A Detailed Guide to Propagation Methods and Pest and Disease Control Techniques for Holly (Ilex)

Holly (Ilex) is an evergreen nursery stock that stays green all year round. It has a graceful tree shape, white flowers, and a faint delicate fragrance when blooming. It can be planted in courtyards or made into bonsai, making it a very good landscaping nursery stock. Below, the editor will explain the propagation and pest and disease control methods for holly, so that everyone can grow it.

Propagation Methods

Holly can be propagated by sowing seeds or by cuttings.

Seed Propagation

① Seed collection and treatment. Holly seeds mature from November to December. Select vigorous, pest-free large trees that are 30-40 years or older for seed collection. Generally, the fruits are collected after they are fully mature. The seeds are extracted by hand and rinsed repeatedly with clean water. Select plump seeds with no defects or deformities. Sow them immediately after collection, or stratify them to break dormancy and sow in spring. Stratification to promote germination: choose a dry, well-ventilated indoor space. First spread a 10 cm thick layer of wet sand on the ground. Then layer the seeds and wet sand in alternating layers at a ratio of 1:3, building the pile to a height of 40 cm. Cover the top with another 10 cm of wet sand. Insert several perforated bamboo tubes or straw stalks into the sand pile for ventilation. The sand moisture should be such that it forms a ball when squeezed in the hand and shows a few large cracks when released.

② Nursery site preparation. Choose flat sandy loam with convenient transportation and water sources as the nursery site. Before cultivation, clear away tree roots, bricks, plastic, weeds, and other debris from the nursery site.

a. Soil preparation. In late autumn or early winter of the previous year, deep-plow the nursery site once to a depth of 35 cm, without harrowing. After a winter (about 2 months) of sun-drying and frost exposure, this helps change the soil properties and reduce the occurrence of pests and diseases. Taking advantage of the winter slack season in rural areas, dig drainage ditches around the nursery site (commonly called perimeter ditches), with a width of 40 cm and a depth of 35 cm, to facilitate drainage. In mid-to-late February of the following year, apply fully decomposed farmyard manure per mu of nursery land, and each fertilization method can be supplemented with 100 kg of superphosphate to improve soil fertility and help young plants absorb nutrients and survive. After fertilizing, harrow the nursery site 3-4 times consecutively to level it thoroughly.

b. Ditching and bed making. To prevent sunscald damage to seedlings, seedbeds are mostly oriented north-south. Manually mark lines at a width of 1.5 m and dig bed ditches to make seedbeds. The seedbed width is 1.2 m, the ditch width is 30 cm, and the ditch depth is 25 cm. Make the perimeter ditches, middle ditches, and bed ditches "three ditches" interconnected. Deep ditches and narrow beds facilitate drainage, irrigation, and worker operations.

c. Disinfection. For nursery sites where pests and diseases have occurred, it is best to carry out insecticidal and fungicidal treatment once before sowing. For sterilization, ferrous sulfate (15-20 kg/mu) or 70% daconal wettable powder (1-1.5 kg/mu) can be mixed with fine soil and broadcast. The effect is good. For insect control, combine with drilling sowing and apply 3% carbofuran (furadan) granules per mu.

③ Sowing. In March, sieve out the holly seeds that have been stratified to promote germination, remove moldy seeds, and then drill-sow. Manually mark lines and open drilling furrows. The row spacing is 25 cm, and the furrow depth is 1.5-2 cm. Sow the holly seeds evenly in the furrows and cover with fine soil to 1.5 cm. Acetochlor can be sprayed to seal the soil to delay weed growth. Then cover with pine needles, sawdust, rice straw, etc., to retain moisture and allow air penetration. After sowing, water appropriately according to weather conditions and soil moisture to maintain suitable humidity in the seedbed. Seedlings emerge around late April, at which time the rice straw and pine needles should be removed.

Cutting Propagation

Holly cuttings are divided into hardwood cuttings and softwood cuttings. Hardwood cuttings are mostly carried out in late February or early March, using already lignified branches. Softwood cuttings are mostly carried out from May to July, using current-year semi-lignified branches.

① Hardwood cuttings. Holly hardwood cuttings involve steps such as nursery site preparation, scion collection and cutting, and post-cutting management.

The preparation of the holly cutting nursery site is the same as for the sowing nursery site, but no fertilizer is applied. The seedbed is made into a turtle-back shape to facilitate drainage. Build a shade shed according to the cutting area and cover it with 50% shade netting. Connect the nets with wire or strong rope, and fix the perimeter of the nets with wire or rope. The shade shed must be sturdy enough to withstand strong winds.

