Bitter Melon (Momordica charantia).
Bitter Gourd is also known as Bitter Melon and Balsam Pear, and is an herbaceous, annual vine. It is up to 3 to 4 m long, and is a weed of the tropics and subtropics. Bitter Gourd is grown for its edible fruit, which is among the most bitter of all fruits due to its high levels of momordicin.
Momordicin is used to treat Parkinson’s disease and strokes. The mature fruit and seeds are toxic and should not be eaten.
Bitter Melon lives about three months, and it has an unpleasant smell if you crush the leaves. It has a taproot system with a spreading but not profuse root network.
It is found throughout Northern Queensland, but is also in NSW and the NT. Bitter Gourd competes with crops and native plants, and also interferes with the growth of vegetables, orchard and plantation crops. As it climbs over these it aggressively competes for light, nutrients and water.
In Australia, Bitter Gourd is not a prohibited or restricted invasive plant. By law, everyone has a general biosecurity obligation to take reasonable and practical measures to minimise the risks associated with invasive plants under their control.
The distribution map for Bitter Gourd is from The Atlas of Living Australia.
There are several reasons why this is so invasive:
- It tolerates 500 to 4000 mm of rainfall a year;
- Bitter Gourd grows in a wide soil pH range (4.3 to 8.7);
- It grows rapidly;
- There are only 30 days between germination and flowering and
- Bitter Melon has tenacious tendrils that coil and act like a spring to raise the stem.
After you read this, you will be able to:
- Identify Bitter Gourd, Balsam Pear or Bitter Melon.
- Know where Bitter Melon grows.
- Know the best options to control Balsam Pear.
How to Identify Bitter Gourd.
Category: Broadleaf (Dicot).
Photosynthetic Pathway: C4 Weed.
Flower: Bitter Gourd has yellow flowers that have five petals, that are about 2 cm across. These flowers open early in the morning before daylight with the flower buds being fully open and functional at dawn (anthesis).
Height: Vine.
Leaf length: Each deeply lobed leaf of Bitter Gourd is 4 to 10 cm long, and has a round outline.
Leaf width: The soft, mid-green leaves are on stalks. They are deeply divided into 5 to 7 shallow scalloped lobes, that are up to 15 cm across.
Reproduction: Bitter Gourd spreads by seeds and by underground stems. When ripe the fruit is orange-yellow, 10 to 20 cm long, ridged and covered with blunt warts. Once the fruit matures, it bursts along its length and curls back to expose the edible scarlet flesh around its many black seeds.
If you keep the seeds in dry storage, they remain viable for up to 24 months.
Comments: Does not cope well in frost.
Habitat: You often find Bitter Gourd in uncultivated habitats such as roadsides, gardens, fencelines and around houses and farm buildings.
For more information on weeds check out our weed ID Chart.
How to Control Bitter Gourd.
You can control Bitter Gourd or Bitter Melon by cultural and chemical means, but successful management of this weed is best if you adopt an integrated approach.
Cultural control:
You can hand pull individual plants and small infestations, but you must make sure that you remove all roots and stem fragments. These should either be bagged and taken to the dump or hung up off the ground to prevent reshooting.
You can also cut plants at soil level. This is however, a very labour-intensive practice as you will need to repeat this several times to achieve control as the roots will regrow from the taproot.
Chemical control of Bitter Gourd.
The key to control Balsam Pear is to reduce the seed bank, and keep it at a low level. There is only one herbicide (flumioxazin) currently registered for control of Balsam Pear in commercial and industrial areas.
Permit (PER11463) is for the control of this weed, but you must read and understand the conditions of the permit. Products on this permit include 2,4-D and Fluroxypyr. Work in sugar cane shows that a mixture of fluroxypyr at 260 g a.i /Ha and Dicamba is an effective control method that achieves 83% plant mortality.
Overseas work has shown that effective control occurs after three rounds of spraying with a post emergent herbicide.
In Brazil they use the following herbicides to control this weed: Glyphosate, Dicamba and Triclopyr.
The non-selective Glyphosate, can control this weed although herbicide resistance has been reported overseas. If you use Glyphosate and water quality is an issue then we recommend the use of ProForce Manta Ray.
Other Non selective options worth looking at are Numchuk Quad and Cortex Duo. Both of these are great knockdowns but also have a long term residual of up to 12 months after you use them. These are ideal for along fencelines or around buildings.
