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Tomato care – watering, fertilizing, companions, pruning…

Tomato care
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Truth be said, tomato plants reign as kings in every vegetable patch, be it in the ground or on a balcony or terrace. Never does one get bored with that tasty, juicy flesh. Notwithstanding this aura, sometimes they play hard-to-get and at times even require full-time care.

Here are the keys to care for tomato plants!  →  Read also: posts about tomato

Watering tomato

Tomato with drops on it
Wet leaves trigger fungus: water the base only

Cool, very rich soil and lots of sun is what tomato plants need to thrive. Regular watering is best but without soaking the soil too much, or else you’d unwillingly create the perfect environment for diseases.

Keeping the soil cool and spacing watering in time during summer is easy if you spread a layer of mulch. Tomatoes most appreciate mulch prepared from compost, leaves, and grass trimmings. For an impressive long-term enrichment, try ramial wood chips out, perhaps mixed in with either grass or coffee grounds, or other plant material with high nitrogen content.

What’s absolutely critical when watering tomato plants is to only water the base of the plant, keeping the leaves dry. Since it’s vulnerable to disease, tomato really fears wet leaves because it triggers fungus.

Fertilizer for tomato plants

Well-fertilized tomato are well-cared for
A ravenous plant that demands nutrient-rich soil

The tomato is a ravenous plant that requires nutrient-rich soil. An ideal practice would be to add fertilizer even before actually growing the tomato plants. For instance, you can sow green manure seeds. Phacelia, purple clover or medick are excellent examples.

Cast the seeds of these ground cover crops between late winter and mid-spring. They’ll be ready for pulling out in late spring-early summer, just as your tomato seedlings need space for transplanting.

As they grow, these types of green manure replenish nutrients to the soil, enhance soil structure, and lock nitrogen in to keep it from washing out. Don’t get rid of them upon pulling them out: just spread them around your young tomato seedlings for mulch.

Nothing goes to waste! Plan for the next year in Fall: layer compost all over the growing bed in autumn and cover that with mulch for the entire winter. If it hasn’t yet broken down entirely, remove the mulch to sow the green manure or seeds will have trouble germinating.

Companion planting

To avoid tomato blight, we recommend planting basil or garlic chives around your tomato plant. On the other hand, set your potato plants far away. The reason is that potato is very vulnerable to blight. It catches it earliest and then contaminates nearby tomato plants.

All sorts of companion flowers can also help our favorite Solanaceae! Zinnia, all types of marigolds – common, French, Mexican… – will help repel nematodes, whitefly and aphids. In addition, French and Mexican marigolds hinder appearance of Alternaria pathogens responsible for early blight.

Tomato plants give back to the garden, too! Tomato disorients and repels flea beetle, large white, cabbage fly, diamondback moth, carrot fly… That’s why you’ll often pair tomato and cabbage, or why tomato trimmings are spread under cabbage heads. However, tomato roots will tend to choke out fennel, leek, bell pepper, carrot, lettuce, escarole and melon. Differences in climate and local pest profiles mean some experimenting is needed to find the right combination for your garden.

Good and bad neighbours for tomato

Some plants protect tomato, some threaten it, and tomato itself defends part of the vegetable patch while starving other crops. Here is what the article recommends putting close by, and what to keep well away.

Good and bad neighbours for tomato
Plant Where to put it What happens
Basil or garlic chives Right around the tomato plant Helps avoid tomato blight
Potato As far away as possible Very vulnerable to blight, catches it earliest and contaminates nearby tomato plants
Marigolds – common, French, Mexican Among the tomato plants as companion flowers Repel nematodes, whitefly and aphids; French and Mexican also hinder early blight pathogens
Cabbage Paired with tomato, or mulched with tomato trimmings Tomato disorients and repels flea beetle, cabbage fly and diamondback moth
Fennel, leek, bell pepper, carrot, lettuce, escarole, melon In another bed entirely Tomato roots tend to choke them out

Differences in climate and local pest profiles mean some experimenting is needed to find the right combination for your garden.

Pruning tomato plants

Vines with leaves pruned off, leaving tomato to ripen
Pruning aims at earlier fruit and less blight

Clearly, a divisive topic: some people find it mandatory, others prefer not to snip a single stem.

  • People who advocate pruning mention that it leads to earlier fruit fruit formation and reduces vulnerability to blight.
  • People who prefer to not prune put forward the fact that more leaves mean more photosynthesis, and better resilience in case of too much sun.

If you do begin to trim your tomato, the time to start is around one month after planting. Remove every single sucker, which is what secondary shoots emerging from leaf nodes on the main stem are called. These tend to drain the plant’s energy. In cooler regions, however, it’s recommended to behead the main stem as soon as 4 or 5 clusters of flowers have started forming.

Tomato remove leaves
Defoliation lets sun reach the ripening fruits

At the end of Summer, you may want to remove any leaves that cast shade over ripening fruits, so that the sun’s rays hit them directly and speed maturing up. This is called defoliation. Just as with suckers, there’s a permanent debate on how effective this is, so try it out on some plants to see if it matches your situation!

To make them easier to trim and prune, go for staking or use a cage.

  • In some cases, you might prefer foregoing stakes altogether: no-stake tomato!

Greenhouse magic

Wooden greenhouse is excellent to care for tomato plants
Under cover, foliage stays dry and disease is avoided

Growing tomato in a greenhouse is a great way to avoid diseases. Indeed, foliage will stay completely dry since you avoid dew and rainfall.

The occasional drops lining leaf edges, in this case, are the sign of a healthy plant: guttation.

Thanks to the shelter, it’s much easier to control watering. Soil can stay cool while leaves stay dry, which is ideal. Sow in late winter and transplant to the ground as early as mid-spring. This is usually a full month earlier than if you were planting outdoors. It’s the most effective way to extend the growing season. Drawbacks are the need to water and fertilize more often, since natural processes like rain and nutrient breakdown don’t happen anymore. Remember to ventilate your greenhouse to make it inhospitable for other types of pests.

Selecting your own seed

Tomato seeds from ripe fruit
Seed saving starts with scooping a ripe fruit

An unexpected secret to vigorous and bountiful plants is actually to perform your very own seed selection every year from your harvest. It isn’t very difficult: all you have to do is scoop out seeds from the inside of a ripe fruit.

  • Soak them in a container filled with water for 2-3 days. This detaches flesh from the seeds themselves.
  • After that, wipe them off and let them dry, at which point you can gather them in a paper pouch. Remember to label the pouch correctly!

Year in and year out, your plants will evolve to perfectly match your growing environment!

One note of caution: there’s no point in gathering seeds from an F1 hybrid tomato. A hybrid results from forced cross-pollination, and F1 hybrids are sterile or degenerative.


Images: adobestock: NinaMalyna, CC BY-SA 2.0: Vicki Burton, Pixabay: Alexei Chizhov, bbffrrhthh, SirPixalot, Public Domain: USDA, CC BY 4.0: Kim & Forest Starr

Written by Gaspard Lorthiois | Loves helping out, especially when it comes to growing things. Worked in herbal medicine, runs a farm, and dabbles in tech. Master's degree and engineer.

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