Tomatoes – Complete Growing Guide from Seed to Harvest

Tomato (Solanum lycopersicum) is by far the most beloved vegetable among Czech gardeners – over 80% of people with even just a small plot or balcony grow it. And no wonder: the taste of a fully ripe tomato from your own garden is something supermarkets simply cannot offer. This guide will walk you through the entire process from variety selection through sowing and seedling cultivation to harvest, processing, and disease control.

1. Types and Varieties of Tomatoes

Before you reach for seedlings or seeds, it's good to know what types of tomatoes exist and how they differ. The basic classification is based on growth habit and fruit size.

By Growth Habit

Indeterminate (vine) tomatoes grow continuously throughout the season and reach heights of 150–250 cm. They require support (stakes, string, or cages) and regular removal of suckers. They produce fruit gradually from July until the first frosts. Most traditional Czech varieties belong here.

Determinate (bush) tomatoes grow to a compact height of 40–80 cm, stop growing after a certain number of flower clusters, and their fruits ripen approximately all at once. Suckers are not removed, and support is usually not necessary. They are ideal for containers, balcony planters, and small plots. The harvest tends to be concentrated in time but abundant.

By Fruit Size

Cherry and cocktail tomatoes have fruits weighing 10–40 g. They are sweet, early, extremely productive, and excellent for salads, fresh consumption, and drying. Popular varieties include Sweetie, Tumbling Tom, Black Cherry, and the Czech Zlatava.

Medium tomatoes (50–120 g) form the largest group and are universally useful – for salads, sauces, and preserving. This category includes classics like Stupické polní rané, Saint Pierre, or Moneymaker.

Beefsteak tomatoes weigh 150–500 g or more. They have dense flesh with little juice, making them ideal for slicing, sandwiches, and grilling. Typical representatives are Marmande, Coeur de Boeuf (Ox Heart), or the American Brandywine. Expect a longer growing season and higher heat requirements.

Pear and plum tomatoes have an elongated shape, firm flesh, and low water content. They are excellent for sauces, drying, and preserving. The most famous variety is the Italian San Marzano; from local varieties, Roma is well-known.

2. Sowing and Seedling Cultivation

Tomatoes have a long growing season in our climate (60–90 days from transplanting to harvest), so they must be started indoors. Direct sowing in the garden in the Czech Republic is practically not an option.

When to Sow

• Indeterminate and beefsteak tomatoes: mid-February to early March
• Cherry and bush tomatoes: early to mid-March
• Late varieties with longer growing seasons: early February

Sowing too early (January) leads to seedling etiolation due to insufficient natural light. If you don't have supplemental lighting, sow about two weeks later – seedlings will make up the lost time quickly after transplanting into warmth.

How to Sow

1. Substrate: Use fine seed-starting mix with low nutrient content. Regular garden soil is too coarse and overfertilized for germination.
2. Containers: Suitable options include seed trays, mini propagators, or pots with drainage holes in the bottom.
3. Sowing depth: 0.5–1 cm. Lightly cover seeds with substrate and press gently.
4. Watering: Carefully mist with a spray bottle. The substrate should be evenly moist, not wet – overwatering leads to rot.
5. Germination temperature: Optimum is 20–25 °C. Below 16 °C germination slows significantly; above 30 °C the embryo can be damaged.
6. Cover the tray with film or transparent lid to maintain moisture. Ventilate briefly daily to prevent mold.
7. Germination: The first sprouts should appear within 5–10 days.

After Germination

As soon as the sprouts emerge above the surface, immediately remove the cover and move the seedlings to the brightest possible location – ideally a south-facing window or under a grow light. Reduce temperature for 5–7 days to 15–18 °C during the day and 12–15 °C at night. This phase, called hardening-off of seedlings, prevents etiolation and significantly strengthens the root system.

Then raise the temperature again to 18–22 °C. Lighting should provide a minimum of 12–14 hours of daylight – without it, seedlings will inevitably etiolate by March.

