How to Grow Zinnias: The Complete Zinnia Flower Guide (2024)

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Choosinga location that gets full sun (6 to 8 hours of sunlight per day) is essential to getting plentiful blooms throughout the season. Additionally, a site that offers good air circulation will help to prevent foliar diseases such as powdery mildew later in theseason.

Zinnias are able to adapt to most soil conditions, but the idealsoil will be rich in organic matterand well-draining.Soil pH should ideally be between5.5 and7.5.If soil is amended with compost (humus), the flowers will grow more quickly. Learn more about soil amendments and preparing soil for planting.

When to PlantZinnias

• It’s recommended that you grow zinnia from seed right in the garden bed, as they do not like to be transplanted. From seed, they will grow very quickly in the right conditions.
  • Note: Zinnias can be started from seed indoors if you prefer—just transplant them while they’re young and do socarefully.
• Zinnias are sensitive to frost, so do not seed until the last frost has passed in your area. See your local frost dates.
• Zinnias will grow in aminimum daytime temperature of about 60°F (16°C), though a range of74–84°F (23–28°C) ispreferred.
• Sow a round of seeds every week or so for several weeksto extend the floweringperiod.

How to PlantZinnias

• Space plants 4 to 24 inches apart, depending on variety.(Many common varieties are planted6 inches apartwithin the row and 2 feet in between rows.) See the back of the seed packetfor variety-specificadvice.
• Sow zinnia seeds only about1/4-inchdeep.
• Most zinnia varieties grow tall and need staking to prevent their heavy stems from laying along the ground. A few weeks after planting, stake close to the plant stem. Take care not to injureroots.
• Gardeners who grow many zinnias (especially for cutting) stretch pea netting over young plants between stakes and bamboo canes; the zinnia heads are then supported gently by the almost-invisiblenetting.

• You’ll see zinnia seedlings in only 4 to 7 days for most varieties, though it will be anywhere from several weeks to a couple months before blooms appear (depending on planting site andclimate).
• When seedlings reachthree inches tall, thin them so that they’re 6 to 18 inches apart to maximize air circulation. This reduces the chance of powdery mildewdeveloping.
• Maintain moderate soil moisture and fertilize lightly to maximize growth andblooms.
• After the zinnias flower, cut off the old flowers (a process called “deadheading”)to encourage more flowers toform.
• Zinnias are annuals andwill die with the first hardfrost of fall. However, if you want them to reseed, let the last flowers of the season mature fully and scatter theirseeds.

• Get a full-size flower on a compact plant with cultivars of the Dreamland Series.Dwarf and compact, these zinnias have fully double flowerheads, up to 4 inches across in a wide color range; stems are 8–12 inchestall.
• The Thumbelina Seriescultivars aredwarf and spreading, with single or semi-double, weather-resistant flowerheads in many colors. Their petals are 1-1/4 inch across and stems grow up to 6 incheslong.
• The State Fair Seriesare one of the biggest and tallest of them all, with large, double flowerheads that are 3 inches across.Stems grow to 30 inchestall.

• Zinnias generally take 60 to 70 days from seed to flower (though it depends on conditions and variety). They work great in a flower bouquet!

Saving ZinniaSeeds

To save zinnia seeds for replanting, simply collect a few blossoms that are at least halfway brown and let them dry in a paper bag until the seedsshatter.

• Find the dark, pointed seeds at the bases of outer petals, with more along the center of theflower.
• Dry on a paper towel until hard and almostcrisp.
• Store in a paper bag in a dark, dry location until you plant again in thespring.

Catherine Boeckmann