Giant Rhubarb Seeds (Gunnera manicata)

Giant Rhubarb Seeds (Gunnera manicata)

Price for Package of 10 seeds

🌿 Gunnera manicata, commonly known as Giant Rhubarb or Brazilian Giant Rhubarb, is a spectacular herbaceous perennial grown for its enormous leaves and dramatic architectural appearance. It is native to mountainous regions of Brazil and Colombia and is particularly suited to large gardens with permanently moist ground, boggy areas and pond margins.

This giant ornamental plant forms an impressive clump of huge deciduous leaves carried on thick, prickly stems. It is an excellent choice for gardeners looking to create a dramatic tropical or prehistoric appearance around water features and other consistently moist areas.

🌡️ Temperature Resistance and Winter Hardiness

Minimum temperature: approximately -10°C (14°F) with winter protection, according to the supplied information. Other horticultural sources place its practical hardiness around -10 to -12°C (14 to 10°F), depending on shelter, soil moisture and winter protection. :contentReference[oaicite:0]{index=0}

The foliage is deciduous and dies back after frost, while the underground crown can survive considerably lower temperatures when properly protected. A thick layer of dry leaves, straw or other insulating material should be placed over the crown before severe winter weather.

Some horticultural databases rate plants sold under the name Gunnera manicata as suitable for approximately USDA Zone 7 and warmer, although identification is complicated because plants historically sold under this name may actually be the hybrid Gunnera × cryptica. :contentReference[oaicite:1]{index=1}

🌱 Plant Features

Plant Type: Herbaceous perennial

Botanical Name: Gunnera manicata

Synonym: Gunnera brasiliensis

Common Name: Giant Rhubarb, Brazilian Giant Rhubarb

Family: Gunneraceae

Growth Habit: Large clump-forming perennial

Leaf Size: Up to approximately 2.4 m (8 ft) across in its native habitat

Leaf Stems: Up to approximately 1.5 m (5 ft), strongly textured and prickly

Flowers: Small greenish-red flowers arranged in upright inflorescences

Fruit: Small red-green fruits approximately 2.5 mm long

Foliage: Deciduous

The enormous rounded leaves are deeply textured and strongly veined, producing one of the most dramatic foliage displays available for large water gardens. RHS information describes plants sold under the Gunnera manicata name as forming dense clumps with leaves approximately 1–2 m wide and stout prickly stalks. :contentReference[oaicite:2]{index=2}

💧 Growing Conditions

Moisture: Very high

Soil: Fertile, humus-rich and consistently moist

Light: Full sun, partial shade or bright shade depending on climate

Ideal Location: Pond margins, bog gardens, damp borders and consistently moist ground

Gunnera manicata requires considerably more moisture than ordinary garden perennials. It performs best in deep, fertile, humus-rich soil that remains moist throughout the growing season. A position beside a pond or other permanent water source is particularly suitable. :contentReference[oaicite:3]{index=3}

In hot climates, some afternoon shade can help protect the enormous leaves from excessive heat and scorching. Shelter from strong drying winds is also beneficial.

🌾 Sowing Instructions

Propagation: Seeds

Sowing Time: Seeds are best sown when fresh because their viability can decline relatively quickly. Controlled sowing can be carried out under suitable warm conditions. :contentReference[oaicite:4]{index=4}

Growing Medium: Use a fertile, moisture-retentive but well-drained seed starting medium.

Moisture: Keep the growing medium consistently moist during germination and early development.

Temperature: Provide gentle warmth and stable moisture for germination.

Because the supplied information does not provide a reliable exact germination temperature or germination period, these values should not be invented. Fresh seed and stable warm conditions are more important than forcing the seeds with excessive heat.

🌿 Establishment and Growth

Young plants should be allowed to establish before being moved to their final position. Choose the planting location carefully because mature Gunnera requires substantial space and becomes increasingly difficult to relocate as the root system and crown develop.

Provide generous organic matter and maintain high soil moisture throughout the active growing season. Regular watering is particularly important during warm or dry periods.

The plant grows rapidly when supplied with abundant moisture and fertile soil, eventually producing the enormous leaves for which Giant Rhubarb is famous.

✂️ Support and Winter Protection

Gunnera manicata normally requires little pruning during the growing season. After the foliage has been damaged by autumn frost, remove or fold the dead leaves down over the crown.

Use the large dead leaves together with additional dry mulch to create an insulating layer over the crown. This is particularly important in regions where temperatures can fall below approximately -5°C (23°F).

The crown is the most important part to protect. Even when the enormous leaves are completely destroyed by frost, a well-protected crown can produce fresh foliage again in spring.

🌸 Flowers and Fruits

The plant produces relatively inconspicuous green-red flowers compared with its enormous foliage. These flowers are grouped into upright inflorescences and are followed by small red-green fruits.

The primary ornamental attraction is therefore the foliage rather than the flowers. The gigantic leaves provide exceptional scale and visual impact in large landscapes.

🏡 Garden Uses

Giant Rhubarb is particularly suitable for:

• Pond margins

• Bog gardens

• Damp borders

• Waterside planting

• Large cottage and informal gardens

• Tropical-style landscapes

• Architectural specimen planting

• Large garden water features

It should be given plenty of space because a mature specimen can occupy several metres of garden area. Its enormous leaves create an excellent backdrop for large ferns, moisture-loving perennials and other plants suited to wet conditions.

⚠️ Important Notes

Do not confuse Giant Rhubarb with edible rhubarb. Gunnera is not the same plant as culinary rhubarb and should not be treated as a food crop.

The plant requires abundant moisture and is not suitable for dry gardens. Lack of water can cause severe stress and damage to the large leaves.

Winter protection is recommended wherever temperatures can fall below approximately -5°C (23°F), and especially where temperatures may approach or fall below -10°C (14°F).

There is an important taxonomic issue with this plant. The RHS explains that many plants historically sold as Gunnera manicata in Britain are actually the hybrid Gunnera × cryptica, and genuine G. manicata appears to have disappeared from cultivation in Britain and Ireland. :contentReference[oaicite:5]{index=5}

The RHS also lists plants sold under the misapplied Gunnera manicata name as invasive in the UK. Local regulations should therefore be checked before cultivation. :contentReference[oaicite:6]{index=6}

This product contains 10 seeds.

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