Sowing and Growing Tomatoes

Introduction

This guide serves as an overview for growing tomatoes, reflecting ongoing experiments and our journey. We acknowledge the variability in tomato cultivation based on variety, sowing date, weather conditions, and lighting access. For instance, in 2021, friends in the south struggled to harvest tomatoes by September, while we had already begun picking since July using a similar approach. Over time, the we have worked diligently to minimise variables, achieving consistent and excellent results with the outlined methods.

Why Grow Tomatoes?

Tomatoes score highly in our ranking due to their exceptional flavour (with outdoor-grown tomatoes often tasting superior to those grown in polytunnels), productivity, and relatively high market prices. Additionally, their short growing season—from mid-May to October—allows for two or even three additional crops in the same space.

How Many to Plant?

For fresh consumption, especially if one enjoys cherry tomatoes, it is recommended to grow 2-3 bush or trailing plants per person. Planting at least two successions, spaced 3-4 weeks apart, ensures a continuous harvest throughout the summer, utilising just two 30-litre containers or large hanging baskets. For those interested in making sauces or drying tomatoes, planting cordon or indeterminate varieties may require at least 5-6 plants per person, alongside determinate varieties, which are typically easier to grow and ready earlier. Cordon varieties for preserves may necessitate a space of at least 3 square meters per person.

Suitability for Different Growing Environments

Tomatoes are among the most adaptable plants to cultivate. With the right varieties, they can thrive on a sunny windowsill, in hanging baskets, containers, or directly in the ground. They can be grown outdoors or under cover, with the potential for extending the season to even harvest them for Christmas. Success hinges on selecting the appropriate timings and varieties.

Lifecycle

Tomatoes follow a predictable lifecycle: they are sown in spring, transplanted after the last frost, harvested in summer and early autumn, and perish with the first frost. Attempts to extend this growing period often result in disappointment, as inadequate light leads to weak, leggy plants that are more susceptible to pests and diseases, yielding small harvests of poor quality.

It is feasible to grow early tomatoes with additional warmth and grow lights, but this method can be costly and is typically reserved for dedicated enthusiasts or commercial growers.

Sowing and Harvesting Periods

Super Earlies (Sow in Early February for a Harvest in May)

This planting schedule is suited only for passionate growers with access to grow lights and a heated greenhouse. Starting in early or mid-February, seedlings should be grown under LED lights after pricking them out. A cooler environment is ideal for preventing excessive warmth. Continue growing under lights until April, then transfer to large hanging baskets.

By April, sufficient light is available in a sunny greenhouse, but heating may still be required to maintain temperatures around 10°C at night. Early tomatoes should be ready for harvest by mid to late May. The author has found that six baskets can produce enough early tomatoes to cover greenhouse heating costs in April.

First Earlies (Sow in Early March for a Harvest in Early Summer)

We have reservations about growing early tomatoes due to low yields, insufficient quantity for weekly consumption, inferior taste compared to main crops and local organic options, and the challenges associated with their maintenance. Space constraints also limit early tomato cultivation, as other crops typically occupy available areas.

Despite these challenges, the we continues to experiment for enjoyment and aims for high-yield, flavourful results. The current experimental approach involves:

1. Altering the method of growing peppers to create space for a few bush tomatoes at home.
2. Dividing polytunnel strawberry hanging baskets into two batches, allowing half to remain in the tunnel while the other half is moved outside, thus creating additional space for tomatoes.

The chosen varieties include Shirley’s Pixie for bush tomatoes, valued for its taste, and Tumbler for hanging baskets, known for its early growth and favourable germination characteristics.

Early Main Crop (Sow in Late March for a Harvest Under Cover in Mid-Summer)

Late March is an optimal sowing time for tomatoes if one has access to grow lights or sunny windowsills. Planting in mid-May is ideal for polytunnel cultivation, as it is generally safe from frost, although fleece protection may still be necessary.

A later start allows plants to avoid stress, maximising their yield potential. Since the author has early crops growing, there is no urgency for an early harvest; the focus is on a stress-free cultivation approach.

Main Crop (Sow in Early April for a Harvest Outside in Mid-Summer)

Two weeks after the early main crop sowing, the author begins planting outdoor main-crop tomatoes, all bush or trailing varieties, which often mature alongside the cordons in the polytunnel. The flavour of outdoor-grown tomatoes is attributed to the full spectrum of light they receive.

Bush tomatoes are noted for their impressive yields, albeit over a shorter period than cordon varieties. Therefore, planting two successions spaced a few weeks apart may be beneficial.

Outdoor tomatoes thrive when grown next to a wall, which offers wind protection and re-radiated heat during the night, making them suitable for home gardens rather than allotments.

