211 · Cosmos Rubenza

About this plant

The darkest cosmos you can grow from seed — blooms open a rich velvety burgundy over burnished gold centers, then age to a soft antique rose, so one plant carries several shades at once. At a compact 24 inches it stands up without staking and is superb for cutting. A summer flower for us: plant it out as the soil warms and it will run from June to frost. Note: Frost tender — do not plant out until after last frost and soil is warm. Will not be in bloom at the sale; this is a summer flower, expect first blooms around June.

Planting it at home

When to plant out

Wait until after our last frost (about mid-February) and warm soil — usually March. Until then keep the pot in a sunny, sheltered spot and bring it in on cold nights.

Where

Full sun, mid-to-back of a border, or a dedicated cutting row. Lean soil.

Spacing

10 in (Baker Creek)

Size

24 in tall — compact for a cosmos (Baker Creek)

Support

Bush / compact — little or no support

Care

Sun

6–8 hours full sun

Water

Moderate; drought tolerant once established. Poor to moderate soil gives the best flowering

Feed

A light flower fertilizer every 3–4 weeks while blooming (general guide).

Pick / harvest

Cut when the buds are just cracking open but not yet fully unfurled — cosmos continues opening in the vase. Morning harvest. Vase life is short (roughly 5–6 days), so cut often; it is cut-and-come-again.

Deadhead

Cut off spent flowers to keep new blooms coming.

Good to know

Caution

Edibility unsure. Do not eat.

Grown from

Seed — sown by FHCG volunteers

Life cycle

Annual

Heirloom or hybrid

Heirloom — saved seeds grow true

Pollinators

Honeybees, native/solitary bees and butterflies; the open single form with an exposed gold disc gives easy nectar and pollen access

Days to bloom

60–90 days to maturity (Baker Creek)

Heat (our summer)

Good — heat and drought tolerant once established; thrives through low-desert summer where calendula fails

Cold

No — frost tender. Do not plant out until frost danger has passed

Color

Opens deep luxuriant burgundy/ruby red, matures to a faded antique rose, with burnished gold centers. Single blooms. This depth of red is genuinely unusual in cosmos.

Edible

Unsure. Some sources say the petals are edible. Do not eat.