Grow Araucaria angustifolia from seeds. How the seed storage at different temperatures affects germination rate

Published on 23 November 2023 at 12:28

Araucaria angustifolia, the Paraná pine, Brazilian pine or candelabra tree (pinheiro-do-paraná, araucária or pinheiro brasileiro), is a critically endangered species in the conifer genus Araucaria. Although the common names in various languages refer to the species as a "pine", it does not belong in the genus Pinus.

The genus Araucaria was part of terrestrial flora since the Triassic and found its apogee in Gondwana. Today, it is restricted to the Southern Hemisphere and has 19 species.

It is native to southern Brazil (also found in high-altitude areas of southern Minas Gerais, in central Rio de Janeiro and in the east and south of São Paulo, but more typically in the states of Paraná, Santa Catarina and Rio Grande do Sul).

It is an evergreen tree growing to 40 m (130 ft) tall and 1 m (3 ft 3 in) diameter at breast height.

It is usually dioecious, with the male and female cones on separate trees. The female cones (seed), which mature in autumn about 18 months after pollination, are globose, large, 18–25 cm (7–10 in) in diameter, and hold about 100–150 seeds. The cones release the approximately 5 cm (2 in) long nut-like seeds, which are then dispersed by animals.

It prefers well drained, slightly acidic soil but will tolerate almost any soil type provided drainage is good. It requires a subtropical/temperate climate with abundant rainfall, tolerating occasional frosts down to about −5 to −20 °C (23 to −4 °F).

It is a popular garden tree in subtropical areas, planted for its unusual effect of the thick, 'reptilian' branches with a very symmetrical appearance.

Germination method
Araucaria angustifolia seeds are recalcitrant seeds, which means that they loose viability during long storage at room temperature due to loosing their moisture content.
Thus it is recommended to store the seeds in the fridge until sowing.
As the study showing the germination rate of fresh seeds of A. angustifolia is about 35%, where as seeds stored at 0-4°C for 4-6 month increased germination to 80-90%!!!
After 8 month of storage the seeds loose viability rapidly (only 20-30%) (see the file attached).

Refrigerated Storage Of Seeds Of Araucaria Angustifolia Over A Period Of 24 Months
PDF – 119.1 KB 67 downloads

My first experiment was A. angustifolia seeds was with the seeds stored in the fridge for 3 month and the germination rate was close to 100%.

Sowing

After suggested cold storage (stratification) came to the end (approximately 3-4 month just in time for spring) prepare the deep pots with well draining potting medium with good moisture content. Milk cartons is the perfect choice as the taproot of A. angustifolia is long and fast growing. Remember to make the drainage holes!
Though some sources do not recommend using peat that was my only available choice and the seeds germinated well. As additives to peat you can use perlite, sand, pumice and vermiculite.
Drench it with water and let it sit till the excess go down.
Before sowing soak the seeds in room temperature water for 24-48 hours or until they sunk to the bottom.

Plant the seeds sharp end in the soil about 1/3 of its size with the top part above the surface. The medium must be kept moist but not soggy.


Germination

Germination can occur as quickly as 1-2 weeks after sowing at 20-25°C, but it is not possible to see anything (except removing the seed from the medium) until much later.

The deep pot will allow the root to grow straight for the first months.

Once the germination started the seed will be pushed out from the soil. Do not remove it!!! as the plant still using the nutrients ("feeding") from it.

Seedlings care
Once the germination began, patience is needed. Araucaria species are slow growers, especially at the beginning. The young seedlings should be protected from scorching summer sun as the young spouts will be burned with low chance of recovery.
Find the spot in the shady area in your garden or under shaded canopy. Regular watering is required without excess. Some diluted fertilizer would help the plant to grow healthier.

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