Heirloom Tomato Grow Guide

Ah, the heirloom tomato – a treasure trove of taste, a rainbow of colours, and a link to our gardening heritage. Unlike their supermarket cousins, heirloom tomatoes come with stories and history, with a depth of flavour that can turn a simple sandwich into a feast.

In this guide, I will share with you the secrets and pleasures of growing heirloom tomatoes, in your garden or on your allotment.

What are Heirloom Tomatoes?

Heirloom tomatoes are favoured tomato varieties that have been passed down through generations, often over 50 years or more.

They are the antiques of the tomato world, cherished for their unique flavours, shapes, and colours. Unlike hybrid tomatoes, bred for uniformity and shelf-life, heirlooms are celebrated for their diversity and character. Each variety has its own story and its own niche in the tapestry of culinary and horticultural history.

From the sun-kissed, sunset orange ‘Lucid Gem’ to the quirky green, pear shaped ‘Michael Pollan’, each heirloom tomato brings its own personality to your garden. Some are sweet, some are tangy, and others offer a complex, almost wine-like depth.

This diversity is not just a joy for the palate; it’s a boon for biodiversity, encouraging a healthy, vibrant selection of tomatoes for our gardens and kitchens.

When to Sow Your Tomato Seeds

In the earnestness of spring, it’s tempting to start sowing your heirloom tomato seeds at the first hint of warmer weather. However, timing is a delicate dance in the world of gardening, particularly in our variable UK climate. Sowing too early can lead to complications that compromise your seedlings’ robustness and your overall harvest.

Avoiding leggy seedlings: Sowing seeds too early often results in ‘leggy’ seedlings. This happens when plants, desperate for light, stretch their stems thin and weak, reaching for the sun. The lack of light in late winter and early spring can make it challenging for young plants to develop the sturdy foundation they need. Leggy seedlings are more than just unsightly; they are vulnerable, often lacking the strength to bear their own weight and more susceptible to disease.
Managing indoor space: Another practical consideration is space. Sowing too early means your plants will likely outgrow their indoor confines before it’s warm enough to move them outside. Heirloom tomatoes, especially the indeterminate varieties, can become quite substantial even before the last frost has passed. This can lead to a real conundrum: large, unwieldy plants that need more room than your windowsill or greenhouse can provide but are still too tender to brave the outside world.
Timing and local climate: In the UK, the ideal time to sow tomato seeds is typically 6-8 weeks before the last expected frost. Use local frost date guides to determine this time. For most regions, late February to early March is a safe bet. This timing allows your plants to grow strong and sturdy indoors without becoming too large, and it syncs well with the warming outdoor temperatures, ensuring a smoother transition to their final growing spot.

How to Sow Tomato Seeds

Sowing heirloom tomato seeds is not just a gardening task; it’s a ritual that celebrates the beginning of the growing season. It’s a process that combines science, art, and a touch of personal intuition.

Let’s break down the basics to ensure your seeds have the best start possible.

Choosing the right soil mix: The ideal soil mix for sowing tomato seeds is light, well-draining, and nutrient-rich. A seed starting mix, available at most garden centres, is perfect. It’s designed to provide the right texture and moisture retention for young seedlings. Avoid your own garden’s soil as it can be too heavy and may contain pathogens harmful to young seedlings.
Preparing your containers: Cleanliness is vital. Clean old pots or use new sterile trays or pots to prevent disease. You can use anything from small individual pots to larger trays with cells. The size of the container should be sufficient to allow the seedling to grow for several weeks before needing to be pricked out and potted on.

Sowing Techniques

Depth and spacing: Sow your seeds about 1-2 cm deep. This depth provides enough cover to keep the seeds moist but not so deep that they struggle to reach the surface. Space the seeds about 2-3 cm apart to give each seedling enough room to grow without competing for light and nutrients.
Labelling: Remember to label your pots or trays, especially if you’re growing multiple varieties.
Watering: Water gently to avoid disturbing the seeds; keeping the soil moist but not waterlogged is important too. A spray bottle can be a gentle way to water onto the compost, reducing the risk of dislodging the seeds.
Warmth: Seeds need warmth to germinate. A sunny windowsill, a spot above a radiator, or a heated propagator are all good choices. The ideal temperature for tomato seed germination is around 18-21°C. Too much warmth can be just as detrimental as too little, so aim for a consistent, moderate temperature.
Light: Once the seedlings emerge, they need plenty of light to avoid becoming leggy. A south-facing windowsill or a grow light can provide the light they need. Rotate your pots or trays regularly to ensure even growth, as seedlings will lean towards the light source.

