Making Better Bonsai With Mycorrhizae by David Johnson What is mycorrhizae? Mycorrhizae is a fungus that interacts with a plant¼s roots and benefits both. The mycorrhizae "grow(s) within the plant root and extend(s) out into the surrounding soil or medium acting as an extension of the root system. This relationship greatly increases the absorptive surface area of the root system and with the help of the fungus, the plant is able to obtain more mineral nutrients from the soil or medium." (Premier Tech Biotechnology Research Report) There are two or three main types of mycorrhizae depending on the source. Ecto-mycorrhizae grows on the outside of feeder roots that appears white and mat-like on most conifers. This mycorrhizae extends the plant¼s reach with the fungus penetrating further into the soil. Endo-mycorrhizae grows inside the roots and is less visible on trees like junipers and maples. Ectendo-mycorrhizae grows both inside and outside the roots and occurs only on plants of the "Ericaceae" (heaths) family (International Bonsai 1994 no. 4). "Each variety of tree that has mycorrhizae has its own characteristic type - the mycorrhizae of a pine, for example, would not live on the roots of a spruce tree and vice versa. Within the same variety, however, trees that have very little or no mycorrhizae may be inoculated with some from another tree at the time of repotting," (Bonsai, D. Koreshoff, p.109). Mycorrhizae¼s Benefits In two articles by Jerald P. Stowell in International Bonsai 1994 no. 4 and 1995 no. 4, the author states the capabilities of mycorrhizae: It increases root absorption surfaces. It has the ability to render unavailable substances in the soil and make them available to the host plant (phosphorus, zinc manganese and copper). It detoxifies the environment for the host plant. i.e. protection against pathogenic invasion. Protection is by utilizing root carbohydrates and other chemicals which would be attractive and would be utilized by the pathogens. It provides a physical barrier to pathogens in the form of a fungus mantle. It secretes antibiotics which inhibits or kills pathogens. It supports a protective rhizosphere (non-mycorrhizal root area - DJ) population of other micro-organisms. It stimulates root cells of the host plant during symbiotic periods to elaborate chemical inhibitors. Inhibitors function to maintain symbiosis but may also inhibit infection by pathogens. While I don¼t fully understand all of the technical terminology above, I understand enough to determine that mycorrhizae can do some good for our bonsai. I was encouraged to write this article when I came across some relatively new products that consist of various types of mycorrhizae made by Premier Tech Biotechnologies in Quebec. I also obtained a research report and other brochures from Premier Tech (Toronto Bonsai Society will try to obtain additional copies of these documents and make them available to interested club members through our library). The report has findings from various studies on the results from using mycorrhizae and the compatibility of these products with insecticides, fungicides and fertilizers. The report has yet to be finalized. How to get Mycorrhizae? Mycorrhizae grows in the soil naturally so collected trees may have it and washing the roots would wash away the fungus too. Some of the old soil can be re-introduced. In the case of azaleas whose roots are washed, Premier Tech¼s literature states that their mycorrhizae will not colonize rhododendrons and azaleas anyway. Stowell suggests these sources for mycorrhizae: collect its fruiting bodies (mushrooms), collect composted forest leaf mould or buy it commercially (International Bonsai 1995 no.4). Maintaining Healthy Mycorrhizae Once you introduce the mycorrhizae into your bonsai, how do you keep it happy? Keep in mind the recommendations from Premier Tech regarding the use of their product and various pesticides, fungicides and fertilizers in the tables below. Additionally, some