The cell structures of vegetable plants differ in that some vegetables have plant cells that will burst if they freeze or encounter even a light frost.. Cool weather vegetables tend to have the ability to freeze without cell damage. They are designed for the cooler temperatures. The cells can freeze and defrost in the sun without damage to the plant leaf. When a extend cold comes that will freeze the roots or area where the roots meet the stem, that is when the plant usually dies or is damaged. So you have a lot of time to grow cool-season vegetables!
Cool-weather vegetables enjoy cool soil temperatures as well as ambient temperatures but most plants regulate themselves based on the soil temperatures. The cool-weather crops thrive when soil temperatures remain in, generally speaking, a range of 50-65 degrees. As the soil temperatures increase, the plants often move from leaf, bulb and bud production into full flower production mode. That is when you see lettuces bolt and flower, broccoli and cauliflower heads flower, radishes become pithy and our cool-weather crops have one goal. That goal is to flower and produce seed. When the soil temperatures leave that 'cool' range that is when we often pull them and plant our warm-weather or warm-season crops.
Cool season vegetables prefer the cooler weather. This group of vegetables grows best and taste their best with ambient temperatures of 50 degree (F) nights and 60-70 degree (F) days. These temperatures are easy to look up than soil temperatures. Cool-weather vegetables can be broken into two sub-categories which are Hardy and Semi-Hardy.
Fully Frozen and Survived: The Rusted Garden |
Hardy Cool Weather Vegetables:
This group of vegetables can manage well with mid 40 degree days and can survive a prolonged frost. Many vegetables in this group can over-winter in your garden and bring you early spring greens. Vegetables in this group can be planted up to 4 weeks before the average last frost date in your area. You can probably even get away with 6 weeks if you like pushing garden limits.
Semi-Hardy Cool Weather Vegetables:
This group of vegetables doesn’t fare as well with frost although they can handle a light frosting with minimal to no damage. They prefer daytime temperatures in the 50’s and nights that don’t fall below 40 degrees, although they can handle nights in the 30’s. Vegetables in this group can be planted up to 2-4 weeks before the average last frost date in your area.
Cool-Weather Crops Can Often be Planted Twice a Season
In many gardening areas, you actually have two cool weather seasons. I plant in Maryland. I can start my cool-weather plantings March 1st and I can plant them again mid August for a fall crop. I actually also plant at this time to also establish vegetables that I will let over-winter. Your cool season crops can be planted in the spring and fall. In the spring, we often seed start indoors as the ground temperatures are to low for a speedy germination. In the fall we can direct sow the seeds as the warm soil temperatures actually increase the speed of germination. The key with fall planting is timing, as you are planting into the coming winter and freezing temperatures. You want to have enough time for your crops to mature.
Different Types of Cool Weather Vegetables
The exact split, between hardy (H) and semi-hardy (SH), and where to place a vegetable in the sub-categories is debated. It is best used for general planting guidelines and understanding they simply like the cool weather. My guidelines for each vegetable is based on my growing area in Maryland (Zone 7). I am giving you the general range for first planting of these vegetables when moving from cold weather to warm weather.. You can plant successive crops every 2 weeks as you wish based on your planting zone. I will be doing new blog posts on planting your fall season cool-weather crops. Planting these crops in August doesn't require you to start the seeds indoors or worry about planting around your last average frost date.
Some Cool Weather Vegetable Crops: The Rusted Garden |
Asparagus (H) (Perennial) It takes about 3 years to establish a viable crop. It is a perennial plant that will start sending up stalks in March when planted the previous year. If you are planting it for the first time to establish it your garden, it is best to use transplants. You can grow them from seed in cell trays. They should be planting in the garden in May.
Arugula (SH) It can be started indoors and planted in the garden 2 weeks before last frost date. You can also plant seeds at the same time.
Beets (SH) It can be planted as seeds 2 weeks before last frost date. I have had success growing transplants.
Bok Choy (Pak Choi) (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Broccoli (H) It is best planted as a transplant 4 weeks before last frost date. I would not recommend starting it as seeds in the ground in Zone 7.
Brussels sprouts (H) It is best planted as a transplant 2 weeks before last frost date. I would not recommend starting it as seeds in the ground in Zone 7.
Cabbage (H) It is best planted as a transplant 4 weeks before last frost date. I would not recommend starting it as seeds in the ground in Zone 7.
Carrots (SH) Carrots should not be grown as transplants. They can be seeded in your garden 2-4 weeks before last frost date.
Cauliflower (H) It is best planted as a transplant 2-4 weeks before last frost date. I would not recommend starting it as seeds in the ground in Zone 7.
Celery (SH) It is best planted as a transplant 2 weeks before last frost date. I would not recommend starting it as seeds in the ground in Zone 7.
Cilantro (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date.
Collard Greens (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Kale (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Kohlrabi (H) It can be started indoors and planted in the garden 2 weeks before last frost date. You can also plant seeds at the same time.
Lettuce (H) It can be started indoors and planted in the garden 4 weeks before last frost date. You can also plant seeds at the same time.
Mustard Greens (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Onions (H) If you are using bulbs you can plant them 6 weeks before last frost date. I have not used seeds.
Parsley (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Peas (SH) They should be planted directly in the ground 4 weeks before last frost date. Peas do not like soggy cold soil.
Potatoes (SH) They should be planted directly in the ground 4 weeks before last frost date.
Radishes (H) They should be planted directly in the ground 4 weeks before last frost date.
Spinach (H) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Chard (SH) It can be planted as seeds directly in the garden 2-4 weeks before last frost date. I do recommend growing it indoors and transplanting it into the garden 2-4 weeks before last frost date.
Turnips (H) They should be planted directly in the ground 4 weeks before last frost date
Good Luck with Your Garden,
Gary (The Rusted Garden)
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Great article! Thanks for sharing I added some thoughts on Garden Composting sometime ago
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