Introduction to the Capparaceae Family

Welcome to the Capparaceae, or caper family, named after those pungent but tasty little culinary capers! This is an interesting, mostly tropical family of trees and shrubs that are very closely related to mustards (the Brassicaceae), though you might not notice it at first glance other than them often having 4 petals, but the numerous extra-long stamens that give the flowers a delicate appearance look nothing like most members of the Brassicales order.

My only encounters with this unique family so far have been in Mexico, though it does extend north into the southern United States, especially Florida. I found the flowers fascinating with the long stamens and super long gynophore, and I also love their interesting fruits, especially those amphisarcas (see the morphology grid for what those are)!

If you’re new to plant morphology, the guide below is a perfect beginner’s description if you want to learn how to identify the caper or Capparaceae family, with no need to know any scientific jargon.

Below the guide, you’ll find morphology photos to help you identify the features of the Capparaceae family, information on uses and wildlife values, and pictures of individual Capparaceae species I have photographed in North America, organized by supertribe and tribe, so you can start to see the relationships within the family as well.

Beginner’s Guide to the Caper (Capparaceae) Family

For researchers or those wanting to learn more, further down the page is a Scientific Botanical Description and my genus-level distribution data throughout North, Central, and South America.

Leaves and Stems of the Caper Family:

The Caper family are woody trees, shrubs, or vines, rarely subshrubs (woody base only), with evergreen or deciduous leaves that are arranged alternately on the stem and are usually simple and entire, but occasionally they have compound leaves with 3 leaflets (trifoliate). Leaves may have spiny appendages (stipules) at the leaf bases, or they may be reduced to small extrafloral nectaries. Hairs are usually present and may be simple, star-shaped, T-shaped, or reduced to scales, and they rarely have glands.

Flowers of the Caper Family:

Flowers of the caper family are mostly bisexual, with both male (stamens) and female (ovary, stigma, rarely a style) parts in the same flower. Flowers are arranged in clusters or are solitary in the leaf axils, and they almost always have a characteristically long (occasionally short) stalk (gynophore) that elevates the ovary above the floral receptacle.

There is a distinct calyx and corolla. The calyx has 4 free sepals, and the corolla has 4 free petals, but rarely are there 2 or even none.

Reproductive Features of the Caper Family:

One of the most striking features of the caper family is its usually very long stamens that extend past the petals (exserted), which are often very numerous (polystemonous), giving the flowers a delicate appearance.

The ovary is almost always on a stalk (gynophore), which makes its superior placement (attached above the petal attachment) very obvious. There is usually no style, or if it is present, it is typically short (rarely long and thread-like), and the stigma usually sits on top of the elongated ovary.

Fruits of the Caper Family:

The caper family usually produces fleshy berries, but woody-shelled fruits (amphisarcas) and leathery pod-like capsules are also seen. Pod-like fruits often split apart to reveal a bright red or orange interior (pericarp) and seeds embedded in a juicy pulp (sarcotesta) or wrapped in a fleshy coat (aril), which all entice birds to eat them and spread the seeds.

Morphology of Capparaceae in North America

Some Species of Capparaceae Found in North America

There are no Capparaceae in Canada, and in the USA they are only found in the deep South, so all of my North American observations are currently from Mexico.

Crateva tapia—Toco or Beach Apple

Crateva tapia shows the less common trifoliate leaves and the large indehiscent woody-shelled fruits (amphisarcas) sometimes seen in the Capparaceae family. The woody fruits give the plant the common name “beach apple.” It is a deciduous tree with nocturnal flowers with 14-30+ stamens and a long gynophore 3.5-6 cm long. It is a common tree in the Neotropics, from Sinaloa (where this one was) and Tamaulipas, Mexico, south through Central and South America to Peru and Brazil.

Cynophalla flexuosa—Bay-Leaved Caper

Cynophalla flexuosa, sometimes under the synonym Morisonia flexuosa, is an evergreen shrub, small tree, or occasional scrambling vine with flexuous, hairless branches that often zigzag and droop. It has no spiny stipules; instead, they are reduced to tiny glands (extra-floral nectaries), and it has simple, evergreen, leathery leaves arranged in an alternate spiral on short stalks (petioles). The nocturnal hawkmoth-pollinated flowers have numerous long stamens (polystemonous), seen here in the photo, and the plant produces a fleshy, linear, pod-like capsule 10-30 cm long containing seeds encased in a white aril. This specimen was found in Mazatlán, Sinaloa, Mexico. It is native from the United States (Florida) south to Peru and northern Brazil.

