Critical Weed-Free Period
The goal in managing weeds is to maximize yields - by suppressing weed competition during critical periods of crop development.
This concept is called the Critical Weed-Free Period, when it is most important to control weeds to prevent competition with crops. It is important to understand these facts about the Critical Weed-Free Period:
- If the crop is kept weed-free for the Critical Weed-free Period, no yield reduction should occur.
- Weeds emerging after the Critical Weed-Free Period will not affect yield.
- When weeds are allowed to compete with crops during the Critical-Weed Free Period, the effects may last over several years in perennial crops, especially weeds during the establishment year.
| Critical Weed-free Period for Horticultural Crops | |
| Crop | Critical Weed-free Period |
| Apples, new plantings | During May and June |
| Apples, bearing | Budbreak until 30 days after bloom |
| Beets | First 2- 4 weeds after planting |
| Cabbage, early | First 3 weeks after planting |
| Carrots | First 3- 6 weeks after emergence |
| Corn | 3rd to 8th leaf |
| Cucumbers, pickling | First 4 weeks after seeding |
| Lettuce | First 3 weeks after planting |
| Onions | The whole season |
| Potatoes | First 4 weeks after planting |
| Squash | Early plantings compete better |
| Strawberries, new | During May and June |
| Tomatoes, fresh | First 36 days after transplanting |
There are other valid reasons to control weeds outside of these critical periods such as: attractiveness for PYO customers, harvest efficiency, and reduction of weed seed banks. However, controlling weeds outside of the critical weed-free period will NOT increase yields.
