How to Propagate Araucaria? Key Points of Seed Sowing and Cutting Explained

Araucaria (detailed description) is an evergreen tree of the family Araucariaceae. Its leaves are deep green, and the whole plant is graceful and dignified. Many plant enthusiasts now make Araucaria into bonsai to decorate venues and halls. So how should Araucaria be propagated?

Araucaria (detailed description)

I. Sowing

Araucaria can be propagated by sowing or cutting. Araucaria grown in the north rarely sets seed, so cutting propagation is often used. In spring, collect the upright new shoots growing from lateral buds or vigorous shoots as cuttings (if lateral branches or weak branches are used as cuttings, the resulting plant will have a distorted crown shape and lose its ornamental value). The cuttings should be 7 cm long; inserted into a greenhouse sand bed at 13-16°C with 60-80% relative air humidity, they will root. Alternatively, cut off the top of a young tree, wait for the lateral buds at the top to produce upright new shoots, and then cut the branches for cuttings in spring.

II. Cutting

Before sowing, it is best to scarify the seed coat first to promote germination. Seed-grown seedlings have a long taproot and few fibrous roots, and are prone to dying when transplanted. By paying attention to key techniques such as protecting the roots, planting carefully, keeping warm, and shading, the survival rate of seedlings can be improved. For seedlings with broken roots, wash them in clean water and insert them into plain sand; at a suitable temperature, they will re-root from the cut surface in 1-2 weeks. For seedlings with broken buds or stems but retaining leaves, they can be planted as usual, and after surviving they will sprout new buds after a certain period.

Morphological Characteristics of Araucaria and How to Cultivate and Propagate It

Araucaria is an evergreen tree native to Norfolk Island, Australia. It has many names: based on its place of origin, it is called English pine, Australian pine, Norfolk Island pine, and Araucaria. Based on leaf type, it is called heterophyllous Araucaria, small-leaved Araucaria, and beautiful Araucaria; based on form, it is called tower Araucaria and Hainan Araucaria. Varieties introduced to China include Araucaria cunninghamii and Araucaria heterophylla. Araucaria cunninghamii has an upright trunk and a tower-shaped overall tree form, with branches whorled and extending horizontally, evenly spaced and clearly layered, thornless, and with a dignified appearance. It is a top-grade foliage plant, mostly grown in pots. Araucaria heterophylla is an excellent ornamental garden plant; planted in the ground it can reach a height of more than 30 m. It likes warmth and sunlight, can tolerate high temperatures of 40°C as well as low temperatures of minus 5°C, and can survive in the open ground around the 27°C north latitude line (Norfolk Island is located at 27°C south latitude).

Morphological Characteristics of Araucaria

Branches
Araucaria is a tree, reaching up to 60-70 m tall in its native habitat, with a diameter at breast height of more than 1 m. The bark is grayish brown or dark gray, coarse, with horizontal fissures; the large branches are spreading or obliquely extended. Young trees have a spire-shaped crown, which becomes flat-topped with age. The lateral branchlets are densely borne, drooping, and arranged nearly pinnately.

Leaves
Araucaria has two leaf forms: the leaves on young trees and lateral branches are loosely arranged and spreading, awl-shaped, needle-shaped, sickle-shaped, or triangular, 7-17 mm long, about 2.5 mm wide at the base, slightly curved, slightly four-angled or with an inconspicuous ridge on the upper (ventral) surface, with many stomatal lines on the upper surface, and irregular stomatal lines or nearly no stomatal lines on the lower surface; the upper part gradually narrows, with an acuminate or slightly acute tip. The leaves on large branches and flowering and fruiting branches are densely arranged and overlapping, extending obliquely upward, slightly curved upward, ovate, triangular-ovate, or triangular, without an obvious ridge or with a longitudinal ridge on the lower surface, 6-10 mm long.

