One Tough Tree!

            When it comes to plants, Holly is one of the toughest. It can grow in a huge variety of environments and under numerous conditions. It can grow in light, sandy soil, medium soil, and even relishes in heavy, clay soil. It can survive in extremely acidic environments and prefers soils that range in pH from 3.5 to 7.2. English Holly is also very shade tolerant and is often found as a dominant understory plant. Some Holly plants have been found to withstand complete shade, but these plants often develop leaf spot diseases and have decreased berry production. Other environmental conditions that seldom affect Holly trees are atmospheric pollution, maritime exposure and drought. Most English Holly plants, however, do require dry to moist soil and have difficultly succeeding in water logged environments.

Figure 1: English Holly tree in Winter.

            Ilex aquifolium has adapted well to the dry and cold environments that it resides in. Most of these adaptations have taken place in the leaves of the tree. English Holly leaves have developed an edge covered with several spines to protect against predation by the domestic cow and other cattle. These spines are also adaptations to dry soil conditions, similar to the spines on a cactus, for example the Christmas cactus. Holly leaves have also developed a thick cuticle to prevent water loss and protect against the cold. Because the leaves are smooth and have a twisted shape they are not weighted by snow in the winter. Through these many adaptations English Holly trees are able to survive and produce fruit through the coldest winters and the longest droughts.

Figure 2: The spines and tough cuticles of Holly leaves are important adaptaitions.

            There is a downfall, however, to the tough nature of English Holly. Its ability to survive in a number a soil types and pH ranges, as well as its small dependence on sunlight, make it an aggressive and invasive species. In newly developing regions Holly tends to out-compete any competition by casting a deep shade on any smaller vegetation that has taken root. Its thick, dark-green foliage creates a barrier against other plants and even though it reproduces rather slowly it can quickly overcome any obstacles.

Up next, Reproduction...