So how’s your garden growing? Around here it’s still early, early but we always jump the gun and get out there to plant hoping the weather won’t turn cold, which it did. We lost some 4” tall Basil transplants due to a late season walk about by old Jack Frost. It starts out warm, then gets cool, which is why the tomatoes I buy in April at the Farmer’s Expo here in Kansas City just sit in the ground for a month and don’t start to grow until mid May but I don’t ever seem to learn that lesson.
So when will you be safe to plant without a frost? There is a great tool at Dave’s Garden that allows you to enter zip code and voila, for my area a chart like this pops out:
The chart above indicates that on March 24th there is a 90% chance of a frost but by April 21st there is only a 10% chance of frost.
As discussed previously, Plant Hardiness Zones and Soil Temperature Measurement give us a way to determine when to plant what. Below are two tables listing minimum, maximum, and optimum soil temperatures for a variety of vegetables sorted both alphabetically and by temperature.
Soil Temperatures for Seed Germination
Alphabetical Listing of Minimum, Optimum and Maximum
|
Vegetable |
Min (°F) |
Optimum Range (°F) |
Optimum (°F) |
Max (°F) |
|
Asparagus |
50 |
60-85 |
75 |
95 |
|
Bean |
60 |
60-85 |
80 |
95 |
|
Bean, Lima |
60 |
65-85 |
85 |
85 |
|
Beet |
40 |
50-85 |
85 |
85 |
|
Cabbage |
40 |
45-95 |
85 |
100 |
|
Carrot |
40 |
45-85 |
80 |
95 |
|
Cauliflower |
40 |
45-85 |
80 |
100 |
|
Celery |
40 |
60-70 |
70 |
85 |
|
Chard, Swiss |
40 |
50-85 |
85 |
95 |
|
Corn |
50 |
60-95 |
95 |
105 |
|
Cucumber |
60 |
60-95 |
95 |
105 |
|
Eggplant |
60 |
75-90 |
85 |
95 |
|
Lettuce |
35 |
40-80 |
75 |
85 |
|
Muskmelon |
60 |
75-95 |
90 |
100 |
|
Okra |
60 |
70-95 |
95 |
105 |
|
Onion |
35 |
50-95 |
75 |
95 |
|
Parsley |
40 |
50-95 |
75 |
90 |
|
Parsnip |
35 |
50-85 |
65 |
85 |
|
Pea |
40 |
40-75 |
75 |
85 |
|
Pepper |
60 |
65-95 |
85 |
95 |
|
Pumpkin |
60 |
70-90 |
90 |
100 |
|
Radish |
40 |
45-90 |
85 |
95 |
|
Spinach |
35 |
45-75 |
70 |
85 |
|
Squash |
60 |
70-95 |
95 |
100 |
|
Tomato |
50 |
70-95 |
85 |
95 |
|
Turnip |
40 |
60-105 |
85 |
105 |
|
Watermelon |
60 |
70-95 |
95 |
105 |
Optimum Soil Temperatures for Seed Germination
|
Min (°F) |
Optimum Range (°F) |
Optimum (°F) |
Max (°F) |
|
|
Parsnip |
35 |
50-85 |
65 |
85 |
|
Celery |
40 |
60-70 |
70 |
85 |
|
Spinach |
35 |
45-75 |
70 |
85 |
|
Asparagus |
50 |
60-85 |
75 |
95 |
|
Lettuce |
35 |
40-80 |
75 |
85 |
|
Onion |
35 |
50-95 |
75 |
95 |
|
Parsley |
40 |
50-95 |
75 |
90 |
|
Pea |
40 |
40-75 |
75 |
85 |
|
Bean |
60 |
60-85 |
80 |
95 |
|
Carrot |
40 |
45-85 |
80 |
95 |
|
Cauliflower |
40 |
45-85 |
80 |
100 |
|
Bean, Lima |
60 |
65-85 |
85 |
85 |
|
Beet |
40 |
50-85 |
85 |
85 |
|
Cabbage |
40 |
45-95 |
85 |
100 |
|
Chard, Swiss |
40 |
50-85 |
85 |
95 |
|
Eggplant |
60 |
75-90 |
85 |
95 |
|
Pepper |
60 |
65-95 |
85 |
95 |
|
Radish |
40 |
45-90 |
85 |
95 |
|
Tomato |
50 |
70-95 |
85 |
95 |
|
Turnip |
40 |
60-105 |
85 |
105 |
|
Muskmelon |
60 |
75-95 |
90 |
100 |
|
Pumpkin |
60 |
70-90 |
90 |
100 |
|
Corn |
50 |
60-95 |
95 |
105 |
|
Cucumber |
60 |
60-95 |
95 |
105 |
|
Okra |
60 |
70-95 |
95 |
105 |
|
Squash |
60 |
70-95 |
95 |
100 |
|
Watermelon |
60 |
70-95 |
95 |
105 |
Vegetable Garden Calendar: When to Plant (Kansas Region)
There is a great Vegetable Garden Planting Guide published by Kansas State University available on the KSU website. One of the things I like about this chart is that it reminds us that we get to plant in mid to late summer for fall crops. Check out Sweet Potato planting dates for instance.
These dates are specific for Kansas, but our climate zones make a wide swath across the country from New England down to Kansas, across to Colorado, up into Utah, Nevada, Oregon and Washington as shown on the USDA Plant Hardiness Zone Map.
Keep these charts and references handy you’ll need then next year and pass them on to others who may also have the same questions I hear every year, “When is the best time to plant my [fill in the blank] seeds” and “When is the last frost”.
Happy gardening.
Sources
Vegetable Garden Planting Guide, Kansas State University
Soil Temperature Conditions for Vegetable Seed Germination, Alabama A&M
