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  • Growing tomatoes for the urban farm

    May 10, 2024 6 min read 0 Comments

    Growing tomatoes for the urban farm

    Urban farming transforms underutilized city spaces into productive green havens, and tomatoes are among the most rewarding crops to cultivate. Michael Bell of Dallas 1/2 Acre shares his journey and tips for growing luscious, market-ready tomatoes on an urban farm.

    Why grow tomatoes on an urban farm?

    Tomatoes are most farmers' favorite crop to grow for many reasons. One of the main reasons is the ease of sale. Almost everyone loves a fresh, homegrown organic tomato. Additionally, when growing tomatoes, you plant once and harvest for multiple months. Growing these delicious fruits, like most other things on a farm, can be done in multiple ways, with no one way being perfect for everyone. 

    Tomato Seed Starting

    I like starting my tomato seed like my lettuce and most other seeds, with a simple mixture of coco coir and worm castings. The mixture is ⅔ coco coir and ⅓ worm castings. If you are new to seed starting, Bootstrap Farmer’s Seed Starting 101 article is a deep dive into the process. I also use the same 72-cell air pruning trays I use for lettuce. The combination of this soil mixture and air pruning trays makes a perfect root ball to pot up after a few weeks. 

    Lighting for tomato seedlings

    I usually allow my tomatoes to stay in the 72s for 5-6 weeks. Everyone's situation is going to be different, though. I like to use racks with lights on shelves to control everything; however, if you live in a warm place, you might be able to just place them in a greenhouse. The biggest difference in these two examples is the number of daylight hours the tomato gets. On my shelves, I leave the lights on for 16 hours a day, but if you are in a greenhouse, you are at the mercy of the sun, which can be much shorter in daylight hours, slowing the seedling's growth. 


    Potting Up Size

    Potting up is far from an exact science. I do it when I have time or when I feel like it. It is usually between 4 and 6 weeks from planting the seed. There are two options when potting up tomatoes: you can go with the 3-inch pot or the 5-inch pot. I prefer the 5-inch pot because I really like to have big transplants when they go in the ground, but 3-inch pots are great too, if you plan to plant them outdoors in just a few weeks. Mine routinely stay in the 5-inch pots for 6 more weeks and do great when it’s time for their final transplant outdoors or into my high tunnel

    Potting up Medium

    I use a well-aged compost for my soil medium when potting up. I do not put much soil in the bottom of the pots since I like to plant the starts deeper and allow small hairs on the stem to become roots over time. It also keeps the tomato plant from getting too tall and weak when transplanting.

    After placing about an inch of compost in the bottom of the pot, I will take the seedling from my 72-cell tray and put it in the middle of the pot. I then take a small amount of worm castings and put it around the root ball. Finally, I fill the rest of the pot all the way up with compost and place it back in the tray for another 4-6 weeks, depending on the outdoor temps and when I think it is safe to transplant outdoors. 

    Tomato Tips

    There are a couple of things that I have found that work well for tomato starts between the pot-up stage and transplanting in the ground. First, I like to bottom water all of my starts, so when I fill up my containers with water, I always add a nitrogen liquid fertilizer, usually some sort of organic fish emulsion, just to give them a nice boost in growth. Secondly, I like to get my tomatoes outside as much as possible. 

    If it’s a nice sunny afternoon, I will bring the trays out and let them get sun and then return them to the grow room at night for more lighting. I will do this as much as possible. I am not saying it is foolproof but I can say I have never lost a tomato plant when transplanting! I think giving them random days of outdoor exposure really helps the hardening-off process and prepares them for full-time outdoor living. 

    Transplanting Tomatoes in the Ground

    There are a couple of ways a person can plant tomatoes. One way is pretty well known: simply dig a hole larger than your plant’s root ball, add in your amendments, place the plant in the hole, and fill in the hole. However, I plant mine very differently. My farm sits on very heavy clay. It’s a swamp when it rains, and the Grand Canyon when it's dry due to the ground having massive cracks in it. 

    Dealing with these circumstances, I learned that stripping the lower leaves off of the tomato plant, digging a trench-like hole, and then laying the tomato plant down parallel to your drip irrigation line with only 6-8 inches of the plant sticking up works much better.  This works well for me for several reasons. 

    First and most importantly, During the early season, when the heavy rains come through, it keeps the root ball out of the wet, soggy clay that is below my 8-inch raised bed.  Next, laying the plant down for around 12-18 inches allows those fine hairs on the stem to become roots and absorb more nutrients and water throughout the entire season. Finally, it keeps the tomato plant from being so tall and susceptible to spring storms and high winds, which can often break the plant off. 


    Post-Transplanting Care for Tomatoes 

    After transplanting, I usually wait a week and add a well-rounded organic liquid fertilizer. I feel this just helps get the plant off to a good start, kind of like a welcome-home present! All that is left to do is trellis and harvest. Some small-scale farmers hard prune their vining tomatoes as they trellis them up the string, while others prefer the bushier types. Most vining tomatoes are indeterminate, meaning they continue to set fruit throughout the season. Most bush tomatoes are determinate, meaning they will set one large crop of fruit that ripens all at once. 

    On my farm, I grow indeterminate types since I want the longest harvest window I can get from a single planting.  


    Tomato Varieties

    This leads us to the million-dollar question: What variety should I grow?  In hotter, drier climates, larger tomatoes don't do quite as well because they tend to crack and split. This doesn't affect the taste of the tomato, but unfortunately, customers buy with their eyes, and most do not want ugly tomatoes. 

    With this in mind, I tend to stick with cherry tomatoes, mainly Sun Golds, due to their sweet taste. I also like Jasper and Flavorita varieties to make a pretty mixture that is a nice complement to taste. The yields on all three are also great, with all of them making clusters of at least 8 fruits and producing for a long time. 

    If you want to learn more about tomato varieties, our friend Andrew Mefferd wrote this great article for Growing for Market magazine: How to Choose Tomato Varieties. And if you like his article, be sure to check out this podcast episode over on the Market Gardening channel by Bootstrap Farmer, where Andrew and Randy talk about the myths and facts of growing greenhouse tomatoes.  

    I could spend hours talking about varieties, but once again, it comes down to your growing context, sales outlet, and what you want to grow. I recommend you try one or two new varieties every season, though; there are 1000’s out there, and you never know when you might come across the perfect one for you! 

    Why will your tomatoes be so much better than store-bought?

    As the talented Guy Clark once sang, “There’s only two things that money can’t buy and that’s true love and homegrown tomatoes.”  Clearly, Guy hadn’t been to a good farmer’s market in high summer. But he was right that tomatoes from the grocery store don’t deserve the name. This is because the varieties grown for distribution are bred to be picked unripe and shipped, sometimes thousands of miles, to sit on shelves for weeks.  

    The tomatoes you grow for your customers will be picked at the peak of freshness and delivered carefully. This means you can grow varieties bred for flavor, texture, and perfect acidity levels to balance sweetness. 

    Written by Michael Bell of Dallas Half Acre Farm. 

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