Onion plants are hardy to twenty degrees or less so they can be planted early. The earlier the onion is planted, the more time the onion has to make more top and therefore larger onions. If you refer to the USDA Plant Hardiness Zone Map, the following chart will assist you in determining your planting date.
| Zones | Best Varieties | Dates to Plant |
|---|---|---|
| 9-11 | Short Day | Jan 1- Jan 15 |
| 8 | Short Day | Jan 15-Feb 15 |
| 7 | Short or Intermediate | Feb 15-Mar 15 |
| 6 | Short or Intermediate | Mar 1-Apr 1 |
| 5 | Intermediate or Long | Mar 15-Apr 15 |
| 4 | Long Day | Apr 1-May 1 |
| 1-3 | Long Day | Apr 15-May 1 |
Index