This calendar’s monthly planting guidelines are based on USDA zone 9, but they are adaptable to most zones. To find your zone, go to the National Gardening Association’s website.  If your zone is 7, 8, or 9, you can safely use this guide. If your zone is 4, 5, or 6, then add a month before beginning your spring tasks and start your fall tasks a month earlier. If your zone is 10 or 11, subtract a month to your spring tasks. Your fall and winter tasks should remain the same as the original guide if you are in zones 10 or 11. These are all general guidelines. Your specific microclimate, which depends on the distance to a large body of water (like gigantic lakes or oceans) and elevation, will make your zone fluctuate. Consult your local county extension office, found here, to get more detailed zone and planting guide information.

Tasks for December:

• Select next season’s varieties:

– Understanding the culinary purposes behind tomato shapes

– Climate and sunlight requirements for different tomato varieties

– Disease resistance

• Order seeds
• Soil testing: essential for good results

Selecting next season’s varieties

Understanding the culinary purposes behind tomato shapes

As a master tomato gardener, you should know that tomato shape often dictates what the cook can do with tomatoes. Medium to large round tomatoes is typically called “beefsteaks,” which can come in many different colors: red, pink, yellow, bi-color, green, orange, pale yellow (known as “white”), purple, and brown (the latter two known as “black”). Plus, these colors can also be distributed on the beefsteaks in pronounced lines from top to bottom. Tomatoes with this color pattern are known as “striped.” There are thousands of named varieties of beefsteaks, from Ananas Noire to Zheza.

Regardless of color or name, beefsteaks share something in common: They all tend to be juicy with a lot of interior seeds. These characteristics don’t lend this type of tomato very well to cooking. It’s best for slicing in salads and sandwiches. Also, using a beefsteak tomato in salsas will result in a lot of watery juice at the bottom of the bowl.

The second type of tomato is an “oxheart” variety. These can come in many colors as well and tend to be anywhere from five ounces to a pound. They are heart-shaped, with the stem button on the top, tapering down to a blunt point on the blossom end. Oxheart varieties number in the hundreds, with names, sometimes indicative of their shape, like German Red Strawberry and Brad’s Black Heart.

Oxhearts do double duty in the kitchen because they are almost pure meat with very few seeds. Fantastic as slicers in salads, adding them to a picnic or lunch sandwich keeps the bread from getting soggy, unlike a beefsteak tomato. They are also popular in canning and cooking tomatoes because they have very little watery juice that slows down the cooking process and contributes to overly watery pasta sauces, salsas, and canned tomatoes in jars.

If you’re cooking with tomatoes, then the other odd shapes of tomatoes are for you: plum, pear, elongated, and ruffled (ribbed). These odd shapes mean that the tomato meat is firm, with very little watery juice. This category is called “roma” or “paste” tomatoes. Not the best-tasting “eating out of hand” tomatoes, these shine once cooked. Their thick walls hold up to cooking; because there is little water in them, they produce beautiful salsas, stir-fries, canned goods, ketchup, and quick pasta sauces.

So before you decide on which varieties to grow, ask yourself what you’ll be doing with the tomatoes and how you’ll be preparing them. Most of our gardens are smaller than we’d like and giving up prime space to a paste-type tomato when you only want a fresh slicer would be a waste.

Climate and sunlight requirements for different tomato varieties

There are several factors regarding climate that are particularly important for expert tomato growing: the expected temperature swings each day, the amount of sunlight the tomato plant will get, and the length of your warm season. Let’s take them in turn.

Temperatures

If you live in a corner of the world where the daytime temperatures are very hot and the nighttime temperatures cool off, then this is a tough growing condition. If you live in an area where the temperatures are relentlessly over 90 degrees every day of the summer, that is also a tough growing condition. If your tomatoes will be subjected to cool fog and wind, which happens a lot near some coasts like California and Oregon, then that too is problematic for tomatoes.

Tomatoes are a bit fussy about their temperature range. They prefer to be about 65 degrees at night and 75 degrees during the day. The more you get outside of this range, the more your tomatoes will pout: blossom drop, failure to thrive, delayed ripening, lower yields, increased susceptibility to pests and disease. These are all challenges those of us who live in tough growing conditions must face.

But there are some varieties of tomatoes bred to withstand tougher conditions. For example, Oregon Spring and Siletz were designed to withstand cool, foggy coastal areas. Other varieties have been bred to stand up to excessive heat, like Phoenix, Sun Master, and Heatwave hybrids. So before you choose a tomato variety because it’s pretty or you like the name—or it’s sitting in front of you at the nursery, begging you to take it home—ask yourself whether you’ve got a tough growing condition. If you do, invest in a little research before you give up your precious garden space for a tomato better suited for a different microclimate.

