Cool Season Vegetables

These vegetables prefer cool growing temperatures (60º to 80º) and lose quality in hot weather.  They are often replanted mid-summer for fall harvest.

Hardy Vegetable

Crops: broccoli, cabbage, kohlrabi, onions, lettuce, peas, radish, spinach, turnips

These vegetables grow with daytime temperatures as low as 40 degrees and may survive a frosty nip.  

When to plant:

• Based on soil temperatures
• Plant as soon as soil adequately dries in the spring.
• These crops may be planted as early as 2-4 weeks before the date of the average last spring frost. 

Semi-Hardy Vegetables

Crops: beets, carrots, cauliflower, parsley, parsnips, potatoes, and Swiss chard

These vegetables grow with minimum temperatures of 40º to 50º, but are less tolerant of a frosty night.

When to plant:

• Based on soil temperature.
• Plant as soon as soil adequately dries in the spring.
• These crops may be planted as early as 0-2 weeks before the date of the average last spring frost.

Warm Season Vegetables

These crops require daytime temperatures above 60º.  They prefer summer-like weather with temperatures between 70º and 95º.  They are intolerant of frost and may be sensitive to cool spring winds.

Tender Vegetables

Crops: beans, celery, corn, cucumbers, New Zealand spinach, summer squash

When to plant:

• Based on soil temperature.
• Soil is adequately dry to work.
• These crops may be planted (from seed) around the date of the average last spring frost.  Transplants of cucumbers and summer squash should be delayed until the time listed for the very tender group below. 

Very Tender Vegetables

Crop: lima beans, cantaloupe, eggplant, pepper, pumpkin, winter squash and pumpkins, tomato, and watermelon

These crops are not only intolerant of frost, but also cool spring winds.  A week of daytime temperatures below 55º may stunt the crop.

When to plant:

• Based on soil temperature.
• Soil is adequately dry to work.
• These crops are typically planted two plus weeks after the average last spring frost date.
• Weather is becoming summer-like, (i.e., consistently above 55º (daytime) and breezes should have lost any cool nip.

Table – Vegetable Planting Guide

	germination temperature1
Vegetable	min.	optimum	max.	plant spacing2	planting depth	days to germination	typical days to harvest	age of transplant (weeks)
Cool Season Crops3
Beets	40º	80º	90º	4-6”	¾-1”	7-10	60
Broccoli4	40º	80º	90º	18”	½”	3-10	65T4	5-7
Cabbage4	40º	80º	90º	18”	½”	3-10	85T4	5-7
Carrots	40º	80º	90º	2-3”	¼”	10-17	70
Cauliflower4	40º	80º	90º	18”	½”	3-10	65T4	5-7
Kohlrabi	40º	80º	90º	7-9”	½”	3-10	50
Leeks	40º	80º	90º	4-6”	¼”	7-12	120
Lettuce (leaf types)	35º	70º	70º	7-9”	¼”	4-10	60
Onion, green	35º	80º	90º	2-3”	¼”	7-12	60
Onions, dry (seed) (sets)	35º	80º	90º	4-6” 4-6”	¼” 1-2”	7-12	110
Parsnips	35º	70º	90º	5-6”	½”	15-25	70
Peas	40º	70º	80º	4-6” or 3” x 8”	1”	6-15	65
Potatoes	45º			12-15”	4-6”		125
Radish	40º	80º	90º	2-3/2”	½”	3-10	30
Spinach	40º	70º	70º	4-6”	½”	6-14	40
Swiss Chard	40º	85º	95º	7-9”	1”	7-10	60
Turnips	40º	80º	100º	4-6”	½”	3-10	50
Warm Season Crops
Beans, snap	55º	80º	90º	6” or 4” x 12”	1-1½”	6-14	60
Cantaloupe5	60º	90º	100º	36-48”	1-1½”	3-12	85	2-35
Corn	50º	80º	100º	12” x 30” 9” x 36”	1-1½”	5-10	60-90
Cucumbers	60º	90º	100º	6” trellised 24-36” untrellised	1”	6-10	55	2-35
Eggplant	60º	80º	90º	18-24”		7-14	60T6	6-9
Pepper	60º	80º	90º	15-18”		10-20	70T6	6-8
Tomato	50º	80º	100º	trellised: 24” between plants		6-14	65T6	5-7
Squash, Summer	60º	90º	100º	36-48”	1-1½”	3-12	50	2-35
Squash, Winter	60º	90º	100º	36-48”	1-1½”	6-10	100	2-35
Watermelons	60º	90º	110º	36-48”	1-1½”	3-12	85	2-35

1. Germination temperature – Soil temperature is one of the best methods to determine spring planting time.  Plant when soils reach minimum temperature measured at 8 a.m., 4 inches deep.   Beans are an exception, being measured at 6 inches deep.  Optimum temperatures listed in the table are useful for starting seeds indoors.  Maximum temperatures are listed in regards to high soil temperatures that may interfere with seed germination in the summer.
2. Plant Spacing – Spacings given are equal-distance spacing for crops grown in block or close-row style beds.  For example, beets, with a spacing of 6” are thinned to 6” between plants in all directions.  In other words, beets are thinned to 6” between beets in the row and 6” between rows.  The closer spacing listed should be used only on improved soils with 4-5% organic matter. 
   Close-row or block style planting works well for raised bed gardening, with blocks/beds 4 feet wide (any length desired) and 2 foot wide walkways between blocks/beds.
3. Cool Season Crops – Cool season crops prefer a cool soil.  Lawn clipping and newspapers make an excellent mulch for these crops by cooling the soil, preventing weed germination and conserving water.  Apply fresh grass clippings only in thin layers (less than ½”) and allow it to dry between applications.  Thick layers will mat and smell.  Do not use clipping from lawns treated with weed killers or other pesticides.  Several layers of newspapers covered with grass clippings also work well between rows.  Do not use glossy print materials.
4. Transplanted Cole Crops – Since cole crops (cabbage, cauliflower, broccoli, and Brussels sprouts) germinate better in warmer soil, they are typically started from transplants in the spring.  Days to harvest are from transplants.  In the warmer areas of Colorado, these crops produce the best quality when direct seeded mid summer (early July for the Front Range area) for harvest during cooler fall weather.  Before planting out, harden off seedlings.
5. Transplanting Vine Crops – Vine crop (cucumbers, squash, melons) roots are extremely intolerant of being disturbed, and perform best when grown by direct seeding rather than by transplants.  With the use of black plastic to warm the soil, direct seeded crops germinate rapidly.  If using transplants, select small, young plants, not more than 2-3 weeks from seeding. 
6. Tomato family transplants – The tomato family is traditionally planted from transplants.  In warmer areas of Colorado, they can also be direct seeded with minimal delay.  Days to harvest are from transplants.

Additional Information CMG GardenNotes on vegetable gardening:

• #711 Vegetable Garden: Soil Management and Fertilization
• #712 Sample Vegetable Garden Seed Catalogs
• #713 Block Style Layout in Raised Bed Vegetable Gardens
• #714 Irrigating the Vegetable Garden
• #715 Mulches for the Vegetable Garden
• #716 Water Conservation in the Vegetable Garden
• #717 Growing Tomatoes
• #718 Early Blight of Tomatoes
• #719 Vegetable Garden Hints
• #720 Vegetable Planting Guide
• #721 Sample Planting for Raised-Bed Garden
• #722 Frost Protection and Extending the Growing Season
• #723 Growing Vegetables in a Hobby Greenhouse
• #724 Vegetable Gardening in Containers

[ top ]