Updated: May 21
Tomatoes plants can be finicky to grow and there is much to be learned before becoming an expert at growing tomatoes. Let's look at 10 top tips for growing tomatoes in your backyard vegetable garden, in a pot or in a greenhouse in the zones 2 - 4 growing climates from someone who has struggled with growing tomatoes in Calgary, Alberta herself. Here are tips for how to grow more, tastier and larger tomatoes in your own backyard.
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Tip # 1 - Start Tomatoes From Seed Early
Tomatoes need to be seeded early in the year or purchased already started to be able to grow to maturity and bear fruit prior to our early fall frost. Seed your tomatoes around the beginning of March. (Find my free printable zone 3 seeding chart here.) Aim to have your tomato plants just beginning to bloom by the end of May to allow time for fruit to grow and ripen during the short zone 3 growing season.
When moving your tomatoes from indoors to outdoors carefully harden them off to prevent shock.
Tip # 2 - Transplant Tomatoes Deep
Tomatoes can be transplanted to a soil level deeper than they previously were growing. Tomato plants are unique in that they easily grow roots all up the stem once it is placed in soil. Plant the long stem of tomato seedlings up to the first set of leaves. (Also check out my post How to Fix Leggy Seedlings.) If you plant a number of tomato seeds together in one pot, transplant into their own pots by the time they are 1.5 inches high or else the roots become entwined and are at risk of breaking when you try to separate the seedlings. As your tomato plants grow, continue to transplant them into larger pots. You can snip off the bottom branches of your tomato plant and plant it at a deeper soil level to encourage a bushier and stronger plant.
Tip # 3 - Plant Tomato Plants in a Warm Location
Tomato plants love to be warm! Along with basil, your tomato plants should be the last ones to move outdoors in the spring. Once all risk of frost has passed and you harden your tomato plants off (by having them outdoors for part of each day for 4 or 5 days in a row) choose a warm sunny location to plant them in. Tomato plants love to be inside greenhouses, next to a sunny south facing wall or in raised beds or in containers where the soil warms up quickly in the heat of the day.
Tip # 4 - Water Tomato Plants with Warm Water
If possible, avoid watering your tomato plants with freezing cold water from your tap (specifically a problem where I live in zone 3 Calgary, Alberta) as this will be an unwelcome shock to your plants. A good option when your tomato plants are outdoors is to fill your watering can the day before and allow it to warm up prior to using it to water your tomatoes. Also, tomato plants require a lot of water, especially when they are at the point of growing fruit!
5. Keep the Leaves on Tomato Plants Dry
When watering tomato plants, water at the base of the plant to keep the leaves from getting wet. Wet leaves create a disease thriving environment and also make tomato plant leaves more susceptible to sunburn. Along with keeping tomato plant leaves dry, ensure that there is good ventilation around the plants by pruning and not overcrowding them.
Tip # 6 - Fertilize Tomato Plants
Tomato plants require high levels of nutrients. Fertilizing your tomato plants with an 18-18-21 will go a long way towards encouraging growth and having healthy plants. To read more about what fertilizer to choose for your tomatoes see my post on fertilizer and fertilizer tea. Putting compost around the base of the plant is a great way to feed the plant organically.
Tip # 7 - Pruning Tomato Plants
Pruning tomatoes is a highly debated topic. I have toured a successful farm that sells hundreds of pounds of tomatoes and they don't prune theirs at all! Many tomato growers do choose to prune their tomatoes plants and feel it encourages larger fruit growth. The idea is that pruning unnecessary branches allows the plant to put more energy toward tomato production.
Indeterminate tomatoes grow much taller than determinate varieties and can be pruned as follows: Beginning at the base of the main stem, follow it upwards. When you come to a place where two branches are growing out from the main stem in the same place, trim the middle branch off, right where it meets the stem. This branch is called a sucker branch. It will produce blossoms if left on the tomato plant but it may cause the plant to become heavy and difficult to support, making the tomato plant susceptible to breakage. Suckers can be propagated by trimming the lower leaves and placing it in water for two weeks, then planting into soil. Growing a new tomato plant this way takes much less time then growing it from seed.
Determinate tomatoes grow in a shorter more compact formation and do not require as involved pruning. To prune determinate tomatoes, select 1 to 3 of the large branches at the base of the plant and prune these ones off. The fruit production will happen higher up on the plant and the branches at the base are the ones that have the greatest chance of getting wet and developing disease.
Tip # 8 - Pollinate Your Tomato Plant
Growing marigolds or nasturtiums near your tomato plants are good options for attracting bees. Even with doing this it can be helpful to pollinate the blossoms of your tomato plants yourself, especially if your plants are inside a greenhouse. Do this by taking a Q-tip, paintbrush or even just your finger tips and brushing them gently over each blossom. Pollinating tomato plants yourself ensures none of those precious blossoms get missed.
Tip # 9 - Understand the Difference Between Determinate and Indeterminate Tomato Plants
Like potatoes, tomates also come in two main varieties of plant types - determinate and indeterminate. Determinate tomato plants (also called "bush" tomatoes) are shorter and bushier and may not need support. Indeterminate tomato plants (also called "vine" tomatoes) grow tall and will need a tomato cage or some type of support to prevent the plant from breakage. Indeterminate tomato plants are not good for windy areas in your garden.
Tip # 10 - When to Pick Tomatoes
You do not have to wait until your tomato is fully ripe to pick it. Contrary to common belief, the flavour is said not to change when it finishes ripening indoors. (I have tested this and not noticed any difference in flavour if I leave it to ripen fully on the vine versus bringing it indoors to ripen.) Picking your tomatoes when they are partially ripe allows the plant to put its energy to growing more tomatoes. You may think a sunny window seems nice to finish the tomato ripening process but this will not help. Placing partially green tomatoes in a paper bag or in a box covered with a towel is the best way to ripen unripe tomatoes.
This brings us to final harvest when undoubtedly you end up picking many green tomatoes because winter is fast approaching. When ripening fully green tomatoes, place them in a paper bag or in a box and cover them with a towel. Try to keep them only one layer deep to protect from rotting. Store them in a dark, cool place. Add in a ripe fruit such as an apple. The reason for this is that ripe the fruit produces ethylene gas which causes fruit around it to ripen (thus why your whole bag of apples goes rotten at the same time).
Click here for more on how to ripen green tomatoes.
Tomato Companion Plants
Tomatoes do well planted close to asparagus, basil (may improve tomato flavour), beets, chives, cilantro, cucumbers, garlic, lettuce, marigolds, nasturtiums, onions, parsley, peppers and sage. Avoid planting tomatoes near broccoli, cabbage, cauliflower, corn, dill, kohlrabi or potatoes. (Find my full printable companion planting guide here.)