I often get asked the question, “When can I plant my garden?” It turns out that answer is a little more complicated than picking an arbitrary date. Don’t worry, though; it’s not too complicated.
When asked “When can I plant?” I usually answer with another question: “What is it that you want to plant?” It’s amazing how important that bit of information is. In the post about plant hardiness zones, I talked about how knowing which zone you are in can affect which plants will do well in your garden. However, when deciding when to plant, knowing your hardiness zone isn’t quite as important as knowing your average last frost, average first frost, and number of frost free days. If that’s not something you keep track of in your journal, don’t fret. The good folks at the Utah Climate Center have that taken care of – and not just for Utah gardeners, but for everyone in the United States!
At the Utah Climate Center Freeze Dates page, you can select your state from the drop down menu at the top of the page and then scroll down until you find the weather station nearest you. In some cases, like for Bryce Canyon in the screen shot below, there are multiple weather stations listed for your area. Most of the time the data will be similar among the different stations, but you might want to choose the most recent data (in the “Period” column) or the data averaged over the longest number of years (“in the “Years” column).
I don’t know if I’ve mentioned it before, but I’m a huge fan of the extension service. They will be your best resource in answering the “when can I plant” question – after you’ve already decided on the “what” you want to plant. A lot of university extension websites have vegetable planting guides available that give information on planting dates, how many days until the plant reaches maturity (or harvestability…that’s a word, right?), and some may also include information on plant spacing and depth.
For the sake of generalizing, though, we can divide the vegetables into Cool Season and Warm Season types. We can further divide the cool season vegetables into hardy and semi-hardy, and the warm season veggies into tender and very tender.
- Hardy = may survive a frost, can grow when daytime temperatures are as low as 40 degrees F
- these include: broccoli, cabbage, kohlrabi, radish, spinach, turnips, lettuce, peas, onions
- Semi-hardy = less tolerant of frost, but can still grow when daytime temperatures are between 40-50 degrees F
- these include: beets, carrots, cauliflower, parsley, Swiss chard, potatoes, parsnips
- Tender = intolerant of frost, need daytime temperatures above 50 degrees F; grow best in warmer conditions
- these include: beans, celery, corn, summer squash, cucumbers
- Very tender = intolerant of frost, may be stunted by prolonged periods of 55 degree F temperatures, need daytime temperatures of 60 degrees F or more, but prefer at least 70 degrees F
- these include: tomatos, cantaloupe, pepper, watermelon, lima beans, eggplant, winter squash, pumpkins
Around these parts (northern Utah), you can still plant any of the cool season crops along with some of the tender warm season crops; with protection (like with a wall of water) you could also start planting out the very tender vegetables. Just know that if you ask any of the old timers they’ll tell you to wait until Memorial Day to put in your garden.