How to Grow Summerlong Basil
Summerlong Basil
Ocimum basilicum 'Summerlong'
herbSummerlong basil is a productive Italian-type basil variety bred for extended flowering and continuous harvesting throughout the growing season. Known for its robust growth habit and resistance to bolting, it maintains tender leaves and flavor longer than standard basil varieties. This cultivar is ideal for gardeners seeking reliable, season-long basil production.
When should you plant Summerlong Basil in your zone?
Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.
Example Summerlong Basil timeline · Pittsburgh, PA (Zone 6b)
-
Plant Summerlong Basil
Around Apr 17Near Pittsburgh's average last spring frost.
-
Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
-
Harvest Summerlong Basil
Around Jun 6≈ 50 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Summerlong Basil dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 4-11; grown as annual in cooler zones, perennial in zones 10-11
Sign up free to see if Summerlong Basil grows in your zone — and get a personalized planting timeline.
Get my Summerlong Basil timeline →Growth Stages
Seedling
2-3 weeksTender cotyledons emerge within 5-10 days; first true leaves develop, appearing delicate and light green
Keep soil warm (70-75°F) and consistently moist; provide bright light to prevent leggy growth; thin seedlings to proper spacing when 1-2 inches tall
Vegetative Growth
3-4 weeksPlant develops multiple stems with increasingly larger, glossy green leaves; bushy habit forms as lateral branches emerge
Pinch off flower buds and top shoots regularly to encourage branching and leaf production; maintain consistent moisture and warmth; fertilize every 2-3 weeks with balanced fertilizer
Established Harvesting
4-8 weeksPlant reaches 10-15 inches tall with full bushy form; leaf production peaks; plant shows delayed bolting compared to standard varieties
Begin regular harvesting by pinching 1/4 inch from stem tips; this maintains bushiness and delays flowering; harvest 1-2 times weekly for best quality and production
Late Season & Flowering
2-4 weeks before heavy floweringSummerlong variety maintains vegetative vigor longer; when flowers finally appear, they form dense spikes of small white/pale purple blooms
Continue pinching flower buds if leaf production is desired; if allowing flowers for pollinators, flowering still produces harvestable leaves; provide afternoon shade in extreme heat (90°F+) to extend season
Maturation & End of Season
2-3 weeks until frost or senescencePlant may become woody; leaf quality declines as temperatures cool or plant ages; flowers mature and set seed
In frost-prone zones, plan replacement plantings for fall; in warm climates, prune heavily to rejuvenate; allow final plants to flower for seed saving or pollinator support
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
-
Hand-pick in early morning; use row covers; encourage parasitic wasps; neem oil as last resort; rarely severe on basil
-
Strong water spray to dislodge; insecticidal soap; neem oil; encourage beneficial insects like ladybugs and lacewings
-
Yellow sticky traps; insecticidal soap; neem oil; maintain good air circulation; reflective mulches
-
and
Hand-pick at dawn/dusk; beer traps; copper barriers; encourage ground beetles; remove hiding places like dense mulch
-
Ensure well-draining soil; avoid overhead watering; remove infected plants; use disease-resistant varieties; sanitize tools
-
Improve air circulation; avoid wetting foliage; use sulfur fungicides; copper-based treatments; remove infected leaves
Uses
Fresh Pesto, Cooking & Salads
CulinarySummerlong basil's extended harvest window makes it ideal for fresh pesto production throughout summer. The tender leaves work beautifully in fresh salads, pasta dishes, soups, and as a garnish for Italian cuisine. Its bright, aromatic flavor holds well in fresh applications. [source]
Herb Preservation & Drying
CulinaryBasil can be dried, frozen, or infused in oils and vinegars for winter cooking. Summerlong's abundant production supports preservation projects without over-harvesting. Dried basil retains significant flavor for tea, seasoning blends, and herbal preparations. [source]
Anti-inflammatory & Digestive Support
MedicinalBasil contains eugenol and other volatile oils with anti-inflammatory and digestive properties. Traditional herbalism uses basil leaf tea for digestive support, inflammation reduction, and mild antimicrobial effects. Fresh or dried leaves can be steeped into gentle herbal infusions. [source]
Natural Insect Repellent & Aromatics
HouseholdBasil's aromatic volatile oils naturally repel certain insects and mosquitoes when planted near outdoor seating or dried indoors. Fresh or dried basil can freshen indoor air and is traditionally placed on windowsills for pest deterrence. Its pleasant scent makes it valued for herbal sachets and natural fragrance. [source]
Pollinator & Beneficial Insect Support
WildlifeWhen allowed to flower, basil provides nectar and pollen for bees, butterflies, and other beneficial insects critical to garden health. Summerlong's delayed bolting means flowers appear later in season when pollinators need forage. A single flowering plant supports diverse insect populations. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Begin harvesting when plant has 6-8 true leaves; pinch off the top 0.25-0.5 inches of stems regularly to promote bushiness and prevent early flowering. Harvest in the morning after dew dries for best flavor and oil content. Regular harvesting (1-2 times weekly) maintains tender leaf quality and extends production season. Remove any flower buds immediately to prioritize leaf production. Cut flowers can be used fresh but will slightly reduce leaf yield. Use a clean knife or scissors to avoid crushing stems.
Fun Facts
- 🌱 Summerlong basil was specifically bred to resist bolting (premature flowering) under heat stress, solving a major problem gardeners face with standard basil varieties during hot summers.
- 🌱 Basil has been cultivated for over 5,000 years and holds cultural significance across cuisines; the name 'basil' comes from the Greek word 'basileus,' meaning 'king,' suggesting it was considered the 'king of herbs.'
- 🌱 Pinching off basil flower buds redirects the plant's energy from reproduction toward leaf growth, which is why regular harvesting can nearly double the harvestable leaf production compared to unmanaged plants.
Gardening Terms
New to gardening? Learn about terms used in this guide:
Join 30,000 gardeners planning their gardens with LizPlants.
Get your personalized Summerlong Basil planting timeline
Tell us your zip code and we'll calculate exactly when to start Summerlong Basil seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.
Get my Summerlong Basil timeline →