Khao Yai National Park is a fertile forest with many colonies of plants, resulting in massive floral bio-diversity. There are many distinctive plant species to see on the nature trails. 

Eagle Wood, Agarwood

Scientific Name : Aquilaria crassna Pierre ex Lecomte
Family : Thymelaeaceae

An evergreen tree growing to 30m tall, having ellipsoid leaves with sparse hairs, and scented white flowers in bunches of 4-6 florets. It flowers in the hot season and fruits from May-June. The ellipsoid, almost rounded fruit are 2.5-3.5 cm long. The oil extracted from the wood of this tree is among the most expensive scented volatile oils in the world.


Where to find it:

Scattered in rain forest and mixed deciduous forest, likes to grow near water, such as on Nature Trails 1, 2 and 6.

Dipterocarpus gracilis

Scientific Name : Dipterocarpus gracilis Blume
Family : Dipterocarpaceae

A tall dipterocarp found in evergreen forest. Its tall canopy is buffeted by wind and so relies on wind for seed dispersal. Its seeds have evolved to be long and thin to spin in the wind.

Where to find it:

Evergreen dipterocarp forest and rain forest. They can be observed from any of Khao Yai’s Nature Trails.

Calamus viminalis (Willd.)

Scientific Name : Calamus viminalis Willd.
Family :  Arecaceae

A species of palm with strong spathes covered with sharp thorns. The tissue inside is soft, crispy, white and with a bitter taste. The leaves have thorns, the fruit are rounded and green at first, ripening to a yellow white with an astringent taste

Where to find it:

Dry to wet rain forest

Wild Nutmeg

Scientific Name : Knema globularia (Lam.) Warb.
Family : Myristicaceae

A hardy perennial growing to 10-25 meters tall. At the crown of this tree is a tall, rounded bush, and the bark is brown, inside pink. Young shoots, leaves and flower buds have a brown crust. The fruit are spheroid or oval and their skin has brown hair. They start as green and ripen to orange, breaking in two halves, around June to August.

Where to find it:

Rain forest

Aphanamixis polystachya (Wall.) R. Parker

Scientific Name : Aphanamixis polystachya (Wall.) R. Parker
Family : Meliaceae

Large evergreen tree with a dense crown and leaves growing in 3-7 pairs. Small round yellowish flowers and spherical fruit, which ripen into three segments with three dark-brown seeds covered with bright red flesh.

Where to find it:

Rain forest


Scientific Name : Schima wallichii (DC.) Korth.
Family : Theaceae

A tall evergreen tree standing 35 meters high, having a dense crown with single leaves in a spiral. Buds have stems and flower singly or in a group on the leaf axil. The flowers have 5 white petals and the fruit are hard.

Where to find it:

Rain forest

Magnolia baillonii (Pierre)

Scientific Name :  Magnolia baillonii Pierre
Family : Magnoliaceae

A tall 35 meters tree with ovoid leaves coming to short points with hair underneath. The white scented and curved flowers come out in bunches.

Where to find it:

Dry and montane forest to elevations of 1,300 meters.

“Wai Daeng” Renanthera coccinea Lour.

Scientific Name :  Renanthera coccinea Lour.
Family : Orchidaceae

This is an orchid growing from rock crevices and is found throughout clearings of dry forest in Khao Yai National Park, The orchids grow in profusion from the cliffs by the stream of Huay Lamtakong close to Pha Kluay Mai (“orchid cliff”) Waterfall, giving the waterfall its name.

Renanthera coccinea has long parallel stems, and is about 1.5-3 cm. wide and 7-8cm long, ending in a concave leaf. It flowers in dividing bunches. The flowers are dark red and measure 3.5cm in full bloom. The petals at the bell are small, while the end of the petal is a long and sharp protrusion.

Where to find it:

Pha Kluay Mai Waterfall

Recommended time: Flowers in the dry season around February-April

“Samek Khao” Agapetes bracteata Hook. f. ex C. B. Clarke

Scientific Name : Agapetes bracteata Hook. f. ex C. B. Clarke
Family : Ericaceae

A single-habitat plant in Thailand, it is a round bush some 2m high with hair at the end of its branches, axils, inflorescences and flower stems. Oval leaves are 5cm. The ends of the leaves are long and pointed, and inflorescences are 5-7cm long.