Sunlight hours

Tomatoes need sunlight shining directly on their leaves, not banked or reflected; tomatoes absolutely require it. And the bigger the tomato fruit, the more sunlight that plant needs. Whenever you’re buying a tomato, try to ascertain how big the fruit is expected to get. Then match it up with how many sunlight hours you can offer it in your garden. We all have shadier and sunnier patches in our gardens. Be brutally honest with yourself to figure out the number of direct sunlight hours your tomatoes will get. Your tomatoes are the stars of your garden, so put them in the sunniest spot and grow your carrots and lettuces in shadier locations.

A good rule of thumb to follow if you’re trying to grow a big beefsteak type, such as Cherokee Purple or Brandywine, is to ensure the plant is getting at least seven hours of direct sunlight. “Large” fruiting tomatoes are anything over 10 ounces. Medium-sized tomatoes, such as Early Girl or Ramapo, can successfully be grown with five to six hours of direct sunlight. Smaller fruiting varieties, such as Matina, Green Zebra, and cherry varieties, will do much better than beefsteaks if you can only give them three or four hours of sunlight. These smaller-fruiting varieties will also fare better if you live in a tough growing area, such as those with extreme daily temperature swings.

Note that all tomato varieties, regardless of size, would prefer eight or more hours of sunlight, but if you simply don’t have that due to a shade impediment such as trees, fences, or buildings (even fog reduces daylight hours), then you’ll have much better luck growing medium to small fruiting tomatoes.

Disease resistance

Another important thing to think about is disease resistance. Some areas of the world have conditions that often bring on late blight, a deadly disease that can kill tomatoes and their kin within a week. Other gardeners have individual concerns about poor or disease-infested soils. If you’ve had trouble growing tomatoes before and suspect your soil may have an issue, consider growing tomato types that have been specifically bred for disease resistance.

You can often spot which types of tomatoes are hardier by whether there are letters (acronyms) after the variety name. For example, an “N” or “V” after the tomato variety name indicates that the tomato has shown resistance to harmful nematodes and Verticillium wilt. Not all seed companies offer those notations, however; you may need to investigate the cultivar to ascertain any disease-resistant properties the tomato may have.

Note that heirloom varieties are generally fussier than hybrid varieties. The downside is there are fewer choices of color, flavor, and size with hybrids, and the seeds are more expensive than heirloom seeds due to the arduous task of creating the hybrids. Regardless of these detriments, if you’ve experienced problematic or diseased plants in the past, help the situation by choosing disease-resistant hybrids. Caring for them in a more masterful way and ensuring your soil is up to snuff are also necessary, but those are discussed in different month guides. For now, you are just selecting your tomato varieties to grow next season.

Order seeds

Once you’ve honestly evaluated what you can offer your tomatoes and what you want out of them, now is the time to order your seeds. Yes, it can be done in December, January, or February, but many tomato varieties sell out particularly the more popular ones. Crop failures for seed companies happen too, and they may have a limited supply of something you want.

Note that saving tomato seeds properly is done by taking a sample from at least 20 tomato plants of the same variety. If you swap seeds with a home gardener or buy from an unknown source, the seeds can be mixed, contaminated with seed-borne illnesses, or harbor genetic diseases due to being inbred or not saved from a large enough population. Always deal with a reputable supplier.

After receiving your seeds in the mail, store them properly in a cool, dark location that’s safe from mice and damp. Oftentimes, storing them in a hobby greenhouse will kill them due to fluctuating temperatures, and we’ve seen plenty of mouse-eaten tomato packets stored in garages. They don’t want to be stored in the refrigerator or freezer (too cold and damp).

Soil testing

Most long-term, successful gardeners know the importance of soil testing, and December is an excellent, not-so-busy gardening month in which to do that. Your local county extension office may do free or low-cost soil testing. Contact them to find out. If they don’t, they may know a local lab that will test your soil for a fee.

Note that farms are always getting soil analyses and plant tissue analyses to suss out problems and remediate them. A home gardener has the same tools in their arsenal if only they take advantage of them. Your county extension office can be found using this handy online resource.

Soil testing can reveal excessive amounts of good nutrients. For example, boron is essential for plant health; however, too much of it can lead to extremely poor results in the garden. There are dozens of factors such as these that will either make or break your garden, including pH, which is also something revealed by a good soil test. Also, a test will reveal the “tilth” of your soil. Simply stated, “tilth” is whether the soil is sandy, loamy, or clay. Extremes like sand and clay will affect how much you should be watering and fertilizing. Knowing what type of tilth your soil contains will allow you to amend it to get it closer to “loam,” which is the most desirable tilth. Your soil test not only will tell you what type of tilth you have but also the steps to take to get it up to snuff.

Whoever you use to do your soil testing, follow their instructions to the letter and mail off or hand-deliver your samples. Once you receive their feedback, you’ll be in a good position to implement those changes once the ground becomes workable in the early spring. “Workable” just means neither too cold nor saturated with rain.