In both D. stramonium and D. metel the plants are glabrous, hairy in D. inoxia
The deciding difference between D. metel and D. stramonium is that mature fruit of D. metel is drooping, covered with short blunt tubercles barely exceeding 3 mm; in D. stramonium mature fruit is erect covered with long spines up to 5 mm long.
In addition the following may help. Plants of D. metel are generally taller less branched and erect often reaching 1.5 m and tend to have purplish stem, in D. stramonium plants are shorter, more branched and spreading, stems not purplish.
The leaves of D. stramonium are generally parted, whereas they are not parted in D. metel 


Luckily you can distinguish them from vegetative plants and flowers also.
1. Plants glabrescent; calyx 5-angled; corolla less than 12 cm long; leaves sinnuate-dentate, anthers less than 5 mm long (capsule erect, 4-valved, with stout up to 5 mm long prickles)…D. stramonium
1a. Plants glabrescent or hairy; calyx cylindrical; corolla more than 12 cm long; leaves entire or sinuate but not
dentate, anthers longer than 1 cm (capsule deflexed, irregularly dehiscent)… 2
2. Plants gladular-pubescent, not purple; calyx 8-10 cm long; corolla 15-18 cm long, anthers 10-17 mm long (capsules deflexed, covered with slender prickles, pubescent, irregularly dehiscent)………………….D. inoxia
2a. Plants glabrescent, often purple; calyx 4-9 cm long; corolla 14-20 cm long; anthers 10-12 mm long (capsule deflexed, with short broad-based short prickles, irregularly dehiscent)……………D. metel


  

From
Floral Database of Tamilnadu
:

 

Binomial Habit               Notes References Distribution Common name
Datura
cornigera
Hook. (syn. of Brugmansia arborea (L.) Steud.)
Shrub Western Ghats,  High Altitude, Cultivated, Native of
Tropical America
Flora of Tamil Nadu, VOL. II,
1987
Nilgiri
Datura
ferox
L.
Herb Plains, Naturalized, Native of
China
Flora of Tamil Nadu, VOL. II,
1987
Coimbatore, Tirunelveli
Datura
innoxia
Mill.
Herb Plains , Naturalized, Native of
Tropical America
Flora of Tamil Nadu, VOL. II,
1987
All districts Oomatthai
Datura
metel
L.
Herb/ Under shrub Plains , Native of Tropical
America
Flora of Tamil Nadu, VOL. II,
1987
All districts Karu Oomatthai, Oomatthai
Datura
sanguinea
Ruiz & Pavon (syn. of Brugmansia sanguinea (Ruiz & Pav.) D.Don)
Shrub Western Ghats,  High Altitude, Cultivated, Native of
Tropical America
Flora of Tamil Nadu, VOL. II,
1987
Dindigul, Nilgiri
Datura
stramonium
L.
Herb/ Under shrub Western Ghats & Eastern
Ghats, Moist Deciduous Forests
Flora of Tamil Nadu, VOL. II,
1987
Coimbatore, Namakkal,  Nilgiri, Salem, Tiruvannamalai Seemai Oomatthai

 

Species with description &
pictures in Flowers of India
 as on 1.1.14:

 

Botanical name Synonyms Family Common name


































Datura ferox Solanaceae Fierce Thorn Apple
Datura innoxia Solanaceae Datura
Datura metel ‘Blackcurrant Swirl’ Solanaceae Datura Blackcurrant Swirl
Datura metel ‘Flore Pleno’ Solanaceae Datura Double Purple
Datura metel Solanaceae Datura Triple Yellow
Datura stramonium Solanaceae Jimsonweed
Datura wrightii Datura meteloides is a synonym of Datura innoxia Mill. Solanaceae Sacred Datura


  • Datura
    fastuosa L.

  • Datura
    innoxia Miller

  • Datura
    stramonium L.

  • Datura
    suaveolens
    Humb. & Bonpland ex Willd.
    (syn. of Brugmansia suaveolens (Humb. & Bonpl. ex Willd.) Bercht. & J. Presl as per GRIN & The Plant List)


     

  • Datura
    metel L.

  • Datura
    stramonium L.

  • Datura
    suaveolens
    Humb. & Bonpl. ex Willd.
    (syn. of Brugmansia suaveolens (Humb. & Bonpl. ex Willd.) Bercht. & J. Presl as per GRIN & The Plant List)


  •  
     
    Indigenous Drugs Of India By Chopra R N, I.C. Chopra (2006- Details-
     
    Medicinal Plants in Andhra Pradesh, India By T. Pullaiah (2002- Details-
     
    Datura arborea L. is a synonym of Brugmansia arborea (L.) Steud.,
    Datura sanguinea Ruiz & Pav. is a synonym of Brugmansia sanguinea (Ruiz & Pav.) D.Don &
     
    Brugmansia & Datura : 1 post by 1 author.
    I have updated efi page on Brugmansia & Datura.
    Attempts have been made to incorporate most of the species available in India & nearby areas with details & keys directly or through links.
    Any comments are welcome.


     

     
     
     
     

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