Mycorrhizal fungi form mutually beneficial relationships with over 95% of common plant species. They surround and even enter the roots of these plants, and provide nutrients such as phosphorus (and to a lesser degree, nitrogen) and water to plants in exchange for carbohydrates.
Electron microscope image of endomycorrhizal fungi with spores attached to the hyphal strands
In fact, some plants may trade more than 50% of their carbohydrates with these fungi and other microbes. The fungi also greatly improve soil characteristics. And, amazingly, they act as a line of defence, protecting the roots in the soil environment.
My clients and I have both seen huge benefits from using mycorrhizal fungi when planting. The product seems to be especially helpful in improving the quality and health of a newly seeded lawn. Gardeners have also reported reduced plant losses when planting in less than ideal conditions.
In soil that has recently been tilled/worked, compacted, water logged, drought stressed, or treated with chemicals, mycorrhiza will be lacking. They are not present in imported topsoil or potting soil mix, either, and they cannot be multiplied in compost as they need a living plant host to survive.
In any of these scenarios, they need to be added back to the soil. They are essential to optimum plant health and should always be used whenever planting or seeding.
There are two main categories of mycorrhizae relationships: Endomycorrhizal fungi (arbuscular mycorrhizal fungi) form relationships with over 90% of plants (including turf grasses). Ectomycorrhizal fungi form relationships with fewer plant species, but some of them are quite common, such as hedging cedars, other conifers, and many hardwood trees.
Please note that there are a few plants that do not respond to either endo or ectomycorrhizal fungi, namely members of the brassica family (broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, and rutabaga); members of the Ericaceae family (rhododendron and azalea, blueberry, cranberry, heath and heather, huckleberry, lingonberry), as well as beets, mustard, spinach, and orchids.
Mycorrhizal Fungi Products
Myke Pro WP is a highly concentrated wettable powder containing Glomus intraradices. Used for seeding, laying sod, taking cuttings, potting up, and generally planting / transplanting / dividing plants, or for applying to established lawns and gardens. Suitable for most annuals, herbs, flowers, and vegetables; turf grasses and ornamental grasses; ferns; perennial flowers; most fruit trees; common deciduous and broadleaf evergreen ornamental trees and shrubs.Info/Buy
Endo/Ecto - Root Rescue, a concentrated wettable powder containing eighteen different species of Glomus, Gigaspora, Rhizopogon, Pisolithus, Laccaria, and Suillus fungi. Used for propagating, planting, or transplanting. Besides plants that partner with endo-mycorrhizae, Root Rescue also covers those woody plants that benefit from ecto-mycorrhizal fungi (or take both endo and ecto), such as: most conifers including hedge cedars, Douglas Fir, true fir, hemlock, larch, pine, and spruce; as well as alder, arbutus, beech, birch, chestnut, eucalyptus, filbert/hazelnut, hickory, linden, oak, pecan, poplar, and willow.Info/Buy
Mycorrhizal Fungi Application
The best time to apply mycorrhizal inoculant is at the plant production stage, but since your plants probably didn't have that done, the next best time is at planting/seeding/sodding. This will promote contact between the fungi and plant roots.
Rub the product directly on the root ball if possible, or sprinkle in the planting hole. You can also mix the powder with water and apply the liquid. Bare roots can be dipped into the liquid. For seed, mix the dry powder with the seed before spreading. For sod, sprinkle it dry or spray the liquid on the soil right before laying the sod, or even better, right on the bottom of the sod (I know that can be time consuming). You could spray it on after as well.
The other choice would be to apply the mycorrhizal fungi products to existing landscapes. For trees and shrub beds, grab a garden fork and poke a lot of holes around the feeder root zone, away from the trunk. This will help both powder or liquid to enter the soil and get to where it's needed.
For turf, it is best to do this right after aerating so that more of the spores get down to the roots. Otherwise, it can be watered in, but will not be as effective on heavy clay or very compacted soils.
Be sure to keep agitating / stirring the liquid as the powder tends to settle at the bottom. Mixing several smaller batches rather than using the entire amount at once helps ensure even distribution.
The powder can be mixed with other microbial products and organic fertilizers and applied at the same time, although there is no benefit to foliar feeding with mycorrhizal fungi products, as they need to touch the roots.