Remember that the most beautiful things in the world are the most useless; peacocks and lilies for instance.
Many of us know that the flowering plants are divided into two groups: the dicotyledons (dicots) with two seed leaves and the monocotyledons (monocots) with a single seed leaf. The dicots tend to have net-veined leaves and four- or five-parted flowers, while the monocots generally have strap-leaves with parallel veins and three-parted flowers. Grasses, palms, gingers, lilies, orchids, and irises are all monocots. In the garden, many of the monocots we grow have traditionally been placed in the lily family (Liliaceae). The Liliaceae sensu lato (meaning “in the broad sense” and often abbreviated s.l.) includes daylilies, tulips, trilliums, greenbriars, onions, and yuccas, in addition to lilies. Needless to say, this group comprises a lot of distinctly different plants. Although easy to remember, this family is an unnatural grouping, including many plants that are only distantly related.
Botanists have long been aware that the Liliaceae s.l. is a huge, heterogeneous assemblage of plants. At one time, most insect-pollinated monocots with relatively simple flowers were combined with the lilies. Other large, unnatural plant families were divided into smaller, more natural groupings in the nineteenth century, but not so with the lily family. Monocots tend to be simpler in structure than dicots, and there is much evolutionary convergence and parallelism in the group. Most botanists agreed that the family should be split up, but no one could agree on how to do it. One approach was to place plants with inferior ovaries into a segregate group, the amaryllis family (Amaryllidaceae), but this resulted in plants as diverse as daffodils and agaves being clumped together. Obviously a better solution had to be found.
A group of scientists centered around Rolf Dahlgren looked at all monocot characters, including many obscure and/or microscopic ones, and came up with a new classification. Rolf Dahlgren, H Trevor Clifford, and Peter Yeo published this in 1985 as The Families of Monocotyledons. However, this new classification was so radical, especially in its narrow view of families within the old Liliaceae s.l., that botanists (and everyone else) were reluctant to accept it. Plants originally in that one family were distributed in forty “new” families in four orders! Most of these families had actually been named by other botanists over the last two centuries, but few of them had ever been widely recognized.
Now, more than a decade after its publication, the family groupings proposed by Dahlgren et al are being assimilated into a botanical and horticultural consensus. Botanists who study plant relationships by comparing DNA sequences in different plants have hastened this process. Not all plants have been studied yet, but the early results confirm the unnatural nature of the traditional lily family and the more appropriate groupings in The Families of Monocotyledons.
It will probably be some time before all gardening books and floras include the new families, but many technical books are already acknowledging these changes. So the curious reader can be prepared, the list of forty families formerly included in the old “garbage-can” Liliaceae is summarized in the adjoining box. (Monocots that have not traditionally been included in the lily family, such as orchids and irises, are not listed here.)
Many of these new groupings do make sense once you start thinking about it, even if the technical differences are esoteric. The following families, in particular, have characteristics that are generally easy to see.
Agavaceae: Usually massive, fleshy, succulent rosettes with fibrous leaves. The flowers are large with erect tepals and borne on tall panicles or false racemes. The seeds are black.
Alliaceae: Bulbous plants with basal leaves. The flowers have a superior ovary and are borne in a leafless umbel subtended by bracts.
Amaryllidaceae: Usually bulbous herbs with contractile roots and basal leaves. The flowers have inferior ovaries and are borne in umbels with subtending bracts.
Asphodelaceae: Small to large plants with fleshy or succulent leaves, often with tannin or mucilage cells. The seeds have an extra coat (aril).
Convallariaceae: Woodland herbs with wide leaves and small pale flowers with fused tepals borne in racemes. The fruit is a berry.
Hyacinthaceae: Bulbous herbs with basal leaves and flowers borne in racemes. Black seeds.
Liliaceae: Bulbous herbs with contractile roots and erect stems. The large flowers often have spotted or striped, free (not fused) tepals. The pale seeds are flat and stacked like coins in the dry fruit.
Nolinaceae: Woody plants with many long fibrous leaves. Flowers are creamy, small, and unisexual. They are borne in very large panicles. The dry fruit is lobed or winged.
Uvulariaceae: Woodland herbs with rhizomes bearing stems with wide leaves. The flowers have nectar glands at the base of each free (not fused) tepal and they are borne in sparse panicles.
The New Families of the Old Liliaceae
Note: Families that include commonly cultivated plants are shown in boldface, and some of the familiar genera within them are listed. Families with an asterisk are monotypic (containing only one genus).
Agave (century plant)
Cordyline (cabbage tree)
Dichelostemma (blue dicks)
Triteleia (Ithuriel’s spear)
Tulbaghia (society garlic)
Alstroemeria (Peruvian lily)
Amaryllis (naked lady)
Eucharis (Amazon lily)
Galanthus (snow drops)
Haemanthus (blood lily)
Hippeastrum (Dutch amaryllis)
Hymenocallis (Peruvian daffodil)
Lycoris (spider lily)
Pancratium (sea lily)
Sprekelia (Aztec lily)
Zephyranthes (rain lily)
Chlorophytum (spider plant)
Eremurus (foxtail lily)
Kniphofia (red hot poker)
Cordyline (cabbage tree, ti plant)
Blandfordia (Christmas bells)
Calochortus (mariposa lily, fairy lanterns)
Colchicum (meadow saffron)
Gloriosa (gloriosa lily)
Aspidistra (cast iron plant)
Liriope (lily turf)
Maianthemum (false lily-of-the-valley)
Ophiopogon (mondo grass)
Polygonatum (Solomon’s seal)
Smilacina (false Solomon’s seal)
Dracaena (dragon tree, corn plant)
Sansevieria (snake plant)
Hesperocallis (desert lily)
Bowiea (climbing onion)
Camassia (camas lily)
Eucomis (pineapple lily)
Muscari (grape hyacinth)
Urginea (sea onion)
Curculigo (palm lily)
Cardiocrinum (giant lily)
Erythronium (fawn lily)
Helonias (swamp pink)
Veratrum (false hellebore)
Beaucarnea (pony-tail palm)
Lapageria (Chilean bellflower)
Phormium (New Zealand flax)
Ruscus (butcher’s broom)
Scoliopus (fetid adder’s tongue)
Disporum (fairy bells)
Tricyrtus (toad lily)
Xanthorrhoea (Australian grass tree)