Hydrocotyle (Hydrocotyle spp)

Hydrocotyle is also known as Pennywort, Dollarweed and Kurnells Curse. It is a perennial weed, and a problem in wet lawns and turf areas. It has the name Dollarweed because of the shape of its leaves, which resemble a dollar, or a lily pad.

Dollarweed is a prostrate, aggressive weed. Left untreated, Hydrocotyle tends to form a dense mat which outcompetes any existing vegetation. Its ability to spread underground and establish quickly makes Dollarweed difficult to control.

Hydrocotyle has horizontal creeping stems, and it roots at each node. When you crush it, it gives off a strong smell.

 After you read this, you will be able to:

• Identify Hydrocotyle.
• Know the habitat of Hydrocotyle.
• Know the best cultural and chemical options to control Pennywort.

For more information, please check out our weed ID chart. Hydrocotyle or Pennywort is a good indicator weed of wet soils.

Thanks to The Atlas of Living Australia for the distribution map for Hydrocotyle.

Hydrocotyle Identification.

Pennywort has a large taproot and many small taproots. 

Category: Hydrocotyle is a broadleaf (Dicot) weed.

Photosynthetic Pathway: Dollarweed is a C3 Weed.

Flower: Hydrocotyle has yellow or white flowers. These can be present all year round, but are mainly seen from October to February.

Height: Pennywort is a prostrate weed.

Leaf Width: The leaf blade of Kurnell Curse is circular to elliptical, and is 25 to 50 mm in diameter.

Reproduction: Hydrocotyle spreads via seeds, rhizomes, and sometimes by tubers.

Comments: The dull, hairless green leaf of Dollarweed, has a roughly scalloped edge. The leaf divides into distinct segments.

Hydrocotyle is often mistaken for Kidney Weed. A good way to tell these apart is to look at where the leaf stem joins the leaf. The stem of Kidney Weed is at the edge of the leaf, while the stem of Hydrocotyle is in the centre.

Habitat: Hydrocotyle favours moist soil conditions, and thrives in weak, thin turf.

The image below is courtesy of Clemson University.

Cultural or mechanical control is generally unsuccessful. However, you can consider the following:

• Do not over water, and fix any drainage issues that cause wet soils. Dollarweed thrives in wet soils, so if areas don’t drain well improve the drainage and deal with any low spotLow areas that don’t drain very well are ideal for Dollarweed so deal with low spots etc.
• Irrigate properly. The University of Florida has shown that if you reduce the irrigation frequency it results in less Hydrocotyle.
• Mow at the right height for your turf grass. A dense, thick turf cover goes a long way toward the control of Hydrocotyle.
• If shade is an issue manage this. Turf in shade remains damp for longer.
• Hand removal of Hydrocotyle does not work well. What tends to happen is the weak leaf stem snaps off, and leaves the underground rhizomes behind. It then regrows from this.

Hydrocotyle on Bowling Greens.

On a sandy, well drained bowling green or golf green, over watering is a common problem. Growth of Hydrocotyle is most aggressive in damp areas, so if you remove slight hollows and don’t overwater, it discourages Hydrocotyle.

When you mow at a low height of cut, the leaves of Dollarweed tend to be smaller. In unmown areas the leaves are larger, being up to 20 mm in diameter.

Pre-Emergents for Hydrocotyle.

The following are registered for Hydrocotyle in the USA.

• Gallery and
• Indaziflam (Specticle)

These are pre-emergent herbicides that give some control of Dollarweed in warm-season turfgrasses, but are not currently registered for this in Australia.

Post Emergent Control.

Choose the right herbicide for your turf type and use it in the late Spring and Autumn. Ideally, this is when Pennywort is small, and actively growing. Herbicide effectiveness reduces as this weed matures.

You will need repeat applications to control Hydrocotyle, as one treatment does not deal with this weed.

You can control Kurnell Curse if you use non-selective herbicides like glyphosate, but be aware that this kills all vegetative material.

Other non selective options like Cortex Duo and Numchuk Quad also kill Hydrocotyle, but then prevent anything growing back for between 3 and 12 months respectively.

• Glyphosate (Rapid Fire 800).
• Cortex Duo and
• Numchuk Quad.

If you use Glyphosate to control Hydrocotyle, and water quality is an issue, then add the spray buffer ProForce Manta Ray to your spray mix