Name: 'Sonnenherz' Oxheart Tomato - Solanum lycopersicum
Brand: Benjis Seeds
Price: 3.0 EUR
Availability: OutOfStock

'Sonnenherz' Oxheart Tomato – early-ripening classic with multicolored, flame-patterned fruits.

This variety is a large-fruited oxheart tomato with an exceptional sweet-fruity flavor and a high flesh content. It ripens early and is ideally suited for cultivation in greenhouses, protected outdoor beds, and large containers. Robust, very high-yielding, and perfect for self-sufficiency as well as organic cultivation.

Origin & History

‘Sonnenherz’ is an open-pollinated oxheart tomato, developed in the late 1990s as part of the organic breeding movement. The aim was to create a robust, easy-to-grow, and early-ripening beefsteak tomato with a distinctive appearance and high flesh content.

Its hallmark is the multicolored fruit – ripening yellow-orange with red streaks in the flesh. Today it is considered a modern classic among oxheart tomatoes and is especially valued by lovers of open-pollinated varieties. Its unique flavor profile and spectacular appearance make it a true enrichment for any variety garden.

Appearance & Characteristics

The plant grows indeterminately as a stake tomato and reaches a height of about 200–220 cm. It develops an airy yet robust growth habit with strong fruit clusters and bears dark green foliage.

Fruit details:

Size: Large, approx. 250–350 g per fruit
Shape: Heart-shaped, multi-locular
Color: Yellow-orange with red streaks – multicolored, flame-like pattern
Texture: Juicy, high flesh content, little gel mass
Flavor: Sweet, fruity, and aromatic – full-bodied and intense

Usage & Cultivation Highlights

The fruits of the ‘Sonnenherz’ variety are excellent for fresh salads, as a flavorful topping on bread, and for decorative garnishing of dishes. With their spectacular multicolored appearance and sweet-fruity taste, they are a true highlight on the table.

Thanks to its robustness, this tomato variety thrives reliably in protected outdoor beds, greenhouses, and large containers. The early-ripening plants are easy to care for, with airy growth and very high yields. For outdoor cultivation in wetter and cooler regions, a rain cover is recommended.

Compared to other oxheart tomatoes, ‘Sonnenherz’ ripens particularly early and is visually striking – ideal for those who appreciate robust, open-pollinated tomatoes with impressive appearance.

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Origin & Cultivation at a Glance

First mention:

1990s

Origin:

Switzerland

Breeder:

Unknown – propagated through conservation initiatives

Propagation site:

Hesse - Germany

Suitable for:

Open field, Greenhouse, Polytunnel, Balcony / pot, Raised bed, Urban gardening, Vertical cultivation

Care requirements:

Low – easy to care for, ideal for beginners.

Overwintering:

Not winter-hardy – can be cultivated outdoors as an annual. Can be overwintered in a greenhouse in mild climates.

Special features:

High-yielding, Resilient, Low-maintenance, Sun-loving / sunny, Shade-tolerant / partial shade

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Cultivation guide for

Sonnenherz

Growing difficulty:

Easy

• In subtropical climates, pre-cultivation is possible from January - transplant outdoors from March in full sun, once day and night temperatures remain consistently above 15 °C.
• In temperate regions, start indoors from March – transplant outdoors in full sun from mid-May after the last frost.
• Sow in deep, well-drained, humus-rich and nutrient-rich loamy soil - 0.5-1 cm deep. Plant spacing: 50 × 70 cm.

Cultivation tips:

• Beefsteak tomatoes are typically grown with a single stem to promote better air circulation and fruit development.
• In temperate climates, a rain cover is recommended – a simple roof or plastic tunnel is sufficient.
• A sturdy support structure with tomato hooks provides secure hold for the stems, boosts yield, and makes plant care easier.
• When transplanting seedlings, plant them deep into the soil up to the base of the seed leaves – this encourages strong root development and supports healthy growth.
• Consistent watering enhances fruit quality and promotes healthy plant growth.
• At temperatures below 5 °C, plant growth slows significantly - cold stress can hinder development.
• Regular harvesting encourages new fruit set and increases overall yield.
• Biochar and rock dust improve soil structure and enhance the retention of nutrients and water.

