Why Grow Tomatoes in Containers?

This is the first year that I am growing the majority of my tomatoes in containers, and wow, are they doing well! I decided to go with containers because I’m using my raised beds for a cutting garden, and I’ve found that growing tomatoes in my regular garden beds results in slow growth and late-season diseases. I planted one tomato in the ground and it is definitely lagging behind the guys in the containers.

Why grow tomatoes in containers? A few reasons:

An 18-inch container may be a little tight, but most tomatoes do well in 18- to 24-inch containers.

1. You control the soil. For my container tomatoes, I used large containers and a high-quality potting mix.  The mix has most of what the tomatoes need in terms of nutrients and I will add some bone meal or liquid fish emulsion as the tomatoes produce fruit to keep the calcium and fertility levels up.  The potting soil also lacks all the soil-borne diseases that tend to hang out in the ground—that’s a good thing!

2. Decent drainage. We’ve had a pretty wet early summer in Minnesota. (We had a solid 3 inches in the past week and many areas of Minnesota had much more.) Unlike the ground, which can get water-logged, containers drain well. (I’m considering adding pot feet to my containers to ensure even better drainage.) They have holes in the bottom so excess moisture moves away from the roots, preventing root rot. One disadvantage of container tomatoes is that in dry spells you have to stay on top of watering. Tomatoes need consistent—but not excessive—moisture throughout the growing season to perform best and avoid blossom end rot.

3. Air circulation, easily. Every time I plant tomatoes in the ground, I end up putting them too close together. They look so little when they go in the garden and it’s hard to imagine how big they will get — and how entwined in each other.  With tomatoes in pots, I can move the pots if they get bigger than expected and start encroaching on their neighbors. Air circulation is another important factor in the health of tomatoes.

4. Easy to cage. The pots I chose for my tomatoes are all 18 inches in diameter. For really large tomatoes, you could go even bigger, but the 18-inch pots are a perfect fit for the standard size tomato cage, which I put on the tomatoes a few days after planting. Don’t wait to cage your tomatoes.

Green tomatoes already on some of the plants!

5) Easy to pick. Container tomatoes are elevated by the height of the pot so it’s easy to see when fruit is ripe. The elevation also makes it harder for rabbits and voles (though unfortunately, not squirrels) to get at the tomatoes. For squirrels — a bit more engineering may be necessary.

Many of the usual instructions for growing tomatoes apply to container tomatoes — place them in a very sunny spot, plant them deeply in the container to allow roots to form, and pinch extraneous foliage to keep the plant focused on producing fruit. Generally, determinate tomatoes are recommended for container growing, though I’m growing several types of heirloom tomatoes and I think most of them are indeterminate.

I will report how things go as the season progresses! Do you grow tomatoes in containers?



411 on Cracked Tomatoes

I was out of town Wednesday night and came home to three inches of rain in the rain gauge and a handful of cracked tomatoes.  The two items are related.

Why Tomatoes Crack: To grow well and fruit profusely, tomatoes need even, consistent moisture. I water tomato plants during dry periods to encourage fruiting and healthy growth. But when Mother Nature dumps a bucket of moisture on the ground, the plant naturally takes it up and the fruits crack. Their skins can’t grow fast enough to take in the extra moisture. Cracking is most common with a heavy rain after a long dry spell, though this was not the case here because we have had an unusually rainy August. As typically happens, the fruits closest to ripeness cracked.  The cracks in the fruits provide an entry point for bacteria and fungi, and typically the fruit will rot quickly—in fact, I tossed one really rotten tomato before taking the picture.

Can you prevent cracking? You can’t prevent cracking from extreme storms, but you can prevent losing tomatoes due to cracking, by harvesting tomatoes most susceptible to cracking. Green or very unripe tomatoes are less likely to crack, so picking those that are ripe or nearly so before a big storm is a good way to prevent cracking. Since I was away during the last storm, I picked a lot of ripe or nearly ripe fruit right after I got home. You can prevent cracking if the problem is dryness by watering regularly.  You also can reduce cracking by growing tomatoes in raised beds, which drain more thoroughly than in-ground gardens, and by applying a layer of compost or other mulch to keep soil evenly moist in dry periods.