Cones
The cones of Araucaria are ovoid or elliptical, 6-10 cm long, about 4 cm wide, broad at the base, gradually narrowing or slightly rounded above, with an acute or blunt tip, and a distinct or indistinct midrib. The upper surface is grayish green, covered with white powder, and has many stomatal lines; the lower surface is green, with irregular, sparse stomatal lines only in the middle and lower parts. Male cones are solitary at the tips of branches, cylindrical.

The cones of Araucaria are ovoid or elliptical, 6-10 cm long, 4.5-7.5 cm in diameter; the bract scales are cuneate-obovate, with thin wings on both sides, broad and thick at the tip, with a sharp ridge, and an acute long tail-like point in the center that curves markedly backward; the tip of the seed scale is thin, not fleshy; the seeds are elliptical, with a membranous wing formed by fusion on both sides.

Ecological Habits of Araucaria

Araucaria likes light, while seedlings prefer shade; Araucaria likes warm, humid climates and is not tolerant of drought or cold. It prefers fertile soil. It grows relatively fast, has strong sprouting ability, and is resistant to wind.

In winter, Araucaria needs sufficient sunlight, and in summer it should be protected from strong direct sun. It fears the dry, violent winds of the northern spring and the scorching sun of midsummer. It grows best under conditions of 25°C-30°C and relative humidity above 70%. For pot culture, use a loose, fertile potting soil with high humus content and strong drainage and aeration.

Cultivation Techniques for Araucaria

Selection of Mother Plants for Root Cuttings

The mother plant for root cuttings is the propagation source that provides high-quality propagating material, and it must be strictly selected to ensure the superior characteristics of the mother plant are maintained. Generally, trees 5-10 years old that are suitable for landscaping seedlings are used, with robust growth, no pests or diseases, deep green leaves, tightly arranged whorled branches, and good overall performance.

Collection of Root Cuttings

April-May each year is a good period for landscaping and also the best time for cutting propagation. Large numbers of landscaping seedlings leave the nursery; take this opportunity to collect the remaining root systems after seedlings are dug up, or dig up part of the root system from shallow parts of the soil surface around Araucaria heterophylla trees. Use these as material for cutting propagation.

Treatment of Root Cuttings

The treatment of root cuttings in vegetative propagation is an important step related to the survival and rooting of cuttings. Araucaria heterophylla root cuttings should be treated promptly as follows: select roots with a cross-section of 0.8-1.2 cm, cut them to about 10 cm, arrange them in order from head to tail, tie them in bundles of 20-30 roots, and place them in a cool, ventilated place to encourage the fleshy roots to evaporate excess water and prevent rot. The drying time is generally about one week. Selection of cutting medium and environment: for the cutting medium, choose sieved pure river sand with a particle size of 0.5-1.0 mm, which has the advantages of good aeration and drainage.

Construction of the Cutting Bed

The cutting bed is built with bricks, 25 m high and 100 cm wide, with the length determined by the number of cuttings. The bottom of the bed should be level, and the cutting medium is placed inside and slightly leveled and compacted before use.

Selection of the Cutting Environment

The selection of the cutting environment is very important for the survival of cuttings. The suitable rooting temperature for Araucaria heterophylla is 15-25 degrees, the humidity is 70%-80%, and there should be sufficient light, preferably light shading. Choosing a cutting site with such humid conditions for cutting propagation makes it easy to form adventitious roots and adventitious buds, resulting in a high survival rate.

Cutting Method: Root cuttings are best inserted in rows, with a plant spacing of 4 cm and a row spacing of 6 cm. Use a strip of board 6 cm wide, 100 cm long, and 2 cm thick as a ruler, place it on the sand bed to mark the row spacing, and use a small shovel to open slanted furrows along the edge of the board to a depth of about 7 cm. Insert the cuttings into the sand bed to about 2/3 of their length, then place the cuttings neatly in the furrow at equal intervals of about 4 cm, making sure the heads face upward, then cover with sand and compact. After inserting all cuttings, water thoroughly once.

