Grosso lavender

Sun

Full sun, with at least 6 hours of direct sunlight daily.

Water

Water regularly during establishment, letting the soil dry between waterings. Once established, water deeply only during prolonged dry spells; avoid frequent light watering.

Soil

Lean, sharply drained sandy, gravelly or chalky soil, preferably neutral to alkaline. Heavy clay and wet winter soil are unsuitable unless drainage is substantially improved.

Height

2-3 ft (0.6-0.9 m), including flower stems

Spread

2-3 ft (0.6-0.9 m)

Flowers

Violet-purple flowers in dense spikes from early to late summer, generally later than English lavender; timing varies with climate.

Foliage

Evergreen. Narrow, aromatic, silver-grey to grey-green leaves on a rounded, woody framework.

Growth

Moderate; usually reaches a substantial flowering size within 2-3 years.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Heat tolerant
• Low allergen
• Fragrant

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

   1.6 ft (0.5 m)

2. After 1 year

   1.8 ft (0.55 m)

3. After 2 years

   2 ft (0.6 m)

4. After 3 years

   2.1 ft (0.65 m)

5. After 5 years

   2.5 ft (0.75 m)

   full size

About 5 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

Toxic

Growth rate

Moderate

• Plant with the crown at soil level, in a sunny position with good air circulation.
• Water new plants through their first growing season, allowing the soil to dry between soakings.
• Avoid routine feeding and rich compost; excess nutrients encourage soft, floppy growth.
• Use a thin gravel mulch rather than moisture-holding organic mulch, keeping the crown clear.
• In pots, use a free-draining mix and unobstructed drainage holes; keep containers out of standing water.
• In cold climates, shelter from winter wind and wet, and protect container roots from severe freezing.

Pruning. After the main flowering flush, remove spent stems and lightly shape the leafy growth, leaving plenty of green foliage. In spring, remove winter damage once new growth is visible; do not cut hard into bare old wood, which may not regrow.

Spring

Check for winter damage and trim dead shoots back to living, leafy growth.

Spring

Plant after severe frost has passed, allowing room for the mature spread.

Late spring

Weed around plants and refresh a thin gravel mulch without covering the crown.

Summer

Water establishing plants during dry weather; check pots more often than plants in the ground.

Late summer

After the main flowering flush, trim spent stems and lightly shape the plant; avoid late pruning where early frosts are likely.

Autumn

Clear fallen leaves from the crown and check that winter rain can drain freely.

• Plant as a low, informal hedge along a sunny path, allowing room so flower stems do not block access.
• Repeat in gravel borders with santolina and thyme for contrasting silver foliage and a long-lasting summer display.
• Use in sunny borders with roses, keeping lavender out of heavily irrigated or richly fed planting pockets.
• Grow in large, well-drained containers beside seating areas where the fragrance can be enjoyed.

Garden styles it suits: Mediterranean, French country (Provençal), Dry gravel garden, Cottage garden, Pollinator garden and Sensory garden.

Plant it with: Santolina, Creeping thyme, Russian sage, Yarrow, Bearded iris and Catmint.

Wildlife: Flowers attract bees and other nectar-feeding insects. Leave some flowering stems uncut while pollinators are using them.

• Root and crown rot: wet soil causes wilting, dieback or collapse. Improve drainage, reduce watering and replace badly affected plants in a better-drained position.
• Woody, bare centres: missed pruning and age leave plants open and leggy. Trim leafy growth annually; replace plants that no longer have enough green growth to reshape.
• Winter dieback: cold winds, severe frost and winter wet can damage shoots. Choose a sheltered, freely drained site and wait until spring growth appears before removing damaged stems.
• Spittlebugs: frothy deposits may appear on young stems in spring. They usually cause little harm; remove by hand or rinse off if necessary.

Lavender contains linalool and linalyl acetate and is considered toxic to cats, dogs and horses if eaten; ingestion may cause digestive upset and reduced appetite. Ordinary garden contact is not generally a concern, but concentrated lavender oil poses a greater risk. It is not generally considered poisonous to people in small culinary amounts, though 'Grosso' is usually grown for fragrance rather than food; concentrated oil should not be swallowed and may irritate skin.

• English lavender (Lavandula angustifolia)

  Usually smaller and earlier flowering, with shorter, typically unbranched flower stalks; 'Grosso' has longer stalks that often branch.

• French or Spanish lavender (Lavandula stoechas)

  Has conspicuous upright, petal-like bracts resembling rabbit ears above short flower heads; 'Grosso' lacks these showy top bracts.

• Provence lavender (Lavandula × intermedia 'Provence')

  Usually has paler violet flowers in looser spikes, while 'Grosso' has darker, denser flower heads; nursery labels are more reliable than appearance alone.

The hybrid name intermedia means intermediate, referring to its position between its parents, English lavender (Lavandula angustifolia) and spike lavender (Lavandula latifolia).

Propagation. Take softwood cuttings in late spring or semi-ripe cuttings in summer, using non-flowering shoots and a free-draining rooting mix. This hybrid is generally sterile; cuttings preserve the 'Grosso' cultivar.

Accepted botanical name

Lavandula intermedia

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