Pulau Tekukor has 151 vascular plant species from 61 families, of which 86 species are native, 44 are nonnative, and 21 are cryptogenic weeds. The native species include one presumed nationally Extinct species, 10 nationally Critically Endangered species, four nationally Endangered species, seven nationally Vulnerable species, 63 species that are not nationally threatened, and one that has not been accessed. The 5.07-ha island consists of 4.01 ha of natural vegetation and 1.06 ha of other landscape features.

St. John’s Island, officially known as Pulau Sakijang Bendera, has 258 vascular plant species from 81 families, of which 154 species are native, 76 are non-native and 28 are cryptogenic weeds. The native species include 22 nationally Critically Endangered species, 15 nationally Endangered species, 20 nationally Vulnerable species, 96 species that are not nationally threatened and one that has not yet been assessed. The 41.23-ha island consists of 13.19 ha of coastal forest, 24.98 ha of managed vegetation, 2.94 ha of built-up structures, and a small 0.12-ha water body.

Clementi Forest lies between Clementi Road and the former Keretapi Tanah Melayu (KTM) railway line on Singapore Island. We surveyed Clementi Forest by sampling five 20 × 20 m plots, and through some opportunistic exploration. Within each plot, all species of vascular plants were recorded, and the diameter at breast height (DBH) was recorded for all woody stems with a DBH ≥5 cm. A checklist of vascular plant species was compiled. Ninety-eight species of vascular plants from 54 families were recorded. Fifty-three species are native, 43 are exotic, and two are cryptogenic. One native species of note is the rediscovered terrestrial orchid, Dienia ophrydis (J. König) Seidenf., which was previously classified as presumed nationally extinct. Unsurprisingly, among the measured trees, the Pará rubber tree, Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg., was found to occur most frequently on average. The fact that exotic species comprise almost half of the recorded species can be attributed to the land use history of Clementi Forest. However, the presence of a presumed nationally extinct species and a number of nationally threatened native species suggests that this forest has value for the conservation of native biodiversity.

A checklist of vascular plant species was compiled for Punggol End Forest. This secondary forest is located on the northern end of Punggol Road on Singapore Island. It is expected to be cleared within the next 15 years to make way for housing developments. Five 20 × 20 m plots were sampled within the abandoned rubber plantation region of the forest in the year 2011, and the resultant species list was supplemented with information from other surveys conducted in the years 2010–2011. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. We recorded a total of 147 species from 58 families, of which 136 are dryland forest species, and 11 are mangrove forest species. Eighty-one of the recorded species are native, 60 are exotic, and six are cryptogenic. Among the measured trees, the Pará rubber tree, Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg., was found to occur most frequently on average. The fact that exotic species comprise almost half of the recorded species can be attributed to the land use history of Punggol End Forest.

A checklist of vascular plant species was compiled for Lentor Forest, a patch of secondary forest located at the junction of Yio Chu Kang Road and Lentor Drive on Singapore Island. In 2012, we sampled five 20 × 20 m vegetation plots within the abandoned rubber plantation region of Lentor Forest. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. The resultant species list was supplemented with information from another survey conducted in 2013. We recorded 126 species from 65 families. Eighty-four of the recorded species are native, 39 are exotic, and three are cryptogenic. Of the native species, 13 are nationally critically endangered (five of which are likely to have persisted from cultivated rather than native stock), six are nationally endangered, and 16 are nationally vulnerable. We note a new record of an exotic casual species for Singapore: Merremia vitifolia, a climber from the family Convolvulaceae. Among the measured woody stems, Hevea brasiliensis was found to occur most frequently on average

A checklist of vascular plant species was compiled for Windsor Forest, a patch of secondary regrowth forest bounded by Island Club Road, Venus Drive, Windsor Estate, and the Central Catchment Nature Reserve. We sampled five 20 × 20 m vegetation plots within the abandoned rubber plantation region of this forest. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. We conducted additional opportunistic surveys to supplement the plot data. A total of 311 species from 97 families was recorded, of which 276 are native, 30 are exotic, four are cryptogenic, and one has not yet been assessed. Of the native species, 57 are nationally critically endangered (three of which are likely to have persisted from cultivation rather than being from wild, native, genetic provenance), 49 are nationally endangered, and 75 are nationally vulnerable. Among the measured woody stems, Pará rubber (Hevea brasiliensis) was the species found to occur most frequently on average, but apart from this, all other species that were measured are native. Windsor Forest is likely important as a refuge for many nationally critically endangered species and as a buffer to the Central Catchment Nature Reserve.