In February to March, select vigorous, pest-free large seedlings that are 6 years or older, and cut vigorous branches 1-2 years old from the outer part of the large seedlings. Stack the collected branches in a cool, wind-sheltered place and cut them into short sections. The cutting length is 10-12 cm. Remove the lower leaves, keeping only 1-3 leaves at the top. Cut the upper end of the cutting straight across and the lower end at an angle into a horse-ear shape. Tie the cut cuttings into bundles of 50, with the lower ends aligned. Soak the lower ends in 1100 mg/kg ABT No. 1 rooting powder solution for 2 hours, then they are ready for cutting. The cutting depth is 2/3 of the cutting length. After finishing 1 bed, quickly water thoroughly with a watering can , so that the cuttings make full contact with the substrate. Use bamboo to build a small arch shed and cover it fully with 2 m wide medium film. Seal the edges of the medium film with stones or soil. Hang 1 thermometer and hygrometer in one of the arches.

After holly cuttings are inserted, the main management is temperature and humidity. Before cutting (within 25 days), the humidity inside the small arch shed should be maintained above 90%, and the substrate humidity at about 60%. After about 25 days, the wounds of the holly cuttings begin to heal and root. When all cuttings have rooted and more than 50% have begun to leaf out, the film must be opened at both ends for ventilation and hardening of the seedlings. After proper hardening, remove the film and shade netting to increase seedling resistance, but suitable humidity in the seedbed should still be ensured. Spray a 1000-fold diluted solution for sterilization at intervals of 7-10 days.

② Softwood cuttings. Holly softwood cuttings can be carried out in a greenhouse. This helps cuttings survive easily.

From May to July, build seedbeds inside a full-light intermittent misting greenhouse (covered with imported plastic film), and fill the seedbeds with a mixture of vermiculite, perlite, peat, and other materials. Fix the perimeter of the seedbeds with 15 cm high wooden boards or stone slabs.

After the seedbeds are prepared, collect the cuttings. Place the collected green branches indoors and wait for disinfection and cutting. To allow the cuttings to receive light evenly, orient the leaves in one direction as much as possible, and use a cutting density such that the leaves do not cover each other. After cutting, spray immediately to retain moisture and prevent the cuttings from dehydrating and dying.

After the holly cuttings are inserted, full-light intermittent misting management is required. Before the cuttings heal and root, relatively high air humidity should be maintained in the plastic greenhouse. After 15 days, the holly cuttings begin to heal and root. Misting can be carried out after the water film on the leaf surface has completely evaporated. On sunny days, mist about once every 2-3 hours; do not mist on rainy days or at night. Every 10-15 days, pull out the rotted holly cuttings and burn or bury them. In the evening, after stopping misting, spray with a 1000-fold solution of 70% thiophanate-methyl for sterilization and disinfection. In spring, the seedlings can be transplanted to the field.

Pest and Disease Control. Holly has very few pests and diseases. Among diseases, sooty mold is harmful and can be sprayed with 800-fold diluted 0.3 Baume lime-sulfur mixture. Among pests, aphids and stem borers damage leaves and trunks, and can be sprayed with a 1000-fold diluted solution of 40% omethoate.

The common holly propagation method is seed propagation. This method has low cost, but the propagation time is long and the result cannot be guaranteed. Another method is cuttings, which can increase the survival rate. In the editor's view, holly is a very excellent landscaping nursery stock. It can be enjoyed for both flowers and foliage, and is worth planting for anyone who likes flowers, plants, and nursery stock.

Main Disease Control of Japanese Holly (Ilex crenata)

Japanese holly (Ilex crenata) is an evergreen dwarf shrub in the genus Ilex of the family Aquifoliaceae. It tolerates low temperatures, and its leaves are deep green and glossy, with the upper leaves golden yellow, especially more vivid in spring and autumn. It has fine dense foliage, slow growth, strong branching, and is extremely tolerant of pruning.Four SeasonsIt is evergreen and other characteristics, and can be planted in areas south of the Great Wall. It is widely used in urban landscaping, either as a specimen plant or in pattern plantings, forming garden landscapes.

