How to Grow Sweet Basil USA

By the SoilCommander Editorial Team, under the guidance of Nitin Sharma, Co-Founder · · How we check our facts

On this page
  1. Sweet basil (Ocimum basilicum)
  2. Quick Facts
  3. At a Glance
  4. Diseases
  5. Pests
  6. Soil & Growing Conditions
  7. Growth Stages
  8. Harvest & Storage
  9. Companion Planting
  10. Pollination
  11. Plan your Sweet Basil planting
  12. Growing Sweet basil in another region
  13. Sources
  14. Frequently Asked Questions

Sow sweet basil once soil temperature reaches 68°F (20°C).

The short answer

Site
6+ hours of sun, soil pH 6–7
Biggest risk
Grey mould

Core growing advice on this page is checked against named horticultural sources — see References.

Sweet basil (Ocimum basilicum)

A healthy bushy sweet basil plant — “Starr-110822-8253-Ocimum basilicum-leaves with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (25010109901)” by Forest and Kim Starr is licensed under CC BY 3.0 us.

Also known as: Basil, Common basil, Garden basil · 6 sources cited · Verified

Quick Facts

A healthy bushy sweet basil plant
A healthy bushy sweet basil plant. Photo: “Starr-110822-8253-Ocimum basilicum-leaves with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (25010109901)” by Forest and Kim Starr, CC BY 3.0 us.
Factor Value
Soil pH 6 - 7
Sunlight 6-6 hours direct sun
Germination temp 68°F (20°C)
Optimal growing temp 64-81°F (18-27°C)
Minimum growing temp 45°F (7°C)
Soil texture Moist, peat-free, free-draining compost/soil
Drainage free_draining
Documented problems 4 diseases, 3 pests

At a Glance

A basil flower spike
A basil flower spike. Photo: “J20160709-0013—Ocimum basilicum (28118020912)” by John Rusk from Berkeley, CA, United States of America, CC BY 2.0.
Ocimum basilicum Sweet basil Grey mould Damping-off (seedling c… Basil downy mildew Fusarium wilt (basil) Aphids Snails Slugs DISEASES PESTS

Diseases

Basil leaves showing downy mildew symptoms on the underside
Basil leaves showing downy mildew symptoms on the underside. Photo: “Starr-110822-8255-Ocimum basilicum-leaves and spores with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (25010112931)” by Forest and Kim Starr, CC BY 3.0 us.
Fuzzy grey-brown Botrytis mould covering a tomato stem — Rasbak, CC BY-SA 3.0
Rasbak, CC BY-SA 3.0
Grey mould
moderate

Botrytis cinerea

Soft brown fruit decay; Fuzzy grey-brown mould

RHS lists grey mould among basil's common problems. Reused disease entity (shared with tomato and strawberry); both of its existing treatments automatically apply to basil via the shared entity -- no new treatment rows…

Damping-off (seedling collapse)
high_at_seedling_stage

Rhizoctonia solani

Damping-off (seedling collapse at soil line); Wilting with chlorotic, dropping leaves

RHS: basil seedlings are prone to damping off, especially if overwatered. Reused disease entity, now linked to 4 taxa.

Basil downy mildew
high

Peronospora belbahrii

Angular chlorosis with underside sporulation (downy mildew pattern)

Basil-specific new disease entity (Peronospora belbahrii). Single-sourced to Cornell; regional (UK) prevalence flagged for follow-up verification.

Fusarium wilt (basil)
high_once_symptomatic

Fusarium oxysporum f. sp. basilicum

Shepherd's-crook wilting with vascular stem discoloration

Basil-specific new disease entity (Fusarium oxysporum f. sp. basilicum). Single-sourced to UMD; regional (UK) prevalence flagged for follow-up verification. Persists in soil 8-12 years -- important for…

Pests

Bushy sweet basil leaves
Bushy sweet basil leaves. Photo: “Starr-110822-8248-Ocimum basilicum-leaves with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (24476536533)” by Forest and Kim Starr, CC BY 3.0 us.
moderate

Aphididae (various spp.)

RHS common-problems list for basil. Aphids entity now reused across 4 taxa.

Snails
moderate

Gastropoda (snails, various spp.)

RHS common-problems list for basil.

Slugs
moderate

Gastropoda (slugs, various spp.)

RHS common-problems list for basil.

Soil & Growing Conditions

A basil bed growing in the garden
A basil bed growing in the garden. Photo: “Starr-110822-8246-Ocimum basilicum-habit with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (25077054526)” by Forest and Kim Starr, CC BY 3.0 us.

Water: Moderate and even; water in the mornings and avoid wetting foliage -- RHS notes basil "hates having wet roots overnight". Prone to damping off if overwatered as a seedling.

