| 36 | Cassia sophrea L. | Ponnavarai | Caesalpiniaceae | Shrub |
| 37 | Catharanthes roseus L. | Nithyakalyani | Apocynaceae | Shrub |
| 38 | Celosia argentea L. | Kolikondai | Amaranthaceae | Herb |
| 39 | Celosia cristata L. | - | Amaranthaceae | Shrub |
| 40 | Cenchrus ciliaris L. | Kolukkaaipullu | Poaceae | Grass |
| 41 | Cerapegia juncea Roxb. |
| Asclepiadaceae | Herb |
| 42 | Cereus pterogonus Lemaire. | Otthakalli | Cactaceae | Shrub |
| 43 | Chloris barbata Sw. | Kodaipullu | Poaceae | Grass |
| 44 | Chrysopogon fulvus (Spreng.) Chiov. | Cholapullu | Poaceae | Grass |
| 45 | Cissus quadrangularis L. | Perandai | Vitaceae | Climber |
| 46 | Cleome gynandra L. | Nallavelai | Cleomaceae | Herb |
| 47 | Cleome viscosa L. | Manjakadugu | Cleomaceae | Herb |
| 48 | Clitoria ternatea L. | Karkakartum | Fabaceae | Climber |
| 49 | Coccinia grandis (L.) Voight. | Kovai | Cucurbitaceae | Climber |
| 50 | Cocculus hirsutus (L.) Diels. | Kaatukodi | Menispermaceae | Climber |
| 51 | Commelina benghalensis L. | Adutinnathalai | Commelinaceae | Herb |
| 52 | Commelina diffusa Burm.f. | - | Commelinaceae | Herb |
| 53 | Corollocarpus epigaeus (Rottl. & Willd.) Hooker. | Akashagarudan | Cucurbitaceae | Climber |
| 54 | Croton bonplandianum Bail. | Reilpoondu | Euphorbiaceae | Herb |
| 55 | Cuscuta chinensis Lam. | - | Convolvulaceae | Climber |
| 56 | Cyperus difformis L. | - | Cyperaceae | Grass |
| 57 | Dactyloctenium aegypticum (L.) Willd. | - | Poaceae | Grass |
| 58 | Dalbergia sissoo Roxb. | Sisu-itti | Fabaceae | Tree |
| 59 | Datura metal L. | Oomatha poo | Solanaceae | Shrub |
| 60 | Delonix regia (Boij. ex Hook.) Raf. | - | Caesalpiniaceae | Tree |
| 61 | Digera muricata Forssk. | Thoyyakeerai | Amaranthaceae | Herb |
| 62 | Dodonea viscosa (L.) Jacq. | Virali | Sapindaceae | Shrub |
| 63 | Ecbolium viride (Forrsk.) Alston. | Nilambari | Acanthaceae | Shrub |
| 64 | Echinocola colona (L.) Link . | Karumpullu | Poaceae | Grass |
| 65 | Eclipta prostrata (L.) L. | Kavanthkara | Asteraceae | Herb |
| 66 | Eragrostiella brachyphylla (Stapf) Bor. | - | Poaceae | Grass |
| 67 | Euphorbia hirta L. | Amampatcharisi | Euphorbiaceae | Herb |
| 68 | Euphorbia tirukalli L. | Tiru-kalli | Euphorbiaceae | Shrub |
| 69 | Euphorbia tortilis Rottl. ex Ainslie. | Thirugakalli | Euphorbiaceae | Herb |
| 70 | Euphorbia thymifolia L. | - | Euphorbiaceae | Herb |
| 71 | Evolvulus alsinoides (L.) L. | Vishnukrandi | Convolvulaceae | Climber |