Caring For Your Tomato Plants Throughout The Season
We have found one of the most important things you can do to keep your tomato plants happy is to add mulch. Mulch does so many things:
- moderates soil temperature
- keeps soil evenly moist (very important for tomatoes)
- reduces the need for manual watering
- suppresses weed growth
- adds nutrients back to the soil as it decomposes.
There are lots of organic materials you can use for mulch, but we prefer straw. You can purchase straw bales inexpensively at feed stores or garden centers. Make sure you get straw rather than hay, because hay is bundled with seed heads intact and you will be doing a lot of weeding in the future. If you can’t get straw, other options include shredded leaves, grass clippings or pine needles. Avoid using wood-based mulches because when the wood mixes into the soil over time it can tie up nitrogen, making this important element less available to your plants.
The timing of mulch application is important. Here in Colorado it takes a while for the soil to warm up, so we don’t mulch until a few weeks after planting. If you live in a warmer climate, you might want to mulch right when you plant your tomatoes. When it’s time, add mulch about 3 inches deep around your plants.
As tomatoes grow, they produce new stems, often referred to as “suckers”, from the point at which a lateral branch meets the main stem (at about a 45 degree angle). These suckers will grow into another main stem, eventually producing more fruit and more suckers. Pruning your tomato plant means that you remove some or all of these suckers as they appear.
The debate about pruning applies to indeterminate tomato plants—DO NOT prune determinate varieties. In its most extreme form, some gardeners prune all of the suckers on an indeterminate plant so that the plant growth is limited to one stem, while less aggressive pruning might result in 3-5 stems (or even more). Some growers prefer not to prune at all.
Benefits of pruning: fruit may ripen earlier, fruit size may be larger, reduces spread of foliar diseases, can plant with closer spacing
Drawbacks to pruning: pruned plants produce less fruit over the growing season, labor intensive, plants grow taller, limited capacity to make up for blossoms that drop during high heat or other adverse weather conditions, sun scald
The question of whether to prune has been long debated by tomato aficionados and gardeners tend to be entrenched in one camp or the other. The truth is, there is no correct answer, and a lot depends on the length of your growing season and your goals (e.g. do you want the largest fruit possible, or more, smaller fruits?).
At Umbel Organics we have developed a strategy that blends the benefits of each method in order to maximize yields while keeping plants manageable and healthy. We always let the suckers produced early in the season grow in order to increase yields. Knowing that it takes anywhere from 6-8 weeks to go from flower to ripe fruit, in late July we begin pruning new suckers aggressively so the plant will concentrate on ripening existing fruit by early October, when the weather is still agreeable (your target date may differ depending on your climate).
Any suckers produced after this time are unlikely to yield high quality fruit due to cool autumn nights and early frosts, so we are not really sacrificing production. In early September, we “top” plants, which means pinching off the growing tips of all the main stems so the plant will not get any taller. This will allow the plant to focus on ripening existing fruit.
Pruning is quick and easy and doesn’t require any special tools, just your fingers. Try to prune suckers before they grow larger than 4 inches—you can prune larger suckers but it might cause the plant a little bit more stress. At the point where the sucker meets the stem, grab it between your fingers and pinch it off. It should snap off quite easily. When the plant is putting on a lot of new growth, just make sure to check for suckers at least every other day because they will grow rapidly.
One Pruning Strategy All Gardeners Should Practice
As the season unfolds, periodically remove the lowest hanging lateral branches from your plants to allow for more air circulation. These lower branches are a major risk for disease. Many of the most common tomato diseases, like early blight, result from water splashing up from the soil and spreading spores onto foliage.
Supporting Your Tomato Plants
We recommend giving your tomato plants some support by implementing the staking, caging or weaving method. A supported tomato plant is less susceptible to mold, critter bites, and foliar pathogens like early blight. There are many ways to provide support, and the method you choose depends on your pruning strategy.
- If you prune to 1-3 stems, then the easiest training method is to place one or more stakes in the ground near the plant and periodically tie the stems to the stake. We use jute twine, which is gentle enough on the plants to prevent damage to the stems. Stakes must be at least 6 feet tall for indeterminate plants. We use inexpensive furring strips, and use a jig saw to create a point at the end so they can easily be hammered into the soil. You can also use bamboo, plastic, or metal tomato stakes or T-posts.
- Less aggressive pruners often choose to use tomato cages, which contain and support the multitude of stems produced by an unpruned plant. Unfortunately, if you are growing indeterminates, you are probably going to have to make your own custom tomato cages. The ones you see at the store just aren’t big enough, unless you are growing determinate varieties. Remember that an unpruned indeterminate tomato plant will easily grow 5 feet tall or more. Learn how to build your own tomato cage here.
