Johnson grass is an invasive plant species, considered the top noxious weed that affects all annual crops. It was introduced in the 19th century as a forage crop from Turkey to Southern California.
It contains fibrous and thick roots and thick horizontal rhizomes that generally remain close to the top in moist soil. The color of the root changes from creamy to white and orange scales as the plant matures.
Johnson grass leaves are between 0.5 and 1 inch wide and can grow to about 12-30 inches long. Also, the leaves are alternately arranged and have a distinctly white midrib.
The flowers are loose and have hairy purple panicles. Flowering takes place between May and October. Also, the seeds are about 1/8 inch long and reddish-brown.
Seeds and rhizomes produce the crop of Johnson grass. Each rhizome nodule can grow to new roots and shoots. Then the seeds remain dormant while in the soil until ideal conditions are reached.
Removing and eradicating Johnson grass from contaminating the soil is very challenging because of a high volume of seed production, the longevity of the seeds, herbicide resistance, high spread rate, and rapid growth.
However, the control depends on the weed attacking in a specific area. There are several ways on how to get rid of Johnson Grass completely.
How to Identify Johnson Grass?
The most common characteristics of Johnson grass include an extensive rhizome system, conspicuous midrib, and ribbed leaf sheath with a large and purple panicle of 50cm tall. The unbranched stems can grow to about 1.8 to 2.1m tall.
It typically colonizes vineyards, orchards, ditch banks, roadsides, disturbed places, vegetable crop and agronomic fields. Sometimes Johnson grass is mistaken with shatter cane, but these shatter cones do not produce rhizomes and are annual plants.
How to Get Rid Of Johnson Grass
1. Boiling water
Boiling water can help to get rid of Johnson grass. It is the most eco-friendly way to kill this weed. You need to pour hot water on the leaves and roots.
Do it well to ensure no residue is left so that you can use this method time and again. However, be careful when pouring hot water on weeds because it can affect nearby plants, vegetables, or flowers.
For this reason, it is advisable to pour a small drop of hot water to stop it from spilling on other plants.
2. Pull by hand
This is another way to get rid of Johnson grass. You can do this by simply pulling the grass from the base with its rhizomes because leaving some behind can cause the grass to grow again.
Start pulling Johnson grass in early spring, as the soil is soft and moist during this time, so you can successfully remove the rhizomes.
3. Newspaper mulch
You can use newspapers to get rid of these grasses by suffocating them. First, you should cut the area as very short as possible and then discard the piece.
Then place the newspapers in an area where Johnson grass is growing. Use old, non-glossy newspapers and spread them out on the grass.
Ensure the newspapers overlap one another to prevent sunlight, water, and air from entering the gaps.
If you want to prevent newspapers from flying, apply a thick wet wood chip layer of organic mulch over the layer of newspapers. In between 2 and 4 weeks, the Johnson grass will start to decompose. This is useful because it organically enriches the soil and provides a more fertile area.
4. Removing rhizomes
Those people who can access cultivation equipment like sweeps and shanks can use them to bring the rhizomes to the surface once they dry out. Follow this with the spike tooth harrow to drag rhizomes out from the field.
If the soil is mowed regularly for about two years, the growth of Johnson grass will be stunted, and the rhizomes will be extremely close to the ground.
It can deplete the energy of the rhizome and prevent the grass from growing. Mowing occurs every 2 to 4 weeks when the plants are 20 to 30 centimeters tall.
The technique can kill the seedlings, though the rhizomes may not be affected yet. Leave the rhizomes on the surface, and they will dry with time.
6. Plowing and tilling
You can get rid of Johnson grass by repeatedly plowing and tilling every few weeks during the summer period. During winter, freezing rhizomes can help control infestation. After autumn, when frost starts, plough the rhizomes and roots of Johnson grass to expose them to the cold.
The propane burner can be used to get rid of Johnson grass. You can use this technique after every two weeks or months to deteriorate the growth of the rhizomes.
