Here’s how to grow zinnias from seed and what you need to do to care for them well.
If you’re looking for a burst of beautiful cut flowers to add to your garden space without the extra hassle or care, then you really should consider adding Zinnias to your list of flowers this year.
Zinnias add a massive arrangement of bright colors that scream summer in colors such as pink, red, yellow, green, orange, and white. You’ll see a variety of shapes, heights, and types of flowers within the Zinnia family.
How to grow zinnias from seed for a show-stopping garden
At a glance:
- Easy to grow, even for beginner gardeners
- Huge variety of colors and sizes
- Must be replanted each year: will die with the first frost
Zinnia flowers (official name Zinnia Elegans) are in the Asteraceae family and are native to Mexico. These flowers are a frost-sensitive annual. Therefore they won’t return year after year and must be sown in the soil after the last frost.
Zinnias require total sun exposure and bloom from summer to the first frost date.
Gardeners love Zinnias because they are easy to grow from seed. They attract beneficial pollinators, can be used as a stunning cut flower, tolerate summer heat, survive pesky deer, and are good in containers.
Why you’ll love growing zinnias
- They attract hummingbirds and butterflies: a group of these colorful blooms will be a light to invite butterflies to your area.
- The flowers bloom all the way up to frost
- If you keep cutting, you’ll have more blooms than you know what to do with
- They’re a great choice for warmer climates
Picking the right zinnia seeds
- Benary’s Giant This is a classic choice, with big flower heads and a huge variety of colors. If you’re overwhelmed by choices, pick a Benary’s giant mix.
- Fireball blends are varieties in the red, orange and yellow color scheme.
- California Giants are varieties in the red, rose, yellow and orange color scheme. They grow tall and are the first of the varieties to bloom. California giants flowers and blooms are similar to dahlia flowers with tall stems and large double blooms.
- Cactus Flower Blend Cactus Zinnia flowers have rolling, feathery petals and are absolutely spectacular in bouquets or as garden adornments. This zinnia blend is 4″–6″ wide making it one of the largest zinnias available! Double and semi-double blooms in brilliant shades of pink, white, red, orange, and yellow. The petals are long with rolled edges that turn and twist. Each individual flower lasts a long time on the plant and in the vase. Zinnias are edible but have little flavor. The colorful flowers can make a pretty garnish to salads, desserts, cold drinks, or serving trays. Cactus variety is very tall, blooms are very large, and the pollinators absolutely love them. Wide range of beautiful colors, but not garishly bright. Makes a beautiful bouquet. Highly recommended by many gardeners including beginners.
- Cupcake Blend Cupcake blends are beautiful varieties of the Zinnia that resemble Scambiosa. The crested center ruffles and unfolds and looks like a cone-shaped once fully in bloom.
- Thumbelina These varieties are perfect for borders as they are dwarf and spread with single or semi-double smaller flowers in all sorts of colors.
- Peppermint Stick Peppermint zinnias are a fun and playful variety to grow. Growing 2 – 4 inches tall, these striped and speckled flowers come in delightful, cheery colors.
- Polar Bear. The white varieties such as the polar bear of the zinnia flower are beautiful and go well in cut flower bouquets with greenery and sprigs of lavender.
Step by step zinnia
Finding the best location
There’s no reason why any beginner (or advanced!) gardener would not want to add zinnias to their garden this summer. Try adding tall zinnia varieties as a backdrop in your flower garden plan. Use short zinnia varieties along perennial borders..
Zinnias are a great addition to an annual butterfly garden amongst other flowers such as milkweed. Attracting honeybees and butterflies are a critical sustainable practice to consider when gardening not only for yourself but to improve nature and the natural landscape.
Zinnias grow well anywhere, but they do need full sun. (This means 6-8. hours of sun per day, so some afternoon shade is fine, and often appreciated)
Zinnias are lovely in their own cut flower garden, amongst perennial garden spaces as borders and even as companion plants to vegetables such as zucchini, beans, and chard.
Zinnia plants also thrive when grown in containers. Smaller varieties make good potted plants for your porch or deck. Choose a clean container with drainage holes.
Starting seeds indoors
You can start zinnias from seed indoors four to six weeks before your average last frost date. Transplant outdoors after the last frost date. Most gardeners choose not to start seeds indoors as there is no benefit from being sown early and prefer to wait for warmer weather.
If you’d like an extra-early start on your blooms, you can plant zinnia seeds under fluorescent plant lights, either in trays, peat pots, or soil blocks. Put them on a heat mat, keep the soil moist, and the zinnias will germinate quickly (within five days).
They grow quickly, so be prepared to move them into the garden within a few weeks (don’t start them too early!)
Direct sowing zinnias
Soaking zinnia seeds before planting for about 12-24 hours will help reduce germination time.
Sow zinnia seeds about ¼ inch deep and lightly water after planting. After about a week, you’ll see seedlings emerge from the soil.
