Will my weed torch cause an underground fire?

May 16, 2010 6:30 PM

I bought a 100,000 BTU weed torch to kill the weeds in my driveway and etc. Can I safely use it to burn weeds in my lawn and other dirt areas without starting an underground fire that will spread for miles and burn uncontrollably forever? FWIW, I'm in Seattle.
posted by carterk to Home & Garden (14 answers total)

Yeah, you can.
posted by mr_roboto at 6:33 PM on May 16, 2010

Heh....unless you're sitting on a coal mine or a peat moss field , you should be ok!
posted by HuronBob at 6:37 PM on May 16, 2010 [1 favorite]

Don't do it anywhere near trees. Douglas Fir root fires are no joke, and are really difficult to stop once they get started. I spent an entire weekend once putting out a root fire in Fall city. It took three of us, gallons of water and digging 3-4 feet into the ground.
posted by Maude_the_destroyer at 6:39 PM on May 16, 2010 [1 favorite]

I should add that conifer root systems are very shallow and root fires can smolder for days before you catch them.
posted by Maude_the_destroyer at 6:45 PM on May 16, 2010

If you want free somewhat effective protection from brushfires, do it after rain.

Oh, Seattle - I guess you can start right away :)
posted by Inspector.Gadget at 6:58 PM on May 16, 2010

I stand corrected!
posted by HuronBob at 6:59 PM on May 16, 2010

I don't have an authoritative answer here, but I had a runaway fire on me due to dry pine needles. I had raked most of them back from a small brush fire but not enough, and the fire went nuts once it got to some stray needles. Fortunately I had the hose nearby and was able to put it out... but definitely be cautious around pine.

Interesting about root fires.. I had never known about that.
posted by crapmatic at 8:18 PM on May 16, 2010

I burn my whole lawn annually to rejuvenate it. Works great but yeah avoid trees, rake leaves, trim dead grass, do it on a cold day with water nearby and no wind etc. With those torches you are going more for a quick scorched than a real flaming fire anyway
posted by fshgrl at 8:52 PM on May 16, 2010

You don't need to actually set the weeds on fire, just go at them until they look plenty unhealthy. Have some buckets of water around as well as a hose, and water down the areas you treated with the torch after. Pick a day that isn't windy, or a root fire may be the least of your troubles.
posted by yohko at 10:11 PM on May 16, 2010

You should be OK if you mind nearby trees and watch for root fires. As a further anecdotal point - I used to fight forest fires with the US Forest Service as a hand crew. Generally speaking if we were not cutting a fire line, we were digging up root fires and extinguishing them. They can burn quite hot and for a very long time.

It is worth noting that one fire I worked on happened in northern Minnesota in February. A gentleman was burning trash too near a spruce and started a ~17 acre fire that destroyed his neighbors house. This happened despite there being 2-3 feet of snow still on the ground and temps in the mid 20s.

Point is, be careful - if conditions are right, a fire can get big pretty fast.
posted by Pogo_Fuzzybutt at 10:25 PM on May 16, 2010 [1 favorite]

Yes, but for the love of all that's not setting everything in site on fire, get one of these. As mentioned, the goal of a flame weeder is not to burn a weed, it's to heat the water in the cells until it turns to steam and causes the cell to burst. In our neck of the woods, I'd use the flamer earlier in the year rather than later. Not only will the increased moisture reduce the risk of fire, it'll make the flamer more effective. If you're getting smoke from more than the occasional bit of random dry plant residue, you're not using the tool as intended.

In ag, a typical use of a flamer is to plant carrots, beets, or some other slow-germinating crop, give the weeds a few days to start growing, and then flame the bed before the crop germinates, killing the weeds but leaving the pre-germination seeds intact. Keep in mind that the rule of thumb is to bury a seed to approximately its diameter in soil, and that a carrot seed is very small indeed. Used as intended, the flamer doesn't damage the seeds just below the surface of the soil.

For me, I typically use my Red Dragon to weed ~2' paths between rows*. This year, I'm going to see if I can push it to a 1' path. When I'm done, what I hope to see are a bunch of wilted plants. In the next few days, I'm aiming to flame a 20' x 4' raised bed and a chunk of overgrown grass. There's no way I'd try the latter later in the year, but the grass is very juicy this time of year. This is way different from the trash fire mentioned above. Brush fires aren't legal where I'm at, but now I'm terrified to light one.

This applies only to use of a flamer in vegetated areas. I've no idea the correct way to flame weeds in a driveway crack, only time I tried something similar is was trying to flame scotchbroom and blackberries from my gravel driveway. That was a bad idea, btw.

* When, of course, I'm not using it to chase you kids off my lawn!
posted by stet at 12:06 AM on May 17, 2010

I don't really know myself, but I will say that my father-in-law who is a forester and was a forest fire fighter in the Pacific Northwest for decades has one of those things and seems to use it with abandon and relish. So if he's any role model for you burn away!
posted by Pollomacho at 4:12 AM on May 17, 2010

Why don't you soak the area with the hose first? That'll reduce the chances of setting adjacent stuff on fire, absent peat bogs, coal seams and conifer roots.
posted by electroboy at 6:47 AM on May 17, 2010

my father-in-law who is a forester and was a forest fire fighter...

I wouldn't take him as a role mode, fire fighters are better at fighting fires than the average person, and I've also seen some do things that are really unsafe. One in my area managed to set his house on fire (not burning weeds though).
posted by yohko at 8:39 AM on May 17, 2010