Every gardener, including myself, looks forward to temperatures warming up. I want to bid adieu to the snow & frost and welcome anything remotely green. It’s no secret I’m eagerly awaiting the moment I can start working the soil in my planter box garden.
One advantage above ground garden boxes have is the sheer fact soil warms up sooner than in-ground garden plots. Warmer soil temperatures allow crops to be planted earlier, especially in northern climates. By adding even a couple of weeks to the growing season, I can help ensure my vegetables have adequate time to mature.
Optimal soil temperatures for spring planting range from 50°F to 80°F. As long as you can maintain a plant/seed specific minimum temperature, your seeds will germinate and the process of sprouting can take place.
For early spring planting, minimum soil temps will still allow growth but the lower the temperature, the slower the growth. If you are looking to get a head start, the charts below can help you reference which crops are appropriate and at what soil temperature.
Early Spring Planting Minimum Soil Temperatures
40°F <—————————————————————————————-> 46°F
Spinach Radish Lettuce Onion Peas Potato Cabbage Carrot
Spring Planting Minimum Soil Temperatures
60°F <————————–|———————————-|—————————> 75°F
Tomatoes Cucumbers Beans Corn Squash Peppers Melons Sweet Potatoes
When daylight hours reach approximately 8-10 hours and daytime temps are consistently in the 50°-60°F range, it’s a good indication your soil may be ready for planting.
Early spring crops such as potatoes and onions can be planted as soon as the soil is tillable. Last fall I ended the season by incorporating a year’s worth of compost into my garden boxes. By planning ahead, I should be able to turn the soil and be ready to plant as soon as temperatures allow.
One important key in planting onions and potatoes started from bulb or tuber is to keep them from freezing or being damaged by frost. By using a hoop house or high tunnel, plastic sheeting or a layer of straw, you can help insulate the soil and retain heat. Because these forms of protection are relatively simple to install, you could easily use them 2-3 weeks prior to planting to get a jump-start on increasing your soil temperatures.
For those new to gardening – now is the time to start planning, ordering seeds and finding a reputable garden supply store to purchase your supplies. Don’t make the mistake of using sub-par materials; in this case, quality can make all the difference. A good garden center should be able to answer any questions you have about starting your first garden plot, raised bed or container garden. Happy planting!
TIP: Do not use store-bought potatoes for planting. They are chemically treated to prevent sprouting!