Silex, MO planting calendar
- USDA zone
- 6b−5 to 0 °F
- Last frost
- Apr 13avg, 32°F
- First frost
- Oct 23avg, 32°F
- Growing season
- 188days
Silex, Missouri is in USDA plant hardiness zone 6b. Its average last spring frost is around April 13 and the first fall frost around October 23, giving a growing season of about 188 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Silex planting calendar
Each crop's windows are counted from Silex's average frost dates. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Feb 16 – Mar 2 | Apr 20 – Apr 27 | Jun 19 – Jul 9 | — |
| Pepper | Very tender | Feb 2 – Feb 16 | Apr 27 – May 4 | Jun 26 – Jul 26 | — |
| Cucumber | Tender | Mar 16 – Mar 23 | Apr 20 – Apr 27 | Jun 9 – Jun 29 | — |
| Summer squash / zucchini | Tender | — | Apr 20 – Apr 27 | Jun 4 – Jun 19 | — |
| Bush bean | Tender | — | Apr 20 – Apr 27 | Jun 9 – Jun 19 | Aug 24 – Sep 3 |
| Sweet corn | Tender | — | Apr 13 – Apr 27 | Jun 12 – Jul 12 | — |
| Basil | Very tender | Mar 2 – Mar 16 | Apr 20 – Apr 27 | May 20 – Jun 4 | — |
| Lettuce | Half-hardy | Mar 2 – Mar 16 | Mar 16 – Mar 30 | Apr 30 – May 15 | Aug 10 – Aug 25 |
| Pea | Hardy | — | Mar 2 – Mar 16 | Apr 26 – May 11 | Jul 31 – Aug 15 |
| Spinach | Hardy | — | Mar 2 – Mar 16 | Apr 11 – Apr 21 | Aug 20 – Aug 30 |
| Carrot | Half-hardy | — | Mar 23 – Mar 30 | May 22 – Jun 11 | Jul 21 – Aug 10 |
| Broccoli | Half-hardy | Feb 16 – Mar 2 | Mar 16 – Mar 30 | May 10 – May 30 | Jul 26 – Aug 15 |
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00230856. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 (p10 for spring, p90 for fall) — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Apr 27 | May 12 | Oct 12 | Oct 25 | 166 |
| 32°F (freeze) | Apr 13 | May 1 | Oct 23 | Nov 5 | 188 |
| 28°F | Apr 2 | Apr 18 | Nov 2 | Nov 18 | 213 |
| 24°F | Mar 23 | Apr 8 | Nov 13 | Nov 29 | 234 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 3,712 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 6,080 | cool-season crops (brassicas, greens) |
Hardiness zone 6b
Silex sits in USDA plant hardiness zone 6b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −5 to 0 °F. That number tells you which perennials, shrubs, and trees reliably survive an average winter here; it does not set your planting dates, which come from the frost calendar above.
Explore more places in zone 6b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Silex?
- Silex, Missouri is in USDA plant hardiness zone 6b on the 2023 map (average annual extreme minimum temperature −5 to 0 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Silex?
- The average (median) last spring frost at 32°F is around April 13, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as May 1, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Silex?
- The average first fall frost at 32°F is around October 23. That leaves a growing season of about 188 days between the average last spring and first fall frosts.
- When should I start tomatoes in Silex?
- Start tomato seeds indoors about Feb 16 – Mar 2 and transplant them outside about Apr 20 – Apr 27, once the danger of frost has passed. Estimated first harvest is around Jun 19 – Jul 9.
- How long is the growing season in Silex?
- About 188 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~April 13) and the average first fall frost (~October 23). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00230856 (Bowling Green 1 E, 27.2 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.