How to Grow Heirloom Tomatoes (Complete Beginner’s Guide)
Quite frankly, the perfect red and round tomatoes can become pretty boring over time. I’m pretty sure I’m not the only one thinking this. So if you’re up for the challenge, you should try your hand at cultivating heirloom tomatoes at home. Don’t worry, I promise you the taste will be more than worth all the effort you’ll be putting into growing them!
Grow heirloom tomatoes with 1) 5–15 gallon containers, 2) well-draining nutrient-rich potting mix, 3) 75–150 oz of water every week, 4) 8–14 hours of direct light exposure, 5) temperatures around 60–90°F, 6) humidity levels of 40–70%, and 7) the application of phosphorus and potassium-rich fertilizer every 2–4 weeks once fruits start forming.
After several decades worth of seed-saving and growing, heirloom tomatoes are considered “pure breeds”. But this also makes them susceptible to numerous issues, which can be a real headache for newbie home gardeners. You’ll learn how to avoid them in this guide!
Heirloom Tomato Care Guide Table (Ready to Print!)
| Common Name | Heirloom tomato |
| Scientific Name | Solanum lycopersicum ‘Heirloom’ |
| Perennial/Annual | Perennial in warm weather Annual due to harsh winters |
| Planter | 5–15+ gallon plastic pot |
| Soil Composition | Well-draining rich loamy soil 5.8–6.8 pH |
| Watering | 75–150 oz of water per week Daily only for very hot & dry summer days |
| Light | Full sun for 6–8 hours Grow light for 14–18 hours |
| Temperature | 60–90°F (16–32°C) |
| Humidity | 40–70% |
| Fertilizer | Complete fertilizer 1–2 times a month (Spring to summer) |
| Common Pests | Aphids Cabbage loopers Cutworms Flea beetles Fruitworms Hornworms Leafminers Mites Nematode Potato beetles Sap beetles Slugs Stinkbugs Thrips Tomato fruitworms Tomato pinworms Whiteflies Wireworms |
| Common Diseases | Alternaria stem canker Anthracnose Bacterial spot Blossom-end rot Catfacing Early blight Fusarium wilt Late blight Root-knot nematodes Septoria leaf spot Sunscald Tobacco mosaic virus Verticillium wilt |
| Disease Resistance | Little to none |
1. Planter
Bush heirloom tomatoes can grow well in pots as small as 5 gallons. Whereas, vining heirlooms will require planters at least 10–15 gallons for good growth and yield.
Considering the great diversity there is in heirloom tomato plants, you must first determine their growth habit.
An heirloom that stays relatively compact and bushy is considered a determinate tomato. In comparison one that has a wine-like habit—continuously growing from the terminal ends—is classified as an indeterminate heirloom tomato.
Explore this topic in greater depth in our article on determinate vs indeterminate tomatoes!
From this, it makes sense to grow determinate varieties, like Applause, in smaller pots and indeterminate heirlooms, such as Mortgage Lifter, in much bigger pots.
The heirloom tomato plant’s mature size generally corresponds directly to the amount of space it needs to grow prolifically.
Regardless of the pot material you choose to work with, it needs to have enough drainage holes to allow excess water to escape the soil.
But if you ask me, I think the top 3 best materials for heirloom tomato pots are plastic, clay, and fabric.
If your soil dries up too fast, go for plastic containers. Then, if your high-quality potting mix gets too wet, too fast, for a long time unglazed clay pots and fabric grow bags will help you prevent root rot while also aerating your soil.
2. Soil
All heirloom tomatoes thrive in slightly acidic, fertile, well-draining soil. When grown in containers, however, it’s best to use a soilless potting mix.
To encourage their roots to form vigorously, make sure that your soil or potting mix is relatively loose. Roots of heirloom tomatoes don’t handle heavy or compacted soil.
A prime example of bad soil? Clay-rich garden soils. The fine particles of such soil type retain moisture well but hinder the much-needed exchange of gases between the tomato roots and the soil.
In the UK, where I live, such soil is very common and it is a no-no for growing such beautiful plants.
Want to know more? Check our article on sand, silt, and clay!
