Tomatoes have been called the gateway plant to serious gardening. For many, a fresh, ripe organic garden tomato is an irresistible incentive to learn how to grow healthy tomato plants for flavourful fruit and abundant yields.
Tomatoes are quite easy to grow from seed (shop our tomato seeds here) and each plant yields on average 25 lbs of fruit. They’re also very simple to freeze or can in a hot water bath, so that you can enjoy the tomato harvest all year long. Check out our Canned Late Summer Salsa recipe for some canning inspiration.
For gardeners and farmers, every growing season is different and comes with its own set of challenges - a wet season could lead to fungal disease; a period of drought could cause splitting and sunscald; a pest-free year could be followed by an infestation. So what can you do to encourage healthy tomato plants?
- Learn how to build healthy, soil
Learn to identify common diseases, disorders, and pests
- Focus on prevention
These are the best gardening tools to have with you as you grow the best organic tomatoes of your life this year!
Starting Tomato plants from seed
One method to optimize water uptake in your tomato patch is to build strong root systems and then plant your transplants deeply.
We start our tomato seeds in a bit of soil at the bottom of a makeshift pot, usually a milk cartons scored from a local cafe. As the tomato seedlings grow, we pinch off the lower leaves and add more soil. We continue this process until the soil level is flush with the top of the pot. This allows for your transplants to develop massive roots.
Transplanting tomato seedlings
You’ve seen the little white hairs on the stem of a tomato? Each one is a potential root. When you bury them, they begin to grow.
So after a Spring focusing on growing tomato roots, we plant them deeply in the garden. The hole you dig depends on how tall your tomato plant is from the very base of the root, to the bottom of the leaves. For us, the root is the depth of a milk carton, so we dig our holes to one foot. Think of that root’s ability to expand and to collect water from deep in the Earth, all Summer long.
Building healthy soil for tomatoes
We’ve said it before and we’ll keep on repeating it: healthy soil is the most important ingredient for healthy plants. The best way to keep your tomato plants disease-free and pest-resistant is to ensure the soil has plenty of organic matter, balanced nutrients and healthy soil microorganisms. Biologically active soils, with regular inputs of compost and cover crops, provide all the nutrients tomato plants need to thrive.
Tomatoes do best in well-drained slightly acidic soil, with some nitrogen. Too much nitrogen will encourage foliage over fruit; a shovelful of compost per plant should do the trick. In Spring and Fall, before transplanting seedlings and following harvest, plant a cover crop - like white clover (image above) - in your tomato bed to increase soil fertility.
Caring for your soil will help it to become naturally disease-suppressing to support strong, healthy plants.
A note on watering tomatoes
Conditions like yellowing leaves, cracking or splitting fruit, and sunscald all stem from issues related to watering. Tomatoes do need a lot of water, but they can handle long dry periods because of their large root systems. It is best to water tomatoes deeply once a week during dry periods.
If soil moisture is too inconsistent - for example if you overwater after a dry spell - the fruits can crack or plants can develop blossom end rot (we’ll get to that soon).
It’s best to avoid watering the leaves at all to prevent fungal disease. If you feel the need to apply a foliar spray such as seaweed or compost tea to boost general disease resistance, do it in the morning so any moisture on the leaves has time to slowly evaporate throughout the day. Watering any plant in the heat of the day can lead to sun burnt leaves!
Mulch your plants to conserve moisture in the soil, reduce weeds, and also keep watering from splashing up onto the leaves. If there are leaves touching the soil, remove them.
Common tomato diseases and disorders
Preventative care is the best way to deal with disease, which is why the simple act of paying attention is an important part of your work as a gardener. When you recognize early signs of disease, there are still things you can do to prevent it from doing further damage to your plants and soil.
Make a habit of strolling around your gardens once a day to inspect plants - who doesn’t want a garden stroll on their to-do list anyway?
There are many possible diseases in the nightshade family (which tomatoes belong to), and there are some great books and resources out there that dive deep into these topics. This is by no means comprehensive, but these are a few of the most common diseases and disorders in tomato plants.
Blight is a common fungal disease that can affect the stems, leaves, roots, and fruit of tomato plants. Early blight and late blight are quite different beasts to contend with.
