bloom time.

While different zinnia varieties and growing conditions may alter your timing slightly, this guide will give you a good idea of when to plant, as well as some tips for what to look for each year so that you can find just the right time to start.

TIP: Remember, regardless of your plant date, zinnias need lots of light! For healthy plants, choose a spot that offers at least 6 hours of sunlight per day. Using nutrient-rich, well-drained soil will also help to give your plants a boost.

With plenty of light and the proper timing, you’ll soon have vibrant colors bursting throughout your garden!

Why I Love Growing Zinnias

Oh, there are so many reasons to love growing zinnias! If you haven’t tried them yet, you should definitely consider adding zinnias to your garden this year. Here are my top 3 reasons for growing zinnias year after year:

They’re easy! Zinnias are some of the easiest flowers to grow. With their long stems, bright blooms, and variety of colors, they make a great addition to any flower garden, front porch patch, or even your fourth story balcony (zinnias can grow wonderfully in pots!).
They bloom quickly. Zinnias only take about two months to bloom. Even if you direct sow them (which is my favorite method!), you’ll be enjoying stunning flowers in just 60-80 days.
They make the perfect cut flowers. With their bright colors and long-lasting blossoms, zinnias are ideal for cut flower arrangements. They last in a vase for up to 10 days! Whether you want to send flowers home with your friends and neighbors or fill your house with the scents of summer (or both), planting zinnias in increments can give you enough flowers to last late into the season.

My Favorite Zinnia Mix

You can pick up a zinnia seed packet from your local garden center or online garden store. I love using the Earth Science Zinnia Mix (you can get it on Amazon!). It’s a combo mix of seeds, fertilizer, and soil improvement, so it makes it easy to ensure your zinnias have the boost they need!

A colorful mix of zinnia seeds in a bag! — **My go to zinnia mix bag!**

If you don’t use a combo mix, you may want to add some organic matter to your soil before planting. Compost and organic soil work well! See my post on what to fill your raised beds with.

After you find your ideal planting date using one of the methods below, head over to my Guide to Growing Zinnias and I’ll walk you through every step of the planting process!

When to Plant Zinnia Seeds Based on Your Planting Method

The timing for planting your zinnias will vary depending on the planting method you choose. I love to direct sow zinnias! I find that they do well with this method, so there’s not really a need to plant them indoors or transplant seedlings.

However, if a different method works best for you, go for it! No matter what method you choose, you’ll want to wait until all danger of frost has passed before planting or transplanting outdoors.

Indoor or Greenhouse Planting

If you want to get a head start, late spring – April or May – is a good time to start planting your seeds indoors or in a greenhouse. You should aim to start planting about 4-6 weeks before your zone’s last frost date.

Zinnia plants love warm weather, so it’s important to make sure that you don’t start your seeds too soon. Otherwise, the outdoor soil won’t be warm enough for the young plants.

When to Plant Zinnia Seedlings

If you start your plants indoors or buy seedlings from your local garden center, you can plant them in the late spring or early summer once the soil has warmed up. Ideally, your soil temp should be about 70°F. In many zones, late May or June is the optimal time for this temperature.

When you plant seedlings, be careful to avoid disturbing the roots as much as you can, and touch them as minimally as possible. Zinnia roots can be sensitive!

Zinnias can grow upwards of four feet tall!

Direct Sowing Zinnia Seeds

This is my favorite method, because it’s easy! For direct seeding, the best time to sow is generally a couple of weeks after the last frost date. Zinnias love warm temperatures, so it’s important not to plant them too early. Wait until the daytime temperatures are about 70°F. In my zone (5b), this is generally around early- to mid-May. I have more tips for finding your zone and last frost date HERE.

When to Plant Potted Zinnias

Zinnias are an excellent choice for those with limited space. You can enjoy them in containers on your porch, patio, or apartment balcony. Anywhere that has full sun and a large enough pot will do!

To plant potted zinnias, sow your seeds in a container indoors in the late spring (around April). Then, move them outside once outdoor temperatures reach about 70°F during the day.

When to Plant Zinnia Seeds Based on Your Zone

Zinnias grow well in USDA zones 2-11.

The best time to direct sow zinnias is a couple weeks after your last frost date. Ideally, daytime temperatures should be between 70°F and 85°F. Here’s a cheat sheet of the average last frost date for each zone, so you have an idea of when to plant your seeds.

Last Frost Dates by Zone

(These do change each year so I suggest Googling, “My last frost date Farmer’s Almanac” and then entering your location for a precise date!) A general framework is below.

Zones 3-4 – May 1-31st
Zone 5, 6, and 7 – March 30 – April 30
Zone 8 – February 22 – March 30
Zone 9 – January 30 – February 28
Zone 10 – January 30 or earlier

purple zinnia where can I plant zinnias and when?

When to Plant Zinnias by Zone

Remember, wait until all threat of frost has passed before planting. Zinnias are a warm season flower and don’t do very well in cold temperatures, so you’ll want to wait until your garden beds have warmed up to about 70°F for best results.

Here’s a general guide for planting based on last frost dates, but keep an eye on the weather to find the optimum time.

Zones 3-4 – Mid-May to mid-June
Zone 5, 6, and 7 – Mid-April to mid-May
Zone 8 – Early March to Mid-April
Zone 9 – Mid-February to mid-March
Zone 10 – Mid-February

When to Plant Zinnia Seeds for Your Ideal Bloom Time

On average, zinnias take about 2 months to bloom, or around 60-80 days.

One of the beautiful things about zinnias is that you can plant them in increments so that you keep getting new blooms into the late summer and early autumn. They’re the perfect addition to your cut flower garden, since they can provide beautiful flowers all summer long (and beyond)!

If you want to get continuous blooms, plant every 2-3 weeks.

Have an ideal time you want to pick your zinnia flowers? Here’s a guide to finding the right time to direct sow your seeds for your ideal harvest.

Keep in mind that these are approximate dates, since climate, growing conditions, and the seeds you use will all play a factor in your bloom dates.

Zinnia Harvest Times

Harvest Mid-April – Plant in mid-February
Harvest Mid-May – Plant in mid-March
Harvest Mid-June – Plant in mid-April
Harvest Mid-July – Plant in mid-May
Harvest Mid-August – Plant in mid-June
Harvest Mid-September – Plant in mid-July
Harvest Mid-October – Plant in mid-August

Important: Although this schedule covers all zones, it’s imperative to wait until a few weeks after your zone’s last frost date to plant. Zinnias are native to Central America and Mexico and thrive in warmer climates.