Vegetable Planting Guide
Temperature Comparison Between Cool Season and Warm Season Vegetables
| Cool Season: broccoli, cabbage, and cauliflower | Warm Season: tomato, pepper, squash and melons | |
| Germination | 40°F to 90°F 80°F optimum | 50°F to 100°F 80°F optimum |
| Growth | Daytime 65F° - 80°F preferred 40°F minimum Nighttime greater than 32°F for tender transplants down to mid-20s°F for established plants | Daytime 86°F optimum 60°F minimum Week below 55°F will stunt plant, reducing yields. Nighttime above 32°F |
| Flowering | Temperature extremes lead to bolting and buttoning. | Nighttime: Below 55°F, non- viable pollen (use blossom set hormones). Daytime: Greater than 95°F by 10 a.m., blossoms abort |
| Soil | Cool Use organic mulch to cool soil. Since seeds germinate best in warm soils, use transplants for spring planting, and direct seeding for mid-summer plantings (fall harvest). | Warm Use black plastic mulch to warm soil, increasing yields and |
Vegetable Planting Guide
| Vegetable | Germination Temperature | Germination Temperature | Germination Temperature | Plant Spacing | Planting Depth | Days to Germination | Typical Days to Harvest | Age of Transplants (weeks) |
| minimum | optimum | maximum | ||||||
| Cool Season Crops | ||||||||
| Beets | 40° | 80° | 90° | 4-6” | ¾-1” | 10-Jul | 60 | 2-4 |
| Broccoli | 40° | 80° | 90° | 18” | ½” | 10-Mar | 65T | 5-7 |
| Cabbage | 40° | 80° | 90° | 18” | ½” | 10-Mar | 85T | 5-7 |
| Carrots | 40° | 80° | 90° | 2-3” | ¼” | 17-Oct | 70 | 3-4 |
| Cauliflower | 40° | 80° | 90° | 18” | ½” | 10-Mar | 65T | 5-7 |
| Kohlrabi | 40° | 80° | 90° | 7-9” | ½” | 10-Mar | 50 | 4-6 |
| Leeks | 40° | 80° | 90° | 4-6” | ¼” | 12-Jul | 120 | 8-10 |
| Lettuce (leaf types) | 35° | 70° | 70° | 7-9” | ¼” | 10-Apr | 60 | 3-4 |
| Onion, green | 35° | 80° | 90° | 2-3” | ¼” | 12-Jul | 60 | 4-6 |
| Onions, dry (seed) | 35° | 80° | 90° | 4-6” | ¼” | 12-Jul | 110 | 8-10 |
| Onions, dry (sets) | 4-6” | 1-2” | 8-10 | |||||
| Parsnips | 35° | 70° | 90° | 5-6” | ½” | 15-25 | 70 | direct-seeded |
| Peas | 40° | 70° | 80° | 4-6”or 3” x 8” | 1” | 15-Jun | 65 | direct-seeded |
| Potatoes | 45° | 12-15” | 4-6” | 125 | 2-4 | |||
| Radish | 40° | 80° | 90° | 2-3” | ½” | 10-Mar | 30 | 3-4 |
| Spinach | 40° | 70° | 70° | 4-6” | ½” | 14-Jun | 40 | 4-6 |
| Swiss Chard | 40° | 85° | 95° | 7-9” | 1” | 10-Jul | 60 | 4-6 |
| Turnips | 40° | 80° | 100° | 4-6” | ½” | 10-Mar | 50 | 6-8 |
| Warm Season Crops | ||||||||
| Beans | 50° | 80° | 90° | 6” or 4” x 12” | 1-1½” | 14-Jun | 60 | direct-seeded |
| Cantaloupe | 60° | 90° | 100° | 36-48” | 1-1½” | 12-Mar | 85 | 3-4 |
| Corn | 50° | 80° | 100° | 12” x 30” or 9” x 36" | 1-1½” | 10-May | 60-90 | direct-seeded |
| Cucumbers | 60° | 90° | 100° | 6” trellised 24-36” untrellised | 1” | 10-Jun | 55 | 3-4 |
| Eggplant | 60° | 80° | 90° | 18-24” | ¼” | 14-Jul | 60T | 6-8 |
| Pepper | 60° | 80° | 90° | 15-18” | ¼” | 20-Oct | 70T | 6-8 |
| Tomato | 50° | 80° | 100° | trellised: 24” between plants | ¼” | 14-Jun | 65T | 6-8 |
| Squash, Summer | 60° | 90° | 100° | 36-48” | 1-1½” | 12-Mar | 50 | 3-4 |
| Squash, Winter | 60° | 90° | 100° | 36-48” | 1-1½” | 10-Jun | 100 | 3-4 |
| Watermelons | 60° | 90° | 110° | 36-48” | 1-1½” | 12-Mar | 85 | 3-4 |
- 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.
- 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 inches are thinned to 6 inches between plants in all directions. In other words, beets are thinned to 6 inches between beets in the row and 6 inches 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 two-foot wide walkways between blocks/beds.
- 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 half-inch) 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.
- 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.
- 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 two to three weeks from seeding.
- 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.