Hartweg's sundrops

Sun

Full sun; tolerates light afternoon shade in very hot climates.

Water

Low once established; water regularly during establishment, then during prolonged dry spells.

Soil

Well-drained sandy, gravelly or rocky soil; tolerates lean and alkaline soils but dislikes wet, heavy ground.

Height

0.5-1.5 ft (0.15-0.45 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Yellow flowers from late spring through summer, sometimes continuing intermittently into early autumn in warm climates.

Foliage

Narrow green to grey-green leaves on branching stems; foliage may persist in mild winters.

Growth

Moderate

Care needed

Low

• Pollinators
• Drought tolerant
• Heat tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Moderate

• Plant in full sun with the crown at soil level and sharp drainage around the roots.
• Water deeply during the first growing season, allowing the soil to dry between waterings.
• Once established, water during extended drought rather than keeping the soil constantly moist.
• Avoid routine feeding; rich soil and excess nitrogen encourage loose growth and fewer flowers.
• Use a light gravel mulch rather than moisture-holding mulch against the crown.

Pruning. In early spring, remove dead stems and lightly shorten surviving growth to encourage a compact shape, retaining live leafy shoots. After the main flowering flush, trim straggly stems lightly if needed.

Early spring

Remove winter-damaged growth and check that water drains freely around the crown.

Spring

Plant after the soil begins to warm; water new plants thoroughly.

Late spring

Check establishing plants for dry soil and keep surrounding weeds down.

Summer

Water established plants only during prolonged dry spells; lightly trim sprawling stems after the main flush.

Autumn

Collect ripe seed if wanted, and remove fallen leaves that trap moisture around the crown.

Winter

Keep containers out of standing water and protect plants from persistent winter wet.

• Plant along sunny border edges for a low band of yellow flowers.
• Combine with small ornamental grasses and upright salvias for contrasting shapes.
• Use among rocks and gravel where its loose mound softens hard edges.
• Group on a sunny, well-drained bank with other drought-tolerant perennials.

Garden styles it suits: Dry gravel garden, Desert / xeriscape, Southwestern, Pollinator garden, Low-maintenance and Cottage garden.

Plant it with: Blue grama, Prairie dropseed, Purple coneflower, Blanket flower, Autumn sage and Catmint.

Wildlife: Flowers provide pollen and nectar for visiting bees and other insects.

• Crown or root rot in wet soil: improve drainage or move the plant to a raised, gravelly position; avoid frequent watering.
• Leggy growth and poor flowering: provide more sun and stop nitrogen-rich feeding.
• Winter losses in poorly drained sites: keep the crown free of wet organic mulch and choose a sheltered, freely draining position.

Not known to be toxic to people, cats, dogs or horses, but species-specific toxicity information is limited. No particular part is established as poisonous; it is not a food plant.

• Missouri evening primrose (Oenothera macrocarpa)

  Usually has larger yellow flowers, broader leaves and a more trailing habit; its seed capsules have conspicuous wings.

• Narrowleaf sundrops (Oenothera fruticosa)

  Generally grows more upright, with broader leaves and flowers grouped toward the tops of the stems, rather than forming a finely branched, narrow-leaved mound.

The species name hartwegii honours Karl Theodor Hartweg, a nineteenth-century German plant collector.

Propagation. Sow seed in spring, covering it lightly, or take softwood cuttings from non-flowering shoots in late spring or early summer. Seed-grown plants can vary in habit and flowering.

Accepted botanical name

Oenothera hartwegii

In the US and Canada

Native in the lower 48 states.

Native range

Arizona, Colorado, Kansas, Mexico Northeast, Mexico Northwest, Mexico Southwest, New Mexico, Oklahoma and Texas.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.