3. Pricking Out (Transplanting Seedlings)

Pricking out is the transplanting of young seedlings into individual containers. This is done when the seedling has its first pair of true leaves (not cotyledons) – typically 2–3 weeks after sowing.

Pricking Out Procedure

1. Prepare pots about 8–10 cm in diameter filled with quality growing substrate.
2. Carefully remove the seedling from the seed tray – ideally using a wooden stick or pencil slipped under the roots.
3. Bury the seedling deeper, up to the cotyledons. Tomatoes have a unique ability to form adventitious roots along the entire stem length – deeper planting directly strengthens the root system.
4. Press the substrate around the stem and water.
5. Keep seedlings in partial shade for 1–2 days, then return to full light.

Why Prick Out

• Each plant gets enough space for unimpeded root development.
• Deeper planting stimulates the formation of a strong and branched root system.
• When pricking out, you can remove weak, deformed, or diseased seedlings.

Approximately 3–4 weeks after pricking out, either transplant seedlings into larger pots (12–15 cm diameter) or wait for direct transplanting outdoors.

4. Hardening Off and Transplanting to the Garden

Hardening Off

One to two weeks before transplanting, begin systematically hardening off seedlings – expose them to outdoor conditions gradually:

1. Days 1–3: Place in a sheltered spot outdoors for 2–3 hours during the day, initially avoiding direct sun.
2. Days 4–7: Extend outdoor time to 4–6 hours, gradually adding direct sun exposure.
3. Days 8–14: Leave outdoors all day, possibly overnight (if temperature doesn't drop below 8 °C).

Seedlings that undergo thorough hardening off will experience virtually no transplant shock and will continue growing immediately.

When to Transplant

Golden rule: only after the last frosts. In the Czech Republic this means:

• Lowlands and cities: mid-May (after the so-called "Ice Saints," May 12–14)
• Foothills and higher elevations: late May to early June
• Greenhouses and hoop houses: from mid-April (depends on specific conditions and heating method)

Soil temperature should be at least 12 °C, ideally 15 °C. At temperatures below 10 °C, tomatoes barely grow and roots are susceptible to rot.

How to Transplant

1. Spacing: Indeterminate tomatoes 50–60 cm in the row, 80–100 cm between rows. Bush tomatoes 40–50 cm.
2. Planting depth: Again, plant deep – cover the stem up to the first leaves. This increases plant stability and promotes root formation.
3. Support: For indeterminate varieties, immediately install a stake (at least 150 cm) or stretch vertical string.
4. Watering: Water thoroughly immediately after transplanting so substrate adheres to roots.
5. Mulch: Cover the soil with a layer of straw, mowed grass, or other organic mulch. It maintains moisture, suppresses weeds, and – particularly important – prevents soil splash on lower leaves, significantly reducing fungal infections.

5. Caring for Tomatoes During the Season

Watering

Tomatoes need regular and even watering. Alternating between dry and waterlogged periods causes fruit cracking and physiological disorders called blossom end rot (BER).

• Water at the base of the plant, never on leaves. Wet leaves are an entry point for fungal infections.
• Ideally use drip irrigation or water in early morning hours.
• During fruiting expect 5–10 liters per plant per week, depending on current weather and soil type.
• Greenhouse tomatoes dry out faster than outdoor ones and require more frequent watering.

Removing Suckers

Suckers are side shoots that grow in the angle between the main stem and the leaf. Their removal is a crucial operation for indeterminate tomatoes.

Why remove suckers:
- The plant directs energy into fruit formation and ripening instead of vegetative growth.
- Better air circulation between leaves reduces fungal risk.
- Fruits tend to be larger and ripen earlier.

How to remove suckers:
- Break off suckers in the morning when they are tender and easily snap off with thumb and forefinger.
- Remove them while small (5–10 cm) – large wounds heal poorly and are more prone to infection.
- Bush (determinate) tomatoes are not suckered.
- Most commonly tomatoes are trained to 1–2 stems: keep the main stem and possibly one strong sucker just below the first flower cluster.

