Garlic planted last fall in hugelkultur bed

Bob Dluzen
Special to The Detroit News

Last fall was the first time we ever planted garlic in a hugelkultur bed. If you don’t know what a hugelkultur bed is, I wrote about it a while back, you can scroll through my posts to find about it. It’s basically a type of garden growing bed that uses decomposing wood as a source of plant nutrients for garden plants.

This year’s garlic is the most vigorous crop we’ve ever had growing in our garden. The tops are lush and green while the necks are thick and strong. That is a good predictor of how the crop will turn out. I’m looking forward to a greater percentage of extra large bulbs this time around.

This year’s garlic is making exceptional progress.

Much the improvement I’m sure is the balance of plant nutrients being released into the soil as the wood in the bed decomposes. But there may be more to it than that because in past years I’ve always made sure our garlic crop was well fertilized which meant the plants had access to plenty of nutrients.

My thought is there may be a mycorrhizal effect going on between the garlic and soil fungus.

Often, the first thing that comes to mind when we think of fungus as it relates to gardening is the damage caused to plants by fungus infection. But not all fungi are harmful to plants. Some species have no effect at all while others are actually beneficial.

Mycorrhizal fungi are a type of beneficial fungi that live in the soil and have a symbiotic relationship with plants. Fungi of this type can turn insoluble, unavailable soil minerals into a form that can be readily used by plants to encourage optimum growth. This can happen with just about any kind of plant.

The hyphae, or “roots” of the fungus grow as very fine, long strands that are much thinner than plant roots and as a result, can be in contact with many more soil particles.

Depending on the species of plant, the fungus may live on the surface of the roots or even live inside the roots as a kind of advantageous infection. It’s been well documented that arbuscular mycorrhizal (AM) fungi actively living inside garlic roots will measurably enhance garlic growth in fertile soils. 

For all of the work the fungus does, it gets something in return: carbohydrates produced by its host plant as a result of photosynthesis.

Could it be that we unwittingly inoculated the soil in the bed with a species of AM fungus when we added rotting wood to the bed? We had wood from several different kinds of trees, shrubs and vines, plus some weed stems to boot.

Usually these kinds of interactions between organisms are species specific, meaning one type of organism will only infect one specific type of plant. Plus decomposer fungi are different species from the mycorrhizal type.  I don’t know enough about mycology to know what’s going on with the soil fungus population when decomposing wood is introduced to the mix.

It could simply be that the extra nutrients released into the soil by the rotting wood accounts for the vigorous garlic growth but I still have an inkling there is more to it than that.