A checklist of vascular plant species was compiled for Admiralty Forest, a secondary forest located at the junction of Woodlands Avenue 4 and Woodlands Avenue 9 on Singapore Island. In 2011, we sampled 10 plots of 20 × 20 m each within Admiralty Forest—five in the northern half and five in the southern half of the forest patch, which have different land use histories. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm to estimate species dominance. The resultant species list was supplemented with information from other surveys conducted in 2012. We recorded 122 species from 56 families. Eighty-six of the recorded species are native, 32 are exotic, and four are cryptogenic. Among the measured woody stems, Hevea brasiliensis was the species found to occur most frequently on average. The high native species richness of Admiralty Forest and the presence of iconic, large native trees support the conservation of Admiralty Forest in the face of proposed development.

A checklist of vascular plant species was compiled for four patches of secondary regrowth forest in the Bukit Batok urban planning area of Singapore Island. In 2012, we sampled five 20 × 20 m vegetation plots within each forest patch, and recorded all vascular plant species, as well as the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. The resultant species list was supplemented with information from other surveys conducted in 2013. We recorded 254 species from 91 families. The highest percentage of native species (79.6%) was found in Bukit Batok Hillside Park, while the highest percentage of exotic species (35.3%) was found in Bukit Batok Nature Park. The highest percentage of nationally threatened species was found in Bukit Batok Town Park, where they made up an average of 22.0% of the species in each forest patch. Among the measured stems, Pará rubber (Hevea brasiliensis) was most frequent on average, but the rest of the tree community was predominantly native. The patches of secondary forest in Bukit Batok may act as refuges for native species and have conservation value as a consequence.

A checklist of vascular plant species was compiled for Dover Forest, a secondary forest located at the junction of Clementi Road and Commonwealth Avenue West on Singapore Island. We use ―Dover Forest‖ to refer collectively to two adjacent forest patches that are separated by a mowed lawn. In the year 2011, we sampled five 20 × 20 m plots within the patch closer to Clementi Road. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. The resultant species list was supplemented with information from other surveys conducted in the years 2010–2011. We recorded a total of 136 species from 55 families. Sixty-nine of the recorded species are native, 57 are exotic, and 10 are cryptogenic. Of the native species, one was presumed nationally extinct, eight are nationally critically endangered, five are nationally endangered, and seven are nationally vulnerable. Among the measured woody stems, Dillenia suffruticosa was the species found to occur most frequently on average. The fact that exotic species comprise almost half of the recorded species can be attributed to the land use history of Dover Forest

A checklist of vascular plant species was compiled for Upper Thomson Forest, a patch of secondary regrowth forest bounded by Old Upper Thomson Road and Upper Thomson Road on Singapore Island. In 2012, we sampled five 20 × 20 m vegetation plots within the abandoned rubber plantation region of this forest. Within each plot, we recorded all vascular plant species and measured the diameter at breast height (DBH) of all woody stems with a DBH ≥5 cm. We recorded 219 species from 80 families. 146 of the recorded species are native, 68 are exotic, and five are cryptogenic. Of the native species, 20 are nationally critically endangered (of which five are likely to have persisted from cultivated rather than native stock), 15 are nationally endangered, and 31 are nationally vulnerable. Among the measured woody stems, Pará rubber, Hevea brasiliensis was found to occur most frequently on average. This site has conservation value as a native species refuge and as a buffer to the Central Catchment Nature Reserve.