Here’s a handy chart to help you determine when to get vegetables into the ground. They’re divided into two groups: Cool-Season and Warm-Season with each having varieties that are hardier than the rest (these are noted by color in the chart below).
First, here’s an introduction to both:
Cool-Season: Most are frost-tolerant and can tolerate below freezing temperatures (some only short term). They thrive in cool weather with most seeds needing the cold temperature to germinate.
Transplants should be hardened off a minimum of 7 days before planting to help them adjust to the cold weather. It’s also recommended to let them dry out between waterings during the hardening off period and to stop fertilizing them.
Warm-Season: These are not frost-tolerant and are more tender, they require waiting until the last frost date has passed. Some are more delicate than others and require waiting at least one to two weeks after the last frost.
Seedlings should be hardened off outdoors before planting. They may be planted sooner with some protection (cold frames, cloches), allow the chosen method to first heat the soil a few days before planting.
The chart below is a general guideline only, use this to determine what can be planted early and what needs to wait. Research your local zone to determine how much earlier you can plant as some climates are harsher than others right up to the last frost date so it’s impossible to give more definitive dates.
When to plant: 2 to 4 weeks before frost-free date
Color Code: Blue = Hardy; White = Half-hardy.
Warmer zones may fine that “Hardy” varieties can be planted up to 6 weeks before the last frost.
When to plant: 1 to 2 weeks after last frost
|New Zealand Spinach
Color Code: Blue = Tender; White = Very Tender.
Warmer zones will find they can plant “Tender” varieties on the last frost date or right after, others will need to wait a week or two.
- Knott’s Handbook for Vegetable Growers by Donald N. Maynard and George J. Hochmuth
- Better Homes & Gardens Vegetable, Fruit & Herb Gardening
- Growing With Gardening by Bibby Moore and Kendal Brown