Species

Iris sibiricaSiberian Iris

26 other cultivars

perennial

That Siberian Iris

Iris sibirica 'That'

The Story

Plant Bio

Iris siberica is known for its graceful, slender foliage and elegant blue flowers that bloom during early summer.

The cultivar 'That' is particularly noted for its vibrant color and its ability to thrive in wetter conditions compared to other bearded irises.

Uses & Benefits:

Iris siberica That provides vibrant blue flowers early in the season, adding color and texture to perennial beds.

Its hardy nature makes it a low-maintenance choice for borders and rock gardens.

Supports pollinators such as bees and butterflies, contributing to local biodiversity.

SpeciesIris sibiricaSiberian Iris

Essentials

At a Glance

Plant Type

Perennial

Height

36 inches

Width

24 inches

Light

Full Sun, Partial Sun

Zones

4, 5, 6, 7, 8

Water

Moderate to high

Humidity

Moderate

Lifespan

10+ years

Native To

Central Europe to temperate Asia

Toxicity

Toxic if ingested, can cause skin irritation.

Bloom period

Early summer – Late summer

In flower about 3 months of the year

Planting

How to Grow

Tuck seeds into well-draining soil in early fall for natural stratification.
Water regularly to keep soil moist but not soggy during the growing season.
Mist cuttings if propagating via division in early spring for best root development.
Thin out overcrowded clumps to improve air circulation in late winter.
Apply a balanced fertilizer in early spring to promote vigorous growth.
Mulch around plants in late fall to protect roots from cold temperatures.

Pro Tip

Plant iris siberica That in full sun for best flowering and well-drained soil for healthy roots.

Keep It Thriving

Care Guide

Do

Water deeply during dry spells 🌱
Deadhead spent flowers to encourage more blooms
Divide clumps every 3–4 years to maintain vigor

Don't

Avoid overly wet soil to prevent root rot ❌
Do not fertilize with high nitrogen in late fall
Never ignore signs of pests or disease

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Deadhead
Divide
Fertilize
Plant
Spring Cleanup

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Sandy-colored perennial borderWildflower meadow accent

Companion Plants

EchinaceaRussian sage Sedum

Multiply

Propagation Methods

Good to Know

Common Questions

That Siberian Iris questions

What zones can That Siberian Iris grow in?

That Siberian Iris is hardy in USDA Zones 4–8. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is That Siberian Iris deer resistant?

Yes — That Siberian Iris is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.

When does That Siberian Iris bloom?

That Siberian Iris typically blooms in early summer through late summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does That Siberian Iris need full sun?

That Siberian Iris does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.