Get Growing: On Mars, gardening starts with bugs

Mickey Rathbun

Mickey Rathbun


Published: 12-08-2023 4:41 PM

A recent headline in the New York Times caught my eye: “Mars Needs Insects.” As the article explained, if we are to create a human-friendly habitat on Mars, we will need to grow food there.

Unlike the nutrient-laden soil that covers the earth, the surface of Mars is covered with regolith, a gritty mix of eroded rocks and minerals that has practically no nutritional value for plants. Thus the need for insects that will generate Martian fertilizer to enrich regolith so it can sustain plant growth. Experiments are underway to combine frass — the excrement of larvae (in this case, the larvae of black soldier flies) — with simulated Martian regolith to produce agriculturally viable soil.

The idea is that humans and flies could eventually be sent to Mars, where the space travelers’ excrement would be eaten by the insect larvae, to be excreted as nutrition-rich frass. The frass would feed growing plants that would feed humans in a complete, self-sustaining cycle.

This model also posits that the astronauts could include protein-rich larvae in their own diets. (This may be a bridge too far. Years ago I wrote a Gazette feature about attending a bug dinner and choking down a few bites of African meal worm stew, an experience I’m not likely to repeat anytime soon.)

The article described a current experiment in which peas are being grown in various mediums, including ordinary commercial potting soil and frass-enriched simulated regolith. The scientists have been trying out different blends of regolith and frass and have thus far concluded that 10% frass seems the optimal amount. Plants grow at the same rate in the 10% frass blend as they do in potting soil. Too much frass means too many nutrients, not good for plant health; too little means that plants don’t receive enough nitrogen.

You might ask where the scientists obtain simulated regolith. It turns out there’s a company in Texas called The Martian Garden that uses rock from the Saddleback basalt deposit in the Mojave desert. The deposit was formed 20 million years ago when a volcano erupted, causing basalt lava to spill out from the slopes of Saddleback mountain, creating rock similar in mineral composition to Martian rock.

The company mines the rock and crushes it into regolith-like particles. The primary use of simulated regolith has been to test NASA’s rovers and other Mars-bound equipment to see how they perform when exposed to Mars regolith, which can be as fine as dust or as coarse as gravel. The company’s website is fascinating:

This article reminded me of the question I raised in my recent column about making our gardens — curated horticultural environments — a welcome habitat for insects and microorganisms. As the Mars report illustrates, without these basic building blocks, life on Earth cannot survive.

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Any gardener who wants to understand the hows and whys of gardening sustainably should read Douglas W. Tallamy’s “Bringing Nature Home: How You Can Sustain Wildlife with Native Plants.” The book is a must-read for gardeners who want their gardens to be balanced ecosystems where insects, birds, and other creatures thrive along with healthy native plants.

Tallamy, a professor of entomology and wildlife ecology at the University of Delaware, presents alarming data about the decrease in insect and bird populations due in large part to the increasing number of alien plants in the environment. To put it simply, alien plants cannot provide food for native insects and birds because they do not share the same evolutionary history.

Of course, the science is far more complicated than that, but Tallamy explains it in lay terms and with abundant documentation. The book provides a good definition of native and alien species, clarifying a distinction that I suspect has puzzled more than a few gardeners, myself included. A related question has been whether newer, more showy, cultivars of native plants can work in our gardens. Tallamy believes they can.

“Bringing Nature Home” provides detailed guidance on how to create a garden whose diversity attracts an array of insects and birds. If the habitat is balanced, writes Tallamy, insect pests will be controlled by their predators. He envisions a future where acres and acres of suburban gardens that presently consist mostly of lawn grass and alien ornamentals are transformed into gardens full of native plants that sustain insect and bird populations.

The book contains a useful appendix listing native plants by category such as vines, deciduous trees, conifers, etc., further divided by region. A second appendix lists host plants for butterflies and showy moths.

I have been pleased to see our local nurseries and garden centers stocking more native plants and labeling them as such. As Tallamy’s book demonstrates, a biodiverse garden need not be blah. A growing assortment of natives provides an appealing range of size, texture and color for all gardens. And anyone who has enjoyed the sight of monarchs, swallowtails and other colorful insects in their gardens knows the satisfaction of doing their own small part to save the planet.

A final note: Last month the USDA revised its Plant Hardiness Zone Map for the first time in a decade. The temperature adjustments reflect rising temperatures in different regions of the country as well as better data collection methods. This means that we New Englanders might be able to grow slightly less hardy plants that would not have survived our winters in decades past.

Mickey Rathbun is an Amherst-based writer whose new book, “The Real Gatsby: George Gordon Moore, A Granddaughter’s Memoir,” has recently been published by White River Press.