# black knapweed (*Centaurea nigra*)

Black knapweed is a pretty flower that has purple petals and grows in fields and meadows. It attracts butterflies and bees, making it a favorite among pollinators!

- **Category:** [Plants](https://www.snappit.app/explore/categories/plant)
- **Rarity:** Common
- **Danger:** 1/5 · Very low
- **Habitat:** Grasslands

![black knapweed](https://commons.wikimedia.org/w/index.php?title=Special:Redirect/file/Centaurea_nigra-3233.jpg&width=800)

Photo: Julie Anne Workman, CC BY-SA 3.0 · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Centaurea_nigra-3233.jpg)

## Appearance

The black knapweed has striking purple or magenta thistle-like flowers, each head sitting atop a sturdy stem. Its unique feature is the dark, often fringed or scaly bracts that form a distinct blackish base directly beneath the flower.

## Taxonomy

- **Kingdom:** Plantae
- **Phylum:** Tracheophyta
- **Class:** Magnoliopsida
- **Order:** Asterales
- **Family:** Asteraceae
- **Genus:** Centaurea

## Interesting facts

- Its dark flower base inspired the name 'black knapweed'!
- Knapweed was once used to treat sore throats and fevers!
- Some caterpillars use knapweed as their only food source!
- Some say its tough stems were used to make brooms!

## Special abilities

- **Root Anchor:** Black knapweed can grow deep taproots that help it survive dry spells and poor soils.
- **Seed Cannon:** Black knapweed has many seeds per flower head, allowing it to spread widely and colonize new areas.
- **Nectar Beacon:** Black knapweed produces abundant nectar, attracting many insects to help it pollinate its flowers.

## Measurements & details

- **Height:** 30-90 cm
- **Spread:** 30-60 cm
- **Flower Size:** 2-4 cm
- **Bloom Season:** Summer to early autumn (July-October)
- **Edible:** Yes
- **Toxicity:** None
- **Lifecycle:** Perennial
- **Pollination Method:** Insect

## Ecological connections

- **Pollinates:** Honey bee (*Apis mellifera*) — Visits flowers for nectar and pollen.
- **Pollinates:** Painted lady butterfly (*Vanessa cardui*) — Feeds on nectar, aiding flower reproduction.
- **Parasitizes:** Knapweed rust (*Puccinia calcitrapae*) — Fungus forms orange spots on leaves and stems.
- **Eaten by:** Domestic cattle (*Bos taurus*) — Grazes on young leaves, less so on mature plants.

## Traits

- [Flowering](https://www.snappit.app/explore/traits/flowering): Flowering plants are any plants that produce flowers as part of their reproductive cycle.
- [Biennial](https://www.snappit.app/explore/traits/biennial): Biennial plants complete their life cycle over two growing seasons, typically forming foliage in the first year and flowering/seeding in the second.
- [Summer Blooming](https://www.snappit.app/explore/traits/summer-blooming): Summer blooming plants produce their flowers during the summer season, often providing vibrant color when many other plants have finished.
- [Fragrant Flower](https://www.snappit.app/explore/traits/fragrant-flower): Fragrant flowers emit a pleasant aroma, often to attract pollinators or for defense.
- [Colorful](https://www.snappit.app/explore/traits/colorful): Colorful describes organisms or objects displaying a wide range of bright and distinct colors.
- [Grassland](https://www.snappit.app/explore/traits/grassland): Grassland habitats are terrestrial biomes dominated by grasses and herbaceous plants, supporting a variety of grazing animals.
- [Pollinator Magnet](https://www.snappit.app/explore/traits/pollinator-magnet): Describes plants that are particularly attractive and beneficial to a wide range of pollinating organisms.
- [Invasive](https://www.snappit.app/explore/traits/invasive): Invasive species are non-native organisms that cause harm to the environment, economy, or human health.
- [Pollinator](https://www.snappit.app/explore/traits/pollinator): Describes organisms that transfer pollen, enabling the fertilization and reproduction of plants.

## Collections

- [Plants](https://www.snappit.app/explore/collections/plants)

## Safety

**Danger:** 1/5 · Very low

Do not touch plants without asking an adult, as some may not be safe.

## Frequently Asked Questions

### How to identify black knapweed?

Start with the whole plant, then compare leaf arrangement, leaf edges, stems and any flowers or fruit. Opposite leaves grow in pairs; alternate leaves come one at a time along the stem. These details tell you far more together than a single green leaf does. Plant Identifier: upload a photo and compare the visible details.

### How tall is black knapweed?

30-90 cm

### How wide does black knapweed spread?

30-60 cm

### How big are the flowers on black knapweed?

2-4 cm

### When does black knapweed bloom?

Summer to early autumn (July-October)

### Is black knapweed edible?

Yes

### Is black knapweed toxic?

None

### What is black knapweed's lifecycle?

Perennial

## More Plants

- [white snakeroot](https://www.snappit.app/explore/white-snakeroot) (*Ageratina altissima*)
- [tree-of-heaven](https://www.snappit.app/explore/tree-of-heaven) (*Ailanthus altissima*)
- [western sword fern](https://www.snappit.app/explore/western-sword-fern) (*Polystichum munitum*)
- [common milkweed](https://www.snappit.app/explore/common-milkweed) (*Asclepias syriaca*)

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Source: [Black Knapweed: Facts & Places to See — Snappit](https://www.snappit.app/explore/black-knapweed)