Pricking Out Your Seedlings

Pricking out or transplanting seedlings is a delicate yet vital process in the growth of your heirloom tomatoes. It’s about giving each young plant its own space to flourish. This stage requires patience, a gentle hand, and an eye for the right moment.

Timing: The perfect time to prick out your seedlings is when they have developed their first set of true leaves. These are the leaves that appear after the initial seed leaves (cotyledons) and look like a miniature version of a mature tomato leaf.
Preparation: Before you start, make sure to have your pots or cell trays ready. Fill trays with a good quality potting mix, similar to your seed starting mix, but slightly richer to support the growing plants.
Gentle handling: Tomato seedlings are delicate. Always handle them by their leaves, not their stems. The stem is the lifeline of the plant – damaging it can be fatal. Use a dibber or a small stick to ease the seedling out of its original soil.
Transplanting:
- Create a small hole in the compost in a new pot or cell tray.
- Holding the seedling by a leaf, lower it into the hole.
- Very gently firm the soil around the base of the seedling, ensuring it’s upright and secure.
- Space the seedlings adequately to allow for air circulation and growth.
Aftercare: Once pricked out, the seedlings will need a period of adjustment. Keep them in a bright spot, but avoid direct sunlight for a day or two. Water gently, ensuring the soil stays moist but not waterlogged.
Growth monitoring: Keep an eye on your pricked-out seedlings. This is a crucial time as they adapt to their new environment. Look out for signs of stress or disease and adjust their care as needed.

Growing On

As your heirloom tomato plants enter this vigorous phase of growth, the focus on light, watering, and feeding becomes ever more important. It’s a delightful stage, watching them stretch towards the sun, each day a little stronger, a little more eager.

Light: The Lifeblood of Tomatoes

The need for sunshine: Heirloom tomatoes aren’t just fond of light; they thrive on it. They require at least 6-8 hours of direct sunlight a day. In the absence of adequate natural light, especially in the early stages of growth, consider using grow lights.
Maximizing exposure: If you’re growing tomatoes on a windowsill or in a greenhouse, rotate them regularly to ensure each side of the plant receives equal light. This helps prevent leaning and promotes even growth.
Light intensity: The quality of light changes through the season. In the height of summer, be mindful of too much direct exposure, particularly in a greenhouse, where it can get intensely hot. Some shading during the peak summer months can prevent scorching.

Watering: A Balancing Act

Consistency is crucial: Tomatoes dislike fluctuating moisture levels. Inconsistent watering can lead to problems like blossom end rot or cracked fruits. Aim for consistently moist soil, allowing the top inch or so to dry out slightly between watering.
Method matters: Water at the base of the plant to avoid wetting the foliage, which can lead to fungal diseases. Early morning is the best time to water, as it allows any excess moisture on the leaves to evaporate during the day.
Monitoring moisture: Use your fingers to test the soil moisture. Over time, you’ll develop a sense of just how moist the soil should feel.

Feeding: Nourishing Your Plants

Starting right: Once your plants have a few sets of true leaves, they’re ready for regular feeding. This usually begins about 3-4 weeks after transplanting.
Choosing the right fertilizer: A balanced liquid fertilizer, ideally one formulated for tomatoes, is perfect. These fertilizers usually have a balanced ratio of nitrogen, phosphorus, and potassium, which supports overall health, root development, and fruiting.
Frequency: Feed your tomatoes weekly, following the instructions on your fertilizer. As fruits begin to form, you might switch to a fertilizer higher in potassium, which helps in fruit development.

In the world of heirloom tomatoes, the combination of the right light, consistent watering, and regular feeding is akin to a nurturing trio, each playing its part in the tomato plant’s growth.

