Ornamental · Asteraceae
Zinnia
Zinnia elegans
Give a zinnia full sun and dry leaves, and it rewards you with bloom after bloom from summer to frost.
Full sun
Every 5–7 days
68–86°F · 20–30°C
60–70 days
Overview
If this is your very first flower, the zinnia is a forgiving place to begin, since it shrugs off the small mistakes that trip up new gardeners. A member of the daisy family, it came first from Mexico, where it flowered in the wild long before any garden claimed it. Being a warm-season annual, one modest packet of seed keeps color coming from the last spring chill until frost closes the season.
The sizes cover a lot of ground. The little ones hold at about 6 inches and look sweet along a path edge, while the tall cutting kinds rise near 4 feet and keep a vase full for weeks on end. Bees and butterflies drift over the open blooms through the day, and here is the happy part: the more you snip, the more it flowers.
There are really only two things a zinnia asks of you. It wants full sun and dry leaves, because its one real weakness is the mildew and leaf spotting that settle onto crowded, damp foliage. Give each plant a little elbow room and water down at the roots, and most of that trouble simply never shows up.
Care
The short version: give it full sun and well-drained soil, and water low at the base, roughly an inch each week. Leave room between plants so air can pass, deadhead when you remember, and you are rewarded with bloom from summer right up to frost.
Light
Zinnias want full sun, meaning at least 6 hours of direct light each day and gladly more. That sunshine keeps the plants sturdy and the flowers arriving, and it dries the leaves quickly, which is your best guard against mildew.
Water
Water gently at the base in the morning and try to keep the leaves dry, since damp foliage is what opens the door to disease. Offer about an inch a week, letting the top half of the soil dry between waterings, and ease off once the plants are settled, as zinnias take heat and dry spells in stride.
Soil
Give them well-drained loam and they settle right in. Zinnias take any pH from 5.5 to 7.5 without complaint, but soggy roots bother them, so drainage matters far more than rich feeding.
Temperature
Warmth is where zinnias are happiest, most content between 68°F and 86°F (20°C to 30°C). Cold soil makes them sulk and the first frost ends them, which is exactly why waiting for true warmth before sowing is worth it.
Humidity
Zinnias are low-humidity plants, easiest around 40% to 60%. Muggy, heavy air feeds mildew and leaf spot, so moving air helps them far more than any dampness ever could.
Feeding
A monthly feeding through spring and summer with a balanced fertilizer is plenty. Zinnias eat lightly and flower well in ordinary soil, so there is no need to push them.
Pruning
Deadhead the spent blooms and cut for the vase often, and the plant answers with fresh branches and more color. Pinch the young ones early as well, and they fill out bushier with many more buds.
Repotting
not_applicable
Size & spacing
Depending on the type, plants reach 1 to 4 feet (30 to 120 cm) tall. Set them 6 to 12 inches (15 to 30 cm) apart so air can slip between them and the leaves stay dry.
When to plant
Zinnias love warm soil and cannot take frost, so a little patience early on pays off. You can start seed indoors 4 to 6 weeks ahead of your last frost, or simply drop it into warm ground outside, and either way the blooms keep going from midsummer all the way to the first 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
Nearly every zinnia trouble writes itself on the leaves, and almost all of it starts with foliage that stayed wet. The good news is that catching those first marks early lets you stop a small spot before it travels through the bed. Find the match below, then step in while your effort still counts.
Rusty spots with gray middles creeping across the foliage
This is Alternaria leaf spot, the worst of the diseases a zinnia meets, and it can circle a stem and wilt an entire plant once it settles in. The fungus arrives on splashing water and old infected debris during warm, wet spells. Pull and destroy any sick plants, water low at the base, move the bed so zinnias do not return to the same soil for two years, and give the seed a hot-water soak before you sow.
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
A dusty white film across the upper leaves
That pale coating is powdery mildew, a fungus that moves in when plants crowd together in still, damp air. At first it wipes away, but as late summer drags on it yellows and frays the leaves. Open the planting up so air can move, keep your water down at the base, and next season lean on resistant series like Profusion or Zahara.
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
Purple spots hemmed in by the leaf veins
Those sharp-edged marks are bacterial leaf spot, and the straight sides appear because the veins pen the bacteria in. It travels on splashing water and lingers on dirty seed and last year's debris, so it flares after rain or overhead watering. Keep the leaves dry, clear away the spotted ones, space plants so they dry quickly, and begin with clean seed and resistant kinds.
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
Here is a lovely thing for a home full of pets: zinnias carry no toxins at all. The ASPCA lists them as safe for cats, dogs, and horses, and the petals are edible for people too. Should a curious pet chew a leaf, the worst you might see is a passing tummy upset, and nothing here can cause real harm.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Perfectly safe company. A cat that nibbles a leaf out of curiosity might feel briefly queasy, and that is all.
Dogs None
Nothing to fear here. A dog that samples the leaves may go a touch loose in the belly, which settles by itself.
Horses Safe
Marked non-toxic, so a horse grazing beside zinnias comes to no harm.
Rabbits Safe
A rabbit can taste the leaves and flowers safely, though a big helping of any new green may loosen things a little.
Livestock Safe
Cattle, goats, and sheep take no poison from zinnias, and the plants are no danger out in the pasture.
Birds Safe
Birds are quite safe around the plant, and they love to pick at the ripe seed heads once fall arrives.
People Safe
The petals are edible and often brighten salads and the tops of cakes. Nothing on the plant will harm 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 lofty cut-flower giants, so there is a size for every corner of the garden. Here are the ones worth learning by name.
Benary's Giant
A tall cutting favorite that reaches 36 to 42 inches, carrying big, fully double, dahlia-style blooms that keep their looks in a vase.
State Fair
A strong tetraploid that rises 3 to 4 feet and holds very large flowers on sturdy stems.
Profusion
An interspecific Zinnia x hybrida series that brushes off both leaf spot and powdery mildew.
Zahara
A Zinnia marylandica series raised for strong resistance to leaf spot and mildew.
Thumbelina
A little dwarf about 6 inches tall that is lovely for edging and for pots.
Queen Lime
A 30 to 40 inch series loved for its unusual lime-green and soft antique color blends.
How to propagate
Few flowers are as easy to raise from nothing as the zinnia, and seed is by a wide margin the friendliest way in.
SeedEasy
Spring
Zinnias sprout quickly and easily from seed, which is a real treat for a new gardener. Sow straight into the ground after the last frost once the soil warms to about 70°F (21°C), or get ahead by starting them indoors 4 to 6 weeks sooner. Set each seed around a quarter inch deep, keep it at 65°F to 70°F (18°C to 21°C), and you will see sprouts in about 5 to 7 days. Thin or space the seedlings so air flows freely, then pinch the young plants to bring on more branching and a fuller wave of bloom.
Myths
Watering zinnias from overhead keeps them cool and healthy.
A shower from above leaves every leaf dripping, and wet leaves are the one thing powdery mildew, Alternaria, and bacterial leaf spot are waiting for. Water down at the base instead, and let the foliage stay dry.
Every zinnia catches mildew alike, so the variety hardly matters.
The variety you choose makes a real difference. Resistant series such as Profusion and Zahara hold off leaf spot and mildew far better than the older big-flowered types, which tend to look tattered once late summer arrives.