Are there tomatoes that don’t crack? Yes, there are some varieties that resist cracking. (Those that crack the most tend to be heirloom varieties and large tomatoes.) You can find a long list here of crack-resistant varieties. Popular varieties that crack less include Arkansas Traveler, Celebrity, Big Boy, Big Beef, Summer Sweet, Sungold and Yellow Pear. If cracking tends to be a problem with your tomatoes, you may want to choose a crack-resistant type.

What about calcium and cracking? Calcium helps tomatoes regulate their intake of moisture, and a shortage of calcium in the soil is also linked to blossom end rot, another really discouraging tomato problem. Some gardeners add crushed eggshells to the planting hole, antacid tablets or a commercial calcium to increase the calcium available to plants. Consider a soil test before you heavily supplement the soil.

We have more rain in the forecast for the next couple of days, so I will be harvesting more tomatoes today. How are your tomatoes doing during this rainy period?

Best Tips for Starting Seeds Indoors

Over the years, I’ve had lots of successes and lots of failures with indoor seed starting. While seed-starting time is in February or March in many parts of the country, early April is actually a really good time to start seeds indoors in Minnesota, especially if you are planning to grow warm season crops such as tomatoes.

So, here are my top six tips for starting seeds indoors successfully.

seedlingNo. 1 — Put them where you will see them. Many gardeners have to put their seed-starting set up in the basement. They end up forgetting to check them and before you know it, the seeds are dried up or overgrown. Put them in a prominent place so you are inclined to coddle them.

No. 2 — Let the breezes blow. Outdoors, your little seedlings will experience wind (where I live, it’s gale-force a lot of the time), so get them used to it with a fan set up near your seed starting area. Keep the fan on low to get the seedlings used to wind. This will also help reduce fungal diseases.

Tomato seeds planted and labeled.
Tomato seeds planted and labeled.

No. 3 — Label, label, label. You think you will not forget which of the six varieties of tomato seeds you started are in which pots — but you will. My latest trick is to use a label maker to create labels on the seed starting trays. This is much neater than writing it out on a popsicle stick and less likely to fall off or get washed away. When the plants move to the hardening off stage, the label maker will be employed again.

No. 4 — Water gently and sparingly. More seedlings have been killed by drowning than by drying out. Water regularly, not too much, and if at all possible, from the bottom. My current set up includes really great trays I got when I ordered prairie plants from Prairie Moon Nursery. Each cell is 5 inches deep and the cell tray stands in another tray. I just pour the water into the lower tray and the plants drink it up from below. This encourages the roots to go deeper. When seed-starting season is over, I wash the trays thoroughly and give them a dip in a 10 percent bleach solution to kill any bacteria.

No. 5 — Don’t spend too much. If you only are growing a few tomatoes, it may not be worth your time and money to start from seeds. Just buy a few plants at a local farmers’ market or a garden club plant sale. You don’t need a fancy grow system either — a basic shop light, a couple of flourescent bulbs and a way to suspend the shop light above your seed trays, trays of some kind and seed starting mix — that’s all you need. Do buy or make your own seed starting mix rather than using old potting soil or garden soil.

No. 6 — Pot them up. Depending on the size of the cells you use to start your seeds, you may have to move them to larger pots as the plants get bigger. This is particularly true in my experience with those little pellets that expand when you add water. I’ve got some seedlings that were planted about two weeks ago that are going to need to go into a bigger pot very soon. Save small yogurt cups or the pots that purchased plants came in, add some potting soil and very gently move the seedlings into a bigger pot. Pot them up gradually. A tiny seedling might go to a 2-by-2-inch pot or a 3-by-3, even if it eventually will fill a large container.

For more information on seed starting:

Slow Roasted Tomatoes

Ready for a long roast in a low oven.
Ready for a long roast in a low oven.

The tomato season is about to close, so about a week ago, I bought a nice batch of beautiful cherry tomatoes. I didn’t grow cherry tomatoes this year, but slow-roasted tomatoes are too good not to have on hand. They could not be easier to make either.

