Using essential oils to control vectors, intermediate hosts, and disease-causing microorganisms is a promising approach. The genus Croton in the family Euphorbiaceae is a large genus, with many species containing large amounts of essential oils, however, essential oil studies are limited in terms of the number of Croton species investigated. In this work, the aerial parts of C. hirtus growing wild in Vietnam were collected and analyzed by gas chromatography/mass spectrometry (GC/MS). A total of 141 compounds were identified in C. hirtus essential oil, in which sesquiterpenoids dominated, comprising 95.4%, including the main components β-caryophyllene (32.8%), germacrene D (11.6%), β-elemene (9.1%), α-humulene (8.5%), and caryophyllene oxide (5.0%). The essential oil of C. hirtus showed very strong biological activities against the larvae of four mosquito species with 24 h LC50 values in the range of 15.38–78.27 μg/mL, against Physella acuta adults with a 48 h LC50 value of 10.09 μg/mL, and against ATCC microorganisms with MIC values in the range of 8–16 μg/mL. In order to provide a comparison with previous works, a literature survey on the chemical composition, mosquito larvicidal, molluscicidal, antiparasitic, and antimicrobial activities of essential oils of Croton species was conducted. Seventy-two references (seventy articles and one book) out of a total of two hundred and forty-four references related to the chemical composition and bioactivity of essential oils of Croton species were used for this paper. The essential oils of some Croton species were characterized by their phenylpropanoid compounds. The experimental results of this research and the survey of the literature showed that Croton essential oils have the potential to be used to control mosquito-borne and mollusk-borne diseases, as well as microbial infections. Research on unstudied Croton species is needed to search for species with high essential oil contents and excellent biological activities.

Aspidistra peltata, a new species morphologically allied to A. tonkinensis (= A. fungilliformis subsp. formosa; A. formosa) discovered in northern Vietnam, is described and illustrated. From the closely related A. tonkinensis, the new species differs in having an erect stem 4-14 cm tall, much smaller leaves, smaller flowers, filamentose stamens, a pure white style and an entire flat stigma with remarkably inflated margin. The new species is obviously a local endemic of the southern part of the South-Chinese floristic province but it may potentially also found in southern China.

The new species, Gastrochilus dresslerii (G. sect. Microphyllae) discovered in northern Vietnam (Ha Giang Province) is described and illustrated, and data on its phenology, ecology, and distribution is provided. Morphological resemblance of discovered plant with allied species are also discussed.

A species, new to science, is described from Son La province, Vietnam. The new species is similar to B. yongtaiense, B. layae and B. sridithii in the hairy lip at base but clearly differs by the papillose margin and inner surface of dorsal sepal and petals, lip without mid keel and dense hairs on lateral keels, stelidia 2 times longer than 3 similar species.

Mycaranthes latifolia Blume, distributed from Peninsular Malaysia, Borneo, Sumatra to Java is now reported for the first time in Vietnam. A morphological description, colour plate and line drawings, information on habitat and phenology are provided. An identification key to the species of Mycaranthes in Vietnam is also provided.