Late Crop (Sow in Early or Mid-Summer for a Harvest Under Cover in Autumn)

We have faced challenges growing late crops of cordon and bush tomatoes, experiencing limited success with modest yields and declining taste. The late polytunnel cordons grown from side shoots show growth but yield modestly in October, while indoor bush varieties produce acceptable flavour but poor yields and leggy growth prone to mildew.

In 2022, we decided to trial Tumbler, a preferred trailing variety, starting them in the polytunnel and bringing them home only when frost threatens. This strategy aims to prevent legginess while still achieving a harvest through October, after main-crop plants have been removed.

 

How to Sow

Tomatoes are relatively easy to sow. A few seeds should be scattered on the surface of compost and covered with 1 cm of additional compost, followed by a light watering. Germination requires warmth, but tomatoes are less demanding than peppers. It is generally recommended to germinate them indoors on a windowsill above a radiator, out of direct sunlight, to maintain stable temperatures. A propagator is not necessary unless the environment is particularly cold, such as a shed or greenhouse.

Should You Buy or Graft Your Own Tomatoes?

Grafting allows for the selection of a desired variety grafted onto a vigorous, disease-resistant rootstock. However, grafted plants tend to be more expensive, and grafting oneself can be tricky. Approximately 70% of the plants grown in the polytunnel are grafted for their increased disease resistance, which is particularly beneficial when growing in the same ground each year.

How to Prick Out/Pot On

Once the tomatoes reach about 2 inches in height and are easy to handle, they should be pricked out. Loosening the soil around the seedlings allows for careful handling by the leaves. The plants can then be placed into a 6-cell tray. For those who prefer not to prick out, sowing two seeds per cell in a 6-cell tray and snipping off the weaker seedling if both germinate is an alternative approach.

Tomatoes thrive when their stems are buried, so they should be planted deep with the leaves just above the soil level.

Grafting

If opting to graft tomatoes, various online resources provide helpful video tutorials.

How to Grow On

After being pricked out, tomatoes need warmth and ample light, with light being more critical than heat, provided the temperatures remain well above freezing. A sunny windowsill is preferable to an unheated greenhouse unless the latter is heated or the plants are kept in a propagator with the lid closed at night and removed during the day.

Tomatoes grow rapidly, so late sowing is common to keep them in a 6-cell tray until planting time. There is little advantage in growing them into larger plants, as they thrive quickly once planted outdoors in June.

Since many grow tomatoes indoors on sunny windowsills, the plants can become leggy due to insufficient light and excessive warmth. Hence, starting plants later than usual often results in catching up quickly. For leggy plants, three options are available:

1. Plant Deep: While planting deep is an option, it may result in suboptimal conditions.
2. Plant on Their Sides: This technique keeps roots near the surface, where they can access warmth and nutrients.
3. Pinch Out Side Shoots: These can be rooted and grown into new plants that will catch up in growth.

Where to Plant

Tomatoes can be planted in various locations, each with its pros and cons. The following table summarises some options:

	Hanging Basket	Pot	In the Ground
Conservatory/Window	Not recommended	Only for passionate growers	Not applicable
Heated Greenhouse	Only for passionate growers	Only for passionate growers	Only for passionate growers
Unheated Polytunnel/Greenhouse	Great for early crops; fleece should be on hand	Not recommended without automated watering	Good, but watch for disease buildup
Outside	Not recommended unless watered daily	Good for bush or trailing varieties; water every other day	Good for cordon or bush varieties; best taste

How Many to Plant (Spacing)

When using containers, bush varieties should have at least 35 litres of space, while trailing varieties require a minimum of 30 litres. Cordon varieties also benefit from at least 35 litres, though watering can become labour-intensive.

In the ground, 18 inches between plants in a row is the minimum. Closer spacing, particularly in covered environments, can increase the risk of blight, especially with poor airflow.

How to Plant

Tomatoes thrive when their stems are buried, as they can root from their stems. This technique allows roots to access moisture reserves in summer, but certain considerations must be made:

1. For grafted plants, the graft must remain above soil level.
2. Deep planting may place roots in subsoil, away from nutrients and moisture more readily available in the top 6 inches. An alternative is to plant the seedlings on their sides.

Special Notes About Grafting

While burying the graft may not harm the plants, it will reduce the benefits of the rootstock's disease resistance.

Outside

Outdoors, tomatoes should be planted once all risk of frost has passed, typically in early June. Ensuring plants are well-hardened off is also advisable. A sheltered, south-facing spot next to a brick wall is ideal, providing additional warmth.

Protecting and Supporting Plants

Cordon varieties require support using strings or canes, while bush varieties can be supported with canes. Trailing varieties do not require support.