I poured about 3 tablespoons of olive oil on a cookie sheet, then rolled the tomatoes around in it so they were all covered. I salted them lightly and ground some pepper over them. You could also put a couple of cloves of garlic (in the skins) on the tray, too. Then I set the oven to 225 degrees, put the tomatoes in and forgot about them. About six hours later, they were soft and wrinkly. I put some in a jar and covered them with olive oil and put the rest in freezer bags for later use.


These are like candy. They make a great addition to a salad or slice some soft cheese on a cracker (gouda is good-a!) and top it with a tomato. Instant hors d’ourves elegance.


Tomato Takes Root in Fall

Here’s something cool. One of my tomato plants sprouted roots all along its stem. I discovered this Saturday while pulling the tomato up. It was a Beam’s yellow pear tomato plant I bought at the Farmers’ Market and planted late in the season. In July, we had a hail storm. The hail split the plant right down the middle at a point where the two main stems intersected. The stems were barely connected and I thought the tomato was a goner. I didn’t even bother to stake it. I just left it alone in hopes that one side would recover. Both sides continued to grow and produce fruit, and now I know why.

While surprising to uncover the mass of roots under the stems that rested on the ground, it does make sense. Many times people who have leggy tomato plants will plant them very deeply or even lay the leggy stem underground to encourage root growth. You can do this with other plants as well, although tomatoes are especially good at laying down roots. St. Paul gardener Philippe Galandat, who was featured in the November/December 2007 Northern Gardener, uses a method called layering to propagate shrubs. He pulls a branch down, nicks it slightly, then pins it under dirt with a clip. When the new plant roots, it can be separated from the parent plant. Galandat, a frequent garden lecturer and owner of Swiss Gardens, has propagated a hedge of black currant bushes using this method.

Yellow Tomato Jam

It was 42 degrees F this morning when I rode my bike into downtown Northfield, so tomato season cannot last long. Late last week, I harvested what will probably be my last pile of tomatoes off of the Beam’s Yellow Pear bush that has been so prolific and delicious this summer. I’ve had problems with my other tomatoes, but the yellow pears have been great.

Since I had more than I thought we’d eat in the next day or two, I decided to make Yellow Tomato Jam with them. There are a bunch of recipes for this jam at various cooking sites. This one sounds good, if you like things spicy, as does this one. I modified this recipe to make my jam.

Yellow Pear Tomato Jam

  • 4-6 cups pear tomatoes, cut in half with as many seeds removed as is easily possible.
  • 1 lemon
  • 1 orange
  • 4 cups sugar
  • 1 package of pectin
  • Nutmeg, cinnamon, cloves, salt

Prepare the tomatoes and place in a large pot. Grate the lemon and orange zest into the pot, then remove the pith and put the flesh of the lemon and orange in the pot, add a good shake of nutmeg, cinnamon, a dash of salt and cloves. (Heavy on the nutmeg, light on the cloves.) I also added a half cup of water, too, because things were looking dry. Add the pectin, stir, and heat until boiling, stirring occasionally. Dump in the sugar all at once, stir until mixed, and let it boil for 10-15 minutes. It will get thickish. Meanwhile, prepare your canning jars and lids and get a big pot of water boiling on the stove, preferably canning size. Put the jam in the jars, wipe rims, apply lids, and process in a boiling water bath for 10 minutes. (If you don’t like to can, you could probably freeze the jam as well.)

This jam is like a marmalade because of the orange and lemon and the spices. Very good on toast or on a bagel with cream cheese.

A Tough Year for Tomatoes

During my visit to the Minnesota State Fair, I had a chance to chat with the Minnesota Master Gardeners staffing the extension booth in the Horticulture Building. I asked what was the most frequent question they were getting at the fair. The answer: Why do my tomatoes look so bad? Many gardeners (including yours truly) are experiencing blossom-end rot on their tomatoes.

According to the Master Gardeners, fluctuations in moisture and too much fertilizer are the most likely causes of blossom-end rot. “Tomatoes don’t like too much nitrogen,” one of the MGs reminded me. I’m seeing blossom-end rot mostly on my paste tomatoes, which are in a new bed to which I added lots of compost. (Oops.)  For best results with tomatoes, don’t grow them in the same place more than once every three years. Interestingly, my best-performing tomatoes are yellow pears, growing in a mixed bed in which I have never grown tomatoes.