Garlic mustard is an invasive plant that can quickly take over native habitats. Learning how to identify and properly remove this unwanted plant is an important skill for landowners and conservationists. With some knowledge and effort, you can help control the spread of garlic mustard.
What is Garlic Mustard?
Garlic mustard (Alliaria petiolata) is a cool-season biennial herbaceous plant that is native to Europe. It was introduced to North America in the 1800s likely for culinary and medicinal uses. Since its introduction, garlic mustard has spread aggressively and is now considered a noxious weed in many areas.
Garlic mustard flourishes in the understory of forests and wooded edges. It poses a threat to native plants and wildlife because it outcompetes native vegetation and establishes dense monocultures. Garlic mustard releases antifungal chemicals into the soil that disrupt associations between native plants and mycorrhizal fungi. This gives garlic mustard an advantage over indigenous species.
Identifying Garlic Mustard
Being able to accurately identify garlic mustard is the first step in controlling its spread. Here are some key characteristics to look for:
Growth Habit
- Biennial plant that forms a rosette the first year and flowering stems in the second year.
- Grows 1-4 feet tall.
- Has a taproot.
- Emerges early in spring and dies back by late June/early July.
Leaves
- Kidney-shaped with scalloped edges.
- Alternate leaf arrangement.
- Leaves give off garlic odor when crushed.
- Basal leaves can grow up to 6 inches across.
- Stem leaves are triangular and sharply toothed.
Flowers
- Small white flowers with four petals in dense clusters at end of stems.
- Flowers April-June.
Seed Pods
- Long, slender pods that hold small black seeds.
- Pods ripen June-July.
- Each plant can produce thousands of seeds that scatter as pods burst open.
Stem
- Single stem that branches out as it bolts.
- Stem has white sap when broken.
When identifying garlic mustard, be sure to crush some leaves to check for the distinctive garlic odor. This is the best way to distinguish it from other plants with similar features. Compare suspected plants to photographs to confirm.
Where Does Garlic Mustard Grow?
Garlic mustard thrives in disturbed areas and spreads quickly along trailsides, roadsides, and woodland edges. Be on the lookout in these key habitats:
- Forests – Invades forest understories and competes with tree seedlings.
- River banks – Spreads rapidly along riparian corridors.
- Roadsides – Easily moved by vehicles, foot traffic, and mowers.
- Residential areas – Escapes from gardens and spreads to natural areas.
- Edge habitats – Establishes dense thickets along fences, trails, and woodland edges.
Garlic mustard does best in partial shade but can grow in full sun. It prefers moist, nutrient-rich soils. Look for first year basal rosettes along forest edges and floodplains. Second year plants emerge in April and set seed by June.
Dangers of Garlic Mustard
It’s important to control the spread of garlic mustard because it poses a serious threat to native plants and biodiversity:
- Displaces native plants – Grows earlier and crowds out native wildflowers.
- Disrupts soil ecology – Releases chemicals that kill beneficial fungi.
- Threatens wildlife – Reduces habitat and food sources for native insects and pollinators.
- Alters forest structure – Dramatically changes understory community composition.
- Degrades riparian areas – Outcompetes native vegetation along streambanks.
Unchecked infestations can rapidly dominate the understory and decrease plant diversity. Controlling garlic mustard preserves native plant communities and protects ecosystem health.
How to Remove Garlic Mustard
Several methods can be used to control and remove garlic mustard. Integrating multiple techniques is often most effective:
Manual Removal
- Time correctly – Pull just before or during flowering to prevent seed production.
- Hand pull – Grasp low and uproot taproot, being careful not to scatter seeds.
- Use tools – Use a dandelion puller, garden fork, or weed wrench for large infestations.
- Bag plants – Put in bags and dispose of properly so seeds don’t spread.
- Follow-up – Revisit sites for several years to catch new seedlings.
Cutting/Mowing
- Cut stems – Use brush cutters, mowers, or string trimmers to prevent seed production.
- Time carefully – Cut in early summer when flowering, but before seeds form.
- Bag trimmings – Prevent cut plants from producing viable seeds.
- Repeat – Follow-up cutting may be needed.
Herbicides
- Use cautiously – Avoid applying near water or native plants. Always read labels.
- Target rosettes – Spray first year growth for best results.
- Types – Glyphosate or triclopyr most effective.
- Follow laws – Only apply with proper permits and licenses.
Prescribed Burns
- Burn early spring – Control emerging rosettes and seedlings.
- Repeat burns – Help exhaust the seed bank over time.
- Coordinate timing – Burn before native wildflowers emerge.
- Create firebreaks – Prevent fire from spreading to sensitive areas.
- Use experienced crew – Have proper training and equipment.
Best Management Practices
- Learn identification – Properly identify garlic mustard before removing.
- Pull early – Focus on pulling first year rosettes before they flower.
- Bag and dispose – Prevent maturing or dispersal of seeds.
- Clean equipment – Inspect and remove seeds from tools, shoes, and gear.
- Monitor annually – Revisit treated areas to spot new growth.
- Replant natives – Restore areas with competitive native wildflowers.
- Control small patches – Prioritize isolated populations before dense stands.
- Coordinate efforts – Work with neighbors and conservation groups.
FAQs About Controlling Garlic Mustard
How do I know if a plant is garlic mustard?
Crush the leaves. If they smell like garlic, it’s likely garlic mustard. Compare to pictures to confirm identification before removing.
What is the best time to remove garlic mustard?
For pulling, late April to mid-May when flower buds appear is ideal. For cutting/mowing, early June when flowering starts prevents seed production.
Will pulled plants re-sprout?
Not if the entire taproot is removed. Any broken root fragments left behind may re-sprout. Carefully pull and dispose of the entire plant.
How long do seeds remain viable in soil?
Garlic mustard seeds can survive for several years. Continued monitoring and control is needed for several growing seasons.
Is it better to pull or cut garlic mustard?
For small patches, hand pulling is preferable if the entire taproot can be removed. For large infestations, cutting/mowing helps prevent seed production.
What native plants compete well against garlic mustard?
Early spring wildflowers like spring beauty, trout lily, and toothwort help occupy the understory before garlic mustard emerges.
Conclusion
Controlling invasive garlic mustard takes persistence, but will reward you with a healthier native plant community. Learn to identify garlic mustard in all stages of growth. Combine control methods like hand pulling, mowing, herbicides, and prescribed fire for best results. Always properly dispose of plants and seeds to prevent further spread. With repeated efforts, you can help reduce garlic mustard on your property and protect native species diversity. Consistent monitoring and control will provide long-term management of this aggressive invader.