Fundamental Facts
HARDINESS: Zones 4 to 9
PREFERRED SOIL pH: Slightly alkaline to neutral soil
PREFERRED SOIL TYPE: Well-drained loam
PREFERRED LIGHT: Sun to filtered shade
ATTRIBUTES: Statuesque plants with orange or yellow daisy-shaped flowers; for beds, hedges, cutting
Midsummer to frost
SEASON OF INTEREST
FAVORITES: 'Fiesta Del Sol' for orange flowers, short height; 'Goldfinger', 'Torch' for orange flowers, tall height; 'Aztec Sun' for apricot flowers
QUIRKS: Tall varieties need staking
GOOD NEIGHBORS: Ornamental grass, Joe Pye weed, Russian sage, shrub roses
WHERE IT GROWS BEST: Warm summers, average soil, sun
POTENTIAL PROBLEMS: Japanese beetles
CRITTER RESISTANCE: Good
SOURCE: Seeds
DIMENSIONS: 28 in-6 ft (71.1 cm-1.8 m) tall, 3 ft (1 m) wide
Tithonia in the Landscape
If you want to make a bold statement in the garden, tithonia, or Mexican sunflower, is the plant for the job. The 3 in (7.6 cm) diameter, scarlet-orange or yellow blossoms have brazen appeal, and at 4-6 ft (1.2-1.8 m) tall, with large leaves, most tithonias traditionally reside in big spaces. In a small yard, the 6 ft (1.6 m) tall, vibrant orange-flowered 'Torch' may appear too big for its britches and "muscle out" its bedfellows. But the relatively tame, 4 ft (1.2 m) versions, such as the golden apricot-flowered 'Aztec Sun' and deep orange 'Goldfinger', can be grown in the company of midsized plants. The even newer 'Fiesta Del Sol', which reaches a demure 28-30 in (71.1-76.2 cm) in height, can star as a solo act in a pot.
Wherever you plant them, tithonias put a spark into the scene in mid to late summer. Related to both sunflowers and zinnias, tithonias have a dense, bushy habit, with deep green, heart-shaped leaves. Several planted side by side can form a nearly instant hedge for the growing season, and the flowers combine well with ornamental grasses and Russian sage. The riveting, sometimes shockingly bright blossoms make good cut flowers. To maximize vase life, seal the tips of their hollow stems by plunging them into boiling water after cutting, or singe the cut ends with a flame before placing the stems into a vase of water.
Care-Free Pizzazz
Adapted to dry regions with poor soil, tithonias are plants that don't require fussing. In fact, if the soil is too fertile, they will grow leaves at the expense of flowers. As their common name implies, Mexican sunflowers are sun worshipers. In keeping with their tough-as-nails personality, they tolerate drought bravely. However, it's a wise idea to irrigate as needed to provide 1 in (2.5 cm) of water weekly during summer dry spells.
There's one problem inherent in the fact that they are tall and leafy. Tithonias can be toppled in brisk winds. To prevent disaster before it strikes, stake the plant when it nears its full height.
Increasing the Bounty
Tithonias are easy to start from seed and the seedlings sprout and grow rapidly. To get a head start on the season, sow seeds indoors 6 weeks before frost-free weather on moistened commercial seed-starting soil, and lightly press them into the soil.
Keep the soil moist and set pots in a well-lighted place, providing them with warm room temperatures to quicken germination. To keep the roots from becoming crowded, transplant seedlings into 2 in (5.1 cm) pots as soon as the first true leaves develop, and grow on in a sunny place at 60°F (16°C). After the danger of frost has passed, you can transplant seedlings into the garden, or sow seeds directly into sunny, well-drained beds, leaving at least 1 ft (0.3 m) between the seeds.
Tithonias are not prone to diseases or insect infestations, although leaf-chewing Japanese beetles occasionally become a problem in the East. Hand-pick and dispose of beetles in the morning, or apply commercial milky spore product according to package directions to the soil in early spring to kill the larval stage, called grubs.
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