Tomatoes and other warm-weather plants always pose a quandary for those of us in cool climates. If you plant them too soon, you run the risk of subjecting them to a killing frost; yet everyone wants to get their gardens started sooner rather than later, as the thought of fresh, home-grown produce brings on impatience. Our spring planting guide and some tips for season extension will help you make these important decisions.
Soil temperature
Every plant has its optimum growing temperature, and every area has a last expected frost date. Putting them together will help inform your planting plans.
Crop | Best soil temp | Zone 3 Average last frost 5/31 | Zone 4 Average last frost 5/15 | Zone 5 Average last frost 4/30 | Zone 6 Average last frost 4/15 | Zone 7 Average last frost 4/1 |
| Tomatoes/ Basil  | 60° F | Start indoors, plant out June 15 | Start indoors plant out May 31 | Start indoors, plant out May 15 | Start indoors plant out April 30 | Start indoors plant out April 15 |
| Melons Cucumber Squash  | 70° F | Start indoors, plant out June 15 | Start indoors plant out May 31 | Start indoors, plant out May 15 | Start indoors plant out April 30 | Start indoors plant out April 15 |
Beans | 55° F | Direct sow May 31 | Direct sow May 15 | Direct sow April 30 | Direct sow April 15 | Direct sow April 1 |
Okra | 65° F | Direct sow after June 15 | Direct sow after June 1 | Direct sow after May 15 | Direct sow after May 1 | Direct sow after April 15 |
Peppers | 65° F | Start indoors, plant out June 15 | Start indoors plant out June 1 | Start indoors plant out May 15 | Start indoors plant out May 1 | Start indoors plant out April 15 |
| Sweet potatoes  | 65° F | Season too short | Season too short | Plant slips June 15 | Plant slips June 1 | Plant slips May 15 |
This chart provides a guide, but you will still want to keep an eye on the weather. The frost dates are average, and could vary by a week or two. If there is unexpected cold weather after you have planted out your tender crops, you can save them by covering them up. Each layer of material can gain you 5 to 10 degrees.
Floating row cover like Reemay is the best for 24 hour coverage. It is light and breathable, but does provide protection. Doubling up with floating row cover is safe any time. If you are only covering at night you can use something thicker; but remember to take it off when the sun comes out so your plants don’t roast.
That said, you can also use coverage to warm your soil and get things started a week or two early. Setting up small “tunnel rows” will give you a greenhouse effect, enabling you to safely get your plants off to an early start.
Planting tips
Success
You are now signed up for our newsletter
Success
Check your email to complete sign up
Plant your tomatoes deep – they will grow roots from any stem that is submerged, enabling them to collect more water and nutrients from the soil. Don’t worry about the top – it will grow like crazy. Keep them moist, especially when they are setting fruit. Too much water after a dry spell will cause the tomatoes to crack.
Direct sown crops like beans and okra are easy targets for chipmunks and other nibblers. To protect them until they are no longer tender morsels, use a row cover, or place some fencing over top. Once the stems are fairly sturdy they will be less of a temptation.
Sweet potatoes go in the ground when it is already hot. Be sure to plant the slips vertically so the roots are deep and away from the drying sun. Water them promptly if they appear to be wilting.
Cucumbers, melons and squash can be protected from untimely frost by placing an empty pot over individual plants overnight. Depending on the size of your tomatoes and peppers, you can also cover them with a container or wrap them in a blanket.
To keep seedlings from getting dug up by squirrels—ever in search of a nut—place decent sized rocks around the base of each plant. When they have grown enough to establish a strong root system, you can move your rocks to the next babies.
If you fail, don’t give up. Gardening is a lot of trial and error; observing and mimicking nature; and very much dependent on the weather. No year is ever quite the same, so be grateful for what you get and chalk the rest up to experience.