You would need to amend it with sand to improve its texture and drainage. This is why it’s crucial to conduct a soil analysis a year before growing tomatoes in the ground.
Actually, this is one of the reasons I prefer growing heirloom tomatoes—there’s typically no need for soil tests as they have been formulated for good development and fruiting.
High-quality soilless potting mixes (like the one below from Amazon) are specially formulated so that they’re slightly acidic and dense in essential nutrients for plants.
Look for growing mediums such as peat moss, coco coir, perlite, vermicast, kelp meal, compost, and lime in their ingredients list.
3. Watering
Provide heirloom tomatoes with at least 1 inch (approx. 75 oz) of water every week. During the hottest summer months, they can be given up to 2 inches of water (approx. 150 oz). In winter, when they’re dormant, watering can be reduced or stopped.
Just like with any other plant, the best time to water your heirloom tomato is early in the morning when it’s still cool and the sun is not yet too intense.
Pro Tip: Watering heirloom tomatoes this early in the day allows their roots to efficiently absorb as much water as they need. This will also allow any water that may have splashed onto their leaves to dry up completely before sundown—reducing the risk of diseases.
Nonetheless, I don’t recommend watering heirlooms overhead. This will make their leaves excessively wet and attract lots of humidity-loving pests such as leafminers.
Look out for other common tomato plant pests!
It’s best to water heirloom tomato plants at their base, directly into the roots so that their roots can better absorb moisture from the soil.
Be consistent when it comes to watering. Never let the soil go completely-bone dry or overly saturated. Don’t suddenly water it deeply after letting it dry out for too long either.
Applying up to 3 inches of either organic or plastic mulch around your heirloom tomatoes can not only help protect them from the heat of summer but also freezing winters. Otherwise, it will crack and develop blossom end rot more easily.
4. Light
Heirloom tomato plants become more productive with deeper and more flavorful fruits with 8 hours of full sun. Direct exposure to strong full-spectrum grow lights for at least 14 hours, they can be grown indoors.
Sufficient light exposure is important for fussy heirloom tomatoes. This becomes even more crucial because most heirloom tomatoes aren’t as productive as hybrids in the first place.
For the best chances of getting as many big delicious tomatoes from your heirloom plants, give them about 8–10 hours of direct sunlight exposure in a sunny southern garden or window.
Home gardeners that have neither can use a grow light instead. It’s best to get one that’s stronger than 20W as heirloom tomatoes are high-light plants.
Place your grow light on top of your tomatoes by at least 4–6 inches and keep it on for about 14–18 hours every day.
If they receive too little light, they might not even produce any flowers, let alone fruits. Heirloom tomato plants with such lighting conditions are bound to become scraggly too.
That said, heirloom tomatoes can also suffer from too much light. At first, the portion exposed to such intense lighting conditions will turn white before becoming further discolored and moldy. You may be familiar with this by the term sunscald.
Pro Tip: Move your potted heirloom tomato to a shadier spot in the garden when it gets too hot, dry, and sunny in summer. You can also use shade cloth to protect them from intense light without moving them.
5. Temperature
The ideal temperature range for growing heirloom tomatoes is 60–90°F or 16–32°C. Moreover, because it’s a warm-season plant it isn’t tolerant of frost and cold weather.
Both extremely low and high temperatures will result in a lot of problems.
First of all, a major problem with heirloom tomatoes getting exposed to temperatures below 55°F or -3°C and above 95°F or 35°C for days in a row are likely to drop their flowers.
In effect, your heirloom tomato plants are likely to not produce much fruit—if any at all When you are still able to get fruits though, they may be severely deformed.
This is what a cat-faced tomato looks like—seemingly a fusion of various small tomatoes with cracks and crevices all over.
More importantly, heirloom tomatoes don’t handle frost and freezing cold temperatures you’d expect in fall and winter.
So unless you’re living in a warmer region—say Florida—then I wouldn’t recommend starting or transplanting heirloom tomatoes too early in spring or too late in winter.
Pro Tip: Protect your heirloom tomato plants from weather extremes using fabric covers, hotcaps, plastic tunnels, or season extenders.
