In current century, there is an increased interest in urban ecology, in the understanding the role of microbial soil diversity for the installation and coexistence of plants. The city is an ecological complex where the atmosphere is characterized by the mitigation of climatic excesses during the winter, the accumulation of heat during summer, the reduction of ultraviolet radiation and the alteration of the chemical properties with the accumulation of pollutants emitted by different sources. Factories, transport of waste, increased levels of urban noise, human presence all act as pressure elements on urban ecosystems. In cities, the role of ecosystems is assigned to parks, in an attempt to create habitats similar to those of nature. Inside these areas, arbuscular mycorrhizal fungi have the role of increasing the above-ground productivity by transferring nutrients into the roots of their host plants. These microbial processes contribute to plant growth and soil fertility, which are essential to the efficient functioning of ecosystems. Legumes are an important functional group because they can form a tripartite symbiosis with nitrogen-fixing bacteria and fungi mycelium to produce phosphorus. Virtually all leguminous plants are mycorrhized, as a symbiotic supplement with bacteria that produce nodules. Our study was focused on identification of mycorrhizal structures in the root and appreciation of mycorrhizal colonization in the genus Trifolium. The plants were collected from the flora of three parks in the city of Cluj-Napoca. The collection period was autumn-winter 2017, in order to see the symbiotic level during vegetative rest periods. Root samples were taken at a distance of 5 m from the tree stem, to establish the potential for fungal link of their root systems with leguminous and to highlight the wood wide web connections. The evaluated mycorrhizal structures are the number of mycorrhizal fragments, frequency, intensity, arbuscularity and colonization degree (Table 1.). Frequency of colonization is more influenced by the ecosystem than the distance from the tree. As an opposite phenomenon, colonization intensity at 1m distance from tree is 40%, and at 5m 25%. The relationship between frequency and intensity is loose, mycorrhizal development acting opportunistic according to the sampling area. Arbuscules and colonization degree are closely related, the mycorrhizal system having a gradual development in the roots of the analyzed plants. The low value of the frequency negatively influences the colonization degree, the intensity not being able to compensate for this depreciation in root system. An interesting case was the identification of calcium oxalate crystals deposits in an intriguing variety of forms. This is an interesting point for future studies on how mycorrhizas transfer excess nutrients from urban soils to plants and how plants store them. Mycorrhizal systems are present in urban legumes with high colonization values during vegetative rest. Hyphal connections provide an extensive network for nutrient exchange with other plants present in the ecosystem.