It is spring. Is it time to plant veggie seeds?
By Bonnie Orr
WSU Chelan/Douglas County Master Gardener
It has been abnormally warm the last week of February and the first week of March, and the sun has mostly been shining, and it must be time to start the vegetable garden! Let’s look at the factors that ensure the seeds will grow.
First and most important is soil temperature. I have often heard that people should plant pea seeds on Washington’s Birthday. Not only is this a fantasy, but it does not work in North Central Washington. Even this year when the soil in my garden was 44 degrees on Feb. 22, that is not warm enough. When the soil is too cold, the seeds rot. Many times, people blame the lack of the germination of the pea, bean or corn seeds on “those thieving birds.” It is most likely because the soil is too cool, and the seeds rotted.
So how to determine how warm the soil is? WSU Ag Weather Net (https://weather.wsu.edu/) is a free site — registration is required — you can visit to read all the current weather conditions, including soil temperature, specifically in your area. You can also use a digital kitchen thermometer with a 6-inch probe or purchase a specially designed soil thermometer.
Let’s consider tomatoes, the most popular vegetable garden plant. Tomatoes need the soil to be a minimum of 70 degrees to thrive. This is not the air temperature, but the soil temperature. Have you put out tomato plants and watched the leaves turn pale or purple? That means the soil is too cool.
The last few years, my garden soil did not reach 70 degrees until the end of May, the first week of June. A number of people have told me that they have to plant bean seeds two or three times and blame the birds. But if you consider the soil temperature, the optimal germinating temperature for beans is 70 degrees. Planting before that means that germination will be spotty.
There are sources on the internet that list optimal soil temperatures for various vegetable seeds. This is a reliable one: bit.ly/osuextgermtemp.
When planting seeds indoors to get a “jump on spring,” consider when you will be placing the plants in the garden. Some seeds such as pumpkins, cucumber and squash sprout readily in a few days when the soil is warm enough and do not need to be started inside.
If you start seeds inside, and they grow leggy, they will never grow into lush, healthy plants. So, I do not start my tomato seeds until April 15. Six weeks is long enough for the plants to grow before they are set out in the garden. I know this is all discouraging because we want to get the garden in.
The other problem of growing vegetable seeds is the depth of planting the seed. If the seed is set in hard soil with little soil moisture, the seeds will grow poorly. Seeds need moisture and air to germinate and set roots. If the seed is set in the ground too deeply, there will not be enough air, and the seed will not have enough stored energy to poke up through the ground.
Many times, we see lots of veggie plants for sale in the big box stores. It is best to wait to purchase them until the soil is warm enough to put the plants in the garden.
A WSU Chelan and Douglas County Master Gardener column appears weekly in The Wenatchee World. To learn more about your local Master Gardener program, visit bit.ly/MGchelandouglas or call (509) 667-6540.