Helianthus annuus 'Russian Mammoth'
Russian Mammoth
The classic giant from children's books: one straight stem to almost four metres, crowned with a single enormous disc and heavy with edible seed. The cultivar that dominates contests for the tallest sunflower.
Quick answers: Russian Mammoth typically reaches 2.5–3.7 m (8–12 ft) at maturity; 3 m is a realistic average in good garden soil. It forms one head per plant, 25–30 cm (10–12 in) across, holding roughly a thousand or more striped seeds. It flowers about 110 days after sowing, and the seed is ripe some three to four weeks after flowering.
- Scientific name
- Helianthus annuus 'Russian Mammoth'
- Height
- 3–3.7 m (10–12 ft) in good soil
- Flower diameter
- 25–30 cm (10–12 in)
- Days to bloom
- ~110 from sowing
- Light needs
- Full sun
- Water needs
- High, deep-rooting
- Edible seed
- Yes, grey-striped
- Pollen-free
- No, heavy pollen
Origin and breeder
Russian Mammoth (also sold as 'Mammoth Russian' or 'Russian Giant') is an open-pollinated heirloom that appeared in United States seed catalogues as early as around 1880. The name points to the Russian origin of the large-seeded oil sunflower: in the nineteenth century, Russian growers selected plants with ever larger heads, and that seed returned to North America with emigrants. We describe that history — how the sunflower grew into a national crop in Russia — under the history in Russia and Ukraine. The cultivar holds no RHS Award of Garden Merit (RHS, 2023), but remains the benchmark for height contests.
How to identify it
- One dominant stem — unbranched, thick and straight, to 3.7 m (12 ft).
- One giant head of 25–30 cm (10–12 in) across, often bowed forward by its weight.
- Large, heart-shaped leaves up to 30 cm (12 in) wide.
- Classic egg-yolk ray florets around a broad brown centre.
- Thick, grey-striped seed in a dense spiral.
How tall does Russian Mammoth grow?
On the seed packet you will usually read 3–3.7 m (10–12 ft). That is achievable, but the average mature height in a real garden depends on the conditions more than on the name:
| Conditions | Typical height |
|---|---|
| Deep, rich soil, full sun, regular deep watering, sown in situ in May | 3–3.7 m (10–12 ft) |
| Ordinary garden soil, some dry spells | 2–2.5 m (6.5–8 ft) |
| Poor or shallow soil, part shade, crowded or in a pot | 1–1.8 m (3–6 ft) |
The world record for the tallest sunflower, 9.17 m (30 ft 1 in), was set in Germany in 2014 — far beyond what any seed packet promises. Record growers combine giant genetics with very rich soil, heavy watering, a sheltered spot and a long, warm season.
How many heads, and how heavy?
Russian Mammoth is a single-headed cultivar: each plant makes one main flower on top of the stem. In very rich soil, or if the growing tip is damaged early, a few small side heads can appear lower down, but they stay much smaller. Removing those side shoots channels energy into the main head. The ripe head is heavy — easily a kilogram or more when fresh and full of seed — and bows forward and downward as it fills. That weight is why staking matters and why birds find the seed easy to reach. The head loses much of its weight as it dries; see drying sunflower seeds.
Growing notes
This giant needs deep, rich soil, full sun and plenty of water; in thin or dry ground it stays undersized. Sow in situ, because the taproot resists transplanting. Give each plant at least 60 cm (24 in) of room. For the basic technique of sowing and feeding, see growing; for harvesting and drying the seed, the page on the biology of the flower head. Unlike pollen-free cut cultivars, Russian Mammoth sheds plenty of pollen, so it is valuable to bees.
The honest growing flaw
Here, height is also the weakness. The heavy head makes the plant top-heavy, and without sturdy staking the stem snaps in the first summer storm — a common loss just before harvest. So drive a strong stake or bamboo cane in at sowing time and tie the stem at several heights. Russian Mammoth is also not suited to a container: its root system and height demand open ground. If you want to grow in a pot, choose Teddy Bear instead — see also growing in containers.
Companion plants and substitutes
Plant Russian Mammoth against a sunny wall or fence that offers shelter from wind, with lower bloomers in front so the bare lower stem disappears. If you want to go even taller, look at 'Sunzilla' or 'American Giant' in the cultivar database. If the height is too much but you still want a seed harvest, 'Titan' or a single-headed 1.8 m garden sunflower is a calmer choice. The difference between giant and branching cultivars is on the species page.
Pick this if…
you have a sheltered spot with deep soil, want to harvest seed for birds or yourself, are entering a height contest, or want a dramatic focal point at the back of the border.
Don't pick this if…
you grow in a pot or on a windy balcony, cannot or will not add support, have little space, or want a cultivar with several flowers at once.
A packet of Russian Mammoth seed costs about £2 (€2) and usually holds plenty of seed for a whole row. As an open-pollinated cultivar, you can save the seed from your own head for next year.
Sources
- Royal Horticultural Society (RHS) — plant guide, 2023.
- USDA — historical seed catalogues and domestication of the large-seeded sunflower.
Useful products
- Russian Mammoth seeds — the classic giant variety
- Bamboo plant stakes — support for tall varieties in wind
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Frequently asked questions
What is the average mature height of a Russian Mammoth sunflower?
Typically 2.5–3.7 m (8–12 ft). In deep, rich soil with full sun and regular watering, around 3 m or more is realistic; in ordinary or poor soil expect 2–2.5 m or less.
How many heads does a Russian Mammoth sunflower have?
One. Russian Mammoth is a single-headed cultivar with one large flower on the main stem. Occasionally a few small side heads form in rich soil or after damage to the tip; removing them keeps the main head large.
How big and heavy is a Russian Mammoth sunflower head?
The head is usually 25–30 cm (10–12 in) across and, when fresh and full of seed, easily weighs a kilogram or more. It bows downward as it ripens and becomes much lighter as it dries.
What is the tallest sunflower ever grown?
The world record is 9.17 m (30 ft 1 in), set in Germany in 2014. Garden giants such as Russian Mammoth normally reach 3–3.7 m.
Can you eat Russian Mammoth sunflower seeds?
Yes. It is a confection-type cultivar with large, grey-striped seeds that can be roasted and eaten or fed to birds. Harvest when the back of the head turns yellow-brown and dry the seed well before storing.