Frost-tender. Start indoors 4 weeks before your last frost; plant out 1 to 2 weeks after your last frost; sow outdoors up to 2 weeks after your last frost. First blooms 58 to 100 days from sowing.
Photo: “Zinnia Elegans JNTBGRI 3” by Shishirdasika, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.
Full sun6–8 hours or more
6–12 in apartRows 12–24 in
58–100 daysTo first bloom
1–1½ in a weekEven watering
Frost-tenderKilled at 32 °F
Your dates
Put in your ZIP code to see when to start, plant and harvest zinnias where you live, from your own frost dates.
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From seed to harvest
SowSeed goes inWeek 0
SproutFirst shoots showWeek 1
Thin or plant outGive each plant roomWeek 2–4
BudsFlower buds showWeek 6–9
BloomIn full flowerWeek 8–13
Keep cuttingCut often for moreWeek 8–14
How to plant and grow
Wait for warm soil
Zinnias are killed by frost. Sow outdoors after the last frost, 2 to 3 seeds per foot, covered lightly. Keep the surface moist until seedlings come up.
Or start indoors
For earlier flowers, sow 1 to 2 seeds per cell about four weeks before the last frost. Do not let plants get root bound. Harden off before planting out.
Thin for air flow
Thin to 9 to 12 inches apart after the first true leaves. Big varieties need the wider spacing. Good air flow helps prevent powdery mildew.
Pinch for stems
When plants are 8 to 12 inches tall, pinch out the top 3 to 4 inches. This forces side shoots and longer stems for cutting.
Water at the base
Water often while young, then about once a week with 1 to 1.5 inches. Water early in the day and keep leaves dry.
Cut often
Cut in the cool of the day when blooms are nearly open and the stem is stiff. Regular cutting and deadheading keep plants blooming until frost.
Common problems
Photo: “Powdery mildew 9” by Dmitry Brant, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.
Powdery mildewDisease
What you'll see: White, powdery patches on the tops of leaves and on stems. Leaves yellow and dry, and fruit may ripen poorly.
Prevent
Grow resistant varieties.
Give plants sun and space for air flow.
Remove badly infected leaves, and clear debris after harvest.
Organic options
Sulfur or potassium bicarbonate, from the first spots. Sulfur can burn some vine crops in heat, and never use it near an oil spray.
Neem oil. Look for OMRI Listed products.
Conventional options
Myclobutanil or propiconazole, if the crop is on the label.
Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.
Avoid broad insecticides; they kill mite predators and can start an outbreak.
Organic options
Hose leaf undersides hard, often.
Insecticidal soap or horticultural oil on leaf undersides, repeated as the label allows.
Release predatory mites once pest mites are present.
Conventional options
Same as organic. Broad insecticides often make mites worse.
Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.
Photo: “Aphids on Kale leaf” by Sanjay Acharya, CC BY-SA 4.0, via Wikimedia Commons (cropped). The cropped version is shared under the same licence.
AphidsPest
What you'll see: Clusters of small, soft-bodied green, black or gray insects on new shoots and under leaves. Leaves curl, and a sticky film may coat them.
Prevent
Check leaf undersides each week; a few aphids do little harm.
Pull nearby weeds, such as wild mustards, that feed aphids.
Grow flowers for lady beetles, lacewings and hover flies, and avoid broad sprays that kill them.
Organic options
Knock aphids off with a strong spray of water.
Insecticidal soap or horticultural oil on leaf undersides, repeated as the label allows.
Neem oil, or OMRI Listed pyrethrins (without piperonyl butoxide).
Conventional options
Malathion or permethrin, if the crop is on the label. These also kill the insects that eat aphids.
Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.
What you'll see: Flowers and leaves are streaked, flecked or misshapen. Tiny, slender insects hide in the blooms.
Prevent
Remove spent flowers and bag them.
Encourage lacewings and minute pirate bugs, which eat thrips.
Thrips seldom need control in a home garden.
Organic options
Insecticidal soap, neem or horticultural oil, aimed at leaf undersides and blooms.
Conventional options
Same as organic for a flower bed.
Bee caution: Don't spray open flowers. Spray in the late evening, when bees aren't flying.
Read and follow the product label: it is the law. It sets the rate, the crops it is for, and the days between spraying and picking. Products registered vary by state; for organic growing, look for products allowed under the USDA National Organic Program (OMRI Listed). We name active ingredients, not brands or rates.
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Sow
Sprout
Thin or plant out
Buds
Bloom
Keep cutting
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