8. Use the Johnson grass-free livestock feed
Sometimes Johnson grass may be present in particular livestock feed. You need to check the list of ingredients to ensure the feed does not contain Johnson grass.
The livestock can spread this grass through their droppings if eaten in the feed. So, it is good to check its availability in the livestock feed to get rid of it.
9. Clean the equipment that is used for Johnson grass
If you are using the equipment to break the Johnson grass but do not clean it afterwards, you can spread it quickly. Make sure the blades and the bottom of the machines are clean. You can easily wash them with water and soap.
II. Biological way
Grazing Johnson grass can be used to prevent infection from increasing. Care must be taken to ensure it is not stressed by environmental or physical factors when used as feed.
When Johnson grass is under stress, it accumulates hydrocyanic and nitrate acid that is fatal for livestock. Therefore, due to its potential risks, it’s not the recommended control method.
III. Chemical way
Many herbicides can eliminate Johnson grass. The choice is essential to obtain the desired results, and this includes:
1. Table salt
If you want to get rid of Johnson grass, use salt and mix it with hot water and some drops of liquid soap. Mix this solution and pour it inside the spray bottle.
Be careful when using this solution, as it can cause a lot of damage to the soil. It would help if you sprayed the mixture only on the leaves. It can take some time for the effects to work. So, do not stop using this solution until the grass starts to wither.
2. White vinegar
Another chemical way to get rid of Johnson grass is the use of white vinegar. Acetic acid, which is found in vinegar, can kill any grass effectively. It is also very convenient because vinegar is easy to find at home or the local supermarket.
You can use regular vinegar that is 5% acetic acid. Nevertheless, if you want a strong solution, some industrial solutions have 20% pure vinegar, more effective. Put the vinegar in the spray bottle so you can apply it quickly to the leaves.
Glyphosate is a systemic herbicide, which produces effective result after treatment. It is applied to the growing Johnson grass of between 6 and 24 inches tall.
Also, Dalapon is used commercially to get rid of Johnson grass. Nevertheless, follow manuals and guidelines to achieve effective results.
4. Acetolactate synthase (ALS) inhibitors
The use of acetolactate synthase inhibitors, also known as acetohydroxy acid synthase, is effective when getting rid of Johnson grass. It must be applied three weeks after cutting the grass to get the best results.
5. Acetyl-CoA Carboxylase (ACCase) inhibitors
Acetyl-CoA carboxylase inhibitors such as sethoxydim, fluzifop, and clethodim can be used to get rid of Johnson grass infestation. There are several formulations of these chemicals, and this requires you to read the application instructions before using them.
The Lifecycle of Johnson Grass
Even though Johnson grass is perennial, it can be annual in cold climates. In addition to the effective dispersal technique, this weed is productive as the seeds can be dormant for ten years and reproduce for several years.
It has a massive seed production, and one plant can produce about 80,000 seeds a year.
3-4 weeks are enough for the rhizomes to develop from seeds. Once they have formed, they begin to produce many roots and shoots (just a single grass can produce about 5,000 nodes in a year).
When the temperature begins to rise in spring, the old and newly formed rhizomes that have survived the winter season will start to form many buds.
The flowering phase begins two months after the start of the growth, and each Johnson grass flower panicle will produce many seeds in just a single flowering period.
Seedlings grow slower than the rhizomes and need high temperature for germinating than rhizomes to produce buds. However, both development models are fast enough to scale quickly in different environments.
Johnson grass is the type of grass, which can grow alongside many popular plants. If left unchecked, it can kill most of these plants or reduce their production.
There is a need to get rid of them and prevent their spread by using different methods frequently and immediately after harvest or before you prepare your garden.
This can be an organic, biological, and chemical way to eliminate Johnson grass before creating much damage. Also, when you discover there is no grass left in the garden, you need to continue monitoring it to ensure it is eradicated.