Belongs within: Rosales.
Contains: Lecantheae, Urticeae, Boehmeria.
The Urticaceae, nettles and related species, are a group of herbs and shrubs (more rarely lianas or trees) found in tropical and subtropical regions. They are characterised by the production of cystoliths (calcium carbonate crystals) in the leaves. In most species, the filaments of the stamens (or staminodes) are inflexed in the bud, eventually inflating with water to force the bud open through turgor pressure, but bud filaments are erect in the southeastern Asian genus Poikilospermum. Flowers are often unisexual but may be bisexual in the herb genus Parietaria which has the flowers subtended by leaflike bracts that contrast with the chaffy brown perianth and glossy black fruits.
The Boehmerieae have been recognised as a tribe in which male flowers are 4- or 5-merous and female flowers usually have a tubular perianth more or less free from the ovary, but it is uncertain whether they represent a monophyletic group. Myriocarpa is a Neotropical genus of shrubs and small trees with long, pendulous, string-like female inflorescences. Forsskaoleae have male flowers reduced and boat-shaped with a single stamen and tepal.
Dendrocnide is a pantropical genus of trees and shrubs with soft wood and rigid stinging hairs (Harden 1990).
Nettle, where is thy sting?
Published 17 March 2008
Our subject for this page is the Urticaceae, the so-called nettle family. I say “so-called” because, as with many plant families, the supposed representative member is not necessarily that representative at all, but just happens to be the best-known temperate member of a mostly tropical family. Urticaceae includes about 2500 species in a bit under 80 genera found world-wide. Members encompass all growth habits from herbs to lianas to trees, though tree species are relatively few (depending on whether or not the tropical tree genus Cecropia is included in Urticaceae or in a family of its own). They are wind-pollinated, and like other wind-pollinated plants the flowers are quite small and reduced. The stinging hairs for which the nettles are so well-known are actually restricted to a single tribe of Urticaceae, the Urticeae (also known as Urereae—Hadiah et al. 2003), most members of which belong to one of the two large genera Urtica and Urera.
Relationship-wise, the Angiosperm Phylogeny Group classification (Angiosperm Phylogeny Group 2003) includes Urticaceae within the Rosales. However, phylogenetic analyses have established the monophyly of a smaller sub-group of the Rosales including Urticaceae, Moraceae (the mulberry and fig family), Ulmaceae (the elm family) and Cannabaceae (cannabis and hops) that corresponds to the Urticales of previous classifications (Hadiah et al. 2003). Relationships within the Urticaceae are a little more unsettled, a situation not helped by the fact that the family seems to have received relatively little monographic treatment since the work of Weddell in the mid-1800s. Monro (2006), in a molecular analysis centred on the largest genus of Urticaceae, Pilea, suggested that the five tribes originally established by Weddell fell into two clades, one containing the tribes Boehmerieae, Parietarieae and Forskohleae, and the other containing the Lecantheae and Urticeae, though the genus Myriocarpa (previously in Boehmerieae) fell into the Lecantheae-Urticeae clade. Monro (2006) also supported the inclusion of the genus Poikilospermum with the Urticaceae, specifically within the Urticeae (though Poikilospermum lacks stinging hairs). Other authors have included Poikilospermum in the Cecropiaceae, but Monro (2006) placed Cecropia distant from Poikilospermum in a trichotomy with the two Urticaceae clades (so unresolved as to whether or not it should be included within Urticaceae).
Economically, the Urticaceae are not a significant family. Species of Boehmeria, particularly B. nivea, have been used for many years as a source of the fibre known as ramie. Ramie cloth was one of the textiles used for wrapping mummies in the Egyptian pre-dynastic period, but before mechanised methods became available extraction of fibres required a laborious process of repeated soaking and scraping. Industrial-scale production of ramie did not become practical until about the mid-1900s (Cook 1984).
