1	"Plants non-twining subshrubs, erect or trailing"	2
1	"Plants twining vines, often trailing"	8
2	"Plants erect"	3
2	"Plants trailing"	5
3	"Corolla white"	"Hoya odorata"
3	"Corolla yellow"	4
4	"Corolla 18–20 mm wide"	"Hoya multiflora"
4	"Corolla 6–7 mm wide"	"Hoya cumingiana"
5	"Corolla 6–7 mm wide"	"Hoya linearis"
5	"Corolla 12–18 mm wide"	6
6	"Corolla pale green"	"Hoya serpens"
6	"Corolla cream to white"	7
7	"Leaves thin-fleshy"	"Hoya lanceolata"
7	"Leaves thick-succulent"	"Hoya bella"
8	"Leaf margin corrugated"	"Hoya caudata"
8	"Leaf margin entire"	9
9	"Corolla greater than 5 cm wide"	10
9	"Corolla less than 5 cm wide"	11
10	"Adult leaves hairless; corolla maroon to red-purple"	"Hoya macgillivrayi"
10	"Adult leaves silky-hairy; corolla white"	"Hoya magnifica"
11	"Inflorescence a positively geotropic concave umbel"	12
11	"Inflorescence a positively or negatively geotropic convex umbel"	18
12	"Corolla less than 4 mm wide"	"Hoya bilobata"
12	"Corolla more than 4 mm wide"	13
13	"Leaf blade venation prominent, with the lateral veins a different colour from the rest of the leaf"	"Hoya obscura"
13	"Leaf blade venation obscure or barely visible"	14
14	"Corolla red; corona red-yellow"	"Hoya tsangii"
14	"Corolla cream, yellow to apricot, pink-white; corona cream, yellow to apricot, pink"	15
15	"Corolla cream; corona cream"	"Hoya lacunosa"
15	"Corolla yellow to apricot or pink-white; corona yellow to apricot, or pink-white"	16
16	"Adult leaves hairless"	"Hoya micrantha"
16	"Adult leaves with soft velutinous indumentum"	17
17	"Corolla pink-white; corona pink-white"	"Hoya nummularioides"
17	"Corolla yellow to apricot; corona yellow to apricot"	"Hoya parvifolia"
18	"Leaf blade with palmate venation, with 3–7 nerves from the base"	19
18	"Leaf blade penninerved or with venation obscure"	23
19	"Leaf blade 7-nerved from base"	"Hoya samoensis"
19	"Leaf blade 3–5-nerved from base"	20
20	"Leaf blade 3-nerved from base"	21
20	"Leaf blade 5-nerved from base"	22
21	"Leaf blade venation obscure or weakly developed; corolla lobes about 5 mm long, 3–3.5 mm wide"	"Hoya parasitica"
21	"Leaf blade venation prominent; corolla lobes 6–7 mm long, 4.5–6 mm wide"	"Hoya pottsii"
22	"Corolla lobes noticeably glandular-hairy; corona purple-red"	"Hoya cinnamonifolia"
22	"Corolla lobes hairless; corona cream"	"Hoya subquintuplinervis"
23	"Leaves with irregular silver flecking in blade"	24
23	"Leaves without irregular silver flecking in blade"	26
24	"Corolla pink-purple"	"Hoya pubicalyx"
24	"Corolla white to pale pink"	25
25	"Latex clear; leaf blade with 8 or 9 lateral veins"	"Hoya motoskei"
25	"Latex white; leaf blade with 5 or 6 lateral veins"	"Hoya obovata"
26	"Latex clear"	27
26	"Latex white"	28
27	"Corolla 13–15 mm wide; lobes 4–4.5 mm wide"	"Hoya compacta"
27	"Corolla 15–18 mm wide; lobes 5–5.5 mm wide"	"Hoya carnosa"
28	"Corolla with patch of red under corona"	"Hoya australis"
28	"Corolla otherwise"	29
29	"Leaf blade with a pronounced apical notch; corolla 7–8 mm wide"	"Hoya kerrii"
29	"Leaf blade without a pronounced apical notch; corolla 10–20 mm wide"	30
30	"Leaves velvety-hairy"	"Hoya globulosa"
30	"Leaves becoming hairless"	31
31	"Leaf blade greater than 5 times long as wide"	32
31	"Leaf blade less than 5 times long as wide"	34
32	"Corona red"	"Hoya pauciflora"
32	"Corona white"	33
33	"Leaf blade incurved with age; corolla 18–20 mm wide, lobes noticeably papillose only on edges"	"Hoya shepherdii"
33	"Leaf blade remaining more or less flat with age; corolla 16–17 mm wide, lobes noticeably shaggy papillose all over"	"Hoya longifolia"
34	"Leaf blade with lateral venation obscure"	"Hoya diversifolia"
34	"Leaf blade with lateral venation discernible"	35
35	"Leaf blade with less than 5 lateral veins"	"Hoya flavida"
35	"Leaf blade with more than 7 lateral veins"	36
36	"Corolla 9–10 mm wide, pale pink"	"Hoya fraterna"
36	"Corolla 11–13 mm wide, yellow"	"Hoya polyneura"