A few basic questions about applying weed killer

June 4, 2021 8:09 AM

I've purchased some Killex weed killer to apply to my lawn. I've never applied weed killer before and just wanted to know if there's anything I should know about applying it.

Aside from describing the level to dilute it, the instructions don't say a lot. So, I'm hoping that some people who might be more familiar can help. Is it safe to walk on my lawn after applying it? Or should I avoid it for a few days? How long until it's safe for my son to go out and play in the yard after applying it? Do I need to wear gloves when I spray it on? Anything else I should know? My wife has a flower bed and a few vegetable gardens. The vegetable gardens haven't been planted yet. I would guess that I need to be careful around these areas with the Killex, but is it sufficient to just avoid getting too close to the gardens? Or is it better to put something protective like a tarp around them?

posted by NoneOfTheAbove to Home & Garden (10 answers total)

The weed killers I have applied have said to wear long sleeves and pants and change clothes after - I normally wear gloves as well. I generally try to apply early in the morning, so it has a chance to dry before a lot of pollinators are out (maybe not a concern for you!). I definitely wouldn’t get near the gardens, but I don’t think you’d have to cover them? I’ll let someone more knowledgeable speak to that!
posted by needlegrrl at 8:21 AM on June 4, 2021

If you can, only apply the weedkiller to the specific weeds you want killed. Once, when I was away, someone applied weedkiller all over my lawn, and not only killed off all of my herbaceous border, but also made it impossible to re-grow it. Ironically, the weeds reappeared rapidly. This is nearly ten years ago. Now I'm going to build a raised bed, with tarp under new soil.
In the meadows, we have an invasive plant species that is poisonous for the horses who graze there. We go from plant to plant and apply the pesticide very accurately and sparsely, to avoid damaging the other meadow plants. It isn't done in an hour, but we are protecting the soil and the water.
posted by mumimor at 8:47 AM on June 4, 2021 [3 favorites]

Unless you're applying it directly to the stems of the weeds you're trying to kill, be prepared for it not to work very well and kill the wrong things. I'd definitely put something protective over anything you're spraying within less than a foot of.

Honestly after a couple years I decided herbicides are more of a PITA than just weeding, even disregarding environmental concerns.
posted by aspersioncast at 8:47 AM on June 4, 2021 [4 favorites]

On preview, what mumimor said. For poison ivy, which is the one thing I don't just find easier to pull by hand, I actually use a big syringe for this and inject the stuff right in the stem.
posted by aspersioncast at 8:52 AM on June 4, 2021 [1 favorite]

Killex = 2,4-Dichlorophenoxyacetic acid or 2,4-D if you're on first name basis. It is a plant hormone analogue which adversely affects dicots but not monocots. For most commercial purposes monocots are grasses, incl wheat, maize, barley, oats, lawns. All the vegetables [carrots, cabbage, toms, potatoes, beans] and all your shrubbery are dicots. Definitely keep away from them if they are in leaf. The half-life is about 6 days, so if the veg beds are unsown you need some multiple of 6 days to get the levels of toxicity down to acceptable levels.
As a plant hormone it is designed have no effect on insects. It lasts longer in water and has some toxicity to fish: so don't let it wash off into the storm drains if possible.
posted by BobTheScientist at 8:56 AM on June 4, 2021 [1 favorite]

I know Canadian pesticide labels labels have specific instructions, including a re-entry interval (when you can go back into the treated area) and PPE.

The Canadian Killex label says "Do not allow people (other than the applicator) or pets on the treatment area during application. Do not enter treated areas until spray has thoroughly dried." For PPE, it says "Wear long-sleeved shirt, long pants, socks, shoes and chemical resistant gloves." and "Rinse gloves before removal. Wash hands before eating, drinking, using tobacco or using the toilet. If pesticide penetrates clothing, remove immediately; then wash thoroughly and put on clean clothing. Remove clothing and launder separately before reuse, and promptly and thoroughly wash hands and exposed skin with soap and water, then shower. Re-use gloves for pesticide application only."

As for non-target plants, "This product is only effective when applied to the leaves of
actively growing weeds. This product will not prevent new weeds - apply only when weeds are present." and "Desirable broadleaf terrestrial plants can be harmed by contact with product spray. DO NOT directly spray or allow the spray to drift onto ornamental plants and trees, fruits, vegetables or exposed roots of trees and ornamentals."

There are lots of other warnings and precautions about drift and water.

You can search up Canadian registered labels here:

https://pr-rp.hc-sc.gc.ca/ls-re/index-eng.php
posted by fimbulvetr at 9:04 AM on June 4, 2021

Use a watering can on a still day, and don't get it on anything you want to live (except grass!). If it doesnt rain in a couple of days, water it. I'd give it a week before letting children on it, but the RHS tell us it will be safe when it's dry. RHS advice here. The section you want is 'Hormone-type weedkiller'.
posted by StephenB at 10:12 AM on June 4, 2021

I put plastic bags over my shoes so I don't track the residue into my house.
posted by H21 at 1:28 PM on June 4, 2021

Are you planning to apply with a garden sprayer? I recommend labeling it "herbicide" in permanent ink and only using it for herbicide because pesticides are formulated to stick and you really don't want any herbicide residue when you're trying to fertilize plants or treat pests on plants. You will get better coverage with a sprayer than with a watering can and likely need to use less product.

Apply when it's not windy and not too hot and not about to rain - mornings are often good.

Ideally launder the clothes you wear in a load by themselves, at least don't mix with children's clothes. If you have a pair of safety glasses or sunglasses, wearing them is always a good idea.

Often pesticide labels peel open and have more info inside, did you check for that? Highly recommend searching the exact name of your Killex formulation plus "label" and reading the info carefully. Stay away from the flowers! The label should state if you need to wait before planting things - I'm pretty sure you don't and that 2,4D won't affect germination

Here's the Washington State University pesticide search if you want more info: https://picol.cahnrs.wsu.edu/Search/Quick
posted by momus_window at 2:32 PM on June 4, 2021

My neighbour uphill applied weed killer to his yard to get rid of invasive knotweed. His knotweed is going strong but the weedkiller running downhill put paid to my vegetable plot. Only thing that survived was the rhubarb.
posted by Jane the Brown at 1:04 AM on June 5, 2021 [1 favorite]