Morisonia indica—White Willow or Palu Pretu

Morisonia indica, formerly Quadrella indica, is another member of the Capparaceae family that I found growing in Mazatlan, Sinaloa, Mexico, this one at Paco’s Reserva de Flora y Fauna. It is a small evergreen tree or shrub with young twigs and leaf stalks covered in star-shaped hairs, with alternate simple, leathery leaves covered in peltate scales on the lower surface. Flowers are medium-sized and fragrant, with 4 free white petals, 12-25 long stamens, and a superior ovary on a slender stalk (gynophore) 1-2.5 cm long. Fruits are linear, pod-like capsules that split open to reveal a vibrant orange or red inside fruit wall (pericarp) with seeds covered in a white aril. They are native to Mexico, Central America, the Caribbean islands, and northern South America.

Uses of the Capparaceae Family

The unopened flower buds (capers) of Capparis spinosa are pickled in salt or brine and release mustard oils that give them a sharp, pungent flavor, and some species are also used as famine foods, especially the fruits and seeds.  

Several species are used ornamentally (e.g., Morisonia (Quadrella) cynophallophora and Morisonia (Sarcotoxicum) salicifolium), and Crateva religiosa, the “Sacred Garlic Pear” or “Temple Tree,” is often planted near temples and cemeteries.

Capparis species are sometimes used for erosion and dune control, while Boscia senegalensis is sometimes used for water clarification in rural areas.

Ecosystem and Wildlife Values of the Capparaceae

The Capparaceae are mostly found in dry savannas, deserts, and seasonally dry tropical forests, where they often dominate and function as a critical ecological keystone family, providing structure, habitat, nectar, and host plant resources.

The mustard oils in the Capparaceae deter generalist herbivores, but they are critical for specialized pierid butterflies like whites, sulfurs, and orange-tips.

The delicate flowers with their often very prominent and diverse nectaries make them crucial for specialized pollinators, including bees, hawkmoths, and even bats.

Finally, animals, monkeys, and even fish (in seasonally flooded forests) sometimes eat the fruits, especially those of Capparidastrum and Neocalyptrocalyx.

Taxonomy of the Capparaceae Family

The Capparaceae family has approximately 480 species in 15-19 genera and is part of the Brassicales order of the core eudicots.

This family is another one that has gone through significant taxonomic revisions in the past two decades, which include major recircumscription of Capparis, including the removal of some New World genera formerly included there but now raised to their own genera. Additionally, several genera that were previously included, often as a tribe or subfamily, have now been removed and placed in the related Cleomaceae family after modern phylogenetics showed they are more closely related to the Brassicaceae despite their morphological similarities to the Capparaceae.

The fact that we still have several unplaced genera/species shows that the work is not yet done. I have used the most current information I have, but I will update the list as new information becomes available.

Genera of the Capparaceae Family:

The Capparaceae are a small family that is not currently divided into subfamilies or tribes.

Bachmannia (1), Beautempsia (1), Boscia (30), Buchholzia (2), Cadaba (29), Capparidastrum (4 unplaced), Capparis (148), Crateva (21), Cynophalla (1 unplaced), Hypselandra (1), Maerua (71), Mesocapparis (1 unplaced), Morisonia (86), Neocalyptrocalyx (11), Neothorelia (1), Poilanedora (1), Ritchiea (23), Steriphoma (2 unplaced), and Thilachium (16).

Key Differences From Similar Families

The Capparaceae are related to the Cleomaceae and share floral traits including a long gynophore, many stamens, and superior ovaries. However, the Cleomaceae are mostly herbs with dehiscent capsules with a replum present, rather than woody shrubs and trees with either fleshy fruits or dehiscent capsules but without a replum.

The Capparaceae is also closely related to the Brassicaceae and share the characteristic glucosinolate (mustard) oils, but they differ morphologically and ecologically. The Capparaceae are mostly tropical woody shrubs and trees without a replum in their fruits, while the Brassicaceae are mostly temperate and boreal herbs and occasional subshrubs with a replum, but true woody species are very rare.

Scientific Botanical Description of the Capparaceae Family

Habit & Leaf Form of the Capparaceae Family

The Capparaceae are woody trees, shrubs, lianas, or rarely subshrubs, and they usually lack glands and resin. They are often xerophytic but can also be mesophytic, and they may be evergreen, drought-deciduous, or brevideciduous (immediately replacing dropped leaves with new ones).