Seedling Transplanting

Araucaria likes warmth and humidity, is shade-tolerant, and is not cold-tolerant. Seed-grown seedlings have a long taproot and few fibrous roots. They are prone to dying when transplanted. To improve the survival rate of Araucaria seedling transplanting, the following key techniques should be followed.

Root Protection

Because Araucaria seedlings have few lateral roots and fine hair roots, they can shrivel and dry out if not handled carefully, so protecting the seedling root system is very important. First, they should be transported with the pot and soil, and the original potting soil should be kept moist. Second, after the seedlings are purchased, they should be planted immediately; if planting cannot be done right away, place them in a cool, humid place and do not expose them to the sun, so as to protect the seedlings, especially the roots, and keep them fresh. In addition, when winter temperatures are low, the roots are prone to freezing during transport, so attention should be paid to keeping them warm.

Careful Planting

When planting, keep as much of the original soil around the seedlings as possible. The planting soil should be loose and fine, and do not press the soil around the roots too hard. After planting, water thoroughly to settle the roots. In addition, seed-grown Araucaria seedlings have a long taproot, so they should be planted somewhat deeply to prevent the root system from being exposed and the plant from lodging, which would affect survival.

Keeping Warm

Araucaria is not cold-tolerant. If seedlings are purchased and planted in winter or early spring, in addition to protecting against freezing during transport, warmth retention measures should also be taken after planting, such as growing them in a greenhouse or covering them with arched plastic film.

Shading

Araucaria is a shade-tolerant flowering plant, and seedlings are even more afraid of direct sun, so they should be shaded immediately after planting.

Treatment of Broken or Damaged Seedlings

Araucaria seedlings are tender in tissue and easily broken or damaged. The following methods can be used for remediation. For seedlings with broken roots, wash them in clean water and insert them into plain sand; at a suitable temperature, they will re-root from the cut surface after 1-2 weeks, and can be planted after the root system develops. For seedlings with broken buds or stems but retaining leaves, they can be planted as usual, and after surviving they will sprout new buds after a certain period.

Propagation Methods of Araucaria

Propagation by Sowing

Because the seed coat is hard and the germination rate is low, it is best to scarify the seed coat before sowing to promote germination. In addition, sown seedlings are susceptible to pests and diseases, so the soil used should be strictly sterilized. The seeds are best germinated in a sand bed or sown after the above-mentioned shell-breaking method to increase the germination rate; generally they germinate in about 30 days.

Propagation by Cutting

Cutting propagation is relatively easy and is widely used. Cuttings are usually taken in spring and summer, but the main branch must be selected as the cutting; plants grown from lateral branch cuttings are crooked and not upright. The cuttings should be 10-15 cm long. After insertion, under conditions of 18°C-25°C and relatively high air humidity, they root in about 4 months. If the base of the cuttings is soaked in 200 ppm indolebutyric acid (IBA) for 5 hours before insertion, rooting can be promoted earlier.

To obtain more main branches as cuttings, the top of a young tree can be cut off so that many upright new shoots emerge from the top, and these are cut as cuttings in spring. The mother plant after top pruning can continue to produce terminal buds later and can be used as a permanent propagation mother plant. For potting soil for potted Araucaria, it is advisable to use a mixture of 40% peat soil, 40% leaf mold, and 20% river sand. During the growing season, the potting soil should be kept moist; when too dry, the lower leaves will droop and soften, but in winter a slightly dry state should be maintained. In winter, the room temperature should be kept above 5%, as low temperatures will freeze and kill the growing points.

Rejuvenating Plants by Air Layering

If conditions in the shed or greenhouse permit, girdle the plant at an appropriate height and then plant the whole plant in the ground, burying the cut more than 10 cm deep. After about 1-2 years, the plant will rejuvenate and grow sufficient new roots; then lift the plant and pot it. At this time, the old roots have already decayed and can be removed. The new plant is shorter and sturdier, making it more ornamental.

After reading the above introduction on how to cultivate and propagate Araucaria, do you have a better understanding of Araucaria cultivation and propagation? If you want to know more about Araucaria, please continue to follow us.

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