Planting rules used by the calendar
The planting calendar on each station page applies a few generic rules to that station’s frost dates. They are deliberately simple; regional calendars from your extension service and the seed packet for your variety should take priority.
Rules
| Group | Crops in the calendar | Plant outdoors | Source |
|---|---|---|---|
| Hardy (withstand hard frost) | Broccoli, Brussels sprouts, cabbage, kale, leaf lettuce, bulb onions, garden peas, radish, rutabaga, spinach, turnips | 6–8 weeks before the average last frost | [UW] |
| Half-hardy (tolerate light frost) | Beets, carrots, cauliflower, Irish potatoes | 2–4 weeks before the last frost | [UW] |
| Frost-tender | Snap beans, sweet corn, tomatoes, summer and winter squash, okra, Southern peas | After the last frost date | [UW], [NCSU] |
| Need warm soil | Cucumbers, eggplant, muskmelons, peppers, sweet potatoes, watermelons | 10–14 days after the last frost | [UW] |
Starting seeds indoors
- Weeks to sow before the last frost: tomato 6, pepper 8, eggplant 8, watermelon 6; cucumber, muskmelon and squash 4 or less. [C1]
- Broccoli, Brussels sprouts, cabbage and cauliflower: 5–7 weeks from seeding to transplanting, so the calendar counts back from the planting-out window. [C2]
- Harden off transplants over about two weeks before planting out, and keep tender seedlings away from temperatures below 45°F. [C1]
Fall planting estimate
NC State Extension advises adjusting fall planting dates “by noting the frost date and counting backward on the calendar the days to maturity of the vegetables” [NCSU], and Clemson notes that cool-season crops “should be started early enough to mature before hard freezes are expected” [C3]. The calendar therefore subtracts the upper end of Clemson’s “approximate days to harvest” [C3] from the median first fall 32°F date (warm-season crops) or the median first fall 28°F date (cool-season crops). Crops Clemson lists as “not recommended” for fall planting in both SC regions (sweet corn, Irish potatoes, okra, sweet potatoes, watermelon) are marked as such.
Sources
- [UW] University of Wyoming Extension, B-1148R, Extending the Vegetable Growing Season (sections “Cool-season vegetables” and “Warm-season vegetables”).
- [NCSU] NC State Extension, Extension Gardener Handbook, Chapter 16: Vegetable Gardening. See also the Central NC planting calendar.
- [C1] Clemson Cooperative Extension HGIC, FAQs about Starting Vegetable Seeds Indoors.
- [C2] Clemson HGIC 1259, Starting Seeds Indoors, Table 1.
- [C3] Clemson HGIC 1256, Planning a Garden, Tables 1 and 2. This page also has SC planting date ranges for the Piedmont and Coastal Plain.
We summarize these publications in our own words and link to the originals. Nothing here is a recommendation for a particular variety or site.