Humidity: Avoid high humidity/waterlogged conditions, which favour damping off and grey mould

Soil pH range

6 7

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

A basil plant with flower buds forming
A basil plant with flower buds forming. Photo: “Starr-110822-8254-Ocimum basilicum-leaves with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (24807792380)” by Forest and Kim Starr, CC BY 3.0 us.
Stage Notes
Establishment Sow thinly on the surface of moist, peat-free seed compost, cover lightly; needs warmth to germinate (around 20°C/68°F) -- a heated propagator or warm windowsill works well indoors. Only sow directly outdoors once night temperatures are reliably above 50°F (10°C). Highly prone to damping off if overwatered at this stage.
Vegetative Growth Water moderately and evenly in the morning, avoiding wetting the foliage. Pinch out growing tips to encourage bushy growth.
Flowering Flowers form on mature plants in mid-to-late summer. Pinching out flower spikes redirects energy into leaf production and prolongs leaf harvest; flowers left to bloom are valuable to pollinating insects.
Fruit Development If flowers are left unpinched and pollinated, small nutlets (seeds) develop. Home growers rarely take basil to this stage, since leaf quality and flavour decline once the plant flowers and sets seed.
Ripening/Harvest Harvest shoot tips and leaves regularly through summer to encourage continued bushy growth; pick in the morning after dew has dried. Whole plants can be cut for pesto-making.
Senescence/Dormancy Outdoor/unheated-glasshouse plants should be fully harvested and cleared before cold weather -- there is no UK-hardy dormancy stage.

Harvest & Storage

Two basil leaves held in a hand
Two basil leaves held in a hand. Photo: “Starr-110822-8249-Ocimum basilicum-leaves with basil downy mildew Peronospora belbahrii-Hawea Pl Olinda-Maui (24807784660)” by Forest and Kim Starr, CC BY 3.0 us.

When to pick: Pick shoot tips and young leaves regularly once plants are bushy and established; regular picking encourages further branching. Pick in the morning once dew has dried for best flavour. Whole plants may be cut for pesto-making. Pinching out flower spikes prolongs the leaf-harvest period.

Storage

RHS guidance is oriented toward continual fresh picking through summer rather than long-term storage; no specific post-harvest storage protocol was stated in the source.

Companion Planting

Gardener planting tomato seedlings beside a greenhouse — Maasaak, CC BY-SA 4.0
Maasaak, CC BY-SA 4.0
pest deterrent

Solanum lycopersicum

Basil is a non-host plant for glasshouse whitefly; interplanting reduced proportion of marigolds with basil (plus nasturtium and Chinese cabbage) was also shown to reduce whitefly populations on tomato.

Pollination

Pollinating insects (bees and other flower visitors)

RHS: basil flowers are attractive/nectar-rich to bees and other pollinating insects if plants are allowed to bloom, though gardeners typically pinch out flower spikes to prolong leaf harvest -- a direct culinary-yield-vs-pollinator-value tradeoff documented by RHS.

Plan your Sweet Basil planting

When to sow and plant Sweet Basil depends on your own frost dates. Check the USA vegetable planting calendar. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.

Growing Sweet basil in another region

Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.

Sources

  1. Peronospora belbahrii (oomycete); most damaging basil disease in the US since 2007; wind-dispersed and seed-borne; symptoms, resistant varieties, organic and conventional fungicides, and cultural practices (humidity <85%, air movement, avoid overhead irrigation) all detailed.

  2. Fusarium oxysporum f. sp. basilicum; symptoms (stunting, stem streaking, shepherd's crook wilting), seed and soil transmission (persists 8-12 years in soil), resistant cultivars, and biological treatments (Actinovate, Rootshield).

These 3 sources are specific to this region. The full list of 6 sources behind this guide (Cornell University (Cornell Vegetables, Margaret Tuttle McGrath, LIHREC), FAO EcoCrop, PLOS ONE (Conboy, McDaniel, Ormerod, George, Gatehouse, Wharton et al. 2019) and others) is in the references of our UK guide to sweet basil; they describe the plant itself, which is the same wherever it grows.

Frequently Asked Questions

What soil pH does sweet basil need?

A pH of about 6–7. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

What problems affect sweet basil?

Our data links 4 diseases and 3 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.

Get the USA Garden Planner →

Instant PDF download · Written for US growing conditions

SoilCommander Editorial Team — under the guidance of Nitin Sharma, Co-Founder

Every growing guide is checked against RHS, USDA Cooperative Extension, and other named horticultural authorities before publishing. How we check our facts.

How this guide is put together

The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against USDA hardiness-zone and frost-date data, with Cooperative Extension sources cited directly where one exists for a crop. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.

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Last verified 2026-09-02

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