Planting Out Your Tomato Plants

Transplanting your heirloom tomato plants into the garden is a significant step. It marks the transition from the protected world of seed trays and pots to the vast, open theatre of your garden. Let’s explore how to make this transition as smooth as possible.

Understanding UK frost dates: Frost can be a death sentence for tender tomato plants. In the UK, frost dates vary significantly depending on your location. Generally, the safe planting-out period starts from late May to early June. However, always refer to local frost date calendars and keep an eye on the weather forecasts. If an unexpected frost is predicted, be prepared to protect your plants with fleece or bring them indoors for the night.
Choosing a sunny and sheltered location: Tomatoes relish the sun. Choose the sunniest part of your garden for them. However, they also need protection from strong winds, which can damage plants and reduce pollination. A south-facing wall or fence can provide both sun exposure and shelter.
Soil preparation and requirements: Heirloom tomatoes thrive in rich, well-draining soil. Before planting your young plants, enrich your soil with compost and a balanced fertilizer. Ensure the soil is loose and aerated to allow for easy root growth. The ideal pH for tomatoes is between 6.2 and 6.8.
Planting depth spacing: The wonderful fact about tomatoes is that they can develop and send out roots from their stem, so I advise you plant your tomatoes deeper than they were in the pots. Remove the first set of true leaves and bury to just below the second set. This encourages the formation of a stronger root system and a healthier plant. Space the plants about 45-60 cm apart, allowing room for growth and air circulation. For indeterminate (vining) varieties, consider more space or use strings or sturdy supports like cages or stakes.
After planting care: Once planted, water your tomatoes to settle the soil around their roots. For the first few days, monitor the plants closely and shield them from the intense midday sun to help them acclimate.

Planting in Greenhouses

For those who have a greenhouse, planting heirloom tomatoes inside can extend their growing season by protecting them from the unpredictable UK weather.

Temperature Control: Keep an eye on the temperature. Greenhouses can get very hot on sunny days, so ventilation is key. Automatic vent openers can be a handy investment.
Humidity Management: Monitor humidity levels. Too much humidity can encourage fungal diseases like blight. Regularly opening doors and vents can help regulate moisture levels.
Spacing: In a greenhouse, you can control spacing but you are often limited by height. Indeterminate varieties can benefit from the vertical space a greenhouse offers, with the extra heat encouraging tall growth longer into the season.

Planting in Polytunnels

Polytunnels are another excellent option for growing tomatoes, especially if you have more space in your garden or allotment.

- Ventilation: Similar to greenhouses, ensure adequate ventilation in polytunnels to prevent overheating and manage humidity.
- Soil Care: If planting directly into the ground within a polytunnel, try to rotate your crops each year to prevent soil-borne diseases. If space is limited, consider growing in large pots or grow bags to facilitate crop rotation.
- Watering: Be vigilant about watering, as the rain won’t reach your plants inside a polytunnel. Using drip irrigation to provide consistent water and feed will improve results and help prevent blossom end rot.

Growing, Training and Pruning

As your tomato plants begin to grow, they’ll require support and regular maintenance to ensure a healthy and productive crop. Let’s dive into the details of how best to provide this care.

Staking your tomato plants

Types of stakes: Bamboo canes, wooden stakes, or metal rods are all effective. The key is to choose stakes that are sturdy and tall enough to support your plants as they grow. For most heirloom tomato varieties, stakes should be at least 1.5 to 2 meters tall.
Attaching plants to stakes: Use soft ties, like garden twine, soft coated wire, plastic clips or thin strips of cloth, to tie the plant to the stake. Tie the stem loosely to allow room for growth, and attach at intervals as the plant grows taller. Be gentle to avoid damaging the plant.

Cages and Stringing Up Tomatoes

Tomato cages: Cages offer support on all sides and are great for bushier, determinate tomato varieties. Make sure the cage is large and sturdy enough to support the plant’s full growth.
String training: For indeterminate varieties, string training can be effective. Place one end of a strong twine in a loop at the bottom of the planting hole and tie the other end above the plant to a greenhouse frame or support wire. As the plant grows, gently wind the growing stem around the string and it will support itself throughout the season. This method requires a bit of attention to gently guide the plant without breaking the stem.