Protecting Plants

It is often beneficial to err on the side of over-protection. Late planting can yield better results than early planting, which exposes plants to low temperatures.

In a polytunnel, support is typically provided on short canes with eye savers. Fleece can be draped over plants during cold nights. Outdoors, wrapping plants in bubble wrap for the first two weeks can mitigate risks associated with frost and high wind chill.

Supporting Plants

Once all risk of frost has passed, strings can be tied to canes, and plants can be wound around the strings as they grow. Strings can also be buried beneath the root ball at planting, with ties secured to the crop bars once the fleece is removed. In cases where plants resist winding around strings, tying them in place or using clips is a viable option.

How to Feed and Water

In-ground plants typically require watering three times a week once fruiting begins, with a liquid feed applied every other week. The same feed used for tomatoes can be applied to peppers.

Plants in containers demand considerable watering, especially during the hottest summer days. Larger pots may only require daily watering, while smaller pots may need twice-daily watering.

Special Note About Watering

If fruits split, it may be due to unstable moisture levels. Adjusting watering frequency or ensuring deep watering may help. Some varieties are also more prone to splitting than others.

Plants can be grown inside halos, which can serve multiple purposes, such as preventing splashes on stems and directing water below the dry surface of compost.

Special Note About Using Hanging Baskets

During sunny periods, daily or even twice-daily watering may be necessary, along with consistent feeding. A three-day watering cycle could involve alternating between water and various liquid feeds.

How to Prune/Manage While Growing

Bush and trailing varieties typically require little pruning. However, cordons benefit from three key management techniques:

Side Shooting

Only cordon varieties need to be side-shooted. Removing side shoots encourages vertical growth and reduces space requirements. Attention should be paid to side shooting, especially as summer progresses.

Removing Lower Leaves

As plants grow, excess leaves can shade fruits and reduce airflow. Observing plant health can guide decisions on whether to remove leaves.

Pinching Out the Growing Tips

When the plant reaches its maximum height and has numerous flower trusses, pinching out the growing tip can help focus energy on fruit production. However, this can lead to new side shoots, which may result in a tangled upper growth.

How and When to Harvest

During summer, fruits should only be harvested when fully ripe or nearly ripe. If splitting is a concern, slightly under ripe fruits can be harvested and allowed to ripen off the plant.

At the end of the season, green tomatoes left after plant removal can be ripened in boxes, stored with very ripe apples. While bananas can be used, very ripe apples tend to be cheaper and more effective.

If Blight Strikes

In the event of blight, affected fruits should be harvested and ripened off the plants.

How to Store

Typically, tomatoes are not stored for long periods, except for ripening. They are often processed into sauces or passata.

Blossom End Rot

This growth disorder arises from poor calcium uptake. It's often linked to soil temperature, root size, and water availability. To mitigate this:

1. Early fruits can be removed, although this is not ideal.
2. Water with a more bio-available form of calcium or dolomite lime.
3. Consistent watering is key, avoiding extremes.
4. Stimulate early green growth for better water uptake.
5. Fix any calcium and magnesium imbalances as necessary.
6. Maintain lower humidity levels in high-humidity environments.

Blight

Experiments on managing blight have shown that while it's not overly alarming, preventing its spread to nearby plants is crucial. Infected foliage does not need to be destroyed. Since blight survives on living tissue, removing infected leaves is advisable, along with proper disposal of affected fruits and seeds.

When and How to Remove the Plants

To remove plants, cut stems approximately 1 inch below the surface, leaving the roots in the ground. Amendments can then be applied, and the area can be covered with compost before replanting.

What to Plant Before and After Tomatoes

The typical sequence for planting in a polytunnel may include:

1. Tomatoes/cucumbers until October
2. Winter lettuce/spinach/salad onions/Asian greens/green garlic/early onions/parsley from October
3. Asian greens, celery, spring lettuces, and calabrese from February until May
4. Tomatoes in early May
5. Cucumbers in late May

What to Interplant With

In mid-summer, interplanting is minimal, although early crops such as beetroot or basil may be considered. In late summer, Asian greens can be planted for a good yield before the October harvest.

Pest and Disease Control

Pests like whitefly and aphids can impact tomatoes significantly.

To manage pests:

1. Spray the undersides of leaves with water to dislodge pests.
2. Introducing beneficial insects such as ladybirds can help control aphids.
3. Use yellow sticky traps to monitor aphid populations.
4. Apply biological controls to maintain healthy plants.
5. Use reflective mulch or plant companion crops like marigolds to deter pests.

For diseases:

1. Avoid overcrowding to promote airflow.
2. Regularly remove infected leaves and dispose of them properly.
3. Monitor for signs of early blight and manage accordingly.