The average spacing is 6 inches between plants in the row and two feet between the rows for most zinnia varieties. (But check the seed packet!)
Preparing the garden for transplanting or sowing
Prepare the garden bed by cultivating and loosening soil. The young plants are sensitive to cold, and soil temperatures should be in the 50s or 60s before transplanting.
Zinnias do not need rich soil, but a light fertilizer application or a good amount of compost will result in healthier plants.
The best place to find the exact information for spacing distances and seed sowing depths is always on the back of the seed packet. Larger varieties will need more space, and dwarf types can be closer together.
(If you’re planting zinnia seedlings, space them the recommended distance that plants will be after thinning.)
Once the seedlings reach three inches tall, it’s essential to thin them to about 6 to 18 inches apart to allow air circulation and preventative disease control.
When thinning seedlings, try adding the seedlings you are removing from the patch to the end of the row to expand your final garden bed. To do this, you’ll have to make sure that you don’t disrupt the roots.
Zinnias will take 60 to 70 days from being sown in the soil producing mature flowers (depending on the conditions and the variety).
How tall zinnias grow
Zinnia flower varieties range from 24-36 inches tall and 12-18 inches wide.
How to care for zinnias
We’ve already discussed that zinnias are easy to grow, but they will need a few things from you.
Once your seeds have germinated, and the plants are about 6 inches tall, spread organic mulch around them to preserve soil moisture.
Pinch young plants when they are about 12 inches tall. Pinch directly above the leaves, and two stems will form where there was one. Pinching strategically will give you more flowers. You can keep pinching throughout the growing season, and each pinch will produce blooms that you wouldn’t have otherwise had.
Pests and diseases
Your zinnias are susceptible to bacterial and fungal spots, powdery mildew, and wilt. The best way to prevent the disease from bothering your beautiful flowers is to water at the base of the plants in the soil and minimize getting the foliage wet.
Zinnias will often get powdery mildew, especially later in the season when mornings are cool and damp. Give your plants plenty of good air circulation and choose disease-resistant varieties to combat this. But powdery mildew is just a nuisance, and since it usually happens at the end of the season, you can pull the plants that are badly affected.
If you’ve correctly spaced out the plants and you’re watering in the morning at the roots, then your Zinnias should be healthy and happy.
One thing you will not have to worry about when keeping your Zinnias cared for and thriving is deer. Wildlife is always a concern for most plants, but lucky for the Zinnia, they are deer resistant. (Of course, a deer who is hungry enough will eat anything, but they don’t find zinnias particularly delicious.
To maximize growth and blooms, fertilize your plants lightly and use clean garden snippers to deadhead plants by cutting off old flowers to encourage more flowers to form.
Japanese beetles may nibble on the leaves, but they rarely cause severe damage.
If you’re noticing that you’re not getting the blooms you expected from your Zinnia’s, try giving the plants some fertilizer. A fertilizer rich in phosphorous such as bone meal will help encourage blooms.
Harvesting and storing zinnias
Make sure to cut and enjoy your zinnias in bouquets, vases, flower arrangements and dry them throughout the summer months. Remember that by cutting flowers, you’ll encourage new blooms to form throughout the season.
When harvesting zinnias for a cut flower bouquet or vase, make sure to harvest before small yellow flowers emerge between the petals.
Zinnias are annual plants that you can plant every spring. It’s easy to save seeds from open-pollinated varieties such as candy cane and California giant.
Wait for the zinnia flowers to dry before harvesting. Place harvested seed heads on a screen so they can dry all the way around. Remove the seeds over a labeled piece of paper and allow them to dry further.
Place the seeds in a cool, dry place such as a brown paper page in a closet. Don’t forget to label the bag and use it within a few years.
How long does it take for zinnias to grow from seed?
It depends on the variety, but you should be cutting blooms in about 60 days.
What do I need to do to care for my zinnias?
That’s it! They’re one of the easiest flowers to grow. Prevent weed growth, harvest the blooms, and water your garden beds during dry periods.
Should I plant zinnias from seeds or plants?
Direct sow seeds. It’s cheap and easy.
Can I plant seeds in containers?
Sure! Taller varieties might not fit, but most will do great.
Do I need to worry about hot temperatures?
Not really. Zinnias will thrive in warmer climates. Just keep them well-watered on hot days.
Will they do well in cooler climates?
Yes, but to prevent powdery mildew, look for a disease-resistant variety.
How many zinnias will I get from one packet of seeds?
Hundreds! Each seed will produce a plant that will give you dozens of blooms.
What is the best time of year to plant zinnias?
Late spring, when you plant the rest of your tender garden plants such as peppers and tomatoes.
Zinnias are ideal when looking for a bright burst of beautiful cut flowers to add to your garden space. And nothing says mid-summer like a bouquet of zinnias in the kitchen. You really cannot go wrong when choosing to add zinnias to your landscape.
May you enjoy all the benefits of growing zinnias in your garden oasis this year.