Knowing when to plant is tricky, especially when it comes to vegetables, whether from seed or transplants. That’s because the decision is based on a combination of actual weather conditions plus soil temperatures and not -- as is often suggested -- calendar dates.

The problem with calendar dates is they’re highly variable. For example, February, 2021, was the fourth coldest on record (the low was -13 degrees on the 16th!). Last year it was the third warmest. And as is often the case with fickle February weather, we set a record high on Monday, but next week the roller coaster continues with morning lows in the 20s.

But at some point you have to commit to planting. After all, an early start means an early harvest, and cool-season vegetable crops do best when grown under cool conditions. On the other hand, getting started too early can lead to crop failure if temperatures nose dive.

So what can you safely plant now? Well here are the top three.

Asparagus is a perennial vegetable, meaning it’ll come back year after year, usually for 12 to 15 years, but up to and beyond 20 years. Because it’s planted below ground, its gnarly roots  (known as crowns) are insulated from the cold, and by the time its top growth emerges in a few weeks, we should be in the clear weatherwise. A late freeze may damage the tender spears, but new ones will appear in no time.

Because asparagus is so long-lived, it pays to prep the planting area well by adding plenty of organic matter (see last week’s blog below in case you missed it). Choose a spot that gets lots of sun and drains well.

To plant, dig individual holes or a trench roughly six-inches deep in clay soils and up to twice that deep in sandy soils. Space the crowns about a foot apart, and simply lay them on their sides flat. (For decades we’ve been told to spread the roots out “octopus style” on a mound of soil but recent research has shown that to be unnecessary.) Cover with three-inches of soil and as the spears begin to appear, add more soil over the course of a few weeks to ultimately fill the hole or trench. Water well, add some mulch if you like, and you’re done.

Now for the bad news: you can’t harvest any asparagus spears the first year, because you need to let them develop into ferns (top growth) so as to build the strength of the crowns. The second year after planting you can harvest for two weeks and the third year for up to four weeks. After that, you can harvest for six to eight weeks.

But here’s the good news: I think asparagus is the absolute best-tasting homegrown vegetable, and as good as store-bought asparagus can be, it pales in comparison.

Potatoes are my favorite food to eat and to grow. Last year I planted them on February 15 (remember, it was a warm month) and my plan this year is to get them in the ground before March 1, so long as soil temperatures are above 45 degrees, because potatoes produce best in cool soil. They also need full sun and good drainage.

Plant individual potato tubers roughly four-inches deep and about a foot apart. If you want to cut them into pieces, be my guest. Just make sure each piece has a few “eyes,” the point from which sprouts develop, and let the cut flesh dry out for 24 hours or so before planting to reduce the risk of rot. I don’t bother cutting the tubers; never have, never will, and I get lots of taters from each plant (last year, I harvested close to 200 pounds).

As the green growth emerges above ground, begin watering weekly, and be prepared to cover the plants with a beach towel if temps drop below freezing. When the plants flower (mid-May, typically, although not all varieties flower), you can carefully dig a few “new” potatoes, but if you plan on storing your potatoes, let the foliage die back completely, then harvest the entire crop by stabbing a shovel or garden fork deep into the ground (but well away from the center of the plant) and lift to reveal the tasty tubers. Remove some of the soil on the tubers, but don’t wash them until you’re ready to eat them.

You can also plant potatoes in containers in much the same fashion as I described for asparagus. Fill the container with a foot of potting mix (not garden soil!), space the tubers about a foot apart, and cover with an additional six-inch layer of potting mix. As the green growth emerges, add more potting mix, leaving a few inches of growth exposed. Continue this process until the container is nearly full. Just make sure the container -- be it a plastic bucket, old trash can, or whatever -- has lots of drainage holes. Perhaps the best containers of all are those made from fabric. 

All three are extremely cold hardy, and I don’t see any temperatures in the long-range forecast that would prevent me from planting them as early as this weekend. All three are also related, require full sun and weekly watering, and have similar growing conditions.

Onions are available as seeds, sets, or transplants. Seeds are notoriously slow to germinate. It’s too late to start them indoors, but you can sow the seeds outdoors now. Sets are simply bulbs that have yet to sprout. I grow them to produce scallions because the varieties sold will never develop large bulbs in our area. Transplants are just miniature onion plants and are ready to go in the ground and can develop full-sized onions. Place transplants in individual holes or trenches but don’t plant them too deeply -- cover with just enough soil to keep them upright. Keep the planting bed free of weeds and harvest when top growth turns brown and falls over.

Shallots have a milder taste than onions. Plant the bulbs just as you would onion sets, leaving just a tiny bit of the bulb above ground. Harvest when the foliage fades.

Leeks are my favorite of the lot. They too are mild tasting, but their flavor is fantastic. Transplants are often hard to come by, but if you find them, grow them. The key to growing great leeks is to produce as much of the lower, white part as possible. I do that by sticking the transplant deep into the soil -- as much as six inches -- using a long screwdriver or piece of rebar and stabbing it into the ground, then plopping the transplant in the hole and covering with soil. As the plants grow, I add more soil to the base of the plant, preventing sunlight from reaching the base of the plant and creating even more of the white part.

Just how do you know what the soil temperature is? That’s easy. Go online to Oklahoma Mesonet www.mesonet.org or install the app on your phone. The Oklahoma Mesonet is a world-class network of 110 environmental monitoring stations scattered across the state, and it’s run by scientists from OU and OSU. The site displays real-time weather information of all kinds, and detailed maps of soil temperatures, moisture levels, and so much more.

Next week Paul expands his discussion of what to plant with an in-depth look at greens of all kinds (arugula, lettuce, spinach and more), root crops such as beets, carrots, and radishes, and other goodies like broccoli, cabbage, and cauliflower -- that love the cool weather.