In the world of gardening, it's easy to get caught up in the latest trends and products. One such product that has been making waves is mycorrhizal inoculants. But are they really necessary for your CT home garden? Let's take a closer look at the science behind mycorrhizae and whether these products live up to the hype. Personally, I think it's important to understand the role of mycorrhizae in plant growth and whether adding an inoculant is truly beneficial. What are mycorrhizae, and why are they significant? Mycorrhizae are fascinating partnerships between plant roots and soil fungi. These fungi extend their fine threads, called hyphae, into the soil, expanding the area from which plants can absorb water and nutrients. In return, the plants provide sugars produced through photosynthesis. This ancient relationship is crucial for the growth of many plant species. Now, let's delve into the different types of mycorrhizal fungi. Arbuscular mycorrhizal fungi (AMF) are the most common type, often found in lawns, vegetables, and ornamentals. Tomatoes, peppers, corn, squash, beans, grasses, and flowers typically form these partnerships. However, not all plants rely on AMF. Oaks, birches, hickories, and conifers commonly associate with ectomycorrhizal fungi, while blueberries and rhododendrons form ericoid mycorrhizae. This diversity highlights the importance of understanding the specific needs of your plants. One question that arises is: do you already have mycorrhizal fungi in your soil? The answer is yes, in many established garden beds, lawns, meadows, and landscapes. The abundance and diversity of these fungi depend on factors like vegetation, disturbance history, fertilizer use, and soil conditions. Adding a commercial inoculant to an already established soil community may not necessarily improve the partnership. Recent research has raised concerns about the effectiveness of commercial mycorrhizal inoculants. A meta-analysis published in the journal New Phytologist found that around 80% of commercial inoculant treatments resulted in minimal or no mycorrhizal root colonization. A separate evaluation from the University of Zürich further supported these findings, showing that none of the seven products marketed for home gardening successfully established mycorrhizal symbiosis under controlled conditions. So, what are the reasons behind these disappointing results? One factor is the viability of the fungi during storage. Mycorrhizal fungi are living organisms, and their survival can be compromised. Additionally, different fungal species vary in their ability to associate with specific plants and perform in different soil conditions. The lack of independent quality standards and verification makes it challenging for consumers to assess the viability of the fungal propagules in the product. Now, when might inoculation be beneficial? It's most plausible in severely disturbed construction soils, degraded sites, or soilless and pasteurized growing media used for containers and greenhouse transplants. Even then, the plant must be capable of forming the partnership, and the product must contain viable fungi compatible with that plant. Tree and shrub plantings require extra caution, as many woody species rely on different types of mycorrhizal fungi. When considering inoculation for established gardens, several factors come into play. Firstly, the soil may already contain a functioning fungal community, making it difficult for introduced strains to establish and benefit the garden. Secondly, high phosphorus levels can reduce AMF colonization and the plant's reliance on the partnership. Testing the soil before adding phosphorus or an inoculant is crucial. Thirdly, some common crops, such as broccoli, cabbage, kale, cauliflower, mustard, and radish, generally do not form functional mycorrhizal associations. Applying an inoculant to a bed planted mainly with these crops is unlikely to provide significant benefits. So, what can you do to support beneficial fungi in your garden? Good soil management is key. Avoid unnecessary tillage, as it can break fungal hyphae. Keeping living roots in the ground through perennial plantings or compatible cover crops like annual ryegrass and crimson clover can also help. Testing the soil before adding phosphorus is essential, as high phosphorus levels can reduce the plant's reliance on mycorrhizae. Before buying an inoculant, consider whether improving soil conditions and supporting the existing fungal community might be a better first step. In conclusion, while mycorrhizal inoculants may seem appealing, the science behind them is complex. For most established CT gardens, lawns, and landscapes, these products may not be necessary, as beneficial fungi are often already present. However, in highly disturbed soils or growing media where compatible fungi are scarce, inoculation could be beneficial. As always, it's essential to understand the specific needs of your plants and the science behind the products you use. Remember, the UConn Home Garden Education Office is a valuable resource for research-based information and guidance on all things gardening.
