First, the basic information of elm trees
Elm belongs to the elm genus elm family, also known as: white elm, house elm, elm money, spring elm. Elm trees are also an important tree species for urban and rural greening, and can be used as street trees, shade trees, shelter forests and "four sides" greening trees in the northwest desert, north China and Huaibei plains, hills and northeast barren mountains, sandy lands and coastal saline alkali lands. It can also be planted in a solitary or group plant in the garden. In barren, cold places, it often takes the form of a shrub and is used as a hedge. You can also dig up from the wild to make bonsai.
Second, the morphological characteristics of elm trees
Elm trees are deciduous trees, up to 25 m tall and up to 1 m in diameter. The trunk is erect, the branches are more developed, and the canopy is nearly spherical or oval. The bark of young trees is smooth, grayish brown or light gray, and the bark of large trees is dark gray, rough, irregular longitudinal lobes. The leaves are alternate, ovate oval to oval lanceolate, 2 to 8 cm long and 1.2 to 3.5 cm wide, with multiple serrations at the margins. From March to April, the flowers bloom first and then the leaves or leaves bloom together, the flowers are both sexes, purple-brown, and the polygonal inflorescences grow in clusters on the leaf axils of the previous annual branches. From April to June, the fruit is ripe, and the wing fruit is nearly round, 1.2 to 2 cm long, and there is a concave defect at the apex.
Third, the growth habit of elm trees
Elm is a masculine tree species that loves light, is drought tolerant, hardy, hardy, barren, and does not choose soil. The root system is developed, and the wind resistance and soil retention are strong. Strong germination and pruning resistance. Grow fast and have a long lifespan. Resistant to dry and cold climates and moderate salinity, but not to water and moisture. Anti-pollution, strong leaf surface dust retention ability. It grows well in alluvial soils with deep, fertile and well-drained soils and loess plateaus.
Fourth, elm seedling breeding
1. Sowing and breeding.
Prepare the bed: select sandy loam or loam soil with relatively flat terrain, convenient drainage, deep soil layer, loose and fertile soil, turn 25cm deep in the autumn of 1 year before sowing, apply 2500kg/mu of decomposed stable fertilizer, combine fertilization with ploughing, apply poisonous soil made of 50% octyl thiophosphate emulsion, after the soil is thawed the following spring, level the ground, and then make bed preparation.
Seed selection and germination: sow as you go, but the seeds transferred in need to be soaked in cold water for 3 to 5 h to make the seeds fully absorb water. After fishing out, mix evenly with 2 times the wet sand, spread the sun on the mat or large container on the ground, turn it 3 to 5 times a day, make the seed sand evenly heated, spray water appropriately according to the degree of wetness of the seed sand, maintain the appropriate temperature and humidity, pile up at night with a grass curtain or sack cover, wait for 2 to 3 days after the seed germinates, some seeds are just exposed to white when sown in time, high ridge or high bed sowing.
Sowing direct seeding: 60 cm wide at the bottom of the high ridge, 30 cm wide, 15 cm high, 15 cm in the ditch spacing of 15 to 20 cm, open width 3 to 5 cm, depth 1.5 to 2 cm sowing ditch. Sow the seeds evenly into the ditch and then cover the sand with 1 cm and suppress it slightly. The high bed is sown in a row spacing of 15 to 20 cm on the bed surface, and the horizontal width is 3 cm and the depth is 2 cm sown in the ditch of 4 to 5 kg/mu, and the soil is covered with 1 cm after sowing and suppressed. Fill the bottom water before sowing, and try not to water the head before the seedlings emerge after sowing. Under the appropriate soil temperature and humidity, germination and excavation begin 5 to 6 days after sowing, and seedlings can all emerge in 10-15 days. When the seedling height is 3 cm, the seedling height is 5~7 cm, and the ridge surface is retained 22~25 plants/m. Water in time after interspersing seedlings.
Seedling stage management: seedling stage should often loosen the soil and weeds, irrigate 4 to 5 times a year, apply ammonium sulfate 4 to 5 kg/mu in June to July, apply once every 10 to 15 days, 2 to 3 times continuously, and stop topdressing in early August. At the seedling stage, spray 90% of the enemy insects in time 800 ~ 1000 times the liquid poison to kill elm purple and golden flower insects. The buds are spread 2 to 3 times a year, and the bud picking can be stopped in early August and some of the side branches can be retained.
2. Propagation of cuttings.
After autumn leaves fall or before spring budding, select annual, full and thick branches and cut cuttings growing 15 to 20 cm. In autumn, the seed strips are harvested, and the cuttings are cut and stored in the sand according to different thicknesses, and the cuttings are cut in the following spring. Spring harvesting of seed strips, cut the cuttings according to the thickness of the water soaked for 1 to 2 days, change the water once a day, so that the cuttings fully absorb water, in early and mid-March, according to the plant spacing of 20 cm large ridge single row cuttings, or press 20 cm × 40 cm flat seedbed cuttings.
After cuttings, water once permeable, and then water to keep the soil moist. When the seedlings are up to 10 cm tall, the number of watering can be reduced. In the middle sentence of June and the middle and second sentence of July, 2 to 3 ammonium sulfate 15 to 20 kg/ridge can be appropriately applied. Around the middle of August, topdressing and watering can be stopped. When the seedling is 5 cm tall, the first time the bud is smeared to retain 2 to 3 buds, and when the seedling is 10 cm tall, the second time the bud is smeared, and a strong growth bud is selected to be cultivated, and the rest of the buds are all erased. When the seedling is 60 cm tall, perform the first pruning and cut off the side branches below 1/2 of the seedling height. In late July, when the seedlings are growing vigorously, the second pruning is performed, and the side branches below 2/3 of the height of the seedlings are cut.