Tip… When string training your tomatoes, use a plastic based twine as it will not rot in the soil and snap at the base of the plant. This untethers the plant from its support. You can reuse the twine for many years too.

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Pruning

Removing suckers: For indeterminate varieties, remove the suckers (shoots that grow in leaf axils) to direct the plant’s energy into growing fruits rather than foliage
Lower leaves: As the season progesses and the plants grow taller, remove lower leaves to improve air circulation and reduce the risk of soil-borne diseases. This is particularly important in damp or humid conditions.

Growth Heights

Indeterminate varieties: These continue to grow and produce fruit throughout the season and can reach heights of over 2 meters. In fact, they would just keep growing if it were not for lack of light and frosts in the winter months which kill them off! Regular pruning and training is essential in a greenhouse or polytunnel where space is limited.
Determinate varieties: These grow to a fixed height (usually around 1-1.5 meters) and produce a single, concentrated crop. They require less pruning and are suitable for cages.
Dwarf varieties: Ideal for containers, these varieties grow to about 0.5 meters and require minimal staking or pruning.

Feeding and Watering Your Tomato Plants

Adequate feeding and watering are critical to the health and productivity of your heirloom tomato plants. This aspect of care requires a balance – providing enough water and nutrients without overdoing it.

Watering

Consistency is key: Tomato plants prefer consistent moisture levels. Inconsistent watering can lead to problems like blossom end rot or fruit splitting. Aim for evenly moist soil
Method: Water carefully at the base of the plant to avoid splashing leaves, as this may allow waterborne diseases to infect the plant. Drip irrigation systems are ideal as they deliver water directly to the soil.
Amount: This varies depending on weather and soil type, but a good rule of thumb is to provide at least an inch of water per week. In hotter, drier conditions, more frequent watering may be necessary.

pH Levels

Ideal pH: Tomato plants thrive in slightly acidic to neutral soil, with an ideal pH range of 6.2 to 6.8. Testing your soil’s pH can guide your fertilization strategy.
Adjusting pH: If your soil is too acidic or alkaline, you can adjust it. Lime can raise the pH, while sulfur can lower it.

Feeding

Early growth: In the early stages, focus on formulas that promote strong root and leaf development. Look for fertilizers higher in nitrogen and potassium.
Flowering and fruit production: As the plants begin to flower and set fruit, consider switching to a feed that’s higher in phosphorus and potassium to encourage fruiting. Phosphorus supports healthy fruit development, while potassium helps with overall plant health and disease resistance.
Types of feed: There are various options, including liquid feeds, granular fertilizers, and organic options like compost tea or seaweed extracts. Whichever you choose, follow the instructions carefully to avoid over-fertilization.
Regular Feeding: Once your plants have established, feed them every 1-2 weeks. Adjust based on the plant’s response; if they look healthy and are producing well, your current regimen is working.

Fertigation

What is Fertigation? Fertigation is a horticultural technique that combines fertilization with irrigation. This method allows you to deliver both water and soluble feed to your tomato plants simultaneously, ensuring a balanced and consistent supply of nutrients.
Daily watering and feeding: Implementing fertigation involves watering and feeding your plants daily. This regular, gentle supply of nutrients and water encourages steady growth and reduces the stress on plants that can come from more sporadic, heavier watering and feeding schedules.
Using a water reservoir: Fertigation often uses a water reservoir that contains a mix of water and a soluble feed. The concentration of the feed in the reservoir should be carefully calculated based on the stage of growth of your tomato plants and their specific nutrient requirements.
Drip irrigation system: The use of a drip irrigation system is ideal for fertigation. It allows the nutrient-rich water to drip slowly and directly to the base of each plant. This not only ensures that each plant gets exactly what it needs but also conserves water and minimizes the risk of diseases often associated with wet foliage.
Advantages: Fertigation can lead to more efficient use of fertilizers, as it reduces runoff and ensures that important nutrients are delivered directly to the plant roots. It’s particularly beneficial in regulating the growth of your tomato plants, promoting healthy development and potentially leading to a more bountiful harvest.
Monitoring: As with any feeding and watering regimen, closely monitor your plants for signs of over or under-fertilization and adjust the fertigation mix and frequency accordingly.

