Ornamental · Asteraceae
Zinnia
Zinnia elegans
Give it full sun and dry leaves, and this zinnia won't stop blooming until frost.
Full sun
Every 5–7 days
68–86°F · 20–30°C
60–70 days
Overview
Looking for a beginner flower that won't let you down? Zinnias are it, and they give back way more than they ask. They're part of the daisy clan and came from Mexico, where they bloomed in the wild ages before anyone planted them on purpose. They're a warm-season annual, so one little packet of seed keeps things going from spring all the way to that first hard frost.
There's a zinnia for pretty much any spot. The tiny ones stay around 6 inches and look great up front, while the tall cutting types shoot up to 4 feet and keep a vase full for weeks. Bees and butterflies love the open blooms, and here's the fun bit: the more you cut, the more it flowers.
Zinnias really only ask for two things. They want full sun and dry leaves, since their weak spot is the mildew and leaf spots that creep in on crowded, wet foliage. So give them a little breathing room, water down at the roots, and most of that hassle just doesn't happen.
Care
The short version: full sun, well-drained soil, and water at the base, about an inch a week. Leave some space so air can get through, snip the dead heads off often, and they'll bloom from summer until frost.
Light
Zinnias want full sun, so give them at least 6 hours of direct light a day, and more is even better. All that sun keeps them stocky and blooming, plus it dries the leaves fast, which is your best trick against mildew.
Water
Water at the base in the morning and try not to splash the leaves, since wet foliage is basically an invitation for disease. Give about an inch a week and let the top half of the soil dry out in between, then ease off once they're settled, because zinnias handle heat and dry spells just fine.
Soil
Plant them in well-drained loam and they're happy. They're not picky about pH and take anything from 5.5 to 7.5, but they hate soggy roots, so good drainage beats rich soil every time.
Temperature
Zinnias are warmth lovers, happiest between 68°F and 86°F (20°C to 30°C). Cold soil makes them sulk and frost finishes them off, so that's why you wait for real warmth before sowing.
Humidity
These are low-humidity plants, most comfy around 40% to 60%. Muggy, damp air just feeds mildew and leaf spot, so honestly, airflow matters way more than how moist the air is.
Feeding
Feed them monthly through spring and summer with a balanced fertilizer, and that's plenty. Zinnias are light eaters and bloom fine in average soil, so there's no need to go overboard.
Pruning
Deadhead the spent blooms and cut flowers often, and you'll get fresh branches and more color. Pinch the young plants early too, and they'll grow bushier with loads more buds.
Repotting
not_applicable
Size & spacing
Depending on the type, plants hit 1 to 4 feet (30 to 120 cm) tall. Space them 6 to 12 inches (15 to 30 cm) apart so air can move through and the leaves stay dry.
When to plant
Zinnias love warmth and really can't handle frost, so there's no rushing. Start seed indoors 4 to 6 weeks before your last frost, or just sow it outside once the ground's warmed up, and either way you'll get flowers from midsummer right up to frost.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 4 to 6 weeks before the last frost
- Plant: After the last frost once soil warms to about 70°F (21°C)
- Harvest: Summer to first frost
Troubleshooting
Almost everything that goes wrong with a zinnia shows up on the leaves, and it usually starts with wet foliage. Catch those first spots early, though, and you can stop a little patch before it spreads. Find your match below and jump in while it still helps.
Reddish-brown spots with grayish centers spreading across the leaves
This one's Alternaria leaf spot, the nastiest disease zinnias run into, and it can ring a stem and wilt the whole plant once it gets going. It hitches a ride on splashing water and old debris when the weather's warm and wet. Pull and toss the sick plants, water at the base, move the bed so zinnias skip the same spot for two years, and give the seed a hot-water soak before sowing.
