| Maturity zone¹ | Approximate relative maturity rating | Growing degree days | Planting dates |
|---|---|---|---|
| ¹ See map, Figure 1.4-1. | |||
| 1 | 90–95 | 1,600–1,824 | May 15–25 |
| 96–100 | 1,825–2,024 | ||
| 2 | 101–105 | 2,025–2,350 | May 1–15 |
| 106–110 | 2,350–2,499 | ||
| 3 | 111–115 | 2,500–2,724 | April 25–May 7 |
| >115 | 2,725–2,949 | ||
| 4 | >115 | 2,950–3,174 | April 15–May 1 |
| >115 | 3,175 or > | ||
