2,4-D, scientifically known as 2,4-Dichlorophenoxyacetic acid, is an organic compound widely used as a systemic herbicide. It selectively kills most broadleaf weeds by preventing their growth. You can use it to kill unwanted plants like dandelions, clovers, plantains, and chickweed, among others.
Most gardeners and farmers use 2,4-D as a pre-emergent burndown treatment option before planting their crops. Although the compound is useful in controlling weeds, it can damage a desirable plant if the chemical comes into contact with it.
So, how long after spraying 2,4-D can you plant? You will have to wait between 7 and 15 days after spraying 2,4-D before you can plant. For edible plants, you’ll have to wait for about 30 days. The difference in the duration depends on the environment and the type of plants you want to grow.
However, this is not all. Here’s a breakdown of everything you need to know before you can plant to avoid growing food that contains chemicals.
How long does 2,4-D last in the soil?
Unlike many herbicides, 2,4-D breaks down quickly in the soil and has a low risk of contaminating groundwater.
2,4-D degrades fast because it has a half-life of 6.2 days in aerobic mineral soils such as gardens, lawns, and farms. In aerobic aquatic environments like oceans, lakes, and rivers, it has a half-life of 15 days.
One thing to note is that many manufacturers formulate the herbicide as either amine salt or ester. 2,4-D amine salts and esters are not persistent under most environmental conditions.
Planting intervals will also differ depending on the type of crop you want to grow and the chemical formulation. For example, if you are planning to grow corn or soybean, and you are applying 2,4-D ester, wait until seven days after spraying the chemical at a formulation of four pounds per gallon.
If, you are using 2,4-D amine, plant after 15 days if the chemical’s formulation is four pounds per gallon. Although the half-life of 2,4-D is short, it can be longer in cold, dry soils, or where the suitable microbial community is not present to hasten its degradation.
How long after spraying 2,4-D can I plant vegetables?
Except for specific plants, the best time of planting vegetables is after 30 days of applying 2,4-D. Manufacturers usually recommend that you read the label before planting.
Apart from soybeans and corn, the ideal time to plant crops labeled on the product is within 29 days after spraying the compound. Planting the crops labeled on the packaging soon during the first 14 days may be dangerous because it will damage them.
But under standard conditions, you can plant any crop without risk of damage at least 90 days after application and after the temperature of the soil is above freezing.
If you are using 2,4-D ester to kill grass and other weeds and you are planning to grow crops like corn, soybean, sorghum, small grains, and pasture the best time to plant them following the last application is between 7 and 29 days.
Does 2,4-D have residual?
2,4-D causes a residual effect when applied in pre-emergence in different soils. However, the toxicity of the chemical tends to lessen after its high life ends. For example, when you grow soybeans between one and three days after application, the compound will cause a reduction in the development of the crop.
It will reduce its height and collar diameter and cause extreme cambium constriction because it will inhibit the elongation of branches, thus decreasing its growth. One can avoid the residual effect of the chemical by sowing after 7-15 days of application.
How warm does it have to be to spray 2,4-D?
The possibilities of reduced weed control as a result of cool temperatures will vary depending on the type of unwanted plant and the rate of application. As a burndown herbicide, frost and low temperatures can affect the efficacy of 2,4-D.
2,4-D isn’t effective in temperatures below 40°F after application. Also, controlling the unwanted plants can be effective under cloudy conditions following the first drop of temperature below 40°F.
Understand that the best way of controlling weeds before sowing is when the plants are actively growing. But when the plants are under stress, the efficacy of 2,4-D drops significantly. For example, if the frost is below 25°F, it will cause damage to the leaves of annual plants, making the chemical less potent.
For annual winter weeds that can endure a frost of up to 20°F and continue to grow once the conditions improve, 2,4-D will not cause tissue damage to the plant. You will need to pick the right time in order to apply it effectively.
But as a rule of thumb, the best time to apply 2,4-D is when nighttime temperatures are more than 35°F. Similarly, daytime temperatures should be 50°F or higher for two days consecutively for the chemical to work well.
How long does 2,4-D need to be on before rain?
The rainfast period for 2,4-D is one day. Any amount of rainfall immediately after spraying the herbicide can reduce the absorption, translocation, and the accompanying weed control.
If it rains after applying 2,4-D, its performance will decrease. At the same time, temperatures can determine the efficacy of the chemical, even if it has been a full day before it rains.
When daytime temperatures are below 50°F, the rate of weed growth slows down. The uptake and translocation of the herbicide will be slower. That means the rainfast period will increase from a day to two or even more.
In general, 2,4-D should be on for over 24 hours during daytime temperatures of above 50°F for the chemical to work. Otherwise, wait for better weather conditions before applying it.
2,4-D planting restrictions
If you are planning to apply 2,4-D before planting, you need to adhere to the herbicide’s planting restrictions. Ideally, the best way of using the chemical is to read the label on the packaging. That is because manufacturers use different formulations when making 2,4-D. Thus, application and planting intervals will differ.
As a general guideline, here are planting restrictions for the chemical:
- After spraying the herbicide, wait for at least seven days before planting. But to ensure the safety of your crops, sow after 30 days.
- If you plant corn this year and apply 2,4-D pre-emergent before flooding out the field, your options for sowing forage crops will be small. That is because the replant interval is four months. However, you can plant corn.
Also, consider conducting a bioassay test to determine if it is safe to plant crops, particularly if you did not grow any crops on your farm.
2,4-D is a systemic herbicide that selectively kills most broadleaf weeds. However, it can damage a desirable plant if the chemical comes into contact with it. To prevent this, a farmer or gardener should wait for at least seven days before growing any crops. But based on the formulation of the chemical and the type of plants you want to grow, wait for at least 30 days before sowing.
IW’s Chief Editor and a lover of green spaces.