Tilia americana and its horticultural varieties

Before introducing' Green Umbrella', let's learn about Tilia americana.

Tilia americana is a unique Tilia tree species in North America, which is native to humid forests in the eastern United States. It is a medium to large deciduous broad-leaved tree with a tree height of 18-37 m (some even reach 39 m) and a mature DBH 1- 1.5 m. Tilia amurensis grows faster than most broad-leaved trees in North America, and its annual growth is often twice that of most native American beech and birch trees. Tilia amurensis has a life span of about 200 years, and it blooms and bears fruit in 15 ~ 100 years (the earliest fruit is 8 years).

Tilia amurensis has a hemispherical crown with spreading branches and usually drooping. The bark is gray to light brown with narrow and clear cracks. The root system is huge, deep and spreading. Branchlets are smooth and light green, turn to light gray in the following year, and finally turn to dark brown and brownish gray, with gray dendromatous vegetation. The winter bud is oval, stout, sharp, smooth and deep red, with two visible bud scales.

Leaves alternate, oval to heart-shaped, asymmetrical left and right, with length and width of 10- 15 cm, sometimes up to 25 cm, and long petiole. The tip of the blade is gradually tapered, and there are thick sharp teeth at the edge. The upper part of the leaf is dark green and dull, and the lower part is light and shiny, with brown tufts in the axils of the veins. The new leaves are soft and fluffy, light green, and the stipules fall off soon after the leaves are unfolded. The leaves are dark green when they mature and turn yellow-green to yellow in autumn. The branches and leaves of Tilia americana contain a lot of sticky juice.

Tilia americana is small, with a diameter of about 10- 14 mm, light yellow and fragrant. There are five petals, and each 10 flower forms a drooping inflorescence. Each bunch of flowers has a long 10 cm long bract, which blooms from early summer to midsummer and is pollinated by bees. Flowering consequences are small, round, fluffy, woody, gray-green, and 8- 10 mm in diameter.

The species classification of Tilia americana is controversial. Some scholars regard Tilia americana, Tilia heterophylla and Tilia mexicana as different independent species, while others call them Tilia americana.

Tilia amurensis was widely used in landscaping of major cities in North America as early as 1752, with a long cultivation history. The flowers of this tree can attract bees to collect honey, and the brewed honey is of high quality, so it is also a high-quality honey source tree species. If people can find a hollow bodhi tree in the forest, it will usually be filled with honey. The attractive white wood of Tilia amurensis is often used by bees as beehives and honey racks, and rotten Tilia amurensis is often used by birds to build nests. Tilia americana has fragrant yellow flowers in summer. These flowers can be used to collect honey from bees, or distilled to make perfume or dried to make purple linden scented tea.

Tilia amurensis leaves are edible, which contain fiber substances that are very needed by human beings and livestock. Therefore, Tilia amurensis leaves in deep mountains and forests have also become a life-saving energy supply. The soft endothelium in linden bark is an important raw material for making fiber rope. Native Americans and early European immigrants used linden bark to make ropes, mats and net bags. The English word "bast" is translated into "endothelium, bast fiber" and "hemp", especially linden fiber, so the common name of linden tree in North America (translated into American linden tree) comes from this. In addition, the oil extracted from Tilia americana seed pods is used as a substitute for olive oil.

Tilia wood is light brown, sometimes close to white or reddish, tasteless, light and soft, and not easy to crack. It is a good carving material and a world-famous wood. Many top solid wood electric guitars in the world are made of basswood. Although Tilia amurensis has many economic uses, it is still regarded as an ornamental tree species in landscaping. Tilia amurensis is best planted as a park tree and lawn tree because of its huge dark green leaves and natural crown. A large number of leaves form a thick shade, surpassing all other native trees in the United States. People often plant it on the windward side of the orchard to protect the delicate young trees.

Tilia americana has many horticultural varieties, such as' (Nova',' Bailyard' with tall trees',' Continental' with narrow cylindrical crown, and' ('Redmond' with big leaves.

American Tilia amurensis' Green Umbrella' is the best horticultural variety in China, which has been applied in landscaping projects in Dalian, Beijing and other places. Tilia amurensis' Green Umbrella' is a large deciduous tree with a height of15-24m and a crown width of 9-12m. The tree was pyramid-shaped when it was young, but it became round in the later period. Leaf blade is dark green, obliquely ovate, about 20 cm long and 15 cm wide. Bracts are light green and slender. Flowering from June to July, the flowers are small, yellow and fragrant. The fruit is pea-sized, woody, light gray-green, 5-sided, and bears fruit after flowering. Winter buds and buds are sometimes red.

Growing environment: Tilia amurensis' Green Umbrella' can grow in various climatic conditions. The best growing area is the cold-resistant zone 3-8 (Jilin in the north and Jiangsu and Zhejiang in the south) divided by the US Department of Agriculture, and the suitable soil pH is acidic or weakly alkaline. It can grow in all kinds of slightly wet and well-drained soil, and the ideal soil conditions are wet, fertile and rich in organic matter. Light-loving, shade-tolerant, drought-resistant and water-resistant. Can tolerate a certain dry and hot environment.

Planting and maintenance: easy to maintain, planting soil can be increased during planting to ensure good soil drainage in the planting area. Need to water regularly, the interval is determined according to the local rainfall, usually once or twice a week. Generally, leaves are pruned when they germinate in spring, which can be pruned into rectangles, triangles or circles. The growth rate is moderate, and soil conditions and soil fertility have great influence on tree height and growth rate. No serious pests and diseases, powdery mildew, leaf spot, leaf blight, aphid, red spider, leaf curl and so on can be properly prevented.

Landscape uses: mainly used as ornamental trees for greening residential quarters and large courtyards, also used as hedges and shade trees, or planted in the buffer zone of parking lots, highway green belts or leisure green spaces beside sidewalks. The main landscape uses are: ① hedge; ② Greening of large parking lots; ③ Lawn trees; ④ Expressway buffer zone; ⑤ Shading trees; 6. Commercial real estate landscape trees; ⑦ Pedestrian tree pool; There are 8 street trees in residential quarters.

Note: Tilia amurensis' Green Umbrella' has a wide crown and well-developed root system, so it needs enough growth space, and the planting area should not be too small, otherwise its root system will affect the surrounding pipelines, buildings, sidewalks and roads. At the same time, Tilia amurensis' Green Umbrella' is generally tolerant to urban air pollution and sensitive to snow melting agent, so it is not suitable to be planted as a street tree in urban streets.

American Tilia amurensis' Green Umbrella' is the most popular Tilia amurensis variety in the United States. Its leaves are bigger than Tilia amurensis in Europe. Its open crown and huge shade are deeply loved by city residents. Yellow flowers in full bloom in summer can create a natural and ecological landscape atmosphere. It is a flower ornamental tree, which gives off bright light in hot summer. Often planted as a city shade tree, it is worthy of most cities in China.