Leaves are almost always arranged in an alternate spiral, rarely in an alternate distichous arrangement, and they are petiolate (long or short) and non-sheathing. Leaves are usually simple and entire, with margins that are often involute, although some genera have compound trifoliate leaves (Crateva and Ritchiea).

Leaves sometimes have stipules that may be spiny (Capparis), or in some genera they are modified as extrafloral nectaries, which may also be present as small, sunken, or cup-shaped glands in leaf axils. The leaf lamina is dorsiventral to centric; the abaxial surface is smooth or papillose. Stomata are present and predominantly anomocytic, but anisocytic, tetracytic, or cyclocytic types also occur.

Hairs are often present and are usually simple, unicellular or multicellular, stellate, T-shaped, or peltate–scale hairs that are all mostly without glands, in contrast with the Cleomaceae’s sticky, glandular hairs.

Flowers of the Capparaceae Family

The Capparaceae are mostly hermaphroditic, occasionally andromonoecious or polygamodioecious, and rarely dioecious. Nectaries are virtually always present, often forming a hypogynous disk or discrete glands alternating with the petals, but others are seen, and these are often key diagnostic features when delineating genera and species. Pollination is mostly entomophilous (often by bees and hawkmoths), but occasionally it may be chiropterophilous or ornithophilous. 

Flowers are arranged in racemes, corymbs, or umbels or are solitary in leaf axils (or supra-axillary in vertical series). They are usually bracteate, though they are often small or caducous, and ebracteolate. Flowers are regular to somewhat irregular and are usually 4-merous. The floral receptacle develops a characteristic long (sometimes short) gynophore or, sometimes, a combined androgynophore that elevates both stamen and pistil. A hypogynous disk is present and is typically made of separate members.

The perianth has a distinct calyx and corolla, usually made of 8 parts except in apetalous members (some Old World genera); the perianth is arranged in 2-4 whorls.

The calyx is made of 4 parts in 2 whorls (2 decussate pairs) that are free or basally connate with lobes about the same length or longer than the tube that may be bilabiate or regular and are imbricate.

The corolla is made of 4 free petals that are equal or unequal and sometimes hooded; they are diagonal and in 1 whorl. But rarely 2 petals are also seen, and occasionally they are absent (apetalous). 

Androecium of the Capparaceae Family

The Capparaceae androecium is made of 4 or 6–100+ members that are occasionally isomerous with the perianth (when 4–8) but are mostly polystemonous and maturing centripetally (from the outer margin inward toward the gynophore base) via secondary polyandry rather than true branching of the stamens, as was previously thought. Members are free of the perianth, vary from markedly unequal to equal, and are usually free from one another.

Members may be all exclusively fertile stamens, or sometimes they include staminodes in the form of reduced sterile filaments. Stamens are not didynamous or tetradynamous (c.f. Brassicaceae), and they are filantherous or petaloid and filantherous. Anthers are dorsifixed (often versatile) to basifixed, tetrasporangiate, introrse, and dehiscing via full-length longitudinal slits.

Gynoecium of the Capparaceae Family

The Capparaceae gynoecium is syncarpous, superior, and elevated on a prominent thread-like or stout gynophore; it is more rarely sessile or on an androgynophore. There are usually 2 carpels, but there can be 3-8(-12) due to secondary polycarpelly.

The ovary is unilocular or pseudo-plurilocular due to deeply intruding parietal placentas or fasle septa. Placentation is parietal on 2 to several longitudinal placentas, and there is no replum (by contrast with Cleomaceae and Brassicaceae). Ovules: 10 to numerous per cavity (or 20-50 per placenta) arranged in 2 or more rows; anatropous to campylotropous, bitegmic, crassinucellate.    

The style is usually absent or obsolete, with the ovary tapering to end in a flat or capitate stigma; however, sometimes there is a very brief, thick style, and rarely the style is elongated and filiform.

Fruit of the Capparaceae Family

Capparaceae fruits are diverse, ranging from fleshy indehiscent berries (usually) and woody amphisarcas to dehiscent fleshy or leathery capsules that may split longitudinally into 2-4 valves (lacking a replum) to reveal seeds that are usually arillate or have a colorful sarcotesta. Leathery capsules also may have a red or bright orange pericarp inside that contrasts with the white arils, which help attract birds to spread the seeds. The seeds may or may not be endospermic.