6. Humidity
For good fruit production, humidity levels should stay within 40–70% while the heirloom tomato plant is growing. Lower or higher levels could attract pests and lead to diseases.
As with the previous section, home gardeners must be aware of the various problems that come with the air around heirloom tomatoes that are either too dry or too humid.
Their pollen can also be greatly affected by humidity. Overly low humidity levels can dry them up whereas excessively high humidity levels make them gummy.
Without enough moisture in the air, you might suddenly spot pesky spider mites all over your heirloom tomatoes.
Alternatively, super muggy conditions give way to the proliferation of mold and fungal diseases—especially if wet leaves of heirlooms don’t get to dry up before nightfall.
Humidity during the storage of heirloom tomatoes is also very important. Insufficient humidity may cause the fruit to shrivel up and dry out. Meanwhile, excessive humidity will result in the development of mold and diseases.
7. Fertilizer
Start applying complete water-soluble fertilizers on heirloom tomato plants after it starts producing fruits. Do this regularly, every 2–4 weeks from spring to summer.
Heirloom tomato varieties aren’t that productive or reliable to begin with—only a few exemptions come to mind including Black Krim.
As such, it will greatly benefit from being regularly fed while it’s still producing fruit clusters.
For high yields, avoid using complete fertilizers that have high nitrogen content. These types of plant food will indeed encourage plant growth. But they’ll also inhibit flowering and fruiting.
What you should look for are water-soluble fertilizers that with phosphorus and potassium values (PK) at least double their nitrogen (N) content such as this one from Amazon.
Different manufacturers will have recommended application instructions so always check the labels to avoid fertilization of your heirloom tomatoes.
FAQs
How do you support heirloom tomato plants?
Most heirloom tomato plants are indeterminate so they will require strong support in the form of trellises, cages, and stakes. These can improve airflow, better fruit quality, increase yield, and stabilize them. However, determinate heirloom tomatoes can do without any support if their mature fruit clusters don’t weigh down their stems too much.
Do you need to prune heirloom tomatoes?
The majority of heirloom tomatoes need regular pruning. Pinch off suckers from the sides of the main stems to make them more manageable, minimize the likelihood of disease development, encourage fruit development, and speeds up the ripening of fruits as they are more exposed to sunlight.
What do heirloom tomatoes look like?
Heirloom tomatoes come in a wide variety of shapes, colors, and sizes. There are beefsteaks like Brandywine, grapes like A Grappoli D’Inverno, and so on. Such varieties also come in different colors, from light to dark—such as yellow and orange to maroon and purple. Their fruits may weigh less than 1 oz each or more than 16 oz.
Which tomato varieties in America are heirlooms?
Common heirloom tomato varieties in America include Brandywine, Cherokee Purple, Green Sausage, Black Krim, Nebraska Wedding, Roman Candle, Pink Accordion, Hawaiian Pineapple, Mortgage Lifter, Ponderosa Red, Caspian Pink, Black Cherry, Kellogg’s Breakfast, and Yellow Pear.
Summary of How to Grow Heirloom Tomatoes
Harvest plenty of big and tasty heirloom tomatoes using 5–15 gallon pots, nutrient-rich well-draining potting mix, 75–150 oz of water weekly, and complete water-soluble fertilizer every 2–4 weeks once it starts forming fruits.
Ideal growing conditions for heirloom tomatoes are 8–14 hours of direct light exposure, a temperature range of 60–90°F (16–32°C), and humidity levels within 40–70%.
Sources
- “Heirloom Tomatoes” by Kim Schwind in the University of California, Agriculture and Natural Resources
- “Heirloom Tomatoes” by Cathy Coulter in the University of California Cooperative Extension
- “Heirloom Tomatoes” by Matt Ernst in the University of Kentucky Cooperative Extension Service
- “Tomatoes, indeterminate or determinate; hybrid or heirloom?” by n/a in the Master Gardener Association of San Diego County
- “Growing tomatoes in home gardens” by Cindy Tong, Marissa Schuh, and Jill MacKenzie in the University of Minnesota Extension
- “Tomatoes in the Garden” by Daniel Drost in the Utah State University Extension
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