Black Medic (Medicago lupulina)
Black Medic (Medicago lupulina) is also known as Yellow Trefoil, Hop Clover or Black Clover. It is an aggressive, prostrate Summer annual, and forms a dense, mat across turf.
It germinates in the late Spring, and then continues to grow through the heat of the Summer. Once the weather cools down it dies off.
Black Medic only reproduces from seed.
After you read this, you will be able to:
- Identify Black Medic, Hop Clover, Black Clover or Yellow Trefoil.
- Know what conditions favour Yellow Trefoil or Hop Clover.
- Know the best cultural and chemical controls for Black Medic or Hop Clover.
Although not directly toxic to livestock, if they eat enough of it Black Medic causes serious gastric issues.
it is often mistaken for White Clover or Yellow Wood Sorrel.
Differences between Black Medic and Other Trifoliate Weeds.
You find Black Medic (Medicago lupulina) and White Clover (Trifolium repels) in similar sites, and you often find them together in turf. It is also often mistaken for Creeping oxalis.
Spreading | Trifoliate | Leaf Shape | Tooth at Tip of Leaf | Toothed Leaf Margins | Annual/ Perennial | Soil Conditions | Habitat | Flowers | |
Black Medic | Yes | Yes | Oval serrated | Yes | Yes | Summer Annual | Low pH | Full sun | Yellow |
Creeping Oxalis | Yes | Yes | Heart shape | No | Smooth | Perennial | High pH | Shade | Yellow with 5 petals |
White Clover | Yes | Yes | Smooth rounded | No | Yes | Perennial | High pH | Open areas | White |
The distribution map is courtesy of The Atlas of Living Australia.
More information on lawn weeds is in our weed ID chart. What they reveal about soil conditions is in our blog on indicator weeds.
How to Identify Black Medic.
Black Medic or Black Clover is an indicator weed of low soil N as it outcompetes weak grass. Although it is classed as a cool season Summer annual, in mild Winters some plants can survive and act as perennials.
- It spreads easily by seed and forms large colonies up to 0.75 m across if it is left undisturbed. Black Medic is a low-growing weed, and has three heart shaped trifoliate leaves.
Category: Hop Clover is a broadleaf (Dicot) weed.
Photosynthetic Pathway: Black Clover is a C3 Weed.
Flower: Yellow Trefoil has single round yellow flower heads or flowers in clusters of up to four.
Height: It grows up to 10 to 60 cm in height.
Leaf length: The leaves of Black Medic are 12 to 18 mm long.
Leaf width: The leaves are 3 to 10 mm wide.
Reproduction: Black Medic only reproduces by seed. Immature plants flower within six weeks of emergence, and it produces seeds throughout the growing season. A single plant produces up to 6,600 seeds that remain viable in the soil for several years.
Comments:
- Coarse hairs cover the leaves, and the root system has a coarse branched taproot that may form nodules. These nodules add N to the soil.
- Black Medic has a symbiotic relationship with Rhizobium bacteria. These form root nodules, and fix atmospheric N.
- The leaves of Black Medic have shallow teeth towards their tips, and dark spots near their centre.
- Each leaflet has a small spur at its tip.
Habitat: This weed is a good indicator of soil problems. It thrives in droughty, low N, well-drained, compact soils and bare areas.
Black Medic handles a wide range of mowing heights. It is often found in disturbed areas or lawns, as well as in fields and pastures.
How to Remove Black Medic from your Lawn.
Cultural Control of Black Medic.
- Manage Black Medic through good turf management practices. The aim is to encourage a dense stand of turf, and make it difficult for this weed to persist.
- Hand pull or use a weed tool. It’s important to make sure that you remove the large taproot.
- As it favours compact soils, soil aeration also helps manage this weed.
- Bear in mind to keep N up to your turfgrass. This helps the grass outcompete this weed.
- Black Medic does not grow well in shade so if you adopt practices that increase turf competition it helps control it. Practices like mowing at the right height for the turf type, and watering properly will all help.
Management Calendar for Black Medic.
Management Calendar for Black Medic | ||||||||||||
Summer annual/sometimes perennial | ||||||||||||
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
Germination | ||||||||||||
Mowing/Hand Pull | ||||||||||||
Flowering | ||||||||||||
Pre emergent Herbicide | ||||||||||||
Post Emergent Herbicide | ||||||||||||
Chemical Control of Black Medic.
