sowing flower seeds ad using premergent crab grass r #855566

Asked November 20, 2023, 9:49 AM EST

I routinely sow red poppy seeds in the fall and in spring, Larkspur seeds as well as JJuo seeds I have not used premergent nor do I use post emergent herbicide for personal reason, as well as environmental issues , I live in Calvert zone 7 However, t his year bec of illness, I was unable to eradicate weeds on a daily basis and as of August, the weeds esp c crabgrass ahs grown to 3 feet tall Could now sow my red poppy seeds Took almost 2 months to manually pull. my 3 acre. How can I use pre- emergent adn stil be able to get the flower seeds to ermniante? thanks. Unable to send messages earlier for some reason?

Calvert County Maryland

Expert Response

This is a tricky situation. Looking over your past questions has helped us understand your planting areas. You may want to check with your county about the critical area buffer zone and using herbicides. From past photos though, it looks like you are far enough from the edge of the water to safely and successfully use herbicides. 

To help manage the crabgrass, you may need to use a pre-emergent and hand weed (if you don't want to use a liquid systemic herbicide) and wait a few weeks to plant. Typically after applying the pre-emergent it will take 4-6 weeks (it will say on the label directions) before you can seed anything else. Perhaps you could plant the poppies and other annuals in plug or seedling containers and transplant after they are big enough. 

Another thought if you are constantly struggling with weed management, is to incorporate thicker plantings of perennials, and perennial ground covers to help cover bare areas in the garden beds. You could still add in some visual interest with annuals in pockets throughout the garden. Using 'green' or living mulch is a good way to help cut down on weed seed germination in the garden. 

We would not recommend using corn gluten for a preemergent organic alternative since it will make the nitrogen content too high which could wash down into the water. When looking at the labels or searching for a product, you may want to make sure you can find one that is aquatic safe. 

In Calvert county you can apply crabgrass pre-emergent probably around mid- March. You just need to watch the soil temperatures since if you apply it too early it will not be able to activate and if it is too late the seed will start to germinate. This is explained on the link above for pre-emergent. 

If you have further questions on timing or how to apply, please let us know. 


Emily Porter Replied November 20, 2023, 2:18 PM EST
I t is tough I usually sow my red poppy seeds in October, the in early march or April  as soon as the ground is not frozen and workable, I sow the refrigerator cold stratified Larkspur seeds as I understand th ey are seedling which sprouts 14-21 days after sowing no longer going to be hared by freeze nor if I spread pre emergence crabgrass 

However the pre urgent has to wait until the ground is 55 degrees. My understanding, pls correct em if I a m wrong is tha tif crabgrass or weeds develop, the freeze wil kill t hem so to wait til April 15 or early May let nature do the work.

‘By July and August the poem regent barrier is gone. So when do I reapply he second barrier?

Which in your opinion is the best s0lid non liquid preemergent for my need as I cannot manage spray application ?


On Nov 20, 2023, at 2:18 PM, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied November 21, 2023, 8:06 AM EST

There is no easy way to successfully prevent crabgrass from germinating while still being able to direct sow your annual seeds. To get the crabgrass under control you may need to only plant transplanted annuals that you start in containers for this year. The preemergent needs to go down just BEFORE the soil temperature is consistently 55 degrees for multiple days so this could be done around mid-March. You would have to wait to direct sow annual seeds about 4-6 weeks depending on what the label says for the seeds to be able to grow and not be effected by the chemicals. A second application if needed can be applied but you would need to refer to the product label on timing since it could be different for different chemicals. 

A lot of people who plant annual seeds have success with winter sowing in milk jugs and various containers to obtain the cold stratification necessary for many of those flowers. The link is to a blog post which will explain how you can start this.  There are also groups you can join on social media platforms to learn more and they can be really helpful with sharing different techniques of what has been successful for them. 

We don't have a specific product we can recommend for a preemergent but you can explore the different chemicals listed on our Preemergent site to see which is best suited for your needs. 

Just to caution you though, we wouldn't recommend using a product called PREEN with the active chemical of trifluralin since it is harmful to marine and aquatic life. The label explains that it should not be used where it could potentially runoff into a water source. 


Emily Porter Replied November 21, 2023, 11:27 AM EST

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