Wondering when to plant vegetable seeds? Confused by the information on packets? I know I am. Here’s a way to finally understand when to plant vegetable seeds.

Four Groups of Vegetable Seeds (and some fruits)

There are four groups of fruit and vegetable seeds when it comes to planting. Know this and know the average date of last frost in your area and you know when to plant vegetable seeds. Here are the four groups:

1. Hardy vegetables – plant these earliest.
2. Moderately hardy fruits and vegetables – plant these next.
3. Frost sensitive vegetables – the third group to plant.
4. Frost-intolerant fruits and vegetables – plant these last.

Hardy Vegetables – plant first

Hardy vegetables are the first ones you can plant straight into the garden in spring. Other ways to describe hardy vegetables:

1. plant as soon as the soil is workable in spring
2. early spring vegetables, cool season vegetables
3. plant 4-6 weeks before the average date of last frost
4. soil temperature for germination 55F or above - confusingly, not all vegetables marked 55F or above are in the hardy group. However, if you plant them early they’ll just be slow to germinate. See the list below for which are hardy.

Hardy vegetables are plants which do well in northern climates and don’t like heat. They benefit from a little shade in hotter areas, which prolongs the harvest, and are more shade tolerant than other vegetables.

Here’s a list of hardy vegetables:

• peas
• lettuce – all types
• spinach
• broccoli, cabbage, cauliflower, kale
• kohlrabi
• radishes
• onions

Moderately Hardy Fruits and Vegetables – plant second

Above I wrote that some vegetables and fruits can be planted when the soil temperature is above 55F but are not considered hardy. These are the moderately hardy fruits and vegetables. Other ways to describe moderately hardy fruits and vegetables:

1. plant after the danger of hard frosts has passed
2. spring vegetables - sometimes instructions say to plant March to mid-July
3. plant 2-4 weeks before the average last frost date
4. soil temperature varies – might say above 55F, above 60F, or above 70F

Seeds in this group can be planted early, with the hardy vegetables, but they will take longer to germinate and you may get tired of watering daily while you wait. Or you can plant the hardy and moderately-hardy seeds together at the same time – 4 weeks before average last frost.

Here’s a list of moderately-hardy vegetables and fruits to plant 2-4 weeks before your expected last frost:

• carrots, parsnips, turnips, rutabagas, and beetroot
• potatoes
• celery, chard, swiss chard, parsley
• raspberries and blackberries

Frost Sensitive Vegetables – plant third

Frost sensitive vegetables should be planted on the average day of last frost. While tomatoes are normally planted indoors ahead of last frost, beans and corn are planted outdoors. Monitor weather forecasts for late frosts and protect growing plants in this group. If you live in a cool climate you may need to provide protection to grow these and the next group of crops.

Other ways to describe frost sensitive vegetables:

1. sow outdoors in warm soils
2. soil temperature for germination 65-85F
3. after average last frost
   

Here is a list of frost sensitive vegetables for your garden, which should be planted outdoors on or after the average last frost date:

• bush beans, pole beans, edamame
• corn
• tomatoes

Frost Intolerant Vegetables and Fruits – plant fourth

Frost intolerant vegetables and fruits are the most sensitive group. They require heat and need to be planted 2-3 weeks after the date the last frost is expected. For cooler climates and shorter growing seasons some of these can be grown under cover; others are not practical.

Other ways to describe frost intolerant fruits and vegetables:

1. plant when nighttime temperatures are above 50F
2. transplant 2-3 weeks after tomatoes
3. after the danger of frost has passed
4. require warm, dry soils and plenty of sunshine

Fruits and vegetables which are frost intolerant and should be planted outdoors 2-3 weeks after average last frost:

• cucumber
• peppers
• melons
• squash
• pumpkins

I hope this demystified when to plant vegetable seeds for you. If there is a fruit or vegetable I’ve not included above please let me know and I will research which group it belongs to.

You can learn your local average last frost date at your county extension office. For additional information on organic fruit and vegetable growing I recommend The Vegetable Gardener’s Bible (10th Anniversary Edition).