Many of our estimates come from an extension page we’ve read that gets close without pinning the number down. Others are still our own best guess, and on some the sources disagree. Treat them all as a starting point.
Sowing depth — an estimate
Soil temperature for germination — an estimate
Days to maturity — an estimate
Mature spread — an estimate
Mature height — sources disagree
Rules that apply to basil
Don't sow or set out tender crops before your last frost date Well established
Don't sow or set out tender crops before your last frost date
If you skip this, the planting fails. The planner won’t allow it.
How it works: The season's accumulated growing degree days (a running total of its warmth) against the total the crop needs to mature, or the crop's days to maturity against the number of frost-free days.
Evidence: checked against 3 sources in the research-based literature.
Once you know the average dates of the last frost in spring and the first frost in fall, count the number of days between. If the “days to maturity” figure for a desired vegetable is a larger number of days and the “frost tolerance” column indicates “none,” the sad truth is that particular vegetable probably won’t grow to maturity.
… high elevation areas don’t accumulate enough “growing degree units” (GDUs, also called growing degree days and heat units) to support some of the most coveted warm season vegetables
Remedy
Start it indoors and transplant it, choose a variety with fewer days to maturity, or skip this crop at this site.
A basil dropped back into ground where a basil crop wilted and died young tends to do the same (growing normally to a hand's height, then stunting and suddenly collapsing), because Fusarium wilt leaves that ground infective for years. A good hunch
A basil dropped back into ground where a basil crop wilted and died young tends to do the same (growing normally to a hand's height, then stunting and suddenly collapsing), because Fusarium wilt leaves that ground infective for years.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Fusarium oxysporum f. sp. basilici is a soilborne fungus specific to basil (a different fungus from the tomato or watermelon Fusarium); once a planting is infested its resting spores persist in the soil for eight to twelve years. It usually arrives on contaminated seed and is not already present everywhere, so it is a hazard only where infected seed has been sown. Where it is, plants of the mint family carry it without showing symptoms and can hold the ground infective from one year to the next.
Evidence: checked against 1 source in the research-based literature.
Once a field has become infested with the fusarium wilt pathogen, infective propagules may persist in the soil for 8-12 years. During that time, growers should avoid growing sweet basil or members of the mint family
Remedy
Start from seed tested clean for the fusarium fungus, or hot-water-treat your own (twenty minutes at 133-136 °F); where the disease has appeared, grow a resistant variety where one is offered and keep basil, and any standing mint, off that ground for several years. A wait alone is only partial cover, since the spores last the better part of a decade and mints can carry them.
Cold-hardy annuals can be sown or transplanted before the last spring frost (hardy crops about three weeks before, half-hardy about two weeks before). Tender crops wait for the frost itself. Promising
Cold-hardy annuals can be sown or transplanted before the last spring frost (hardy crops about three weeks before, half-hardy about two weeks before). Tender crops wait for the frost itself.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Cold hardiness. Hardy crops tolerate hard frost and half-hardy crops tolerate light frost, so they can occupy the ground weeks before frost-tender crops are allowed in. The offset is measured from the last spring frost.
Evidence: checked against 2 sources in the research-based literature.
Long-season warm crops are started indoors several weeks before the last frost and set out after it. Tomato and tomatillo go about six weeks ahead, pepper and eggplant about eight, basil six. Promising
Long-season warm crops are started indoors several weeks before the last frost and set out after it. Tomato and tomatillo go about six weeks ahead, pepper and eggplant about eight, basil six.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: A frost-tender crop with a long days-to-maturity cannot mature if it is only direct-sown after the last frost, because the frost-free window is too short. A head start under cover buys the weeks the season lacks; the seedling is set out only once frost has passed, so the transplant date is still frost-gated.
Evidence: checked against 3 sources in the research-based literature.
Basil is grown for its leaves. Pinch out the growing tips and remove flower buds as they form to keep the plant making tender leaves and growing bushy. Once basil flowers, it turns toward seed and the leaves fall off in quantity and quality. Harvest and pinch from the top regularly, and take the flower buds off as soon as they appear. Promising
Basil is grown for its leaves. Pinch out the growing tips and remove flower buds as they form to keep the plant making tender leaves and growing bushy. Once basil flowers, it turns toward seed and the leaves fall off in quantity and quality. Harvest and pinch from the top regularly, and take the flower buds off as soon as they appear.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Apical dominance and the leaf-to-seed switch. Pinching the terminal shoot releases the lateral buds below the cut, so the plant branches and grows bushier with more leaf-bearing stems; and because flowering redirects the plant from building leaves to setting seed, removing the buds before they open keeps it in leaf and the foliage tender.
Evidence: checked against 2 sources in the research-based literature.
Continue to pick the leaves regularly to encourage growth throughout the summer
Remedy
Once the plant has several sets of true leaves, pinch or harvest from the top just above a leaf pair on a regular cadence. Don't strip the lower leaves. Watch for flower spikes and pinch or cut them off as soon as they emerge.
If you skip this, the planting fails. The planner warns you.
How it works: On a clear, still night leaves lose heat to the open sky, so a leaf can fall to freezing and ice can form in it while the thermometer, a couple of meters up, still reads a few degrees above.
Evidence: checked against 7 sources in the research-based literature.
Frost occurs when air is warmer than 32°F but plant tissues drop to 32°F or below because plants radiate (lose) heat into the atmosphere, especially during cool, clear nights.
Radiation frosts occur on calm clear nights that lack cloud cover to hold in heat.
Remedy
The evening before, cover the crops at risk with a sheet or frost cloth, never plastic, reaching the ground and loose at the bottom so the soil's warmth can rise under it, and take it off in the morning. A cover helps least in a long, hard freeze.
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