Show Notes
Soil mycorrhizae. What is it? If you’ve seen any of the “Avatar” movies, you would know that James Cameron probably has a good grasp of the subject…and you would have a basic understanding of what we are going to talk about today. Without mycorrhizal activity, there would be very little gardening. To return to the “Avatar” comparison, you know how in those movies, if anyone fell ill or was near death or they needed to call in the National Guard, they could stick a tree root in their ear and they’d get healthy or victorious, and then the movie could have a happy ending? To quote the “Avatar” Wiki: In Avatar, tree roots are critical, bioluminescent conduits for Eywa, Pandora's neural network, allowing Na'vi to connect to their deity and ancestors. Key structures include the Tree of Souls and Tree of Voices, featuring complex, willow-like root systems that facilitate tsaheylu (the bond) for communication and data transfer. Can you see mycorrhizae activity? Yes! If you have a microscope: (p.s. “Arbuscular”: Arbuscular mycorrhizal fungi (AMF) are soil fungi (subphylum Glomeromycotina) that form symbiotic relationships with roughly 80% of terrestrial plant species. They colonize plant roots, forming tree-like structures called "arbuscules" inside root cells that act as exchange sites. AMF improve plant uptake of phosphorus, nitrogen, and water, in exchange for plant carbon, increasing plant biomass and stress tolerance.) Aren’t you glad you asked?
What about if you turn over the mulch that’s beneath your persimmon tree. Is that white stuff on the bottom of the mulch that’s in contact with the soil…is that mycorrhizae? Short answer: No. Long answer: That white stuff on the bottom of mulch is a decomposing fungi, saprophytic fungi. Saprophytes act as decomposers breaking down dead organic matter, while mycorrhizal fungi form symbiotic partnerships with living plant roots. Falling asleep yet? Here’s Ben Faber, a soil, water, and subtropical crops advisor for the Ventura/Santa Barbara UC Cooperative Extension, with his more astute look at mycorrhizae. This is from his newsletter, “Topics in Subtropics”: Mycorrhizae means fungus (myco) root (rhizae). These root-associated fungi predate the evolution of terrestrial plants, and the partnership with mycorrhizal fungi facilitated the establishment of plants on earth. Mycorrhizae form symbiotic associations with more than 70% of land plants across a broad range of terrestrial ecosystems. Plants supplies mycorrhizae with photo-assimilated carbon in exchange for nutrients and water. This is the definition of a perfect relationship whereby the two sides support each other and have a personal interest at maintaining their counterpart well-being for survival. Once mycorrhizae colonize the host plant, its mycelium can grow over large distances to neighboring plants connecting them together by a common network. This extension of the root network allows plants to acquire water and nutrients (especially nitrogen and phosphorus) far beyond its root zone, rendering plants more resilient to drought and nutrient deficiency. The ability of mycorrhizae to form this underground web also enables the connected plant to communicate with each other through chemical signals and exchange water and nutrients. For example, in forest ecosystems, saplings rely on nutrients and carbon supply from older trees sent through the mycorrhizal network. This underground mycorrhizal web has also great physical properties because they improve the soil structure by forming stable soil aggregates thereby limiting erosion and leaching of nutrients. Today’s podcast features two interviews. The first is with Sacramento County Master Gardener Pat Rosales. We discuss the chances of you buying living mycorrhizae that might be an alleged part of that bag of potting soil you’re coveting. Or even more doubtful, an ingredient in the fertilizer you’re reaching for. Science says: doubtful. Science also says: “You’ve got to be kidding me!”
More from Beyond the Garden Basics
The high points of our chat with Lance Walheim in today’s podcast: * Pick the right variety first. Sweet types like navel oranges struggle indoors, so go with acidic fruit that ripens with less heat. * Meyer lemons, kumquats, Bearss limes and calamondins are the best bets. They’re compact, bloom often and fit in containers. * Regular lemons and grapefruit can survive indoors, but don’t expect much edible fruit from them. * Moving trees in and out is workable, but you need a transition period. Going outside in spring, start in shade after the last frost and increase light over several weeks. Coming inside, reverse the process and reduce light gradually. * The shock is real. Outdoor humidity can top 50 or 60 percent, while a heated house can drop to around 10 percent.
