Yes, in spite of the chilly weather we can get into the garden and poke some seeds into the soil.
I have already planted peas, lettuce and arugula, all of which like prefer growing in cooler weather. Other seeds that can be planted outdoors now (late March) include spinach, beets and turnips. Most of these can be planted into mid- or even late April.
This handy Vegetable Garden Planting Guide from K-State Research and Extension provides a graph indicating the best times to plant common vegetables. It is a great guide that I still refer to even after many years of growing vegetables (although I think the older version is easier to read). The guide includes information on how much and how to plant various vegetables, whether to plant seed or transplants, expected time of harvest, and other information packed into charts.
Even though I’m getting ready to put my cabbage transplants in the ground, I’m focusing on seeds today.
Seeds are amazing. Each seed, no matter how large or small, contains an entire plant – seed leaves (cotyledons) that contain sustenance for the seedling plant, a stem (hypocotyl), and a root tip (radicle). Seeds are little miracles waiting to emerge. All they need is the appropriate amount of warmth and moisture to get growing.
Soil temperature is a key factor in determining the appropriate time to plant seeds. Even though we’ve had short bouts of some pretty cold air temperatures, we’ve had enough warm days that the soil temperature should be just about right for planting cool season vegetables. Peas require a soil temperature of just 40 degrees Fahrenheit, while lettuce will germinate in soil as chilly as 35 degrees F. They will take longer to germinate in soil at the minimum of their temperature range, but they will germinate. The optimum range for pea seed germination is 40 to 75 degrees F., while the optimum range for lettuce is 40-80. Seeds also have a maximum soil temperature at which they will germinate. For lettuce that is 95 degrees F., which means that when I want to plant lettuce in the middle of summer I must take steps to keep the soil cooler. Even if the air temperature has not reached 95, sunlight shining on the soil can raise the temperature much higher.
Aside from soil temperature, moisture is a key ingredient in getting seeds to germinate. The light, frequent rains we’ve recently experienced should be helpful in keeping newly seeded beds moist. During dry weather supplemental watering will be required. A daily watering of just the top layer of soil often is needed. During warm or hot weather, seedbeds may need dampened two or more times a day. This doesn’t require a lot of water, since you only need to wet the soil to the depth of the seeds. One trick I’ve found helpful, especially for seeds that are persnickety about germination, is to lay a board over the dampened seed row. Check beneath the board every few days and remove it once a good portion of the seed has germinated. I have found this to work especially well for carrots, and for seeds sown during warmer days, as the board helps keep the soil cooler.
Each type of seed differs in its optimum temperature range, planting time, days to germination (which also is dependent on soil temperature), days until harvest, as well as planting depth. For many common vegetables that information is available on the planting guide. For plants not listed there, that type of information often is available on the seed packet. Another key piece of information is how far apart to plant the seeds, which takes into consideration mature plant size.
For the most part, it is best to plant seeds a little more thickly than recommended and to thin later, to account for the fact that some seeds won’t germinate. Larger seeds, such as peas, beans and okra, are fairly easy to place at appropriate distances, but smaller seeds are tricky. I’ve always just scattered lettuce and other small seeds by hand, figuring I’d thin seedlings later. However, I rarely get around to the thinning.
This year I’m trying something a little different. Seasonings in little glass jars often come with shaker tops. I started using these to plant seed in flats for microgreens, but I also think this will work for scattering small seeds in the garden. It won’t create perfect spacing, but it will (I think) scatter seeds more thinly than I do when dropping them from my hand. Even though they will be planted closer than optimal, the wider spacing will make them easier to thin.
One more seed to plant, if you have packets of seeds that are a few or several years old, you don’t need to toss them. First, do a germination test. You can find a Test Your Seeds guide on this website. I’ve been surprised at how long some of my seeds have remained viable. Okra seed germinated almost 100 percent after 10 years.
For lots more information on vegetable gardening, check out K-State’s Kansas Garden Guide.
Now let’s get sowing!
Written by EMG Sandra Siebert
Master Gardeners of Douglas County, KS 