Grass, brush and mulch are going up in smoke.

At Indiana Mulch & Stone in downtown Indianapolis, the mulch is in high demand this time of year. But the dry spell and heat wave can cause mulch used for landscaping to combust.

Manager Darren McWilliams told RTV6's Ericka Flye that homeowners sometime pack mulch beds too thick. Mulch decomposes, producing heat deep down that can't escape. Combined with the heat from above, the mulch can ignite.

"If that stuff catches on fire, it can go. Just keep mulch to about a 3-inch thickness. That's better for your plants, your landscape and it will cut down on the risk if anything was to happen of it not being so bad," McWilliams said.

Fishers firefighters doused a mulch fire Tuesday night near 116th Street and Olio road, but it's hardly the only charred patch in town.

Ron Lipps with the Fishers Fire Department said there's been a dramatic increase in ground fires, including grass, brush and mulch fires. Last year, there were 34 reports. There are 80 reports so far this year, and 50 in June alone.

"The fires in the medians, those are a nuisance. But the problem is, some of the fires that we have are up against buildings," Lipps said.

And the fires are also threatening homes. A grass fire in Westfield Tuesday creeped dangerously close to a house.

"When that fire gets into the building, it's nothing for it to go into the siding of the house or the structure of a house or business and take off," Lipps said.

Officials said items like improperly discarded cigarettes ignite most of the fires. Using caution can cut the risks.

"Just make sure you use basic common sense, and just keep away open spark and flame," said McWilliams.

Fire officials said occasionally turning mulch can release heat so it doesn't build up. But overall, they advised, just keep an eye on it.