Giant silver mullein

Sun

Full sun.

Water

Low once established; water young plants during dry spells, then allow the soil to dry between waterings.

Soil

Well-drained, preferably lean, sandy, gravelly or chalky soil. Avoid heavy soil that stays wet in winter.

Height

4-6 ft (1.2-1.8 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Summer; yellow flowers open progressively along tall, woolly, often branching spikes.

Foliage

Evergreen. Large, oblong leaves covered in dense white hairs, forming a striking silver-grey basal rosette.

Growth

Fast; usually forms a rosette in its first year and flowers in its second.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• 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

   1 ft (0.3 m)

2. After 1 year

   3 ft (0.92 m)

3. After 2 years

   5 ft (1.5 m)

   full size

About 2 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

Mildly toxic: may upset a stomach

Growth rate

Fast

• Plant in full sun with enough space for the broad rosette.
• Water at soil level while plants establish; avoid keeping the crown wet.
• Do not routinely feed; rich soil encourages softer growth and leaning stems.
• Use a thin gravel mulch rather than moisture-retentive mulch around the crown.
• Stake flowering stems early if the site is exposed to strong winds.
• Keep a few seedlings as replacements, removing extras while small.

Pruning. Remove damaged basal leaves as needed without cutting into the crown. Cut flower stems down before seed ripens to limit seedlings, or leave selected stems to seed and remove the dead plant afterwards.

Spring

Surface-sow seed in pots or on a prepared, well-drained seedbed; do not bury it deeply.

Spring

Plant out young rosettes before their taproots become crowded, allowing 2-3 ft (0.6-0.9 m) between plants.

Late spring

Thin unwanted seedlings and stake developing flower stems on windy sites.

Summer

Water recently planted rosettes during prolonged dry weather; established plants need little supplementary water.

Late summer

Remove fading flower stems before seed ripens, or retain a few for replacement seedlings.

Autumn

Remove dead flowering plants and clear fallen leaves from surviving rosette crowns.

Winter

Check that water drains away from crowns; avoid watering dormant plants in wet weather.

• Place a single rosette beside a path or terrace where its large silver leaves can be seen clearly.
• Repeat plants through a gravel garden with lavender and ornamental grasses for contrasting shapes.
• Use the tall yellow spikes behind lower, drought-tolerant plants in a sunny mixed border.
• Pair with purple-flowered salvias or catmint for a strong silver, yellow and violet combination.

Garden styles it suits: Architectural minimal, Dry gravel garden, Mediterranean, Cottage garden, Pollinator garden and Desert / xeriscape.

Plant it with: Lavender, Catmint, Russian sage, Yarrow, Sea holly and Blue fescue.

Wildlife: Flowers provide pollen for bees. In the UK, the foliage can support mullein moth caterpillars; retained seed heads may provide food for seed-eating birds.

• Crown or root rot in wet soil: improve drainage, keep mulch away from the crown and replace badly affected plants.
• Mullein moth caterpillars, particularly in the UK: inspect leaves in late spring and early summer; tolerate some feeding or move caterpillars by hand if damage is severe.
• Powdery mildew: provide full sun and good spacing, and remove badly affected leaves.
• Flopping flower stems: avoid rich soil and excess feeding; support stems early on exposed sites.

Not known to be seriously toxic to people, cats, dogs or horses, although species-specific safety information is limited. It is not a food plant: do not eat the leaves, flowers or seeds. The dense leaf and stem hairs can irritate skin, eyes or the throat.

Where it spreads. Naturalised in parts of California and capable of spreading by seed on dry, disturbed ground. Prevent seed set near natural areas and check local weed guidance before planting.

• Common mullein (Verbascum thapsus)

  Usually has greener grey foliage and a narrower, mostly unbranched flower spike; giant silver mullein is more densely white-woolly and often develops a broader, branched flowering structure.

• Silver mullein (Verbascum argenteum)

  Also has silvery foliage, but its leaves typically have distinctly wavy or scalloped margins rather than the broader, more softly outlined leaves of giant silver mullein.

• Lamb's ears (Stachys byzantina)

  Forms a low, spreading mat of smaller woolly leaves and bears short spikes of pink-purple flowers, rather than a giant rosette with tall yellow-flowered stems.

The species name bombyciferum means 'silk-bearing', referring to the dense, silky hairs covering the plant.

Propagation. Grow from seed sown on the surface in spring or late summer; light helps germination. Pot on seedlings while small and plant out before the taproot becomes restricted. Division is unsuitable.

Accepted botanical name

Verbascum bombyciferum

Native range

Turkey.

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