When to Plant Basil
Planting Window - Start indoors + transplant
- Start indoors
- 6-8 weeks before last frost, 70°F+ soil
- Transplant outdoors
- 1-2 weeks after last frost, nights above 50°F
| USDA Zone | Typical Window |
|---|---|
| Zone 5 and colder | Start April, transplant early June |
| Zone 6-7 | Start March-April, transplant mid-May |
| Zone 8 and up | April or May, second planting possible |
Basil's timing is governed almost entirely by its total lack of cold tolerance - unlike the hardy perennial herbs on this site, a light frost kills basil outright, and even a cool, non-freezing night can cause visible chilling damage, which makes both the start date and the transplant date more conservative than most vegetables in the same general planting window.
Starting Seeds Indoors
Start basil seed indoors 6-8 weeks before your last frost date, in genuinely warm conditions (70°F or warmer soil) for reliable germination - basil started too early, well ahead of when outdoor conditions will actually be warm enough to transplant into, tends to get leggy and root-bound waiting for the calendar to catch up.
Transplanting Outdoors, Later Than You'd Expect
Wait until nighttime temperatures are reliably above 50°F, generally a week or two after your last frost date rather than right at it - basil transplanted into cool conditions stalls and can develop dark, damaged patches even without an actual frost, so erring toward a slightly later transplant date consistently outperforms rushing it.
Genovese vs. Thai Basil Timing Is Nearly Identical
Thai basil, despite tolerating heat and bolting somewhat better than Genovese sweet basil once established, still follows essentially the same frost-sensitive planting and transplant timing - the heat and bolt tolerance difference between the two shows up later in the season's productivity, not in when either one should actually go in the ground.
Succession Sowing Keeps Flavor Fresh
Because basil's flavor gets harsher once a plant starts flowering, sowing a second or third round of seed through the summer - rather than relying on one spring planting to carry the whole season - keeps young, mild-flavored growth coming even as earlier plantings bolt and decline.
Pinching Flower Buds Keeps Leaves Coming
Pinching off flower buds as soon as they appear keeps a basil plant producing tender new leaves considerably longer than one left to flower, since flowering shifts the plant's energy toward seed production and noticeably coarsens the flavor and texture of the remaining leaves.
Zone boundaries follow the USDA Plant Hardiness Zone Map (2023 revision); frost windows reflect NOAA/NCEI climate normals. Both are typical historical ranges, reviewed annually - not a forecast or a guarantee for any single year. See Methodology & Sources.
Frequently Asked Questions
Why did my basil transplant look damaged even though there was no actual frost that night?
Basil suffers real chilling injury well above freezing - a cool night in the upper 30s to low 40s can blacken leaves and stunt growth even without frost forming, which is why basil's transplant date is set later than the strict frost-safety line most other tender crops use.
Does a mid-summer second round of basil need to be started indoors the way the spring planting does, or can I just direct-sow it outside?
Direct-sowing works well for a mid-summer round, since the soil and air are already warm enough by then to skip the indoor head start the spring planting needs to get ahead of frost. Seed sown directly into a cleared spot in July or August typically germinates and gets going faster than the same seed would have in cool spring soil, without needing any of the indoor lead time.
Is there any reason to let Thai basil flower on purpose, unlike Genovese basil where pinching buds is always recommended?
Some cooks do let a Thai basil plant flower deliberately, since the flower spikes themselves get used as a garnish in some Southeast Asian dishes, which isn't really a thing with Genovese basil flowers. That's a culinary choice rather than a growing recommendation, though - flowering still coarsens the leaves the same way it does on Genovese, so a plant grown mainly for leaf harvest still benefits from the same regular pinching either type gets.
Is purple basil more cold-sensitive than green Genovese basil?
No - all common basil varieties, regardless of leaf color, share essentially the same genuine lack of frost tolerance, so purple, lemon, and green types are all timed identically around waiting for reliably mild nights before transplanting outdoors.