Calibrachoa (million bells)

About Calibrachoa (million bells)

Calibrachoa, sold as million bells or trailing petunia, covers itself in hundreds of small bell-shaped flowers from spring to frost. It's native to South America and only came to gardens in the 1990s, but it quickly became a favorite for hanging baskets and pots. It looks like a tiny petunia but is a separate plant, grown from cuttings, and it needs acidic potting mix to avoid iron deficiency.

Grown as a summer annual almost everywhere; NC State lists zones 7-11 and Oklahoma State zone 9. Illinois notes it often keeps blooming in fall until temperatures drop into the 20s.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

• Set out plants: up to 2 weeks after the last frost

Buy plants: calibrachoa makes little or no seed and is grown from cuttings, and most named kinds are patented (NC State, UMN). Plant outdoors after frost once the soil is above 55 F (UMN). For a fuller plant, clip off the top 2 inches of the stems at planting (UMN).

Soil

Fast-draining, organic potting mix that stays moist but never soggy; it does best in containers and baskets rather than garden beds (UMN, NC State).

Use a fast-draining potting mix rich in organic matter, with a pH of about 5.0-6.5; above that, growth stalls (UMN). Kentucky stresses that it needs acidic potting soil.

Feeding

• Every other week from planting until fall: water-soluble fertilizer (diluted). Feed every other week at the label rate (UMN; NC State says every few weeks); Kentucky notes regular feeding matters for this plant.

High pH in the pot leads to iron deficiency and yellow leaves (Kentucky, UMN), and constantly soggy mix causes root rot; water daily in hot weather but use pots with drainage holes and let the mix dry slightly between waterings (UMN, NC State).

Harvest

Blooms nonstop from late spring until frost (May to October in Illinois). It's self-cleaning, so there's no need to deadhead; pinch back long stems now and then to keep plants compact (UMN, NC State, Illinois).

Varieties (21)

Pests to watch for

Aphids, Twospotted spider mite, Thrips

Diseases and problems

Iron chlorosis, Root rot, Phytophthora root and stem rot

In the kitchen

Safety: We found no toxicity listing for calibrachoa from NC State or the ASPCA, and it isn't on extension edible-flower lists, so don't eat it.

Pets: Not listed by the ASPCA (no entry on its toxic plant lists for dogs or cats).