Supporting Heavy Trusses

Heirloom tomatoes, particularly those with large, robust fruits like ‘Amish Sherbert’ and ‘Summer of Love’, can weigh down their trusses to the point of breaking. Supporting these trusses is not just about preventing breakage; it’s also about ensuring proper nutrient flow to every fruit.

Materials and techniques: Use soft ties, like strips of cloth or twine, to gently lift and secure heavy trusses to your existing support structures. Some gardeners fashion makeshift slings or hammocks from old tights or netting to cradle these trusses.
Strategic placement: Position your supports to distribute the weight of the trusses evenly, ensuring that each fruit hangs free without undue stress on the plant.

When to Harvest Your Tomatoes

Ah, the harvest – the crescendo of our tomato-growing symphony. It’s the time when patience and anticipation finally ripen into fruition. But when exactly do you pluck these jewels from their vines? Especially with varieties like ‘Black Beauty’, which tease us with their unique hues?

Observing colour changes: Colour is your first clue. For traditional reds, it’s that deep, uniform blush, a shift from green to that vibrant red. With ‘Black Beauty’, watch for the deepening of its dark shades, a kind of purplish-black mingled with a smoky red. It’s like watching a sunset captured in fruit form.
Feeling for firmness: Gently squeeze the fruit; ripe tomatoes yield slightly to pressure. They should feel firm, not hard, nor too mushy. It’s a tactile conversation between gardener and tomato, understanding through touch.
The right time: Often, the best time to harvest is in the morning when temperatures are cooler. This helps in preserving the freshness and flavour of the tomatoes.
Taste testing: Sometimes, you need to taste. Pluck a tomato, take a bite, and let your palate be the judge. If it’s a burst of flavour that speaks of sun and soil, then it’s time.

Savouring Your Heirloom Tomatoes

After nurturing your heirloom tomatoes from seed to harvest, it’s time to delight in their extraordinary flavours. Each variety, with its unique taste profile, offers a world of culinary possibilities. Let’s explore some delightful ways to enjoy your harvest, with nods to recipes and resources that can further inspire your tomato-based creations.

Fresh and simple

Sometimes, the best way to enjoy an heirloom tomato is in its pure, unadorned glory. Slice up a ‘Lucid Gem’ or a ‘Summer of Love’ and sprinkle with a pinch of sea salt. The simplicity of this preparation allows the true flavour of the tomato to shine through. For extra flair, add grated hard Italian cheese, a splash of Balsamic vinegar and freshly ground black pepper. Your taste buds will love you for it!

Salads and sandwiches

Heirloom tomatoes can transform a simple salad or sandwich into something extraordinary. Try slicing different varieties and layering them in a salad with fresh basil, mozzarella, and a drizzle of balsamic vinegar. Or, add them to a sandwich with crisp lettuce and creamy avocado for a taste of summer.

Roasting or grilling

Roasting or grilling tomatoes can intensify their flavours. Halve your tomatoes, toss them with a bit of olive oil, and roast until caramelized. Or grill them for a smoky flavour. These methods work wonderfully for making sauces, soups, or as toppings for bruschetta.

Preserving

To enjoy your heirloom tomatoes year-round, consider preserving them. Make homemade tomato sauce, salsa, or chutney, and can or freeze them for later use. It’s a wonderful way to capture the essence of your garden’s bounty.

Recipe resources

BBC Good Food (bbcgoodfood.com) offers a wide range of tomato-based recipes, from simple salads to more elaborate dishes.
The Kitchn (thekitchn.com) provides creative and easy-to-follow recipes that showcase tomatoes in various culinary roles.

Conclusion

As our journey in growing heirloom tomatoes comes to a close, it’s time to reflect on the lessons and joys of the season. Each tomato you’ve grown is not just a fruit; it’s a story, a piece of history, and a connection to generations of gardeners before you. As you enjoy your harvest – whether in salads, sandwiches, or simply on their own – remember that you’re partaking in a tradition that can span centuries.

Gardeners don't just grow plants; they grow memories, experiences, and connections to the earth and its bounty.

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