For optimal germination rates, initiate seed propagation indoors under controlled conditions—unless the species exhibits a high sensitivity to root disturbance. This approach allows precise regulation of temperature, humidity, and light, improving germination consistency and seedling viability. Do not skip any recommended seed treatments, as they are essential for uniform and successful germination.
Plant Specific Instructions (Read “Seed Guide” as well): WARM stratify at 77-86 F (25-30C) for 4-5 weeks. Make sure the humidity is high and constant. Afterwards, COLD stratify at 36 F (2 C) for 80 days (11 weeks). During the cold stratification period, keep it in a dark place. Keep moist (not wet) at all times. Increase the temperatures gradually.
Sow at 72 F (22 C) or more in a seed starting mix. Surface sow – do not cover: Just press the seeds gently into the surface of the moist growing medium so they make good contact. Humidity: Use a humidity dome or clear cover to maintain consistent moisture during germination. Open the dome BRIEFLY once per day to allow fresh air in and reduce mold risk. Remove the dome entirely once seedlings emerge. Moderate but constant humidity is VERY IMPORTANT. Use grow lights to maintain 12–16 hours of light per day. Germinates when the temperatures slowly rise. Slow to germinate. Germinates in 3-12 weeks in optimal conditions. Could take 6 months or longer under suboptimal conditions.
Plants prefer very moist (not wet) and warm temperatures 75-86 F (24-30 C).
Oils from the skin can interfere with germination. Wear gloves when handling the seeds. Read the Seed Guide for Perennials. These seeds lose viability quickly so if you’re not planning on planting them right away, please keep them in the refrigerator (NOT freezer).
Botanical Name: Gunnera manicata
Common Name: Giant Rhubarb, Dinosaur Food, Brazilian Giant Rhubarb
Type: Herbaceous Perennial
Flower Color: Orange/Reddish/Green
Flowering Season: Summer, Fall
Plant Height: 6-15 ft (1.8 to 4.5 m)
Plant Spread: 10-12 ft (3-3.6 m)
Light Requirements: Partial Shade. Full Sun in areas with cool summers.
Water Requirements: Moist. Soil must never be allowed to dry out. Suitable for bogs, water gardens, rain gardens.
Soil Requirements: Well-drained. Average. Prefers fertile, humus-rich soil.
USDA Zones: 6-10
AHS Heat Zones: 12-7