What Are the Large Black Mushrooms Growing in My Yard?

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All yards need moisture, and heavy moisture is sometimes followed by large black mushrooms, if the conditions are right. The good news is, mushrooms rearing their heads in your lawn every now and then is actually a sign that your lawn is healthy. These fungi break down organic matter, such as tree stumps and wood mulch, and the nutrients from these materials become available to your grass and other plants. Unless you have pets or kids who might ingest the mushroom caps or you're concerned about the look of mushrooms on your lawn, there's usually no need to take control measures.

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Where Do Mushrooms Come From?

Mushrooms and toadstools are the fruiting bodies of some types of fungi and produce spores, the reproductive component of these fungi. Similar to plant seeds, fungal spores are transported to different locations by wind, flowing water, animals, and your shoes and tools. When a fungal spore has the right elements needed to grow, such as a moist, nutrient-rich environment, it may germinate. Upon germination, thin, white filaments called hyphae develop. When lots of hyphae are massed together, they form a mat called a mycelium, the equivalent of plant roots in the fungi world.

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Mushrooms may grow in your yard when a mycelium inhabits the soil or thatch layer and the conditions are favorable — often after you've watered too much, there's been a lot of rain recently, or you have a soil-drainage problem.

Black Mushrooms Growing in Your Yard

There are several types of black, partly black, or sometimes-black mushrooms that may pop up in your yard or garden, including:

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  • Black morels (​Morchella angusticeps​):​ Cone-shaped caps that feature honeycomb-like light-brown or tan cells bordered by black to dark-brown ridges. Prized by mushroom hunters and often found growing in groups in a variety of locations, including near fallen, decaying trees and in swampy areas, old stream beds, and areas that have been burned. Only appear from early March through early May, depending on location and climate. Total height ranges from 2 1/2 to 6 inches; stalk and cap, which are fused together, both range from 1/2 to 1 1/2 inches wide.
  • False morels (​Gyromitra​ spp.):​ Some species are poisonous and often mistaken for morels, although instead of the honeycomb-like cells that characterize morel caps, false morel caps may appear wrinkled and somewhat similar to brain tissue or a mass of earthworms. Depending on the species, height is between 2 and 8 inches, and cap color may be black, brown, reddish-brown, gray, or white. May appear in spring, summer, or fall as opposed to morels, which only appear in spring.
  • Puffballs (​Calvatia ​spp.):​ Usually spherical fruiting bodies that resemble mushrooms but lack the characteristic stalk of toadstool-type mushrooms, "hugging the ground," instead of being held aloft by stalks. Puffballs range in size from less than 1 inch up to more than 1 foot in diameter in colors that include white, tan, and dirty brown; when mature giant puffballs rupture, they release trillions of microscopic dark-colored or black spores.
  • Inky caps (​Coprinus comatus​):​ Also known as "lawyer's wig" and "shaggy mane," the caps of this common lawn mushroom, which are borne by tall, while stalks, turn into a black, inky substance following spore dispersal. Often found in late summer and early fall in grassy areas and on wood chips, dung, and hard-packed soil.

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Handpicking or Raking Mushrooms

Picking or raking mushrooms to remove them from the lawn or garden can help protect children and pets from poisonous species, keep the area looking better, and reduce the number of new mushrooms cropping up by reducing the number of spores released. For all practical purposes, though, eliminating mushrooms from your yard for good is impossible because, similar to the tip of an iceberg, mushrooms are only the visible part of a vast underground system.

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Warning

Always wear protective gloves when handling mushrooms, as some species are poisonous.

Minimizing Mushrooms in Your Yard

Warm, wet conditions and the presence of organic matter, such as thatch and decaying trees, promote mushroom growth. Although you can't control the ambient temperature or the amount of rain that falls, there are steps you can take to make conditions in your lawn less hospitable to mushrooms:

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  • Cut back on watering your lawn.
  • Incorporate compost into your soil to improve texture and drainage.
  • Fill low areas of your lawn where water has a tendency to pool.
  • Remove decaying trees, stumps, and branches and prune trees to allow more sunshine to reach your yard.
  • Apply a water-soluble nitrogen fertilizer to the lawn to promote the growth of healthy turf and accelerate the decomposition process. The recommended amount is 1 pound of nitrogen for every 1,000 square feet in early fall and late spring. Avoid slow-release formulations.
  • Dethatch and aerate your lawn. Dethatching means removing the layer of accumulated dead grass that sits on the soil and prevents sufficient oxygen, fertilizer, and water from reaching the roots of your grass. Aeration is the process of removing small plugs of soil from the lawn with a tool called a core aerator so that water and nutrients can more readily penetrate the soil's surface.

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