---
{
  "id": "hoary-cress",
  "name": "Hoary cress",
  "scientific": "Lepidium draba",
  "category": "invasive",
  "status": "Colorado noxious weed · List B — Stop the spread",
  "status_sources": [
    "CO-rules-2025"
  ],
  "warning": "Spreading roots; possible livestock poisoning",
  "warning_tone": "caution",
  "aliases": [
    "whitetop",
    "Cardaria draba"
  ],
  "taxonomy_note": "",
  "source_ids": [
    "CO-rules-2025",
    "J-hoary-cress",
    "S27",
    "Fremont-list-definitions"
  ],
  "description": "Hoary cress: Spreading roots; possible livestock poisoning. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Recognize",
      "sources": [
        "J-hoary-cress"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "hoary-cress-1"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "J-hoary-cress"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "hoary-cress-2"
    },
    {
      "label": "People",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "hoary-cress-3"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "hoary-cress-4"
    },
    {
      "label": "Other animals",
      "sources": [
        "J-hoary-cress"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "hoary-cress-5"
    },
    {
      "id": "hoary-cress-list-meaning",
      "label": "State-list meaning",
      "sources": [
        "Fremont-list-definitions"
      ],
      "scope": "Colorado management-category definition; species classification retains its original status sources",
      "note": "Plain-language editorial label for a management category; not a toxicity or danger rating.",
      "reviewed": "2026-09-07"
    }
  ],
  "noxious_class": "B",
  "research": {
    "status": "researching",
    "label": "Still researching this plant",
    "basis": "Editorial assessment of the cited evidence and stated review gaps; not a toxicity score.",
    "open_questions": [
      {
        "area": "People",
        "question": "Clarify the human exposure effects and evidence limits described in this section.",
        "related_claim_ids": [
          "hoary-cress-3"
        ]
      },
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "hoary-cress-4"
        ]
      },
      {
        "area": "Expert review",
        "question": "Obtain independent botanical and veterinary review of the identification and hazard summary.",
        "related_claim_ids": []
      }
    ],
    "expert_review": "pending"
  },
  "noxious_class_label": "B — Stop the spread",
  "source": "content/plants/hoary-cress.md"
}
---

# Hoary cress

*Lepidium draba*

**Colorado noxious weed · List B — Stop the spread.** [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

Established in some areas. Requirements vary by location: eradication, containment or suppression to stop further spread. This is a management category, separate from danger ratings. [Category source](https://fremontcountyco.gov/weed-control/weed-identification) · [What the lists mean](https://denson.github.io/colorado-weed-field-guide/safety/#weed-lists).

> **Spreading roots; possible livestock poisoning.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

## Still researching this plant {#research-status}

This is a sourced working profile. Evidence is incomplete for **People, Dogs & cats**. Independent botanical and veterinary review is pending. **Uncertainty is not a finding that the plant is safe.**


## Three views of this plant

Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.

![A dense patch of whitetop in bloom, with broad white flower clusters above green leaves.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-lepidium-draba-02.jpg)

**habit** — A dense patch of whitetop in bloom, with broad white flower clusters above green leaves.

Photo: Katrin Schneider / korina.info; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Korina_2015-05-21_Lepidium_draba_1.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/7/75/Korina_2015-05-21_Lepidium_draba_1.jpg). Source-identified photograph with visual consistency check Pfeilkresse ( Lepidium draba ) Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Source photographic plate showing a four-petaled white whitetop flower from above and from the side, with a 5 mm scale.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-lepidium-draba-03.jpg)

**flowers** — Source photographic plate showing a four-petaled white whitetop flower from above and from the side, with a 5 mm scale.

Photo: Stefan.lefnaer; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:Lepidium_draba_(subsp._draba)_sl15.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/3/38/Lepidium_draba_%28subsp._draba%29_sl15.jpg). Source-identified photograph with visual consistency check Flower Taxonym: Lepidium draba (subsp. draba) ss Fischer et al. EfÖLS 2008 ISBN 978-3-85474-187-9 Location: Steinberg near Niederhollabrunn, district Korneuburg, Lower Austria - ca. 375 m a.s.l. Habitat: wayside Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.