Some species of nettles of the genus Urtica are collected as edible herbs—the venom from the stinging hairs is destroyed by heat so cooked nettles are quite harmless. An Indian species, Urtica tuberosa, also produces edible tubers. According Botanical.com, nettles can also be used to produce a fibre in a similar manner to ramie. However, the inferiority of nettle fibre to linen resulted in the decline in its use (though it did have something of a renaissance during the height of shortages in the Second World War). For the most part, nettle stings are more of an irritant than a significant medical issue, though some species are significantly more toxic than others. The New Zealand Urtica ferox, ongaonga or tree nettle, is a shrub of up to five metres in height that produces a strong enough sting to sometimes be fatal. At least one traditional chant of the Ngati Kahungunu iwi indicates that the ongaonga, along with other spined plants, was originally planted by Kupe, the discoverer of New Zealand, to protect the new land (Cowan 1930):
Nau mai, e Tama,
Ki te tai ao nei.
Kia whakangungua koe
Ki te kahikatoa.
Ki te tumatakuru.
Ki te tara-ongaonga;
Na tairo rawa
Nahau e Kupe
I waiho i te ao nei.Thou’lt be a powerful shield against
The weapons of the world;
The sharp and deadly spears,
The pricking darts and stings
That fill the foeman’s armoury;
Thou’lt conquer e’en the barriers
Which Kupe the explorer raised
To guard this new-found land.
I haven’t been able to find anything to support the rather more dramatic version recounted in Wikipedia that claims he placed these obstacles to evade the men whose wives he had stolen, so (unfortunately) I suspect this version to be a little dubious.
Tears of a baby
Published 2 March 2021
For many people, the most familiar members of the plant family Urticaceae are the stinging nettles. However, the nettles make up only one part of this cosmopolitan family and there are many representatives that do not sting. One such plant is Soleirolia soleirolii, commonly referred to by the vernacular name of baby’s tears.
The only species of its genus, Soleirolia soleirolii is a small creeping herb with more or less succulent stems and subcircular leaves half a centimetre or less in diameter (Harden 1990). It grows in damp habitats and may even grow submerged in water. Baby’s tears form a dense flat mat with stems rooted at the nodes. The tiny white flowers reach only a millimetre in size. Wikipedia lists a number of vernacular names for this plants, such as baby’s tears, angel’s tears, Corsican creeper, or mind-your-own-business (I have no idea what this last name refers to).
In its native range, Soleirolia soleirolii is mostly restricted to islands of the western Mediterranean, including Corsica, Sardinia and Majorca, with a localised mainland population near Rome in Italy (Schüßler et al. 2019). A population was also recently discovered near the coast of Algeria (Hamel & Boulemtafes 2017). On the basis of molecular phylogenetic dating, Schüßler et al. (2019) suggested that its current range may be relictual, having gone extinct over most of mainland Europe as the climate changed. However, as those who glanced at the references for this post may have already guessed, Soleirolia has now become established in many parts of the world outside its native range. It has often been grown as a ground cover or houseplant. If it finds itself somewhere it likes, it may become invasive; though easily uprooted, its proclivity for vegetative reproduction means that it can easily return if not thoroughly cleared. And so we have a paradox, where what is regarded as a valuable relict in one location may be considered a vexatious weed in another.
Systematics of Urticaceae
Characters (from Boufford): Herbs or small shrubs (rarely lianas or trees), herbs annual or rhizomatous perennial, usually pubescent, sometimes with stinging hairs, deciduous. Leaves opposite or alternate and spirally arranged, simple; stipules present or absent; petioles present. Leaf blades paired, equal in size (except in Pilea, which may have unequally paired leaves), dotted with linear or rounded marks formed by cystoliths (variously shaped calcium carbonate crystals inside epidermal cells). Inflorescences axillary or terminal, of paniculately or racemosely arranged cymes, or spikelike. Flowers bisexual or unisexual (staminate or pistillate), staminate and pistillate flowers on same or different plants; perianth hypogynous. Staminate flowers usually pedicellate; tepals 4–5, white or green; stamens 4–5, equaling tepals in number; filaments inflexed in bud, reflexing suddenly as flowers open; anthers basifixed, dehiscing by longitudinal slits; pollen ejected explosively; pistillode 1. Pistillate flowers usually sessile; tepals 2–4, hypogynous, greenish or reddish, distinct or connate; staminodes present or absent; pistil 1, 1-locular; placentation basal; ovule1; style present or stigma sessile; stigma linear (rarely capitate); bisexual flowers: tepals 4; stamens 4; pistil 1. Fruits achenes, free or loosely or tightly surrounded by persistent, accrescent perianth.
