Weed Control Methods: Flame Throwers and Weed Burners

Flame Throwers and Weed Burners

Weed burners or flamers are blowtorches adapted to deliver flames to ground level.  They do not have to burn the plants to ash as long as the heat cooks the leaves.  Flamers work best on small weeds with a high moisture content because the plant doesn't have the resources to regrow after the leaves are dead.

Too big for most of us, but a very striking photo from www.lpg-apps.org. 
Flaming the weeds on a large field before planting the crop.

Killing large or mature perennial weeds is possible, but it may require several passes with the flamer. Burn down as much as possible and burn any regrowth in a couple of weeks.

I don't consider this a "no-chemical" means of killing weeds, because you are burning a fossil fuel, usually liquid propane gas, as you kill the weeds. However, it is considered "organic" by most various certifying agencies if that concerns you.

One advantage is that flamers do not disturb the soil and bring a fresh batch of weed seeds to the surface the way tilling does.  Another is that you can work in the rain and on windy days. For best results on windy days, use a burner with a hood.

Sizes available:

• One-burner flamer with a backpack or small trolley for the gas tank.
  These are useful for control of widely scattered weeds and weeds in crevices and paving, but the narrow area covered by the flame makes it tedious to do large areas such as a vegetable garden or alley.
  
• Multi-burner flamer (3-5 burner heads) with wheels supporting the burner heads and hood.
  The flamed area is a foot or more wide.  These are usually pushed by the gardener, and can be an add-on to the single burner models.
  
• Tractor-towed multi-burner flamers of various sizes, with larger, higher pressure tanks, flaming a path several feet or more wide.  Some are shielded so that weeds can be flamed right next to the growing crop, like the one in the linked video.
  
  Video of huge flame weeder in corn

Ways to use flame weeders:

• Let the weeds grow to an inch or so tall, flame the entire planting area, then seed or set out transplants. You can repeat the growing weeds and flaming several times if necessary before seeding.
• Seed a slow-germinating plant such as carrots, then flame weeds just before the crop sprouts. The heat should not damage the crop as long as you keep the flamer moving.  This takes careful timing.
• Flame individual rosette-forming weeds in a lawn or landscape by placing the burner directly over the center of the rosette before turning on the flame.  If you can kill the growth point the whole weed will die.
• In paving and among rocks, flame the visible portion.  Adjust the burner if possible, to deliver a tightly focused flame.
• Around growing plants, hold an insulating flame-proof shield between the desirable plants and the weeds. The metal shields used for spray painting work well.
• ADDED:  (Jan 1,2017) Flamers are useful for killing the few weeds you miss with the glyphosate.

SAFETY PRECAUTIONS:

• The usual storage and usage precautions for gases under pressure, flammable materials, and explosive gases apply. 
• Make sure as you are using the flamer that you don't accidentally set your yard on fire.  Stay away from dry dead vegetation, dead leaves, pine needles and bark mulch.
  
  One of the more spectacular fires I have seen began when the flamer ignited a dead vine, which quickly burned up the palm tree that had supported the vine, and into the dead palm frond skirt.  The tree did not survive.
  
• Flames and flesh do not combine well.  Wear sturdy leather boots and long pants, not flip flops or athletic shoes and cargo shorts.  Explaining to the ER how you barbecued your toes would be embarrassing. The boots are handy for stomping out any small fires you start.
• The burner head will be hot, so keep it away from your shins and let cool before you mess with it.
• Keep pets and children out of the work area.  The flames are not always visible and a curious child or dog can get singed.
• Do not use flamers on poison ivy. The smoke is toxic.

Conclusions:

I have used a single burner model, but for me it has no advantage over glyphosate or a hoe.  The tank is awkward to tow on its trolley, or heavy in a backpack.  Also, the cost of the propane is higher than the cost of generic glyphosate to cover the same area.

If I had a larger area where a multi-burner flamer could be used, such as a small market garden, it might be worthwhile.  If long periods of rainy weather made herbicides impossible to use, it might be worthwhile.

My SO thinks it's great - it hisses like a dragon, it belches fire, and the weeds shrivel immediately.