literature suggests lowering the fertilizer levels in the container, specifically nitrogen and phosphorus. Vitamin B1 and vitamin B both promote mycorrhizal growth (International Bonsai 1995 no. 4). Lack of air space in the soil and too little or too much water discourages the growth of mycorrhizae (International Bonsai 1994 no. 4). n correspondence with David Easterbrook from the Montreal Botanical Garden, he said that a ph of 6.0 to 6.5 is ideal for the growth of endomycorrhizae of most deciduous trees and members of the Cupressaceae family (i.e. juniperus and thuja) and a more acidic ph around 5.5 to 6.0 for ectomycorrhizae which is found on members of the Pinaceae (i.e. larch, picea, pinus and tsuga) and Fagaceae families (i.e. fagus and quercus). Temperatures around 90† F and more, and fungicides which are photoxic to mycorrhizae such as Benlate or Benomyl and Aliette, can kill it. If soil temperatures approach 90† F, the trees can be protected with shade cloth, moss covering of the soil, spraying with water or moving them to a cooler area. If the mycorrhizae dies off, it can be re-introduced which takes eight weeks for maximum growth. The following lists are taken from Premier Tech¼s Research Report on Mycorise(R) Pro and Myke(TM) 2001: Trees colonized by Mycorise(R) Pro Endo (only trees used for bonsai included in this abbreviated list) Acer rubrum (Red Maple) Amelanchier canadensis (Serviceberry) Ginkgo biloba (Maidenhair tree) Magnolia (Magnolia) Malus (Apple) Prunus (Plum) Shrubs colonized by Mycorise(R) Pro Endo (abbreviated list) Buxus (Boxwood) Cotoneaster (Cotoneaster) Ilex (Holly) Juniperus (Juniper) Potentilla (Cinquefoil) Spirea (Spirea) Taxus (Yew) Thuja (Cedar) Vitis (Grape) Trees colonized by Mycorise (R) Pro Ecto (abbreviated list) Abies (Fir) Betula (Birch) Fagus (Beech) Picea (Spruce) Pinus (Pine) Quercus (Oak) Pesticides: "This is a list of pesticides that have been used with Mycorise(R) products. Certain pesticides followed by an * may reduce the colonization rate of the plant roots. These results were obtained with leek plants." Insecticides: Agribrom (bromide-based) Ambush 25 wp Ambush (Permetrin) Cygon (Dimethoate) Diazinon* (Diazinon) Insecticidal soap* Kelthane (Dicofol) Malathion* (Malathion) Morestan (Chinomethionat) Metasystox (Oxydemeton-methyl) Pentac (Dienochlor) Pirimor (Pirimicarb) Vendex (Fenbutatin-oxide) Talstar-Attain (Bifenthrin) Dursban (Chlorpyrifos) Trumpet-Dycarb (Bendiocarb) Enstar (Kinoprene) Margoson (Azateractin) Mavrik (Fluvinate) Orthene (Acephate) Sevin (Carbaryl) Avid (Abamectin) Citation (Cyromazine) Marathon (Imidacloprid) Oxamyl* Fungicides: Aliette (Fosetyl-Al) Benlate* (Benomyl) Bravo (Chlorothalonil) Captan (Captan) (soil) Dithane (Mancozeb) Easout* (Thiophanate methyl) No-Damp (Oxine benzoate) (soil) Phaltan (Folpet) Ridomil-Subdue (Metalaxyl) Terraclor-Quintozene (PCNB) (soil) Rovral (Iprodione) Sulfur-92% Thiram (Thiram) Truban (Etridiazol) (soil) Vitavax (Carboxin) Difolatan (Captafol) Lesan (Fenaminosulf) In its technical guide, Premier Tech recommends using fertilizers with a rating of 10% or more of phosphorus at half strength such as 15-15-30, 30-10-10, 5-10-5, 2-14-0, 6-12-6, 5-10-15 and 8-12-6. Premier Tech also says that 13-2-13, 12-2-14 and 21-5-20 are fertilizers specifically recommended for mycorrhizae. I bought a 1.5 litre tub of Premier Tech¼s "Myke(TM) Tree and Shrub" at a garden centre which retails for $10 (less when on sale). At a rate of several tablespoons for big trees (bonsai) and less for smaller trees, 1.5 litres can go a long way. If you try these products, follow the manufacturer¼s recommendations. Sources: Koreshoff, Deborah R., Bonsai: Its Art, Science, History and Philosophy, Boolarong Publications, Brisbane, Australia, 1984. Premier Tech Biotechnologies, Research Report (2001), Technical Guide (2000), 2002 Product Line (2001). Valavanis, William N. (editor), International Bonsai, 1994 no. 4, 1995 nos. 1 and 4, 1996 no. 3.