When to plant zinnias by city
Sow zinnias outdoors 1–4 weeks after your last frost, once the soil is at least 60°F. Here is what that means for 2027 in cities across the US, using each city’s average frost dates and the date its normal daily temperature reaches 60°F, so cool-spring places like Seattle wait for real warmth (NOAA 1991–2020). Pick the city with the climate most like yours, or enter your ZIP code above.
| City | Last frost | Sow outdoors |
|---|---|---|
| Seattle, WA (9a) | Mar 13 | May 29 – Jun 19 |
| Portland, OR (8b) | Feb 25 | May 24 – Jun 14 |
| Sacramento, CA (9b) | Jan 12 | Apr 5–26 |
| Phoenix, AZ (10a) | Jan 5 | Feb 15 – Mar 8 |
| Salt Lake City, UT (7b) | Mar 31 | May 8–29 |
| Denver, CO (6a) | Apr 30 | May 17 – Jun 7 |
| Dallas, TX (8b) | Mar 2 | Mar 17 – Apr 7 |
| Minneapolis, MN (5a) | Apr 23 | May 19 – Jun 9 |
| Kansas City, MO (6b) | Apr 4 | Apr 25 – May 16 |
| Chicago, IL (6b) | Apr 10 | May 22 – Jun 12 |
| Columbus, OH (6b) | Apr 20 | May 7–28 |
| Nashville, TN (7b) | Apr 1 | Apr 16 – May 7 |
| Atlanta, GA (8a) | Mar 24 | Apr 8–29 |
| Raleigh, NC (8a) | Mar 28 | Apr 13 – May 4 |
| Philadelphia, PA (7b) | Mar 30 | Apr 27 – May 18 |
| Boston, MA (7a) | Apr 4 | May 20 – Jun 10 |
In frost-free parts of Florida, southern California and the Gulf Coast, timing is about heat instead: plant zinnias in late winter or early spring and again in late summer.
Don’t go by the calendar alone. Zinnias planted into cold soil sit still for weeks; wait until the soil 4 inches down is at least 60°F and nights stay above 50°F.
Zinnia spacing
In a square-foot bed, plant 1 per square foot. In traditional rows, space plants about 12 inches apart with 18 inches between rows.
A cut flower that pulls pollinators into the vegetable bed.
How to grow zinnias
Zinnias are among the easiest flowers to grow from seed and among the best for cutting: the more you pick, the more they bloom. They thrive in summer heat, flower until frost, and bring butterflies and other pollinators into the vegetable garden.
Sun and soil
Full sun all day; shade makes leaf diseases much worse. Well-drained soil with plenty of organic matter. Zinnias tolerate a wide pH range and need good air circulation.
Planting
- Direct-sow ¼ inch deep, 1–4 weeks after the last frost, once soil is at least 60°F. Seeds sprout in under a week in warm soil.
- Thin to 12 inches apart in rows 18 inches apart.
- Sow a second batch 3–4 weeks later for fresh plants in late summer.
Care
- Water at the base, preferably in the morning; wet foliage in the evening invites leaf spot and mildew.
- Pinch young plants just above the third set of leaves to get more branches and longer stems.
- Keep cutting flowers or deadheading to keep plants blooming.
- Give plants room; crowding traps humidity around the leaves.
Harvest
Cut flowers in the morning when they are fully open. Hold the stem a few inches below the bloom and wiggle it: if it stays upright, the flower is ready; if it flops, wait a day or two. Cut deep, just above a pair of leaves, to encourage long new stems.
Common problems
- Powdery mildew: Gray-white coating on leaves by late summer. Grow resistant types such as the Profusion series, water in the morning at the base, and give plants space.
- Leaf spots: Reddish-brown spots that spread in wet weather. Avoid overhead watering, remove infected leaves, and clear debris at season end.
- Japanese beetles: Hand-pick into soapy water in the morning, when they are slow.
- Aster yellows: Deformed, greenish flowers. Remove affected plants; there is no cure.
Varieties to try
- 'Benary's Giant' — tall, long-stemmed cut flower
- 'State Fair' — large-flowered tall heirloom
- 'Profusion' series — compact, disease resistant, no deadheading needed
- 'Thumbelina' — dwarf, for edges and containers
Crop rotation
Zinnias belong to the daisy family (Asteraceae). Few shared soil problems; fits anywhere in a rotation. Relatives that count as the same family for rotation: lettuce, red leaf lettuce, sunflower, marigold, calendula.
Frequently asked questions
When should I plant zinnias?
What grows well with zinnias?
How far apart should I plant zinnias?
How long do zinnias take to grow?
Can zinnias handle frost?
Sources
- Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020.
- Hardiness zones: 2023 USDA Plant Hardiness Zone Map, USDA-ARS and PRISM Climate Group, Oregon State University.
- Planting windows and spacing: Vegetable Planting Guide (GardenNotes #720), Colorado State University Extension, and other land-grant extension guides.
- Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023
- Zinnia elegans (zinnia) — NC State Extension Plant Toolbox
- Zinnia — Clemson Cooperative Extension (HGIC)