Where to find it:

Grows on boughs in hill evergreen forest at elevations of 1,200 meters upwards. at Khao Rom, Khao Laem and Khao Khieaw

“Moli Siam” (Reevesia pubescens var. siamensis (Craib) Anthony)

Scientific Name : Reevesia pubescens var. siamensis (Craib) Anthony
Family : Sterculiaceae

A single habitat plant in Thailand, it is a handsome plant standing 5-12 meters tall. Young leaves and flowers are covered with very fine hair. Ovoid leaves come to a point, and the bell-shaped flowers are pinkish-white with a mild scent. The fruit are oval, light green and hairy, and the flesh is hard.

Where to find it:

Around Khao Khieaw

Recommended time: While they flower all year, flowering is especially intense in the rainy season.

“Khreua Phu Ngoen” Argyreia mollis (Burm. f.) Choisy

Scientific Name : Argyreia mollis (Burm. f.) Choisy
Family : Convolvulaceae

A climber with hard stems, which can scale up to 10m. The young branches have a fine white-brown hair. The oval fruits have pointed ends. One inflorescence has 1-5 pinkish-purple flowers with a white bell. Flowers are 3.5-4 cm., and the fruits are round and orange-red.


Argyreia mollis is a plant with many herbal properties. The whole plant can be juiced to make an eye lotion to cure infection. The root can be boiled with water to make a cough medicine. The leaves can be used in a poultice to treat abscesses

ภาพโดยปรีชา การะเกตุ

Where to find it:

In young forest and scrub forest, mixed deciduous forest and alongside trails and roads in Khao Yai National Park, from the lower areas to 1,000 meters above sea level.

Recommended time: It flowers from October-December

“Euang Nam Tarn” Dendrobium heterocarpum Lindl.

Scientific Name : Dendrobium heterocarpum Lindl. 
Family : Orchidaceae 

An epiphyte orchid 15-30cm long in the shape of a spear, 1.5-2.5cm wide and 10-16cm long. It flowers in short bunches with 2-5 florets, which are 4-5cm wide in full bloom. Petals and sepals are creamy white to yellowy-brown. Petals at the mouth are yellow to dark brown with brown stripes, and the flower has an attractive scent.

Where to find it:

Rain forest at elevations above 1,000 meters

Recommended time: December-March

Nervilia khaoyaica Suddee (Watthana & S.W. Gale)

Scientific Name : Nervilia khaoyaica Suddee (Watthana & S.W. Gale)
Family : Nervilia

This is an orchid growing from the soil on the mountains at an average elevation of 733 meters and measures 9 cm. from ground to flower. It has light brown-green sepals, which can be dark brown or even red. Five petals each have a green or yellow band running down the middle surrounded by violet bands and spots. The leaves are heart-shaped and are green or purple.

ภาพถ่ายโดย ดร.วรดล แจ่มจำรูญ

Where to find it:

Scattered around the rain forest on the route to Pha Kluay Mai waterfall.

Recommended time: Flowers in April and produces leaves in March-September

Scutellaria khaoyaiensis A. J. Paton

Scientific Name : Scutellaria khaoyaiensis A. J. Paton 
Family : Lamiaceae

A newly discovered annual species, 20-40cm tall, with inflorescences appearing at the end of a shoot. Petals at the base are fused into a curved dark-blue tube. The lower petals have white spots. Oval leaves have notched edges and sharp points, and the seeds are brown.

ภาพถ่ายโดย ดร. สมราน สุดดี

Where to find it:

Around Khao Khieaw, Khao Yai National Park, on moist rocks by streams

Recommended time: October-February when it flowers and fruits.

Polypleurum ubonense

Scientific Name :  Polypleurum ubonense 
Family : Podostemaceae

This newly-reported species is a herbaceous perennial whose roots are hard plates and leaves are small and scaly. The flowers are very small, bloom singly at the end of the shoot, and have only 2 petals. It sprouts on rocks with turbulent flowing water such as streams and waterfalls, and is adapted to live underwater during the rainy season. When water levels fall it becomes visible, but is often overlooked because of its small size.

ภาพถ่ายโดย ดร. สมราน สุดดี

Where to find it:

On rocks under Lam Takhong stream leading to Pha Kluay Mai Waterfall and Hin Pherng rapids, in the Southern Area of Khao Yao National Park.

Monolophus saxicola (K. Larsen) Veldkamp & Mood

Scientific Name :  Monolophus saxicola (K. Larsen) Veldkamp & Mood 
Family : Zingiberaceae 

An annual growing on moist rock with yellow flowers

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