Alismataceae
Giant Arrowhead (Sagittaria montevidensis)
Sagittaria montevidensis
An easy, fast-growing pond marginal: full sun to part shade, heavy soil that is always wet, and 2-15 cm of water over the pot. It dies back in winter and regrows or returns from seed. It can be invasive, so never release it into natural waterways.
Every 2 days
Bright indirect
° - °C
% - %
Categories
What is Giant arrowhead?
Giant arrowhead (Sagittaria montevidensis) is a easy-care plant from the Alismataceae family. Sagittaria montevidensis is an emergent aquatic plant from the Americas, common in the wetlands of Uruguay, Argentina and southern Brazil and also found in North America, growing on the edges of lagoons and rivers, in marshes and on shallowly flooded mud. It is an annual or short-lived perennial, 60...
Giant arrowhead grows up to 1.2m, spread of 60cm, watering every 2 days. It is not suitable for indoor environments and safe for pets.
Unlike many tropical plants, Giant arrowhead tolerates watering mistakes. Best for beginners. Unlike many popular species, Giant arrowhead is safe to keep around pets.
How to Care for Giant arrowhead?
TLDR: Giant arrowhead needs Bright indirect, watering every 2 days, and temperatures between 15-30°C with 40-70% humidity.
How Often Should You Water Giant arrowhead?
Keep the pot permanently submerged, with 2 to 15 cm of water above the soil, or plant it in the mud of a bog garden. The soil must never dry out; in a pond it needs no watering beyond topping up the water level in summer.
How Much Light Does Giant arrowhead Need?
Full sun to part shade. More sun means more flowers.
What Is the Best Soil for Giant arrowhead?
Heavy loam or clay that stays wet; tolerates acidic, neutral or alkaline and poorly drained soils. Use heavy garden soil or aquatic compost, without loose organic fertilizer that clouds the water.
What Pot Should You Use for Giant arrowhead?
An aquatic basket or pot of 8 litres or more, filled with heavy soil and topped with gravel, set in the pond so it sits under 2-15 cm of water.
What Is Giant arrowhead and Where Does It Come From?
Sagittaria montevidensis is an emergent aquatic plant from the Americas, common in the wetlands of Uruguay, Argentina and southern Brazil and also found in North America, growing on the edges of lagoons and rivers, in marshes and on shallowly flooded mud. It is an annual or short-lived perennial, 60 to 120 cm tall. Young leaves are submerged ribbons; adult leaves are arrow-shaped, up to 30 cm long, and held above the water on spongy stalks. From summer to early autumn it bears white three-petalled flowers about 2.5 cm across with a purple or wine-red blotch at the base, in whorls of three, with female flowers below and male flowers above. It sets abundant seed and is a weed of rice fields and irrigation channels.
How to Propagate Giant arrowhead?
Seed
It seeds heavily: deadhead spent flowers if you do not want it to spread.
- 1 Collect the ripe round seed heads of winged seeds in late summer or autumn
- 2 In spring, sow on saturated heavy soil in a tray without drainage holes
- 3 Keep the soil waterlogged and cover with 1-2 cm of water once seedlings appear
- 4 Pot into an aquatic basket and lower into the pond as it grows
Materials needed:
Rhizome division
Works on plants growing as perennials; annual plants renew only from seed.
- 1 In spring, lift the pot from the pond
- 2 Split off pieces of rhizome with shoots and roots
- 3 Pot each piece in an aquatic basket with heavy soil
- 4 Lower back into the water gradually
Materials needed:
How Big Does Giant arrowhead Grow?
TLDR: Giant arrowhead can reach up to 1.2m tall with Fast growth rate.
Max height
1.2m
Spread
60cm
Growth rate
Fast
Foliage
Deciduous
Plant Uses
Ornamental
Great for decoration
Is your plant showing symptoms?
Click on the symptom to discover possible causes:
Fun Facts
The name montevidensis refers to the old province of Montevideo, where the species was first described.
Each flower has three white petals with a purple blotch; female flowers sit below the male flowers on the same stalk.
The deeper the water, the longer the leaf stalks grow to lift the leaves to the surface.
Frequently asked questions
How deep should I plant giant arrowhead?
Is giant arrowhead invasive?
Why did it disappear in winter?
Is it toxic?
Compare with similar plants
| Attribute | Difficulty | Light | Watering | Pet Safe |
|---|---|---|---|---|
| Field Maple | Easy | Bright indirect | 14d | ✓ |
| Iberian Houseleek | Easy | Direct sun | 14d | ✓ |
| Silver Birch | Easy | Direct sun | 14d | ✓ |
| Common Blanketflower | Easy | Direct sun | 10d | ✓ |
Choose & Compare
Sources & References
- Gardenia.net - Sagittaria montevidensis (Giant Arrowhead)
- Weeds Australia - Arrowhead (Sagittaria montevidensis)
- Planta Daninha (SciELO) - Análise morfológica de Sagittaria montevidensis em diferentes condições de inundação (search snippet)
- Kiddle - Saeta de Montevideo (common names)
- Environment Canterbury - Sagittaria pest status NZ (search snippet)