Distribution of the Capparaceae Family

The Capparaceae are a pantropical family, with only a few members extending into temperate regions of the Northern and Southern hemispheres. In the Americas, they are absent in Canada and the northern USA but are then found from the southern USA south through Mexico, Central America, and most of South America.

Distribution of the Capparaceae in the Americas

Canadian Capparaceae Genera:

Absent.

USA Capparaceae Genera:

Morisonia 3 spp. inc 2 native to AZ, TX, and FL, and 1 intro to HI.

Mexico Capparaceae Genera:

Crateva 2 spp. pantropical genus native to all of Mexico; Morisonia 5 spp. native throughout all of Mexico, inc. the former Quadrella genus.

Neotropical Capparaceae Genera:

Beautempsia monospecific narrow endemic genus of Ecuador and Peru; Capparis 1 sp. introduced to Trinidad-Tobago; Capparidastrum 4 spp. currently with uncertain placement, are native to Colombia (2 endemic), Ecuador (1), and Venezuela (1); Crateva 4 spp. pantropical genus are native to CAM, the Greater Antilles (exc. Haiti and inc. 1 endemic to Cuba and the Dominican Republic), some Lesser Antilles, and tropical SAM S to Peru (1 endemic), Bolivia, and NE Argentina, exc. Uruguay; Cynophalla 1 sp. (unplaced genus), is endemic to N Brazil; Mesocapparis 1 sp. (unplaced genus) endemic to N+NE Brazil; Morisonia 86 spp. mostly neoendemics of CAM, the Antilles, the Bahamas, and SAM exc. Chile, Uruguay, also found north into Mexico and the southern USA; Neocalyptrocalyx 11 spp. N SAM endemic genus of Venezuela, Guyana, Suriname, French Guiana, N+E Brazil, and Ecuador; Steriphoma 2 spp. (unplaced genus) endemic to Colombia.

Patagonia Capparaceae Genera:

Morisonia 1 sp. neoendemic genus, might be native to northern Patagonia in S Argentina, but this is uncertain.

Additional Information and References

• Visit Lyrae’s Dictionary of Botanical Terms to learn the terminology of botanists. If you hover over most words in the articles, you can get definitions.
• Willis, Lyrae (Unpublished). Plant Families of North America. This is where all of the family descriptions come from. Below should be most of my references for this, along with my own personal observations throughout North America.
• Canadensys: Acadia University, Université de Montréal Biodiversity Centre, University of Toronto Mississauga, University of British Columbia. http://data.canadensys.net/explorer (accessed 2020 – current)
• FNA 1993+. Flora of North America. https://floranorthamerica.org/Main_Page. Accessed 2022-current.
• GBIF.org (2020+), GBIF Home Page. Available from: https://www.gbif.org
• iNaturalist.org 2020+. https://www.inaturalist.org/. Accessed 2020-current. If you like plants or nature in general, please join the iNaturalist community and start sharing your observations with others. The data we track is invaluable for scientists like me wanting to track population changes over time.
• Naturalista: CONABIO http://www.naturalista.mx (Accessed 2020–2022).
• Neotropikey: Milliken, W., Klitgård, B., & Baracat, A. eds. 2009+. Neotropikey: Interactive key and information resources for flowering plants of the Neotropics. www.kew.org/neotropikey.com (accessed 2020 – current).
• Patagonia Wildflowers: Wildflower Identification Site. https://patagoniawildflowers.org/ Accessed throughout fall 2020.
• POWO 2019+. Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet: http://www.plantsoftheworldonline.org/. Accessed 2020-current.
• Stevens, P. F. 2001+. Angiosperm Phylogeny Website. Version 14, July 2017 [more or less continuously updated since]. http://www.mobot.org/MOBOT/research/APweb/
• USDA, NRCS. 2020+. The PLANTS Database (http://plants.usda.gov, 2 June 2020). National Plant Data Team, Greensboro, NC, USA; Accessed 2020-present.
• Watson, L., and Dallwitz, M.J. (1992). The Families of Flowering Plants: descriptions, illustrations, identification, and information retrieval. Version: 2nd May 2020. delta-intkey.com. Accessed spring through fall of 2020.
• WFO (2022+): World Flora Online. Published on the Internet: http://www.worldfloraonline.org. Accessed Spring 2022 – current

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You can cite this site as Willis, Lyrae (2020+). Lyrae’s Nature Blog – Plant Families of North America. https://lyraenatureblog.com/