- If you don’t want to shell out the cash or deal with the labor involved with making your own tomato cages, try the Florida Weave method for trellising tomatoes. Space tall stakes (we use 6 ft T-posts) at the end of each row of plants and between every 2-3 plants down the row. When plants are tall enough to need support start by tying jute twine around a stake at one end. Weave the twine around the first plant, then around the next plant, around the next stake, and so on until you get to the end of the row. Make sure to keep the twine taught so it will support the plants. As the plants grow throughout the season you just continue to run additional twine at higher levels. The image below shows our tomato plants using a modified version of the Florida Weave as well as pvc piping and row covers for insect and hail protection.
Watering Tomato Plants
The biggest key to watering tomatoes is to make sure you do it regularly so the soil stays evenly moist. Erratic watering causes all kinds of problems with tomatoes.
Blossom end rot occurs when plants experience wide fluctuations in soil moisture, like going from very wet to dry during fruit set. The plants ability to move calcium to fruits is impaired and you get blossom end rot.
Cracked Fruit- Although this problem is mostly cosmetic, cracks can provide a route of entry for mold or other pathogens. Cracking typically occurs when you have a sudden major influx of moisture as fruit is ripening, especially if it has been dry in the period before. Excess water is sent to fruits and can essentially cause the tomato to burst, hence the crack.
- Rule 1: Keep the watering consistent so the plant doesn’t experience wide fluctuations in moisture. This doesn’t mean that you have to water every day. Just water deeply so the soil is moist to about 6 inches a few times a week depending on your gardening environment. You can check by sticking your finger a few inches in the soil. The very top layer of soil can dry out between waterings, but make sure the soil stays consistently moist a few inches down. If plants are showing visible signs of water stress, like wilting, you need to water more often. Mulch—one of the main benefits of mulching is that it helps keep moisture levels consistent, which greatly reduces problems with blossom end rot and fruit cracking.
- Rule 2: Avoid spraying foliage whenever possible. Wet foliage invites diseases to spread in your garden. Keep the foliage dry by directing the water to the base of the plant.
Fertilizing Tomato Plants
If you have good healthy soil and use slow-release organic fertilizers, you will only need to fertilize tomatoes a few times throughout the season. Avoid giving tomato plants too much nitrogen—you might end up with vines that run rampant in your garden but set very little fruit.
We use an organic fertilizer at planting time, followed by organic liquid fertilizer when plants are established. We use fertilizers specifically formulated for tomatoes since they usually have extra calcium, which, in conjunction with good watering practices, helps prevent blossom end rot. They’re also fairly high in phosphorous and potassium to promote flowering and fruit production.
After fertilizing at planting time, don’t fertilize again until the first blossoms appear. When blossoms appear, use an organic liquid fertilizer. In a few weeks when the plant has set a considerable number of fruit, give plants another dose of organic liquid fertilizer.
Tomato Plant Diseases & Pests
There are many diseases and pests that can wreak havoc on tomato plants. The prevalence depends on where you live, and the best resource by location is to check with your local university extension. We use the Colorado State University Extension, and you can do an online search to find your state extension, or look it up by your zipcode here. Another option is the Vegetable MD online from Cornell University. We’ve found that row covers work well to protect tomato plants from pests in Colorado, and you can read more about how we use row covers here.
Harvesting Heirloom Tomatoes
We get such a bonanza of cherry tomatoes out in the garden that we literally eat them straight off the vine. But for the bigger heirlooms, we have a different approach.
Like many gardeners, we once bought into the myth of the vine ripened tomato. When we first started growing tomatoes, we used to leave fruit on the vine and pick at the peak of ripeness. Through research and experimentation over the years, we’ve learned that picking tomatoes before they are fully ripe (letting them ripen inside) does not adversely affect flavor.
There are many risks involved with leaving tomatoes on the vine until fully ripe, including:
- sun scald on exposed fruit
- cold or hot weather
- insect attacks
We harvest most of our heirloom tomatoes during the “pink” stage, letting the tomatoes fully ripen indoors after picking. We have a post on WHEN TO HARVEST HEIRLOOM TOMATOES with more detail about why we harvest heirloom tomatoes at this stage. For us, there is no perceptible effect on flavor or fruit quality with this method.
In all of our side-by-side taste comparisons, we can’t detect a difference in taste between vine-ripened tomatoes and those harvested at the pink stage and left to ripen inside after picking.
How To Store Heirloom Tomatoes
DO NOT store them in the refrigerator! We store the unripened tomatoes in a large, shallow ceramic dish in the kitchen. The dish sits on a table that’s not in direct sunlight. It’s fine to keep them on your kitchen counter as long as the room temperature stays between 65-75°F.
AVOID placing unripened tomatoes in direct sunlight. They do not need light to ripen. High temperatures can inhibit ripening.
How to tell when your heirloom tomatoes are ripe? A ripe tomato will give slightly to the touch. Be careful not to press too firmly. Use a very light squeeze with your fingers, and the outside of the tomato should give a little.
Shop Heirloom Tomato Growing Essentials