Tulips are classified into 15 tulip groups or tulip divisions. There are an enormous number of large-flowered hybrids and these are classified into 11 of these divisions, according to flowering time, plant shape, flower size and form. Species and species hybrids make up the four remaining groups.
Lets look at each group!
Division 1 - Single early tulips This tulip division flowers have rounded petals forming small deep cup-shaped single flowers, which sometimes open flat in full sun. They flower in mid spring. They grow to 25-60cm (10-24in) high Their stems are thick so they can handle the wind and rain. They are excellent used as bedding plants. Some varieties can be forced indoors.
Popular Single Early tulips are Apricot Beauty (apricot-pink), Bestseller (copper-orange), Generaal de Wet (golden-orange), and Ruby Red (scarlet).
Division 2 - Double early tulips These have large double flowers resembling peonies. They flower in mid spring and are long-lasting. They grow to 25-30cm (10-12in) high. They are good for mass bedding layouts or containers. They prefer a sheltered site.
Popular Double Early tulips are Electra (cherry-red), Mr Van de Hoef (golden-yellow), Oranje Nassau (orange-red), Peach Blossom (rose pink) and Schoonoord (white).
Division 3 - Triumph tulips These are sometimes referred to as Mid Season tulips in bulb catalogs. They have large, single, angular flowers. They flower in mid spring and are long-lasting. They grow to 40-60cm (16-24in) high. They can handle the wind and rain so can be used as bedding plants in exposed sites.
Popular varieties include Attila (violet-purple), Bellona (golden-yellow), Garden Party (white and carmine-pink), Kees Nellis (pink and yellow), White Dream (white) and Orange Bouquet (red-orange) which has several flowers on each stem.
Division 4- Darwin hybrids These have large, round brilliantly colored flowers. They flower in late spring. They grow to 55-70cm (22-28in) high on strong stems. Their colorful flowers make them ideal for the main focal point of a display.
Popular hybrids include Apeldoorn (rich red), Big Chief (pink with white), Elizabeth Arden (salmon pink), Olympic Flame (yellow and red) and Red Matador (scarlet).
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Division 5- Single late tulips These are sometimes referred to as May flowering tulips. They have squared-off, oval or egg shaped flowers. They flower in late spring. They grow to 65-80cm (26-32in) high. These are usually used in bedding or border layouts.
Popular varieties include Avignon (red), Golden Harvest (lemon yellow), Queen of Bartigons (salmon-pink), Queen of Night (maroon black) and Sorbet (white and red).
Division 6- Lily-flowered tulips These have long single flowers with pointed petals, often curving out at the tips. They flower in late spring. They grow to 50-65cm (20-26in) high.
They prefer a sunny site. Popular varieties include Aladdin (crimson and yellow), China Pink (soft pink), Maytime ((mauve lilac with white edges), Red Shine (deep red), West Point (yellow) and White Triumphator (white).
Division 7- Fringed tulips These have flowers similar to those of the Single late group but with fringed petals. They flower in late spring. They grow to 55-80cm (22-32in) high.
Popular varieties include Arma (cardinal-red), Burgundy Lace (wine-red) and Fringed Beauty (red and yellow).
Division 8 - Viridiflora They are also known as Green tulips. These are similar to the Single late tulips but the petals are partly green. The flowers appear in late spring. They grow to 23-60cm (9-24in) high.
Popular varieties include Artist (apricot-pink and green), Golden Artist (orange-yellow and green), Groenland (green-edged rose) and Spring Green (lemon-yellow and green).
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Division 9 - Rembrandt tulips These have large single flowers with petals streaked or blotched with a second color which is caused by a harmless virus. The flowers appear in late spring. They grow to 45-75cm (18-30in) high.
Among the varieties available are lnsulinde (violet and yellow), Lotty van Beuningen (lilac, purple and white) and Jack Laan (purple, yellow and white).
Division 10 - Parrot tulips These have large, often bi-colored, flowers with frilled and/or twisted petals. They flower in mid and late spring. They grow to 50-65cm (20-26in) high. Their stems are often too weak to support the large unsheltered flowers and so staking is sometimes necessary.
They prefer a sheltered position Popular varieties include Black Parrot (purple-black), Fantasy (pink), Flaming Parrot (yellow flamed red) and White Parrot (white).
Division 11 - Double late tulips These are sometimes called Peony-flowered tulips, They have large showy flowers, resembling peonies. They flower in late spring. The plants grow to 40-60cm) (16-24in) high. They prefer a sheltered position.
Popular hybrids include Angelique (pale pink), Gold Medal (golden-yellow) and Mount Tacoma (white).
Division 12 - Kaufmanniana hybrids These are also known as Waterlily tulips. They have long, often bi colored, flowers. They flower in early spring. They grow to 10-25cm (4-10in) high, These tulips are ideal for rock gardens, containers, or along the edges of orders.
Popular hybrids include Hearts Delight (carmine-red, white and yellow), Johann Strauss (red and white) and The First (white tinted carmine-red).
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Division 13- Fosteriana hybrids These have large, long flowers. They flower in mid spring. They grow to 20-40cm (8-16in) high. Their brilliant eye-catching colors make them good for focal planting.
Popular hybrids include Cantata (deep scarlet), Orange Emperor (pure orange), Rockery Beauty (orange-red) and Purissima (white-yellow).
Division 14- Greigii hybrids These have lovely colorful flowers with maroon or purple-brown veined or spotted foliage. They flower in early to mid spring. They grow to 23-50cm (9-20in) high. As most are short, they look best in rockeries and containers. Popular hybrids include Cape Cod (bronze-yellow and apricot), Dreamboat (amber yellow), Plaisir (creamy white with red stripes), Red Riding Hood (carmine red) and Toronto (salmon-orange).
Division 15- Species tulips The flowers of this final tulip division tend to be smaller and more delicate in form than the garden tulips. They are ranging from 7.5-45cm (3-18in) in height. Those listed below are the most readily available species, though others are sometimes sold by specialist bulb growers.
Tulipa clusiana (known as the lady tulip) The clusiana cynthia has red pointed petals flushed yellow with grey-green leaves that are upright and very narrow. They flower in mid spring. The plants grow to 23-30cm (9-12in) high.
Tulipa praestans The praestans Bloemenlust has long red flowers with blunt petals. Each stem has between two and five flowers accompanied by broad grey-green leaves. They flower in early and mid spring. The plants grow to 30-45cm (12-18in) high.
Tulipa tarda The tarda has white narrow petaled flowers with a yellow eye, with up to five flowers on each stem. The narrow mid-green leaves form a rosette at flowering time. They flower in early spring. They grow to 10cm (4in) high.
You can find more detailed information about tulip divisions at
http://www.elegant-tulip-bulbs.com/tulip-divisions.html