Fifth, elm tree seedling cultivation
In the second year of sowing seedlings, a large ridge is transplanted in a single row, and the seedling roots and side branches are properly pruned during transplantation. The transplant plant spacing is 20cm, such as good water and fertilizer conditions, timely care and management, 2 years of seedling height up to more than 1.8m, the diameter of more than 1.5cm. It can produce about 5,000 seedlings per mu. In order to cultivate a good trunk, the pruning method of "winter head, summer control branch" is adopted, that is, when transplanting 1-year seedlings in early spring, 60% to 70% of the seedling stem is cut off, and a strong, upright and upward branch is selected as the main branch in summer, and the remaining side branches or competing branches are shortened to control the growth of side branches, cultivate a straight and thick trunk, and cultivate more transplanted seedlings for 2 to 3 years.
Sixth, the use of elm trees
Branches: Elm sapwood is light yellowish brown, while the heartwood is dark grayish brown, its structure is slightly coarser, the texture is straighter, strong and durable, can be used to make vehicles, agricultural tools, furniture, utensils, bridges, buildings, etc.
Bark: The bark of elm trees can be used for medicine and light and chemical industries; The leaves of elms can be used as feed. The bark, leaves and winged fruits of the elm tree can be used medicinally, which can play a role in calming the spirit and facilitating urination. Elm bark grinding can also be used as a food aid.
Fruit: The elm tree is medicated with fruits, leaves, bark, and roots. Yu Qian, before the spring leaves, pluck the unripe wing fruit, remove impurities and dry them in the sun. Bark, peel off the bark to dry, or in summer and autumn, dry or fresh. Leaves, picked in summer and autumn, dried or fresh. The root bark is harvested in autumn. Yu Qian has the effect of calming the nerves and strengthening the spleen, which is conducive to neurasthenia and loss of appetite. Elm bark and leaves are calming.
7. Control of elm tree diseases and insect pests
Elm diseases:
1. Ulcer disease
Affected elms usually develop diseases in the skin holes and pruning wounds, and the initial lesions are inconspicuous, darker in color, and the cortical tissue becomes soft and dark gray. After the onset of the disease, the bark tissue of the diseased part is necrotic, the injured parts of the branches and cadres become thin and sink, the longitudinal cracking is generated, the spots are produced, and the plants dry up and die. Small trees and seedlings die that year, and large trees die years later. Prevention and control methods: at the beginning of the disease, methyl tolbucin 200 to 300 times liquid, or use 50% carbendazim wettable powder 50-100 times liquid to apply prevention and control.
2. Blight
The initial symptoms are not significant, and there are no more obvious symptoms of the beginning of decay in the cortex, only the leaves on the twigs are wilted, the leaves are very small, and the peeling can show rot diseases. Thereafter, the skin is dehydrated and shrunken, and small vermilion warts will develop. If the sick skin goes around the branches and dries for a week, it will lead to dead branches and dryness.
Control methods: timely pruning of branches, cleaning of diseased insect branches and diseased insect trees and dead standing wood.
3. Anthrax
At the beginning of the disease, irregularly shaped spots are produced on the leaves, light yellow or off-white, and later spots produce black or black-brown granular protrusions, usually arranged in a radioactive arrangement. In severe cases, the leaves turn yellow and fall off early. Control method: When the leaves fall, you can spray 1:3:100 Bordeaux liquid or 45% Daisen manganese zinc 500 times liquid.
Elm insect infestation:
1. Elm purple flower worm
It is a common forest leaf insect pest, also known as elm purple leaf beetle, likes to eat the young leaves and young branches of trees, mainly endangers the growth of elm trees, and is relatively less harmful to other trees. Adult elytra have purple-red stripes. 1 generation occurs in 1 year. Adults overwinter in the soil and come out the following spring when the leaves sprout. Females begin to lay eggs on twigs, and later on the leaves, the eggs hatch into larvae after 5 to 7 days, and the larvae appear in large numbers between May and June, and after 20 to 30 days of maturity, they enter the soil and pupate. The older generation of adults also descend the tree in summer at this time, and in August the newly feathered adults and the old adults who are more summer are pested, until the adults go down to the trees again in late October to overwinter. Larvae and adults are harmful leaves, and large occurrences often eat all the leaves.
Prevention and control methods: 1, can use 3% high-efficiency cypermethrin agent, sprayed according to the ratio of 1:200. 2. When the adult insect goes to the tree in early spring, before the adult insect lays eggs, the artificial shock falls and kills. 3. Spray 90% of the enemy insects 800 to 1000 times the liquid to poison the larvae and adults.
2. Elm poison moth
Identifying characteristics: Adult: body length about 12 mm, wingspan about 25 mm. The body and wings are white , while the tibia and tarsal segments of the foot are orange-yellow. Egg: Oval in shape, grayish-yellow in color, covered with gray-black secretions on the surface of the egg, arranged in clusters. Larvae: The body of the old mature larvae is about 30 mm long and the body is yellowish. The larvae have white hairs on the back of each segment, a black color around the base of the hair, and a large black hairy patch on the first to second segment of the abdomen. Pupae: About 15 mm long, pale green with a black-brown tuft of hair on the top of the head.
Control method: During the peak of larvals, it is necessary to spray 20% saueric emulsion 2500 to 3000 times liquid, or spray 20% permethrin emulsion 2000 times liquid on the plant.