<==Urticaceae
|--ForsskaleaAGF98 [Forsskaoleae, ForskohleaeHQC03]
| `--F. tenacissimaAGF98
|--Parietaria Linnaeus 1753A61 [ParietarieaeHQC03]
| |--P. alsinifoliaAGF98
| |--P. cardiostegiaKM08
| |--P. creticaPT98
| |--P. debilis Forster 1786 [=Urtica debilis Endl. 1833]A61
| |--P. diffusa Mertens & Koch 1823PL04
| |--P. hesperaH93
| | |--P. h. var. hesperaH93
| | `--P. h. var. californicaH93
| |--P. judaicaB00
| |--P. lusitanicaPT98
| `--P. pensylvanicaH93
`--BoehmerieaeHQC03
|--+--Myriocarpa Benth. 1846HQC03, KC01
| | `--M. longipesHQC03
| `--+--LecantheaeHQC03
| `--UrticeaeHQC03
`--BoehmeriaHQC03
Urticaceae incertae sedis:
Soleirolia soleirolii [=Helxine soleirolii]H90
Poikilospermum suaveolensT00, K03
BoehmeriopsisYY22
DroguetiaYY22
GesnouiniaYY22
HemistylisYY22
AstrothalamusYY22
NeraudiaYY22
ObetiaYY22
SarcopileaYY22
AchudemiaYY22
Chamabainia cuspidataDD73
CypholophusYY22
DebregeasiaS77
|--D. hypoleucaSS72
`--D. longifolia [incl. Trema (Parasponia) lancifolia Ridl. 1923]S77
DistemonYY22
FleuryaYY22
GirardiniaYY22
Gyrotaenia myriocarpaJ87
Hesperocnide tenellaH93
LaporteaLK14
|--L. bulbiferaT03
|--L. crenulataDD73
|--L. gigasD16
|--L. interruptaLK14
`--L. terminalisD07
LeucosykeNB03
|--L. capitellaK03
`--L. corymbulosaNB03
Maoutia australisNB03
MemorialisYY22
NanocnideYY22
PipturusNB03
|--P. argenteusNB03
`--P. repandusF37
PouzolziaB00
|--P. asperaSR07
|--P. bennettianaDD73
|--P. hispidaDD73
|--P. macruraB00
|--P. vimineaDD73
| |--P. v. var. vimineaDD73
| `--P. v. var. fulgensDD73
`--P. zeylanicaLK14
Sarchochlamys pulcherrimaBB07
SceptrocnideYY22
TouchardiaYY22
Villebrunea integrifoliaDD73
RousseliaYY22
Oreocnide integrifoliaNB03
Australina Gaud. 1826A61
`--A. pusilla Gaud. 1826A61 (see below for synonymy)
DendrocnideB00
|--D. excelsaH90
|--D. moroidesB00
|--D. peltataJG19
| |--D. p. var. peltataJG19
| `--D. p. var. murrayana (Rendle) Chew 1969 [=Laportea murrayana Rendle ex Baker 1900]JG19
`--D. photinophyllaB00
Urticicarpum scutellum Reid & Chandler 1933CBH93
ForskohleanthiumP92
Girardiana palmataSS72
ConocephalusA78
|--C. naucleiformisA78
`--C. suaveolensA78
Australina pusilla Gaud. 1826A61 [incl. A. hispidula Colenso 1886A61, A. muelleriH90, A. novae-zelandiae Hooker 1854A61, A. septemdentata Gandoger 1919A61]
*Type species of generic name indicated
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