Zinnia Giants of California

Zinnia elegans 'Giants of California' Giant Cactus Zinnia 'Giants of California'

The heirloom cottage Zinnia — huge fully-double dahlia-like flowers in the full bold cottage palette (scarlet, crimson, pink, orange, yellow, white and bicolour) on tall sturdy 90–100cm stems. Zinnia 'Giants of California' is the cottage cutting garden's most flamboyant late-summer-into-autumn performer, producing substantial cut flowers with 10–14 day vase life through July to first frost.

This is the heirloom giant-flowered Zinnia that has been a cottage cutting garden favourite for generations. 'Giants of California' produces huge fully-double flowers up to 10–12cm across — significantly larger than standard Zinnias — in the full bold cottage palette of scarlet, crimson, pink, orange, yellow, white and various bicolours. The flowers sit atop tall sturdy 90–100cm stems built for cutting, with the substantial visual weight that suits dramatic cottage arrangements and the exceptional 10–14 day vase life that distinguishes Zinnias from softer-stemmed annuals. Half-hardy annual (H2). RHS Plants for Pollinators — the huge flat-topped blooms act as stable landing pads allowing butterflies to feed easily in the heat of summer afternoons.

The "Heat-Worshipper" Rule: Zinnias absolutely detest cold and wet conditions. They will "sulk" — turning yellow and refusing to grow — if planted out too early into chilly UK soil. Success depends on waiting for genuine warmth of June before transplanting. Patience is the single most important Zinnia cultivation rule.

A note on growing

Zinnias grow rapidly once weather warms, but require careful handling during establishment. Best practice: sow into module trays or individual pots from mid-April to mid-May to minimise root disturbance (Zinnias resent transplanting). At 18–22°C, germination 7–14 days. Pot on as seedlings develop.

Plant out in JUNE only — wait for genuine warmth, not just the date. In full sun in well-drained moderately fertile soil. Pinch out the central growing tip when plants are 15cm tall to encourage branching and more flower heads.

Critical watering rule: always water at the base of the plant, never overhead. Wet foliage encourages powdery mildew, which Zinnias are particularly susceptible to in humid UK weather. Feed every two weeks with a liquid tomato fertiliser once they start to bloom for sustained flowering through to October.

Where it shines

In the cottage cutting garden as the dramatic statement flower — 'Giants of California' produces blooms substantial enough to be the focal point of any arrangement. In late-summer cottage borders for warm-toned colour. In modern florist-quality cutting where the substantial bloom size suits high-impact arrangements. In wildlife gardens for the butterfly landing-platform value.

Plant alongside

For textural cottage drama, pair 'Giants of California' with Ageratum 'Timeless Mix' — the bold waxy petals of the Zinnia contrast beautifully with the soft fuzzy "powder puffs" of Ageratum, creating a sophisticated multi-dimensional border. For the tropical clash: combine with Amaranthus 'Love-Lies-Bleeding' — the tall upright Zinnia heads paired with the cascading rope-like tassels of Amaranthus create a high-energy exotic look perfect for late summer. With Tithonia 'Goldfinger' for matching heat-loving Mexican origin and bold late-summer drama.