Removing Lower Leaves

Once the fruits in the lowest flower cluster start to ripen, gradually remove the leaves below that cluster. This improves air circulation at ground level and limits pathogen spread from the lower part of the plot.

Pruning the Top

In late August – typically 4–6 weeks before the expected first frost – prune the top of indeterminate tomatoes. Fruits still on the plant gain time to ripen, and the plant doesn't waste energy on unnecessary new flowers.

Staking and Training

Regularly tie indeterminate tomatoes to their stake or string with soft material – twine, special clips, or nylon tape. Never tie directly above a heavy fruit cluster; tie below it so the weight is supported by the stake.

6. Fertilizing

Tomatoes are moderately to highly demanding for nutrients. Proper fertilizing significantly affects both yield and final fruit flavor.

Base Fertilizing Before Planting

Work well-aged compost (3–5 l/m²) or well-decomposed manure into the soil. Tomatoes thrive in humus-rich, well-draining soil with pH 6.0–6.8.

Supplemental Feeding During the Season

Tip: Calcium deficiency causes blossom end rot – a dark, sunken spot on the fruit's bottom. The primary solution is regular watering (calcium reaches fruits only via water flow); secondarily, lime foliar sprays or fertilizers enriched with calcium and magnesium.

7. Diseases and Pests

Late Blight (Phytophthora infestans)

The most feared tomato disease in the Czech Republic. It attacks leaves, stems, and fruits – appearing as dark brown wet spots with white mold on the leaf undersides. In wet summers it can destroy entire crops within days.

Prevention:
- Airy location and adequate spacing between plants.
- Water only at roots, never on leaves.
- Mulch to limit soil splash on lower leaves.
- Grow in a greenhouse or hoop house – a roof overhead is by far the most effective prevention.
- From June apply preventive sprays with copper-based products (Kuprikol, Bordeaux mixture).
- Choose tolerant varieties like Ferline, Fantasio, or Mountain Magic.

If infected:
- Immediately remove affected plant parts and dispose away from the garden.
- Apply fungicidal products according to manufacturer instructions.
- Severely infected plants should be pulled up entirely and destroyed – never compost them.

Powdery Mildew of Tomato (Oidium neolycopersici)

White powdery coating on upper leaf surfaces, particularly common in greenhouses. Affected leaves gradually yellow and dry out.

Solution: Remove affected leaves, spray with sulfur products, and ensure better air circulation – regular greenhouse ventilation is key.

ToBRFV Virus (Tomato Brown Rugose Fruit Virus)

A relatively new, highly aggressive virus spreading across Europe since 2018. It causes brown wrinkled spots on fruits, leaf mosaics, and necrosis. No chemical control exists – the virus is transmitted mechanically (by hands, tools) and through seeds.

Prevention:
- Buy certified seeds and seedlings exclusively from verified suppliers.
- Disinfect tools with 10% trisodium phosphate solution or sodium hypochlorite-based products.
- Immediately remove and burn infected plants.
- Don't smoke near tomatoes – tobacco mosaic virus can be transmitted directly from cigarettes to plants.

Blossom End Rot (BER)

Not an infectious disease but a physiological disorder caused by calcium deficiency in fruits – most often as a consequence of irregular watering. It appears as a dark, sunken spot at the fruit's bottom. Affected fruits are otherwise healthy and edible after removing the rotten section.

Pests

• Greenhouse whitefly: Tiny white insect on leaf undersides. Sucks plant sap and excretes honeydew, on which black sooty mold develops. Solutions: yellow sticky traps, biological control with parasitoid Encarsia formosa, or insecticides for severe infestations.
• Aphids: Classic polyphagous pest. On small plots, garlic extract spray or soapy water works; for heavy infestations, insecticides.
• Colorado potato beetle: Occasionally spreads from potatoes. On small plots, manual collection of larvae and adults suffices.

8. Harvesting and Ripening

When to Harvest

Pick tomatoes when they are fully colored and slightly yielding to gentle pressure. Cherry tomatoes should come off easily – if pulling is required, they're not yet ripe. Most flavorful are fruits ripened right on the plant in warm, sunny weather. Harvest ideally in the morning when fruits are cooler and firmer.

