Rocky Mountain zinnia

Sun

Full sun; flowering and growth become sparse in shade.

Water

Low once established. Water new plants regularly while they root, then let the soil dry between deep waterings.

Soil

Lean, sharply drained sandy, gravelly or rocky soil; tolerates alkaline conditions. Avoid wet clay and heavily enriched beds.

Height

0.5-1 ft (0.15-0.3 m)

Spread

1-2 ft (0.3-0.6 m), eventually wider through underground stems

Flowers

Summer into autumn, with golden-yellow, daisy-like flowers; flowering often increases after summer rain.

Foliage

Small, opposite, narrow, rough-textured green to grey-green leaves on low, branching stems; top growth dies back in cold winters.

Growth

Slow to moderate at first; established plants gradually form spreading colonies.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Heat tolerant
• Wildlife
• 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

   0.7 ft (0.22 m)

   full size

About 4 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

Slow

• Plant in full sun on a slope, raised bed or other freely draining site.
• Water during establishment, then irrigate only during prolonged dry spells.
• Avoid routine feeding; rich soil encourages loose growth rather than a compact mat.
• Use a light gravel mulch, keeping it clear of the crown; avoid thick, moisture-retentive organic mulch.
• Divide or remove rooted sections in spring if the colony outgrows its space.

Pruning. In early spring, trim dead stems back to healthy growth or near ground level before new shoots develop. Deadheading is optional; remove spent flowers if you want a tidier appearance.

Early spring

Cut away dead stems and check that winter moisture has not softened the crown.

Spring

Plant or divide once the soil is workable and no longer waterlogged.

Late spring

Sow seed in a warm, bright position, covering lightly and keeping the seed mix just moist.

Summer

Water new plants as needed; let established patches dry between occasional deep waterings.

Late summer

Remove unwanted spreading shoots or leave the colony to fill open gravel.

Autumn

Clear fallen leaves from the crown and keep drainage channels open before winter rain.

• Use as a low flowering carpet between widely spaced plants in a dry gravel garden.
• Plant along sunny path edges where its spreading stems can soften the boundary.
• Combine with blue grama and compact penstemons for a low, open prairie planting.
• Grow on sunny rock-garden slopes or raised beds where winter water drains away quickly.

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

Plant it with: Blue grama, Prairie dropseed, Husker's beardtongue, Purple prairie clover, Sulphur buckwheat and Plains prickly pear.

Wildlife: Flowers provide nectar and pollen for bees and other flower-visiting insects. Its low colonies also offer shelter for small ground-dwelling invertebrates.

• Crown or root rot in wet soil: improve drainage, reduce watering and move surviving healthy sections to a raised, gritty bed.
• Weak growth and poor flowering in shade: move the plant to an open position with full sun.
• Failure to establish during drought: water newly planted specimens deeply while roots develop, even though mature plants tolerate dry soil.
• Sparse growth during cool, wet weather: avoid extra feeding or watering; provide a warm, sunny site with good air circulation.

Not known to be toxic to cats, dogs, horses or people. Species-specific toxicity information is limited, and no particular part is established as poisonous; it is an ornamental plant, not a food crop.

• Desert zinnia (Zinnia acerosa)

  Usually has white to cream ray flowers, much narrower leaves and a more woody, twiggy habit; Rocky Mountain zinnia has golden-yellow rays and spreads into low colonies.

• Creeping zinnia (Sanvitalia procumbens)

  A frost-tender annual with trailing stems, broader leaves and yellow flowers usually showing a conspicuous dark central disc; it does not form the hardy underground spreading growth of Rocky Mountain zinnia.

Zinnia honours the German botanist Johann Gottfried Zinn, and grandiflora means large-flowered.

Propagation. Sow seed in spring in a freely draining seed mix, covering lightly and keeping it just moist until germination. Divide established colonies in spring, taking sections with roots and shoots, and water them while they establish.

Accepted botanical name

Zinnia grandiflora

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.