A successful tomato garden relies on several key factors. Making the most out of things like container planting, soil chemistry, and adding things like Epsom salt will go a long way toward not just having a massive tomato harvest. It can also make the timing of the harvest more manageable throughout the season, and even reduce the risk of common tomato plant diseases setting up shop in your soil.
If you’re looking to take your tomato garden to the next level, you might want to use a few of the following 15 tips for ultimate tomato success.
Tip 1: Plant Determinate & Indeterminate Varieties
Determinate tomato plants tend to be smaller and will produce all their tomatoes at one time. They’re ideal for planting in a container as the plants don’t sprawl out as much as indeterminate varieties and have a smaller root base, which requires less soil volume.
This will give you a massive harvest for canning and putting up in mid to late summer. Then your determinate varieties can provide you with a modest continuous harvest of fresh tomatoes throughout the rest of the growing season.
Pro Tip
Determinate tomatoes die back after harvest. You can then use the soil in their containers or garden plot to succession plant other crops like radishes and snow peas. It’s a great way to get a fall bumper harvest, and potentially rejuvenate the soil.
Tip 2: Provide Container Tomatoes with 5 Gallons of Soil
If you’re going to grow tomato plants in containers or raised beds, make sure that every plant has at least 5 gallons of soil. This gives room for the root base to expand without getting root bound, while also giving the plant access to the soil nutrients it needs to set the best fruit.
A tomato plant will grow and still provide some fruit in as little as 3 gallons of soil. However, you’ll get a much smaller plant, with smaller fruit, and it will be hard to keep the plant sufficiently watered. This can be a big problem later in the growing season when tomatoes become prone to cracking from drying out and inconsistent watering.
Tip 3: Plant Seedlings Deep to the Bottom Leaves
Planting your tomato seedlings deep, right up to the bottom of the lower leaves, makes use the tomato plant’s ability to produce new roots from the stem. It’s okay to bury whatever remains of the lowest cotyledon leaves if there are any leftovers from germinating.
Ideally, you want to measure from the bottom of the seedling pot to roughly half an inch below the first major branch. Then dig the hole to this depth before inserting the covering of the tomato seedling. If there’s an odd branch in the way, it’s better to bury it than cut it off.
Tip 4: Prune Lower Branches Early
Two or three weeks after planting your tomato seedlings, you should go back and examine the distance between the lower branches/leaves. If there are still branches within 4 inches or so of the ground, you might want to prune them back.
This will greatly reduce the risk of soil fungus getting onto the lower leaves from water splashing up from the ground. It also improves airflow at the ground level, which further prevents diseases and fungal spores from invading lower leaves during rainy weather.
Pro Tip
When pruning the lower branches of a tomato plant, you want to use a sharp knife, or box cutter, and try to plan it for24 hours of dry weather. Ragged edges and moisture give airborne plant pathogens a better opportunity to exploit the pruning site before it heals.
Tip 5: Hand Water or Use Drip Irrigation
Watering your tomatoes with a drip irrigation system ensures that they get the consistent moisture they need, while also preventing splash-back of muddy water onto the lower leaves. This will go a long way toward lowering the risk of common tomato fungal diseases like early blight.
If a drip irrigation system isn’t feasible, you should stick to hand watering each tomato plant directly. A simple scoop from a bigger bucket, gently poured right on the soil at the base of the plant ensures the roots get the maximum amount of moisture. It also keeps the leaves from getting wet and prevents splash-back of soil on the lower branches of the tomato plant.
Tip 6: Add a Layer of Mulch
Adding a layer of mulch to your tomato planting beds helps retain soil moisture while also gradually adding organic matter to the garden over time. A simple blend of ground/composted leaves with grass clippings is usually good enough to boost the bioavailability of your soil nutrients.
Ideally, you want the layer of mulch to be 2 to 4 inches thick. Just be sure to leave a 2 to 4-inch diameter of exposed soil around the tomato plant’s stem. This makes it easier for water to quickly penetrate the soil down to the roots. While also making it harder for potential plant pathogens in the mulch to transfer to the tomato plant.
Pro Tip
Mulching is very important for container-grown tomatoes, which are more prone to drying out due to the smaller volume of soil. If you’re using a hand-watering method, you can go as thick as 4 inches of mulch on a container-grown tomato plant.
Tip 7: Be Proactive About Preventing Diseases
Tomato diseases like early blight, canker, and leaf curl virus tend to live in the soil and can travel through the air. Being proactive in preventing these tomato diseases starts with rotating the place where you plant your tomatoes each year. If you’re growing them in containers, use fresh soil, or don’t use the same container for tomatoes year after year.
If and when a tomato disease strikes your garden, be proactive about treating it as soon as possible. Then write down what it was, the local weather conditions, and any other important information. You can then use this to help predict when a tomato disease might strike your plants in the years to come.
Fungal diseases are the most common in tomato plants. Spraying your tomato plant’s lowest branches and leaves with a copper sulfate fungicide or similar preventive spray early in the summer can also be a sound preventive measure.
Pro Tip
If you’ve had fungal diseases in the past, you should spray your plants at least 2 to 4 weeks before the time of year when they struck before. Plant diseases tend to attack in certain weather patterns and times of year more than others.
Tip 8: Test Spray and Be Mindful of Temperature
Some plant disease sprays can damage a plant in hot weather over 80 degrees. So, if you do need to spray to prevent or treat a disease on a tomato plant, test spray a single plant. Preferably in the early morning when temperatures are low, or doing a stretch of cooler, dry weather.
