Italian cypress is a narrow evergreen tree that shoots lance-like up into the air approximately 50 feet. Its fibrous roots anchor it in rich soils and give it a degree of drought tolerance. Italian cypress can live from 50 to 150 years provided it is planted well. Along with full to partial sun requirements, Italian cypress needs well-drained soil and deep, infrequent watering to help prevent soil-borne fungus diseases from becoming a problem.
Mushroom-type fungi are only present around Italian cypress when the base of the plant is surrounded by sufficient moisture, shade and organic matter to support them. They do not harm the roots of healthy Italian cypress. In fact, mushroom fungi tend to break down deadwood particles in compost and mulch into forms the roots can benefit from. Microbial fungi in the soil have a more intimate relationship with Italian cypress roots, feeding directly from root sugars.
Many varieties of the fungal plant disease Phytophthora exist, but Phytophthora cinnamomi is the one that infests Italian cypress. This fungus infects the roots and destroys them, eventually killing the whole plant. Infected roots will look mushy and dark instead of pale and strong. There are no known cures, so prevention is the best option. Plant healthy Italian cypress in well-drained, uninfected soil.
Mycorrhizae are a group of fungi that have a symbiotic relationship with plants. They attach to the roots, and form branching colonies that resemble roots in scope and function. They absorb water and nutrients and relay them to the plant, meanwhile feeding from sugars that the roots produce. Because these fungi effectively extend the roots, Italian cypress with large colonies of mycorrhizae have enhanced drought tolerance. Studies conducted by the Mycological Society of Japan indicate that cypresses selectively host a small range of mycorrhizae species.
Mycorrhizae have been recognized as a biological control for root fungi in integrated pest management programs. Mycorrhizae form a sheath around the roots of Italian cypress in order to take up root sugars. In the process, they out-compete Phytophthora and other soil-borne diseases for purchase in roots. If not allowed to access roots for several years, these pathogens might eventually die out in the soil. In these cases, fungicides should not be used. Fungicides will kill mycorrhizae, and may not be as harmful to pathogen fungi.
Other Root Fungi
Texas root rot fungus (Phymatotrichopsis omnivora) has been discovered on Italian cypress, though this disease isn't as harmful. According to the Urban Forest Ecosystems Institute, Italian Cypress has a natural resistance to Texas root rot. Good cultural habits such as planting in well-drained soils and buffering the root zone with mycorrhizae inoculations may help Italian cypress perform well in soils infested with Texas root rot.