Whitemouth dayflower.

At a glance

Care level

Easy

Plant type

Perennial herb

Light

Partial shade to full sun

Indoor light

Bright indirect

Water

Every 3 to 7 days

Mature size

1 to 2 feet

Growth rate

Medium

Hardiness

USDA 6 to 10

Bloom time

Late spring to early autumn

Care

Let the top of the soil dry out between waterings to mimic its natural habitat of dry, sandy soils. Watch for yellowing leaves which often indicate the soil is staying too wet. It is a hardy plant that adapts well to most garden conditions.

Watering

Water when the top inch of soil feels dry to the touch.

Feeding

Use a balanced liquid fertilizer during the active growing season.

Pruning

Trim back leggy stems to encourage a bushier growth habit.

Repotting

Move to a slightly larger container once the roots fill the current pot.

Soil

Well draining sandy or loamy soil

Soil pH

6.0 to 7.5

Temperature

-10 to 35°C

Humidity

40 to 70%

Drought tolerance

Moderate

Lifespan

Perennial, typically 3 to 5 years.

Deer and rabbits

Moderate

Safety

People

This plant is generally considered non-toxic, but ingestion is not recommended.

Pets

This plant is generally considered non toxic to cats and dogs.

Children

The plant is not known to be dangerous to children, but it is best to discourage them from eating garden plants.

Contact allergens

Contact with the sap may cause mild skin irritation in sensitive individuals.

Airborne allergens

There are no significant reports of respiratory allergies associated with this plant.

Edibility

While some Commelina species are eaten, this plant is not considered a standard food crop and should be avoided.

How to identify it

• Bright blue three petaled flowers
• Lance shaped alternate leaves
• Upright, clump-forming stems from thickened roots
• White lower petal is inconspicuous

Height

0.2 to 0.6m

Spread

0.3 to 0.9m

Leaves

green, deciduous

Flowers

blue, 1 to 3cm

Problems to watch for

• Aphids · Small insects that may cluster on new growth and flower buds.

Growing it

Propagation

division, seed

When to plant

spring, autumn

Overwintering

The foliage will die back after the first frost. You can trim the dead stems to the ground in late autumn or early spring.

In containers

It grows well in containers, provided the pot has good drainage and is at least 20 cm wide.

Plant in groups to create a lush, meadow-like effect that supports local pollinators.

Grows well with

• Purple Coneflower · They share similar light and moisture requirements.
• Little Bluestem · This grass provides a nice textural contrast to the broad leaves.

Similar species

• Common Dayflower · It is a related species that is often considered more invasive.

Science

Family

Commelinaceae

Genus

Commelina

Order

Commelinales

Class

Liliopsida

Native range

Widespread across the Americas.

Conservation

It is widespread and not of conservation concern.

It thrives in open woods and sandy soils, often colonizing disturbed areas.

Value to wildlife

nectar source

Pollinators

bees, butterflies

Uses

native plant gardens, pollinator borders, ground cover

Taxonomy resolved against GBIF.

Questions people ask

Does it need full sun?

It prefers full sun to partial shade.

Is it invasive?

It can spread readily in ideal conditions but is native to much of North America.

Where the name comes from

The genus honors the Commelijn brothers, while the species name erecta refers to its upright growth habit.

Good to know

• The genus is named after the Commelijn brothers, Dutch botanists.
• The flowers have two large blue petals and one smaller, inconspicuous white petal.
• It is often called widow's tears because the flowers disappear so quickly.