Despite its name, early blight can appear at any time in the season. It won’t necessarily kill a plant, but it can weaken it and diminish yields. It isn’t nearly as devastating as late blight.
Late blight is fast-moving and absolutely bad news. It’s airborne and highly contagious, which means the spores can travel between neighbouring gardens. It thrives in warm, wet weather with cooler nights and shows up mid to late season. You might first notice dark scorched spots on leaves, but these spots quickly grow and spread, turning plants almost black.
If you notice late blight on your plants, you should remove infected plants immediately. Do not leave any plant debris in the area and do not add it to your compost pile.
How to prevent fungal disease:
Improve airflow around your plants
pinch suckers or side shoots
stake or trellis plants
remove leaves that touch the ground
Don’t let water splash on leaves
Practise good sanitation
keep your hands and tools clean when dealing with diseases such as blight.
don’t compost diseased tomato plants and don’t dig them into the soil.
Practice crop rotation
rotate your nightshade crops for three years, if you can
Sometimes nutrient deficiency and fungal diseases can look the same - yellowing leaves and spots.
Blossom End Rot
Blossom end rot is not a disease, but a physiological disorder caused by stress, not pathogens. It indicates a calcium deficiency in the fruit, which could be caused by inconsistent moisture in the soil, root damage, or excess nitrogen in the soil.
It appears as a water soaked, rotten looking spot at the blossom end of the tomato fruit, when they are about half their full size. It is more likely to take hold when your growing season has a wet start and then a long dry period after plants set fruit. (Maritimers: Take note!)
The problem with disorders like this is that your plants may look fine and by the time they show signs of stress, it can be too late. If you see signs of blossom end rot, remove the damaged fruit.
Common Tomato Pests
There are quite a lot of pests that are drawn to the nightshade family, which tomatoes belong to. It's important to know how to identify not only pests, but also the damage they can cause. You will often see the sign of the pest before you see the actual creature!
If you do spot an unidentified insect, don’t panic. There are plenty of beneficial insects that might visit your garden, and you don’t want to kick them out.
Tomatoes can handle up to twenty percent defoliation without impacting yields, and there aren’t many insects that can do this level of harm. However, there are a few culprits that can kill plants, especially when they are still vulnerable seedlings. Here are some of the common threats:
Cutworm larvae are fat little grey/brown caterpillars that you’ll likely find curled up in your soil. They feed at night and burrow during the day. They mature into brown moths, which pose no direct threat to your garden, but will lay hundreds of eggs on leaves and stems.
Their larvae can hibernate in the soil or in piles of garden debris over winter - another reason to clean up your Fall garden! They mature and start feeding in Spring.
Cutworms feed on plant stems - if you find your plant stems have been chewed or cut neatly below or at ground level, cutworms are the likely culprit. They can chop down a whole row of tomato plants overnight! This can be heartbreaking, especially if you’ve just planted out precious transplants that you’ve grown from seed.
A few tips to prevent cutworm damage
Drive a nail alongside the stem, so that they can’t wrap themselves around the stem.
Make cardboard collars for around stem - dig them into the soil an inch or two
Time your seed starting strategically so that your plants will have thick, strong stems when you put them out
Don’t put out your transplants too early - cutworms do most damage in early Spring
Turn your soil in Fall to let birds (or backyard chickens!) feast on the larvae
Clean up any garden debris in the Fall
Note: cutworms love to feast on grass and weeds, so brand new gardens are more susceptible to these pesky pests
Hornworm are quite large, but they are masters of disguise - camouflaging their long, pale green bodies against tomato stems and leaves. You can identify these green caterpillars by their seven white stripes and telltale black or red horn on their rear.
Hornworm can be quite destructive, but if caught early and hand picked, you shouldn’t need to take further measures. You really must take a close look at your plants to spot these, so be vigilant! Be sure to check on the underside of leaves for green eggs as well.
The best way to control hornworm is to handpick them and drop them in a bucket of soapy water.
If you feel overwhelmed. . .
When it comes to tomato diseases, disorders, and pests - an ounce of prevention is worth a pound of cure! You will learn something new every year - our gardens are always sending us new challenges and opportunities for learning, right? If you feel overwhelmed by plant care, just remember to bring it back to basics - high quality seeds and plants, healthy rich soil, and organic practices.