The most important lawn care application of the year... fall pre-emergent!

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It may seem a little strange to you that I am writing about fall pre-emergent herbicides in mid-August when temperatures are pushing 100.

One of the most importance lawn care applications and often most overlooked is coming up very soon. 

The most critical applications are the ones that include pre-emergent herbicides.  Everyone knows the importance of the spring applications, but many don’t realize fall applications are just as critical.

Nothing will set you up for a successful lawn in 2020 more than what you DO or DON’T do in your lawn this fall.

Why are the fall pre-emergent applications so important?

The fall pre-emergent applications are the keys to having a weed free lawn next spring.

The fall pre-emergent prevents poa annua, rescuegrass, cheat, brome, chickweed, and henbit.  These are the weeds that clutter your lawn in the spring.  Weeds that are easy to prevent in the fall - but extremely difficult to control in the spring. 


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Common chickweed is a winter annual broadleaf with a prostrate, mat-like growth (rarely higher than 2") and broad egg shaped leaves spaced evenly and opposite each other along the stem with small white flowers in the spring. One interesting fact about chickweed seeds - they can remain viable in the soil for 7-8 years. Chickweed is another winter annual that is easily prevented and when not prevented is fairly easy to control in the winter to early spring, but very difficult to control once flower production begins in spring. As with many weed issues, the tried-and-true best defense against chickweed is a thick and lush lawn going into the fall.


Henbit is a broadleaf winter annual weed with greenish to purplish square stems, green scallop edged leaves, and reddish purple flower in the spring. Seeds germinate in the fall but the weed often goes unnoticed until we have periods of warn winter weather when henbit grows best. Henbit is easily prevented with fall pre-emergent applications but can be difficult to control in late spring when it is mature, flowering and littering your lawn. As with most weeds, a dense turf is the best prevention against the development of henbit.

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Poa annua, also known as annual bluegrass, is the fall’s equivalent to spring’s crabgrass.  Without a fall pre-emergent, your lawn will not be clean next spring. Just like crabgrass, when it is mature, poa annua is hard to control without causing turf injury.  Next spring, we want your lawn to be focused on emerging from dormancy without the harmful effects of harsh post-emergent herbicide applications.

How a Bermuda lawn looks in April when no fall pre-emergent applications were made.

How a Bermuda lawn looks in April when no fall pre-emergent applications were made.


 
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Poa Annua is an annual grassy weed that invades lawns in the fall and winter. It is a lighter green clumping grass with small white flowers (seed heads) in the spring. Germination occurs in moist soil starting in the fall when night temperatures drop into the 60s and continues through the winter and spring. Poa Annua has a competitive advantage over bermuda in the winter when it is activity growing and the bermuda is dormant.

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Poa Annua germinates and thrives in thin areas of fescue during the fall, winter and spring. Poa Annua does not have a competitive advantage over fescue when it is thick, healthy and actively growing. Overseeding thin fescue in the fall is a great way to prevent poa annua.


Timing of the fall pre-emergent applications is critical.  Annual weeds will germinate throughout the fall as temperatures cool and will dirty your lawn as temperatures warm in the late winter and throughout spring.

The first application for the fall needs to be made sometime between late August and early October. 

A second application should be put on your lawn 4-8 weeks after the first fall pre-emergent to ensure full control until the lawn emerges from dormancy next spring. Research shows that poa annua has developed some resistance to pre-emergent applications.  A second fall re-emergent in October through November increases the prevention of poa annua.

Next spring when the crabapples are in bloom and fescue is green, Bermuda lawns should be weed free. This is only possible if a fall pre-emergent is applied between late August and early October with a second application 4-6 weeks later.

Next spring when the crabapples are in bloom and fescue is green, Bermuda lawns should be weed free. This is only possible if a fall pre-emergent is applied between late August and early October with a second application 4-6 weeks later.

There is only one reason to not put the first fall pre-emergent application on your lawn: Seeding Fescue.

The same pre-emergent herbicide that prevents annual weeds from germinating WILL PREVENT new grass seed from coming up.  Because developing a thick turf is so critical to good weed control, and because September through October is by far the best time to establish a cool season lawn, skipping the fall pre-emergent application is the right thing to do.  Once the new seed is up, actively growing, and has been mowed 3-4 times, you can apply the second fall pre-emergent application. 

Important – If you are planning on seeding all or part of your lawn this fall, please let us know so we can adjust your applications accordingly.

Dormant Bermuda will be weed free in February and March when both fall pre-emergent applications are on schedule.

Dormant Bermuda will be weed free in February and March when both fall pre-emergent applications are on schedule.

We have three types of lawn care customers:

1.     Customers who subscribe to the full 7-step program and enjoy having a clean, healthy and growing turf.  If you are on the 7-step program, you will receive the fall pre-emergent applications.

2.     Customers who want the make sure their lawn receives spring and fall pre-emergent herbicides at the correct times but enjoy applying their own fertilizer.  If this defines you, you are receiving our 4-step weed control only program and will receive the 2 fall pre-emergent applications. 

3.     The occasional application customers who takes a few applications, often the early spring applications.  If this defines you, please don’t skip the fall pre-emergent steps this year.  You will not regret the fall applications next spring when your lawn starts the year weed free.  

Remember – it is always easier to prevent weeds than it is to kill actively growing weeds. 

Nothing will make a bigger difference in the way your lawn looks next spring than applying both fall pre-emergent applications in 2019.

If you have any questions about fall pre-emergent herbicides, please give us a call at (405)367-3873.

Lorne Hall