Weeds are simply unwanted plants. What they have in common with desirable plants is that some are annual varieties and others are perennials. The annual varieties are killed by frost but leave seeds in the soil before they die. The seeds survive the winter and germinate and grow in the spring. This is how crabgrass grows. These type of weeds can be stopped before the grow by using a pre-emergent weed control. Pre-emergent weed control works to keep the seeds from germinating so the crabgrass and other weed seeds won’t grow. The pre-emergent weed control should be applied in the spring in March or April.
The other weeds, the perennials which would include most of the other weeds you mentioned like the dandelions, clover, creeping Charlie, etc. Pre-emergent weed control are not effective on these because they return from the roots in the soil. These weeds have to be controlled with a post emergent weed control. Post emergent weed controls are usually liquids that are sprayed. These need to be sprayed when the weeds are actively growing. The herbicide for these weeds is one from Fertilome called Weed Free Zone. It can be used anytime the temperature is above 45 degrees and the weeds are growing.
For pre-emergent weed control we recommend another Fertilome product called All Season Weed Control with fertilizer. This product contains an herbicide called Prodiamine. Most pre-emergent products only last a maximum of 4 to 6 weeks after they are applied. Prodiamine will last up to 6 months. This means it not only stops the spring germinating weeds like the crabgrass, it continues to work through the summer. This is important because all of the other weeds you are fighting originally came into your yard as a seed. When Prodiamine is in the soil these seeds will not germinate. Over time this will minimize your need for post emergent sprays.
Lastly the best way to keep weeds out of your yard is to keep your yard healthy. If your grass is thick it minimizes any room for the weeds to grow. You can crowd them out. You can accomplish this with a good fertilizer program like our Fertilome Three Step Program. Here’s a link to the program we offer http://bloomingarden.com/lawncare/ .