Redwood Barn Nursery owner Don Shor of Davis, California and myself finally got around to putting the 2026 Tomato season to bed…except for the ones that are hanging on for dear life. In today’s podcast, we sing the high notes and low notes of our tomato growing efforts this year, with lots of gardening advice thrown in for good measure. How was your tomato season? Any favorites? Any failures? Any surprises? Let us know in the comments, and be sure to mention where you were doing your gardening this summer. One of the first to comment was Keith, located in the eastern portion of the San Francisco Bay area. He actually commented before the tomato season was ending: “When you two get together to talk about the 2026 tomato season, I'd like to put in a good word for my San Marzano tomato harvest in Contra Costa County. I had a good crop, mostly because the weather wasn't too hot. Tomorrow is sauce-making day! I have a set-up that lets me cook outside.” There’s a complete, human-edited transcript of the podcast near the bottom of this newsletter. Here are the main points of our podcast conversation:
In today’s podcast, I tell a long, drawn out story about what happened the night before my wedding in 1980. Yes, it is a garden story, about the Cecile Bruner rose. But, we quickly turn to a chat with Ben Hanna of heirloomroses.com, who describes how he and his wife came to own the company after leaving corporate life over a decade ago. He says their shared love of gardening and roses, plus the chance to work closer to family, made the business a good fit. He also notes that all five of his children have worked at the nursery in different roles. In the newsletter, it's a list of the best roses for fall blooming color!
In today’s podcast, we talk with Mark Seibert of Sturdi-Built greenhouses in Oregon. The interview covers key considerations for first-time greenhouse buyers, including choosing the right site, with emphasis on sunlight, southern exposure when possible, and local hazards such as trees or lawn equipment. It also discusses heat control and utilities, recommending ventilation, shade cloth, fans, water access, and electrical service with safety protections. Seibert also explains that lean-to greenhouses can work if the roof pitch and site conditions fit, and says a well-built greenhouse can last 20 to 30 years. Growing Hobby Greenhouse Tomatoes in the Winter If you really want to demonstrate to your friends what a great investment your greenhouse is, nothing beats serving them home grown tomatoes...on New Year’s Day. Here’s What You’ll Need to Grow Greenhouse Tomatoes for the Winter and Spring:
The discussion in today’s podcast focuses on pumpkins. Warren Roberts, Superintendent Emeritus of the UC Davis Arboretum, explains that the pumpkin is botanically a fruit, though it is usually eaten as a vegetable. He says the plant belongs to the genus Cucurbita, which is native to the Americas, especially Mexico and the Andes. He describes pumpkin types and notes that many large pumpkins are hybrids, often involving Cucurbita maxima. He contrasts these with the smaller typical pumpkin species, Cucurbita pepo. The conversation also covers the origin of jack-o’-lanterns, whose purpose, Roberts says, came from hollowed-out turnips or rutabagas used to carry coals before matches were available (a handy skill to remember when AI takes over). Short of Garden Room? Grow Mini-Pumpkins! Admittedly, I got a late start on planting pumpkins this year: in early summer (the 4th of July weekend), and I had only one raised garden bed, 4 feet by 8 feet, still available. So, I planted three pumpkin seeds that would eventually produce medium sized pumpkins, the “Jack O’ Lantern” variety, a fruit that gets about 15 pounds. I won’t make that mistake again. Fast-forward three months, and I have a jungle of green vines from those three seeds that have escaped the confines of the raised bed and are now proceeding to swallow the trunks of my adjacent fruit trees. And it looks like the end-result for Halloween decorations will be only four or five medium sized pumpkins. Not much production, considering the sprawl of the vines. And three of them are still green, making me wonder if they will be nice orange orbs ready for carving at the end of the month. Fortunately for gardeners, many seed catalogs and nursery seed racks feature pumpkin varieties that mature in about 90 days and don’t do much sprawling: the miniature pumpkins. There are several advantages to growing pumpkins that weigh less than a pound: quicker maturity, a smaller footprint, and versatility in shapes, color, and uses.