Batten Blooms
PL. —Zinnia haageanaBotanical illustration — drop image
Zinnia haageana

Mexican Zinnia

SpringSummerFall
2a–11bHardiness zone
Peak bloom windowZone 6b · frost-offset weeks
Winter
Not in bloom
Spring
Peak bloom
Summer
Peak bloom
Fall
Peak bloom
Peak bloom
In bloom
Background

Zinnia haageana is a heat-tolerant annual from Mexico, smaller and more densely branched than common zinnia (Z. elegans). It grows to about 12–16 inches and produces bicolor and tricolor flower heads in combinations of orange, yellow, and mahogany red. The cultivar 'Aztec Orange' holds the RHS Award of Garden Merit. It handles summer heat and moderate drought better than Z. elegans, making it useful where conditions are harsh.

Grow in full sun and well-drained soil. Sow indoors 4–6 weeks before the last frost date, or direct sow after soil temperatures reach 65°F. Thin to 6–9 inches to maintain airflow and reduce foliar disease pressure. Avoid overhead irrigation. Removing spent flower heads at the next leaf node regularly extends production from midsummer into fall. It does not tolerate any frost and must not be planted out until all frost risk has passed.

Mexican zinnia is a reliable nectar source for butterflies and small bees. Its compact, low-mounding form works well in pollinator borders, container plantings, and as a front-of-bed filler alongside taller annuals or perennials.

Good companions
MarigoldCosmosBasilCalendula
Care guide
SunFull sun
WaterLow
SoilWell-drained, average
Spacing6–9 in
Height12–16 in
Zone2a – 11b
Direct sow
Seasonal tasks
spring
sowStart seeds indoors in cell trays at 1/4 inch depth. Maintain soil temperature at 70–75°F; germination takes 5–7 days.
sowTransplant indoor-started seedlings outside after last frost, hardening off for 5–7 days first.
sowDirect sow into warm soil after all frost risk has passed. Space seeds 6 inches apart and thin to 6–9 inches when seedlings reach 2 inches tall.
summer
cutRemove spent flower heads at the next leaf node down to encourage continued production and a tidy habit.
watchCheck leaves for a white powdery coating indicating powdery mildew. Improve airflow between plants and switch to drip or base watering.
watchLook for brown leaf spots with reddish-brown margins, a sign of alternaria blight. Remove affected leaves promptly and avoid wetting foliage.
fall
cutAllow a few late-season flower heads to dry fully on the plant, then cut and collect seeds. Store in a cool, dry envelope for next season.
Common problems

Powdery mildew

Symptoms

White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.

Treatment

Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.

Alternaria blight

Symptoms

Brown circular spots with yellow halos on leaves; spreads rapidly in wet weather.

Treatment

Remove affected leaves immediately. Water at the base only. A copper-based fungicide can help if caught early.

Botrytis (grey mould)

Symptoms

Grey fuzzy mould on petals and stems, worst in cool wet conditions.

Treatment

Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.

Damping Off

Symptoms

Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.

Treatment

Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.

Fungal leaf spot

Symptoms

Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.

Treatment

Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.