- ,Treatment is best in the late Spring to early Summer, and in the early to late Autumn.
- The best time to apply post-emergent herbicides is as early in the season as possible. This is when plants are small.
- You may need several applications to get the complete control.
Pre-emergent Herbicides for Black Medic.
- The herbicide Dithiopyr provides some pre-emergent control in lawns but is not registered for this in Australia for this.
- Oxadiazon and Prodiamine do not work well to prevent this weed.
- Isoxaben (Gallery) is an excellent pre-emergent for Black Medic but has limited areas where it can be used.
Post Emergent Herbicides for Black Medic Control.
The most important factor to effectively control Black Medic is to apply post-emergent herbicides when the plants are small. Treatment is best over the entire area rather than spot spraying.
Post-emergents for Black Medic:
- 2,4-D.
- Duke 100WG.
- ProForce Recondo.
- Contra M. (Do not use Contra M on Buffalo grass).
- Warhead Trio.
- Quinclorac. Not registered in Australia.
- Casper Herbicide controls Burr Medic (Do not use Casper on Buffalo grass).
Table of Black Medic Post Emergent Herbicide Rates.
Product | Active | Chemical Group | Rate/Ha | Comments | ||||
Casper | Prosulfuron + Dicamba | 2 and 4 | 800g-1Kg | Apply from Autumn to Spring. Use high rates in cool months or if high weed pressure. Control takes 4 to 6 weeks. Use an NIS at a rate of 0.25 to 0.5% v/v. | ||||
2,4-D | 2,4-D | 4 | 1.8-3.2 | Wet foliage thoroughly. DO NOT mow lawn for 1 week before and at least 1 weed after application. DO NOT use on Buffalo grass (WA only). | ||||
Duke | Iodosulfuron | 2 | 100g | Always use an NIS or Overtake Oil. Use in 200-500 L/ha water. | ||||
Recondo | Trifloxysulfuron | 2 | 225g | Use an NIS at 0.25% v/v (1000 g ai/L), 0.42% v/v (600 g ai/L) or Overtake Oil at 1%v/v. Ensure uniform placement onto leaves & into crowns. Water volume is 400 to 800 L/ha. You may need a repeat application in 4 to 6 weeks. Allow at least 6 weeks before overseeding. You may see discolouration on Qld Blue and Zoysia. | ||||
Warhead | MCPA + Clopyralid + Diflufenican | 4 + 12 | 5 L | You may see discolouration on kikuyu, carpet grass and Queensland blue. Avoid overlapping. Use an NIS. | ||||
Contra M. | Dicamba + MCPA | 4 | 6.5 L | Apply in 250-400L water. DO NOT use on Buffalo grass. After use do not mow for 2 days before or after application or fertilize within two weeks. | ||||
Non Selective Control of Black Medic.
You cannot use any of these on lawns or turf areas to selectively remove Black Medic.
- Glufosinate-ammonium provides control for 4 to 6 weeks. However, it will re-grow due to the limited movement of glufosinate.
- Glyphosate. You can use Glyphosate but if water quality is an issue then use ProForce Manta Ray.
These are non-selective but also have a long term residual that stops any re-growth of Yellow Trefoil or Black Medic.
- Renegade. Renegade stops germination of Black Medic for up to 12 months. This reduces the need for multiple herbicide applications.
- Numchuk Quad. This gives post and pre emergent control of Yellow Trefoil for up to 12 months.
- Cortex Duo. Cortex Duo gives a rapid knockdown of Black Medic, and residual control for up to 3 months. It is also safe to use around trees.
Table of Non Selective Black Medic Herbicides.
Product | Active | Chemical Group | Rate/Ha |
Glufosinate 200 | Glufosinate-ammonium | 10 | 1-6L |
Rapid Fire 800 | Glyphosate | 9 | 0.9-1.35 Kg |
Numchuk Quad | Terbuthylazine + Glyphosate + Amitrole Oxyfluorfen | 5 + 9 + 34 + 14 | 20-25L |
Cortex Duo | Nonanoic Acid + Oxyfluorfen | 14 | 7L/1000L |
Renegade | Bromacil | 5 | 3.5-6.5Kg |
ProForce Cortex Duo Industrial Herbicide is a non glyphosate weed killer. It is both a non-selective knockdown & a residual herbicide. You can use this to kill seedling & young