However, after Japanese holly was widely used in garden planting, it was found that branch blight and stem base rot occur relatively seriously, causing plants to die in patches or leaves to turn yellow in patches. Below, the control methods for the two diseases are mainly discussed:

I. Branch Blight

This disease is caused by fungi. It generally invades directly from the tips of branches or from wounds after pruning, and then attacks the branch base, causing the branch epidermis to turn brown, obstructing nutrient transport, and causing leaves to turn yellow and wither, until the crown leaves of the entire plant wither, and then the plants die in patches. The symptoms of damage are extremely similar to those of plant death due to dehydration, and it is very easy to mistakenly think it is caused by problems with the plant root system. If this disease is not carefully checked, it is not easy to discover, and once symptoms appear, they are often relatively serious, making control relatively difficult. Therefore, prevention should be the main approach.

Control Methods:

1. Physical control: Loosen the soil, apply more organic fertilizer, and change the soil's physical and chemical properties. Use ferrous sulfate aqueous solution to neutralize the soil, or spray with alum fertilizer water and rice-washing water. At the same time, reduce the temperature difference when watering, and water in the morning and evening.

2. Chemical control: First, prune the dead branchesPruning, cut off the diseased branches and keep them away from the site or burn them. Then use chemical agents for treatment:

(1) Immediately after each pruning, spray Daconil wettable powder 600-fold solution, 50% iprodione wettable powder 800-fold solution, or iminoctadine 800-fold solution for protection, to prevent pathogens from invading through wounds;

(2) In May-June, spray the fungicide iminoctadine 600-1000-fold solution, 70% thiophanate-methyl 600-fold solution, or 75% chlorothalonil wettable powder 600-fold solution, once every 10 days, for two consecutive sprays.

II. Stem Base Rot

At the beginning of the disease, irregular water-soaked patches appear at the base of the stem near the ground, light brown in color. The cortex of the diseased part becomes soft, water-soaked, and easy to peel off, with an off odor when smelled closely. The diseased part gradually expands around the entire stem base, and the color deepens. Later, white granular substances grow on the diseased part. After onset, it affects the upward transport of water and nutrients, causing branches to wilt. As the disease worsens, the branches above the diseased area gradually dry up and die. This disease begins in April, with May-July being the peak period. It is mostly caused by excessive soil moisture and poor ventilation.

Control Methods:

1. In daily maintenance, care should be taken to avoid soil waterlogging, open ditches in time for drainage, plant appropriately sparsely, increase plant spacing, ensure good ventilation inside the plant clumps, increase light exposure, fertilize in a timely manner, and carry out pest and disease prevention, so as to enhance plant vigor, make plants more disease-resistant, and reduce the occurrence of this disease.

2. When the disease occurs, chemical control should be carried out as early as possible. A 1000-fold solution of 50% thiram wettable powder can be evenly sprayed on the stems, for 3-4 consecutive sprays.

Common Pests and Diseases of Holly and Their Control

Common Diseases of Holly

Leaf Spot

Symptoms are gray-brown diseased spots on holly leaves, mostly round or oval, with a gray-white mold layer growing on the surface of the diseased part when humidity is high. Control measures are as follows:

Promptly pick off and burn diseased leaves to reduce sources of infection; apply oak leaves or cottonseed meal to the soil; spray plants with copper preparations such as Bordeaux mixture or fungicides such as ferbam for control, or spray with 75% chlorothalonil wettable powder 600-fold solution.

Branch Blight

This disease causes the epidermis of holly branches to turn brown, and large numbers of leaves to wither and fall. Because the plant cannot obtain nutrients, the plant dies. The symptoms of damage from this disease are extremely similar to plant death due to dehydration, so attention should be paid to distinguishing them and discovering the disease in time. Moreover, once symptoms appear, they are often relatively serious, and control is relatively difficult, so prevention is generally the main approach. Specific control methods are as follows:

① Immediately after pruning, spray Xinzi wettable powder 800-fold solution or iminoctadine 1000-fold solution for protection, to prevent pathogens from invading through wounds;

② Spray the fungicide Junwujun 600-fold solution or Xinziqing wettable powder 600-fold solution once every 10 days, for three consecutive sprays.

Root Rot

Spray with 10% antibacterial agent 401 acetic acid solution 1000-fold solution.

Common Pests of Holly

For pest prevention, first select healthy-growing holly seedlings for planting, use appropriate planting density, and pay attention to ventilation, etc.

For aphids, leafhoppers, and scale insects, spray 50% fenitrothion emulsifiable concentrate 1000-fold solution. When red spider mite damage occurs, spray with 20% tetradifon wettable powder 1000-fold solution.