Deciphering gardener's Latin

G
Gallicus = of or from 
Gaul or France
Geoides = of the earth
Glaucifolius = with leaves that are grey; grey-green
Grandiflorus = with large flowers; free-flowering
Grandifolius = with large leaves

H
Helveticus = Swiss
Herbaceous = not wood-forming; of the nature of 
an herb; dying back to 
the ground annually
Hesperus = of the West; 
of the evening
Hibernalis = 
pertaining to winter
Hortensis = belonging to 
a garden; cultivated

I
Illecebrosus = of the shade; alluring
Illustris = bright
Ingens = enormous; exceeding the expected size
Ionanthus = with violet-coloured flowers

J
Japonicus = Japanese
Jejunus = meager; small

K
Kermesinus = carmine-coloured; purplish-red
Kewensis = in honour of the Royal Botanic Gardens at Kew, England

L
Lacrimans = weeping; causing tears
Laetiflorus = bright- 
or pleasing-flowered
Leucanthus = with white flowers
Lucoris = of the woods
Luteus = yellow

M
Magnus = large
Marinus = growing by 
or in the sea
Medicus = useful as a medicine; curative
Miniatus = vermilion
Mollis = soft; flexible; mild

N
Natans = floating, swimming
Niger = black
Nitens = shining; glossy
Nivalis = snowy; white
Nocturnus = of the night

O
Occidentalis = western
Odoratus = fragrant; scented
Officinalis = medicinal; sold in shops
Oliganthus = producing few flowers
Orientalis = eastern

P
Pendulus = hanging 
down; drooping
Piceus = dark; black
Plenus = full; double
Plumosus = feathery; downy
Purpureus = purple in colour

R
Racemosus = flowers growing in racemes
Recus = straight; upright
Repens = creeping; spreading by runners
Rigens = rigid; stiff
Rubens = red; ruddy

S
Sativus = cultivated; planted deliberately
Semperflorens = 
ever-flowering
Sensibilis = sensitive
Serotinus = late; late-flowering; late-ripening
Speciosus = showy; 
good-looking

T
Tardiflorus = 
late-flowering
Tonsus = clipped; sheared
Tortilis = twisted
Toxifera = poison-producing
Trivialis = common; ordinary

U
Umbrosus = shade-loving
Undatus = wave-like; wavy
Urbanus = city-loving; urban
Ursinus = pertaining to bears; northern
Utilis = useful

V
Vernalis = of spring
Verus = true; genuine; standard
Vespertinus = of the evening; western
Viridis = green
Vulgaris = common; ordinary

X
Xanthinus = yellow
Xylocanthus = woody-spined

Read more in How to and Gardening Basics