Not every cowpea grows the same. These are its main types (its cultivar groups), and the planner sizes, times and supports each one by its own numbers.
Vining cowpea — vine, spacing in row 10 cm4 in, mature height 1.5–2.5 m5–8 ft, mature spread 20 cm8 in, days to maturity 60–90
Bush cowpea — bush, spacing in row 12 cm5 in, mature height 50–75 cm20–30 in, mature spread 30–40 cm12–16 in, days to maturity 60–90
Yardlong bean — vine, sowing depth 2.5–5.1 cm1–2 in, spacing in row 30 cm12 in, mature height 2.7–3.7 m9–12 ft, mature spread 15–30 cm6–12 in, soil ph (in water) 5.5–6.5, days to maturity 40–70, days between succession sowings 14
Numbers we’re less sure of
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.
Mature spread — an estimate
Soil pH (in water) — an estimate
Bush cowpea: spacing in row — an estimate
Mature height — an estimate
Bush cowpea: mature height — an estimate
Bush cowpea: mature spread — an estimate
Yardlong bean: mature spread — an estimate
Monthly temperatures it grows in — an estimate
+6 moreShow fewer
Days to maturity — sources disagree
Yardlong bean: days to maturity — sources disagree
Yardlong bean: mature height — sources disagree
Yardlong bean: spacing in row — sources disagree
Yardlong bean: sowing depth — sources disagree
Yardlong bean: soil pH (in water) — sources disagree
Rules that apply to cowpea
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.
Do not plant legumes in ground that held legumes within 3 years; the root rots build where they repeat, and the worst of them outlast any garden rotation. Promising
Do not plant legumes in ground that held legumes within 3 years; the root rots build where they repeat, and the worst of them outlast any garden rotation.
If you skip this, you lose real yield. The planner warns you.
How it works: Bean and pea root rots (Fusarium solani, Rhizoctonia, Pythium, Aphanomyces) and white mold (Sclerotinia sclerotiorum) survive in soil as spores and sclerotia and build where legumes follow legumes; a three-year break holds the common ones down. Fusarium needs longer, and Aphanomyces oospores and white mold's sclerotia persist for many years, so rotation reduces but cannot clear them.
Evidence: checked against 4 sources in the research-based literature.
Fields with a long history of pulses in close rotations (every 2-3 years) are at greatest risk
Remedy
Plant legumes in different ground, or wait until 3 years have passed since this ground last held them. Where root rot has shown, make it longer, and keep the ground draining freely, because every one of these rots is worse in wet soil.
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.
Beans, peas and other legumes only fix nitrogen with the right soil bacteria. Ground that hasn't grown their kind recently may have too few, so they fix less. Promising
Beans, peas and other legumes only fix nitrogen with the right soil bacteria. Ground that hasn't grown their kind recently may have too few, so they fix less.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Nitrogen fixation happens in root nodules formed by Rhizobium or Bradyrhizobium bacteria specific to each legume group. On ground that has not grown that legume group before (a new bed, a soil-less mix, a long gap in the rotation, a fumigated or strongly acid soil), the matching strain can be absent or sparse, so nodulation and fixation are reduced until a population builds.
Evidence: checked against 1 source in the research-based literature.
Rhizobia bacteria are fairly specific as to which legumes they will infect, form nodules on the roots of, and for which they will fix nitrogen
Remedy
On first-time legume ground, coat the seed at sowing with the inoculant matched to the crop's group (garden peas and beans, soybean, and clover each take a different one). Ground that has grown that legume recently usually needs none. It is a cheap one-time step, advised where the history is absent and never required.
A warm-season bean germinates from warm soil, whatever the calendar says. Sown into cold ground it rots or emerges weak, even after the frost has passed. Promising
A warm-season bean germinates from warm soil, whatever the calendar says. Sown into cold ground it rots or emerges weak, even after the frost has passed.
If you skip this, it still grows, just less well. The planner suggests it.
How it works: Warm-season legumes take up water fast at sowing (imbibition), and in cold soil that first rush of cold water injures the seed tissue before the seedling can establish (imbibitional chilling), so the seed rots or comes up damaged. Soil below about 15 °C (60 °F) at sowing depth is where this bites, and the frost-free date can arrive weeks before the soil is that warm.
Evidence: checked against 2 sources in the research-based literature.
Bean seed planted in cold soil may rot rather than germinate, and plant growth will be very slow in cooler weather
Remedy
Wait for the soil to warm to about 15 °C (60 °F) at sowing depth, which a soil thermometer reads in a minute, or start the beans in warm cells and set them out. Peas are the opposite and are out of scope here. Half-hardy, they germinate in cold soil and are sown early on purpose.
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.
If you skip this, you lose real yield. The planner suggests it.
How it works: A crop grows and makes its harvest within a band of warmth: in months colder than its band it grows too slowly to finish, and in months hotter than it a cool-season crop bolts and turns bitter while a warm-season crop drops its flowers.
Evidence: checked against 9 sources in the research-based literature.
Hold the Tomatoes!UC Master Gardeners of Monterey, San Benito and Santa Cruz Counties, Jazmin Lopez
Average monthly temperatures for cool-season crops during their growing period: 60-65F. This includes, carrots, parsnips, spinach, lettuce, broccoli, and garlic to name a few.
Group D: These vegetables thrive in areas where the mean monthly temperatures range between 15 and 18°C. They are intolerant to temperatures between 21 and 24°C, and tolerate weak frosts. This group includes spinach, lettuce, broccoli, beetroot, Brussels sprout, cabbage, radish, rhubarb and watercress.
In the Top End climate lettuce plantings are restricted to the cooler months from April till July. Hot weather makes the plants to bolt, as they do not form a head but flower instead.
If you skip this, you lose real yield. The planner suggests it.
How it works: A crop grows at the pace its days to maturity assume only in months at least as warm as the low end of its band, and in cooler months it grows too slowly to finish, so a frost-free season of cool months can end before the crop is ready.
Evidence: not yet confirmed. It is cited to 8 sources, which a person has yet to read.
Hold the Tomatoes!UC Master Gardeners of Monterey, San Benito and Santa Cruz Counties, Jazmin Lopez
Average monthly temperatures for warm season crops during their growing period: 65-80F. This includes melons, corn, eggplant, peppers, squash, and tomatoes.
Eggplant needs warm conditions, and will not thrive during a cool season. There are varieties available that thrive in Minnesota’s short summer season.
Most seed packets and variety descriptions in catalogs estimate the days from planting to maturity. Add about 10 days to this estimate because of the cooler, shorter days in the fall.
Plus one working note on how the sources were read.
Remedy
Grow it under cover, in a greenhouse, tunnel or cloche; start it early indoors and choose its quickest variety; or grow a crop whose months these are.
A garden planner built on graded evidence. Every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.