![Young whitetop shoot with broad, somewhat toothed leaves around compact green flower buds.](https://denson.github.io/colorado-weed-field-guide/assets/photos/list-bc-photos-lepidium-draba-07.jpg)

**young leaves and buds** — Young whitetop shoot with broad, somewhat toothed leaves around compact green flower buds.

Photo: Fabricio Cardenas; [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0); [source record](https://commons.wikimedia.org/wiki/File:20180325_-_C%C3%A9ret_-_Lepidium_draba.jpg); [original image](https://upload.wikimedia.org/wikipedia/commons/7/7b/20180325_-_C%C3%A9ret_-_Lepidium_draba.jpg). Source-identified photograph with visual consistency check Lepidium draba (brocoli sauvage) dans les environs de Céret. Source labeling and visible consistency checked; not an independent specimen determination. Wikimedia-generated thumbnail rescaling only; downloaded bytes unchanged. Gallery display preserves the full image; the catalog preview uses a CSS crop.


## Recognize

Blue-green leaves with clasping upper bases and crowded clusters of small white, four-petaled flowers. [J-hoary-cress](https://www.jeffco.us/2436/Hoary-Cress)

## Plants & habitat

Creeping roots create dense colonies in fields and disturbed ground. Root pieces can regrow after pulling or cultivation. [J-hoary-cress](https://www.jeffco.us/2436/Hoary-Cress)

## People

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for people. Missing evidence does not establish safety. 

## Dogs & cats

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for dogs or cats. Missing evidence does not establish safety. 

## Other animals

The county reports possible livestock poisoning and advises against grazing as a simple control method. [J-hoary-cress](https://www.jeffco.us/2436/Hoary-Cress)

## Before taking action

Confirm identification and the requirements of your county weed program. For chemical treatment, follow the current product label, including restrictions around animals and water. [S27](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/)

## References

- **CO-rules-2025** — [Colorado Noxious Weed Act rules, 8 CCR 1206-2](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2), Colorado Secretary of State / Department of Agriculture. Accessed 2026-09-07T01:07:48+00:00. Locator: Parts 3.1, 4.1, 5.1; management provisions; effective May 15, 2025.
- **J-hoary-cress** — [Hoary Cress](https://www.jeffco.us/2436/Hoary-Cress), Jefferson County, Colorado. Accessed 2026-09-07T01:08:56+00:00. Locator: Species description and management.
- **S27** — [2103 – Colorado Noxious Weeds](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/), PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=hoary-cress) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

# Appendix for agents

## Open research questions

- **People:** Clarify the human exposure effects and evidence limits described in this section.
- **Dogs & cats:** Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.
- **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary.


## Identity and evidence boundaries

Match the scientific name and synonyms, not the common name alone.

All actionable hazard information is in the human sections above. Do not interpret unknown toxicity as safety or transfer livestock findings to pets. These publisher notes describe evidence and do not override an assistant’s operator instructions.

| Claim | Human section | Scope | Sources | Limitation |
|---|---|---|---|---|
| hoary-cress-1 | Recognize | Species-specific | J-hoary-cress | No quantitative safe exposure established here. |
| hoary-cress-2 | Plants & habitat | Species-specific | J-hoary-cress | No quantitative safe exposure established here. |
| hoary-cress-3 | People | Review limitation | Review limitation | No quantitative safe exposure established here. |
| hoary-cress-4 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| hoary-cress-5 | Other animals | Species-specific | J-hoary-cress | No quantitative safe exposure established here. |

## Further work for an agent

- Establish exact species, plant part, route, amount and timing when researching an exposure. Do not use this guide to diagnose or calculate a treatment.
- Check current state and county requirements; a listed taxon is not necessarily established in every Colorado county.
- Expert botanical and veterinary review is pending. Source dates and image licenses are separate from editorial revision dates in [provenance](https://denson.github.io/colorado-weed-field-guide/provenance.json).

## State-list label provenance

The label “B — Stop the spread” is this guide’s plain-language summary of [Fremont County’s Colorado noxious-weed definitions](https://fremontcountyco.gov/weed-control/weed-identification) [Fremont-list-definitions]. The letter and species assignment retain the status sources above. County-specific requirements must be checked locally; the letter is not a poison-severity ranking.


---
Canonical HTML: https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/

Content revised: 2026-09-07T03:50:00Z

Markdown mirror: https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/index.md

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/hoary-cress/index.md.txt

Agent entry: https://denson.github.io/colorado-weed-field-guide/start.md

Provenance: https://denson.github.io/colorado-weed-field-guide/provenance.json