HerbBasil
Mammoth Basil
Sweet Basil
Mammoth Basil is the heavyweight champion of the basil world, an open-pollinated heirloom that produces leaves as large as your hand. This robust annual grows 18 to 24 inches tall and reaches harvest in 60 to 90 days, making it a fast-growing addition to any garden, container, or raised bed. The large, shiny green leaves carry an intense, sweet aroma and flavor that elevates pesto, salads, and fresh culinary dishes. For basil lovers, this is the Granddaddy of the family, delivering both visual drama and exceptional taste.
Photo © True Leaf Market(https://www.trueleafmarket.com/products/dill-seeds-mammoth-organic)
Growing Conditions
Sunlight
Full Sun
Water
High
Soil
Well-drained, Fertile Loam
Preferred Temp65-85°F
Growth Stats
24 in
Height
PeriodAnnual
TypeBush
Spacing
12-14 inches apart
Plant Profile
Sunlight
Full Sun
Water
High
Zones
?-?
Size
24in H x ?in W
Growth
Annual
Care
High
Hover over chart points for details
Highlights
The leaves of Mammoth Basil can stretch to 4 inches long, their ruffled surfaces catching light like living jade. This lettuce leaf variety stands out for sheer leaf volume and visual presence in the garden, while the intense, sweet flavor makes it a chef's dream herb for fresh applications. The vibrant green color adds striking visual appeal whether grown in garden beds or containers, and removing flowers encourages even larger leaves to develop.
Common Uses
This basil excels at making pesto, where its large leaves translate into generous yields per harvest. Fresh leaves work beautifully in salads, adding visual impact and aromatic depth. It's also exceptional for culinary dishes requiring substantial basil presence, as the leaf size means fewer leaves needed to fill a recipe. The abundance of foliage makes it efficient for home cooks who use basil regularly.
Growing Timeline
First Bloom
Late Spring
First Harvest
Early Summer
Last Harvest
Late Summer
Care Instructions
Start Indoors
Start Mammoth Basil seeds indoors 6 to 8 weeks before your last spring frost. Sow seeds on the soil surface or just barely covered, keeping them at warm temperatures around 70 to 75 degrees Fahrenheit for reliable germination. Keep soil consistently moist but not waterlogged during the germination period.
Transplant Outdoors
Transplant seedlings outdoors after the last frost date has passed and soil has warmed to at least 60 degrees Fahrenheit, ideally 65 to 70 degrees. Harden off seedlings gradually by exposing them to outdoor conditions over 7 to 10 days. Space transplants 18 inches apart in rows 30 inches apart, or use a similar spacing in containers.
Direct Sow
You can direct sow Mammoth Basil seeds outdoors after the last frost date and when soil temperatures are warm, around 60 to 70 degrees Fahrenheit. Sow seeds on the soil surface or just barely covered, thinning seedlings to 18 inches apart once they develop true leaves.
Harvesting
Begin harvesting Mammoth Basil leaves once the plant has established several sets of true leaves, typically within 60 to 90 days of sowing. Pinch or cut leaves from the top of the plant, taking outer leaves first to encourage continued branching. You can harvest individual leaves or pinch off entire growing tips. For the largest, most tender leaves, harvest in the morning after the dew dries but before heat stress, cutting just above a leaf node to promote branching.
Pruning
Encourage bushier growth and larger leaves by pinching off the top growing tips regularly, especially early in the season. Remove flower buds as they appear to redirect the plant's energy into leaf production rather than seed development. This pinching and deadheading practice is key to maximizing the large leaf size this variety is prized for.
Growing Calendar
Enter your ZIP code to see a personalized growing calendar for this plant.
Companion Planting
Ecology & Traits
Edible
Soil pH Range
6 – 7
Scientific Classification
Ocimum L.
Family
Lamiaceae
Genus
Ocimum
History & Origin
“Mammoth Basil carries the lineage of open-pollinated, heirloom genetics, preserved and passed down by gardeners who recognized the value of its outsized leaves and robust growth. Its heritage as a lettuce leaf basil connects it to varieties developed specifically for their abundance of harvestable foliage rather than compact plant form. This variety has survived in seed catalogs and home gardens because it delivers both practical abundance and culinary excellence.”