Fix:
- Remove and destroy infected plants and debris
- Water at the base of plants and avoid overhead irrigation
- Rotate planting sites and avoid replanting zinnias in the same spot for 2 years
- Treat seed with hot water (125°F for 30 minutes) before sowing
White powdery stuff dusting the tops of the leaves
That's powdery mildew, a fungus that shows up when plants are crammed together in still, humid air. It'll wipe off at first, but as late summer rolls on it yellows the leaves and leaves them looking ragged. Open things up so air can move, keep the water at the base, and grab resistant series like Profusion or Zahara next time.
Fix:
- Improve spacing and air circulation
- Water at the base in the morning and avoid wetting foliage
- Remove and discard heavily infected leaves and end-of-season debris
- Choose resistant types such as the Profusion or Zahara series
Angular purple spots boxed in by the leaf veins
Those sharp-edged spots are bacterial leaf spot, and the straight sides happen because the veins fence the bacteria in. It travels on splashing water and hangs around on dirty seed and old debris, so it flares up after rain or overhead watering. Keep the leaves dry, pull off the spotted ones, space plants so they dry quick, and start with clean seed and resistant types.
Fix:
- Avoid overhead watering and handling wet plants
- Remove infected leaves and plant debris
- Improve spacing so foliage dries quickly
- Start with disease-free seed and resistant cultivars
Toxicity
Got pets? Good news, because zinnias aren't toxic at all. The ASPCA lists them as safe for cats, dogs, and horses, and people can even eat the petals. If a pet chews a leaf, the worst that'll happen is a quick upset tummy, nothing serious.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Totally fine around cats. If one chews a leaf out of curiosity, it might get a quick tummy ache, and that's about it.
Dogs None
No real worry with dogs. A dog that nibbles the leaves might get a bit loose in the gut, but that clears up on its own.
Horses Safe
They're listed as non-toxic, so a horse grazing near zinnias is no problem at all.
Rabbits Safe
Rabbits can munch the leaves and flowers safely, though a big pile of any new green might loosen the stool a little.
Livestock Safe
Cattle, goats, and sheep won't get poisoned by zinnias, so there's no grazing hazard to worry about.
Birds Safe
Birds are perfectly safe around the plant, and they'll happily peck at the ripe seed heads come fall.
People Safe
The petals are edible and pop up as a garnish on salads and cakes. Nothing on the plant is toxic to people.
No special handling required; ingestion of plant material may still cause mild stomach upset in some pets.
Varieties
Zinnias run from 6-inch little dwarfs to towering cut-flower giants, so there's plenty to pick from. Here are the ones worth knowing by name.
Benary's Giant
A tall cutting type that gets to 36 to 42 inches, with big, fully double, dahlia-like blooms that hold up great in a vase.
State Fair
A tough tetraploid that climbs to 3 to 4 feet and carries really large flowers.
Profusion
An interspecific Zinnia x hybrida series that just shrugs off both leaf spot and powdery mildew.
Zahara
A Zinnia marylandica series bred to stand up strong to leaf spot and mildew.
Thumbelina
A little dwarf, only about 6 inches tall, that's perfect for edging and containers.
Queen Lime
A 30 to 40 inch series people love for its odd lime-green and soft antique color mixes.
How to propagate
Zinnias are about as easy as it gets to grow from scratch, and honestly, seed is the way to go.
SeedEasy
Spring
Zinnias sprout fast and easy from seed, which makes them a joy to start. Sow straight into the ground after the last frost once the soil warms to about 70°F (21°C), or get a head start indoors 4 to 6 weeks before that. Pop the seed in about a quarter inch deep, keep it at 65°F to 70°F (18°C to 21°C), and you'll see sprouts in roughly 5 to 7 days. Thin or space the seedlings so air moves freely, then pinch the young plants to get more branching and a fuller round of bloom.
Myths
Watering zinnias from overhead keeps them cool and healthy.
A spray from up top leaves the leaves soaking, and wet leaves are exactly what powdery mildew, Alternaria, and bacterial leaf spot are after. Just water at the base and let the foliage dry off.
All zinnias mildew the same, so the variety doesn't really matter.
Turns out the variety matters a lot. Resistant series like Profusion and Zahara shrug off leaf spot and mildew way better than the old big-flowered types, which usually look pretty rough by late summer.