Ripening After Harvest

If frost threatens and green tomatoes remain on the plant, you have several options:

1. Pull the entire plant with roots and hang it upside down in a dry, frost-proof room – fruits will ripen slowly.
2. Place green tomatoes in a box with an apple (the ethylene released by the apple accelerates ripening) and store at 18–22 °C.
3. Never refrigerate tomatoes – temperatures below 10 °C irreversibly damage aromatic compounds and alter flesh texture.

Processing

• Passata and tomato paste: Blanch tomatoes in boiling water, remove skins, blend, and cook to desired consistency.
• Sun-dried tomatoes: Halve, salt, and dry in a dehydrator at 60 °C for 8–12 hours, or in the sun on screens.
• Freezing: Whole tomatoes can be frozen without blanching – after thawing they're ready for sauces.
• Canning: Tomato sauces, ketchups, and chutneys are excellent ways to process excess harvest.

9. Recommended Varieties for Czech Conditions

Cherry and Cocktail

Medium – Universal

Beefsteak and Slicing

Plum (For Sauces)

10. Greenhouse vs. Outdoor Tomatoes

Greenhouse Advantages

• Protection from blight – the biggest benefit. A roof prevents rainwater contact with leaves.
• Longer season – transplanting from mid-April, harvesting until October.
• Higher and more stable yields independent of weather.
• Better conditions for beefsteak and late varieties with longer growing seasons.

Greenhouse Disadvantages

• Requires regular ventilation – overheating above 35 °C damages pollen and reduces fruit set.
• Dependence on regular watering or drip irrigation.
• Higher incidence of greenhouse whitefly and spider mites.

If you're considering purchasing a greenhouse, check our range of greenhouses and hoop houses. Even a simple hoop house significantly improves conditions for tomatoes and extends the season by 4–6 weeks.

Outdoor Growing

For outdoor cultivation choose early and disease-resistant varieties – Stupické polní rané, Start F1, or Tigrella. Mulch, choose an airy, sunny location, and from June regularly apply preventive sprays against late blight.

11. Tomatoes on Balconies and in Containers

No garden? Tomatoes can be very successfully grown on balconies or terraces – it just requires choosing the right variety and sufficiently large containers.

Suitable Varieties

Choose bush or compact tomatoes: Tumbling Tom, Balkonzauber, Vilma, Losetto, or Heartbreaker. Cherry varieties in hanging baskets are not only productive but also attractive decoration.

Containers

• Minimum volume: 20 liters per plant (ideally 30–40 l – larger containers mean more stable water and nutrient supply).
• Ensure drainage – holes in bottom, layer of clay pellets or gravel.
• Use quality substrate enriched with compost or slow-release fertilizer.

Care

• On balconies tomatoes dry out much faster than in garden soil – water daily, twice on hot days.
• Fertilize every 7–10 days with liquid fertilizer at half-strength.
• Southeast or southwest-facing balconies are ideal – on a north-facing balcony tomatoes won't fruit without sufficient light.

12. Frequently Asked Questions (FAQ)

Can I sow tomatoes directly outdoors?
Practically no in the Czech Republic – the growing season is too short. The exception is extremely early varieties in the warmest areas of south Moravia, but even there seedling cultivation is more reliable.

How deep should I plant tomatoes?
As deep as possible – ideally up to the first true leaves. Tomatoes form adventitious roots along the entire buried stem length, so deeper planting directly strengthens the whole plant.

Why do my tomatoes crack?
The most common cause is irregular watering – after a dry period comes heavy rain or watering and the fruit absorbs water quickly while the skin can't keep up. Solutions include even watering and mulching, which buffer soil moisture fluctuations.

How many tomatoes will I harvest from one plant?
Depends on variety and conditions. Cherry: 200–400 fruits (3–5 kg). Medium: 20–40 fruits (4–8 kg). Beefsteak: 8–15 fruits (3–6 kg). In greenhouses yields are typically 20–40% higher.

Can I grow tomatoes next to potatoes?