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.