Looking for help with spring fertilizer and herbicide!
Photo 1/2: soil test from last spring
Photo 3: lawn a week ago
Photo 4: lawn last July
Photo 5: lawn last fall
• Near Philly, zone 7A/7B
• 50,000–60,000 sq ft grassy area
• Bought house in December 2023
• Dethatched in spring and over seeded in spring and fall, no fertilizer lol
• Overseeded with Black Beauty Ultra (I think fescue)
There is an easy to pull weed all over the yard that is either bent grass or nimblewill (zoom into pictures). I’d like to eliminate as much as I can with a pre emergent and can follow up with roundup once it starts to grow. I figure the true identity of the weed doesn’t matter too much because the same herbicides take care of both.
I’m looking for input on whether a fertilizer with weed killer (I’m thinking Scott’s triple action) or another fertilizer before/after a Mesotrione application makes more sense.
Granular stuff is preferred because of the lawn size but I do have a manual spray pump I can tote around if needed.
A 12,000 sq ft bag of Scott’s triple action is $70 so I’d be looking at $350 for just the one application. No idea how expensive other versions of products are.
Thank you for the help!!
by fiftyshadesofgracee
4 Comments
The common lawn pre-emergents (prodiamine, pendimethalin, and dithiopyr) work to help reduce the germination of certain seeds… Mostly grasses and only a handful of broadleaf weeds. The labels will list which weeds are targeted. To prevent more broadleaf weeds, a specialty broadleaf pre emergent like isoxaben is required.
Pre-emergents work by preventing the germination of seeds of the target species. So in order to be effective, a pre emergent needs to be applied BEFORE those seeds germinate. For winter annual weeds (annual weeds that are present in the fall, winter, and spring, like poa annua), a pre emergent needs to be applied in the fall before soil temps fall below 70F. In order to prevent summer annual weeds (like crabgrass), a pre emergent needs to be applied in the spring before soil temps reach 55F. (In very southern areas, timing can be more closely tied with periods of higher moisture AND climbing soil temps. Consult your state extension service for more specific guidance)
Pre emergents will not kill existing weeds. Pre-emergents alone will rarely control a weed problem. Pre-emergents are tools to **reduce** the need for post-emergents. They rarely eliminate the need for post emergents.
The labels of pre emergents have many important instructions and use restrictions. ALWAYS READ THE ENTIRE LABEL. For example, you are limited to 2 applications of each active ingredient per year.
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Dethatching is a recent trend in lawn care that’s become more common thanks to youtube creators and other non-academic sources. As such, there’s a widespread misunderstanding/misinformation about the topic. This automatic comment has been created in the hopes of correcting some of those falsehoods.
Thatch is the layer of stems and roots, both living and dead, that makes up the top layer of soil. Grass clippings are not thatch and do not contribute to thatch. The thickness of thatch can only be assessed by digging into the soil.
Some thatch is good. While some academic sources say that under 1 inch of thatch is beneficial, most settle for half an inch. Thatch is beneficial for many reasons (weed prevention, traffic tolerance, insulation against high temps and moisture loss, etc) and should not be removed. Over half an inch of thatch may not warrant removal, but the underlying causes should be addressed. An inch or more of thatch SHOULD be addressed. Dethatching as a regular maintenance task, and not to address an actual thatch problem, is NOT beneficial… Again, some thatch is good.
Thatch problems are not typical. Excessive thatch is a symptom of other issues, such as: over-fertilization, overwatering, regular use of fungicides, excessive use of certain insecticides, high/low pH, and the presence of certain grasses (particularly weedy grasses).
Dethatching with a flexible tine dethatcher (like a sunjoe) causes considerable short-term and long-term injury to lawns, and is known to encourage the spread of some grassy weeds like bentgrass, poa annua, poa trivialis, bermuda, nimblewill etc. In some RARE cases, that level of destruction may be warranted… But it must be done with great care and attention.
A far less damaging alternative to dealing with excessive thatch is core aeration. Core aeration doesn’t remove a significant amount of thatch, and therefore doesn’t remove a significant amount of healthy grass. BUT it can greatly speed up the natural decomposition of thatch.
Verticutters and scarifiers are also less damaging than flexible tine dethatchers.
For the purposes of overseeding, some less destructive alternatives would be slit seeding, scarifying, manual raking, or a tool like a Garden Weasel. Be sure to check out the seeding guide [here.](https://www.reddit.com/r/lawncare/s/pUsKCxyvwQ)
Additionally, be sure to check the list of causes above to be sure you aren’t guilty of those.
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If you’re looking for info on how to interpret soil test results, you can find all you need to know [in this post here.](https://www.reddit.com/r/lawncare/s/LPtlW1pau5)
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