Soil Temperatures Are Key to Spring Vegetable Garden Success

Starting a Vegetable Garden in Spring

Tom Ingram: Ask a Master Gardener

Sunday, March 31, 2019

Q: It’s so nice outside, am I safe to start my vegetable garden now? CT

A: Oftentimes, people will suggest certain dates when you can plant your vegetable garden. But dates are only guidelines. To know for sure when we can plant, we must look at the weather and do a little investigation to determine soil temperature.

For example, oftentimes, people will say St. Patrick’s Day is the time to plant potatoes. There is no potato magic in St. Patrick’s Day, other than in a normal year you are probably OK planting on this day. The truth about when to plant potatoes is based on when the soil temperature is appropriate for planting.

According to the OSU Extension, soil temps need to be above 50 degrees before we plant potatoes. At the writing of this article, soil temps at a depth of 4 inches are hovering around 51 degrees. So we’re just entering optimal conditions for potato planting.

Cold soils also inhibit seed germination of some of our more popular vegetables, such as tomatoes, squash, cucumber or peppers. To overcome this challenge, it is common for gardeners to start seeds indoors so the plants will be ready to go outside when it warms up.

If you have been to any of the garden centers in northeast Oklahoma recently, you will have noticed racks of seeds and seed starting supplies. Many of us have already gotten our seeds started and can’t wait to get them out in the sun. But if we move them outside too early, we run the risk of a late freeze damaging our fragile new plants. In northeast Oklahoma, we typically say we should be safe after April 15, which is still a couple of weeks away. But it’s not unusual for us to have a late freeze. Last year, we had one night with a low of 28 degrees the first week of April, so if you jump the gun, be ready to spend some time covering your plants.

Sometimes, talking about the need to find out what your soil temperature is at various depths can be a little intimidating. But don’t let that scare you off. In Oklahoma, we have a wonderful resource called the Mesonet. The Mesonet is a joint project between OU and OSU with at least one weather monitoring station in each county. You can visit mesonet.org for an abundance of weather information, including rainfall and soil temperatures.

For more information on starting and growing vegetables, visit the “hot topics” section on our home page to find a link that will take you to an abundance of information to help you be a more successful vegetable gardener.

Garden tips

• Our annual spring educational Lunch & Learn classes at the Tulsa Central Library downtown have begun.
• One of our most anticipated events is currently underway: The Master Gardener Plant Sale. You can choose from more than 200 plants, including annuals, perennials, grasses, herbs, tomatoes, succulents and stepables.

To find out more information on any of these and other opportunities, visit our website at tulsamastergardeners.org.