Storage instructions:

Store seeds in a cool, dry, dark, and airtight environment to maximize shelf life and germination.

Detailed information on seed storage

Plant Profile

Plant details

Botanical name:

Solanum lycopersicum L. 'Sonnenherz'

Botanical family:

Solanaceae

Plant type:

Fruit vegetables

Growth habit:

Upright growth, Indeterminate growth habit

Plant width:

50 cm

Plant height:

220 cm

Root type:

Deep-rooted, Taprooted

Hardy to:

3 °C – only suitable for overwintering indoors or in a greenhouse.

Cultivation period:

6-8 months

Life cycle:

Perennial (grown as an annual)

Propagation method:

Generative propagation by seed, Propagation by cuttings

Propagation:

• This tomato variety is self-pollinating but can also cross-pollinate via insects. It belongs to the species Solanum lycopersicum and produces bisexual flowers.
• A minimum distance of 20–50 m from other tomato varieties is recommended for seed production to avoid unwanted cross‑pollination by insects.
• This tomato plant is perennial and forms clusters of flowers after blooming, which turn into fruit packed with seeds.
• Tomato seeds are ready for harvest when the fruits are fully ripe and slightly soft to the touch.

Sowing & Planting

Germination type:

Dark germinator, Warm germinator

Sowing depth:

0,5-1 cm

Germination temperature:

22-28 °C

Germination time:

6-14 days

Pot culture:

Requires a minimum container size of 20-30 liters.

Row spacing for baby leaf:

Not suitable for baby-leaf cultivation.

Plant spacing:

50 cm

Row spacing:

70 cm

Pricking out / thinning out:

Thin out seedlings within 2 weeks after the formation of the first true leaf pairs.

Planting time:

Tomato seedlings are ready to be planted outdoors about four weeks after potting up, once temperatures are consistently warm. Plant only in consistently warm weather – ideally after the last frosts, when both daytime and nighttime temperatures are mild.

Soil

Soil type:

Deep, well-drained, humus-rich loam

Soil pH:

6.0-6.8 - slightly acidic to neutral

Nutrient requirements:

Heavy feeder

Soil moisture:

Evenly moist, Sensitive to waterlogging

Soil preparation:

Loosen soil deeply before sowing, Apply compost before planting., Apply lime to acidic soil., Prepare soil weed-free and with a fine crumb structure., Mulch layer for moisture regulation

Companion planting, Crop rotation & Harvest

Companion plants:

Lettuce, Lamb’s lettuce, Spinach, Bean, Onion crops, Carrot, Radish varieties, Basil, Nasturtium, Calendula, Dill, Marjoram, Tagetes

Incompatible plants:

Fennel, Celery, Nightshade family, Cucurbits, Pea, Beetroot, Corn

Crop rotation guidelines:

• Do not plant after other nightshades – a minimum crop rotation interval of 3 years is recommended.
• Repeated cultivation at the same site increases disease pressure, leads to nutrient depletion, and impairs soil structure.
• Ideal previous crops include legumes, onions, root vegetables, and green manure – rotating crops supports healthy soil.
• Crop rotation with low-nutrient-demanding plants is recommended to prevent soil fatigue and maintain healthy growing conditions.
• Plan a green manure crop between heavy-feeding plants and this tomato variety to restore soil fertility.
• Avoid planting directly after heavy-feeding crops – allow the soil to recover and replenish nutrients first.

Harvest time:

Summer, Autumn

Sowing to harvest:

4-5 months

Harvested parts:

Fruits

Suitable for consumption:

Yes - edible raw or cooked.

Intended use:

Diet cuisine, Low Carb, Raw consumption, Salad, Cooking, Roasting, Grilling, Baking, To purée, Juice / juicing, Preserving, Stuffing, Decoration

Care & Cultivation practices

Water requirements:

High

Plant care techniques:

Water regularly - even during dry periods, Fertilize, Removing side shoots, Create a climbing support, Maintain weed-free, Inspect regularly for pest infestation