Ideally, you want to test spray a single plant a day or two in advance to see how it responds. If the leaves start curling up or you see other signs of plant stress, you might not want to use it on other tomato plants in your garden.
Pro Tip
Avoid spraying plants on a day when there’s rain in the forecast. These sprays need time to dry onto the plants’ foliage. Ideally, you want at least 24 to 48 hours of dry weather to maximize the effectiveness of preventative sprays.
Tip 9: Provide Plants with Support
Even smaller determinate tomato plants need some type of support system, like a ground stake. Larger indeterminate tomato plants that sprawl usually need a tomato cage or need to be integrated into a “Florida Weave.”
Pro Tip
If you need to tie the plant to a stake, cage, or other structure, try to avoid hard points and tight knots. Strips of old nylon tights are often ideal, as you can still tie the branches reasonably tight, yet they stretch as the plant grows.
Tip 10: Use Epsom Salt Wisely
Epsom salt is a great source of magnesium that tomato plants use for photosynthesis and the uptake of water from the roots. You don’t have to go heavy with Epsom salt. It’s better to apply it in two small doses.
You mix 1 to 2 tablespoons per gallon of water and add it when wetting the transplant hole. Then give it roughly 2 cups of water in the hole.
The first Epsom salt dose should be right before planting the tomato. This will boost the magnesium micronutrient bioavailability of the soil, which will help the tomato seedlings grow vigorously in the first few weeks after transplanting into the garden.
The second dose of Epsom salt is usually needed after a rainy period in early to mid-summer. The plant will tell you when it needs it. You’ll see the leaves starting to turn yellow, with green veins in between. This is a sign of magnesium deficiency, usually due to excess rain washing the nutrients out of the soil.
Tip 11 : Test Your Soil Chemistry
Tomatoes need a neutral to slightly acidic soil pH to grow successfully. As heavy-feeding plants, they also need nitrogen, phosphorus, and potassium at critical points in their development. Testing your soil several weeks or months before planting your tomatoes allows you to take a more—informed approach to amending the soil, as well as customizing your fertilizing strategy.
You’ll get the most accurate results by submitting a soil sample to your county’s agricultural extension office. However, this costs more than most backyard gardeners want to spend and takes a while. Instead, you can get a pretty good idea of your soil chemistry and available nutrients with a DIY test kit for around $20.
Tip 12: Amend Your Soil & Fertilize with Different Types of Fertilizer
With your soil chemistry information in hand, you can start to develop a successful strategy for amending the soil your tomatoes will be planted in. The best way to do this is to use a customized blend of soluble fertilizers that have high bioavailability as well as granular or insoluble fertilizers that are time-released.
If your soil test tells you that your soil is low on nitrogen, you’ll want to use a soluble nitrogen-rich fertilizer that will be immediately bioavailable to the tomato seedling when you plant it.
Tomatoes need potassium (soluble potash) later in the growing season when they’re setting and developing fruit. If your soil chemistry tests show low potassium levels, you’ll want to augment the soil with a time-released potassium source, which will take time to become bioavailable when the tomato plant needs it the most!
Tip 13: Augment the Soil with Calcium
Tomatoes need calcium to grow strong as well as prevent problems like blossom-end rot when setting fruit. If your soil test comes back showing low calcium levels or a highly acidic pH adding bioavailable calcium and a time-released form of calcium to the soil when tilling will address both problems.
Tip 14: Change Fertilizers as the Season Goes
Early in a tomato plant’s life, it wants a lot of nitrogen to grow leaves and foliage. This boosts photosynthesis throughout the plant, and all the sugars it produces are stored in the fruit.
Tomatoes are also short-day plants and will start flowering in earnest after the summer solstice. By switching to a fertilizer with slightly higher phosphorus around this time, the tomato plant has more of the nutrients it needs to flower vigorously.
Once the plant starts to set fruit, the tomato needs more potassium to help develop the fruit. It also helps with drought resistance to reduce the risk of tomatoes cracking in the hot days of late summer.
Tip 15: Choose Container Mix with Organic Material
If you’re planning to grow your tomatoes in containers, you need a potting soil mix that is roughly 50% organic matter. This means reading the ingredient label and looking for high amounts of peat moss and/or coco shells. Wood chips is a poor organic matter additive that doesn’t offer much to plants.
Ideally, you want to see vermiculite or perlite in the potting soil mixture. This helps with water retention as well as helping the soil stay loose. The tomato plant’s roots will spread easier and be less prone to becoming root-bound later in the season.
BONUS TIP: Choose Heirloom & Open Pollinated Varieties
A lot of the tomato plants you see sold in garden centers like Beefsteak and Early Girl are hybrid tomato varieties. They’re made by combining two different types of tomato, but the seeds they produce don’t breed true. If you select seeds from hybrid varieties they’ll have a very poor germination rate, and any plants that do grow will produce poorly.
Heirloom and open-pollinated varieties like San Marzano, Cherokee Purple, Mortgage Lifter, Matt’s Wild Cherry, Opalka, and many more will breed true. Seeds saved from these tomatoes will have a favorable germination rate and grow strong. Technically, all heirloom tomatoes are open pollinators. However, the term heirloom is only assigned to varieties with a history dating to 1940 or earlier. Many heirloom seed vendors use the two terms interchangeably.
Written By
Amber Noyes
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.