Pittosporum Crassifolium
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''Pittosporum crassifolium'', karo, stiffleaf cheesewood, kaikaro or kihiki is a relatively fast-growing large
shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...
or small
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...
with an erect, fastigiate
growth habit Habit, equivalent to habitus in some applications in biology, refers variously to aspects of behaviour or structure, as follows: *In zoology (particularly in ethology), ''habit'' usually refers to aspects of more or less predictable ''behaviour' ...
. It is endemic to
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
. This species is self-supporting with a simple form that can grow up to 10m tall. ''Pittosporum crassifolium'' is part of the wider
Pittosporaceae Pittosporaceae is a family of flowering plants that consists of 200–240 species of trees, shrubs, and lianas in 9 genera. Habitats range from tropical to temperate climates of the Afrotropical, Indomalayan, Oceanian, and Australasian r ...
family, which has over 160 species in the southern hemisphere.


Description

The
leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...
on this species are approximately 5-10x2-3cm and are oval shaped, dark green and leathery with grey tomentum (fine hairs) on the undersides of the leaves including the petioles and
inflorescences In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( pe ...
. This tomentum provides protection against coastal winds by preventing salt damage and moisture loss.The leaves are
simple Simple or SIMPLE may refer to: *Simplicity, the state or quality of being simple Arts and entertainment * ''Simple'' (album), by Andy Yorke, 2008, and its title track * "Simple" (Florida Georgia Line song), 2018 * "Simple", a song by John ...
and are alternately arranged and are very dense at the furthest point away from the
stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...
. The leaf
margins Margin may refer to: Physical or graphical edges *Margin (typography), the white space that surrounds the content of a page *Continental margin, the zone of the ocean floor that separates the thin oceanic crust from thick continental crust *Leaf ...
are recurved, thick and leathery (hence the name ''crassifolium'' which translates from
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
to "thick
leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
") and they often show signs of
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
damage. The
apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...
of the leaf can vary from being obtuse (blunt and rounded) to acute (sharp and tapered) The petioles are the stalk between the leaf and the
stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...
, and they measure approximately 4-14x1-3mm. When in ideal growing conditions, karo can grow into small trees (up to 5 metres (16 ft)) with multiple trunks. The
bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...
on karo is dark brown and black and has distinct lenticels which allow for breathing. Juvenile plants often appear different from the adult form as the branchlets are covered with tomentum until they mature and become darker. During the spring to early summer, karo produce fragrant burgundy red
flowers Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
that are around 10cm long with long stalks and are borne in terminal umbels meaning that they grow in clusters, similar to the shape of an umbrella. These terminals are also hairy, unlike the flowers which gives this plant extra protection from salt spray. The flowers of the karo are
unisexual Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...
, meaning each terminal produces between 5-10 male flowers and up to 5 female flowers. A distinct feature of the karo flowers is the fragrance which “pervades the evening air”. The
sepals A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...
of the flower (the green part below the flower
bud In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...
) measure approximately 7-11mm x 1.5-3mm and they have small
cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...
(hairs) and brown
tomentose Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...
along the margin. After the karo has flowered, it produces green capsules, that then develop into woody seed pods with black
seeds In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...
that are sticky and shiny and are protected inside a trigonous capsule (three angled) which measures approximately 25mm x25mm and is filled with black glutinous matter. Although
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to the upper
North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
of
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
, this species has now spread both nationally and internationally and is now considered a
weed A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...
in areas where it is non-endemic. The main way of distinguishing ''Pittosporum crassifolium'' from other native New Zealand pittosporums such as '' Pittosporum tenuifolium'' and '' Pittosporum eugenioides'' is the distinct grey tomentum on the underside of the leaves which differs from these other species. The leaves of ''Pittosporum crassifolium'' also have less undulation than these other species.


Range

Karo's original distribution was generally the top half of the
North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...
, although now it has naturalised throughout New Zealand and overseas in
Norfolk Island Norfolk Island ( , ; ) is an States and territories of Australia, external territory of Australia located in the Pacific Ocean between New Zealand and New Caledonia, directly east of Australia's Evans Head, New South Wales, Evans Head and a ...
,
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
and the
Isles of Scilly The Isles of Scilly ( ; ) are a small archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, Isles of Scilly, St Agnes, is over farther south than the most southerly point of the Great Britain, British mainla ...
. This species has been recorded on
iNaturalist iNaturalist is an American 501(c)(3) nonprofit social network of naturalists, citizen scientists, and biologists built on the concept of mapping and sharing observations of biodiversity across the globe. iNaturalist may be accessed via its web ...
in many other countries. The
Integrated Taxonomic Information System The Integrated Taxonomic Information System (ITIS) is an American partnership of federal agencies designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagenc ...
has compiled a list of these countries which includes
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
,
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
and
America The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. These areas where it has been found are all
coastal A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...
, which has allowed this species to handle the conditions due to the natural
adaptations In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...
it has. Karo is endemic to the north part of the North Island and is found from North Cape to
Poverty Bay Poverty Bay (Māori language, Māori: ''Tūranganui-a-Kiwa''), officially named Tūranganui-a-Kiwa / Poverty Bay, is the largest of several small bays on the east coast of New Zealand's North Island to the north of Hawke Bay. It stretches for ...
and in the
Kermadec Kermadec or de Kermadec may refer to: Geography * Kermadec Islands, a subtropical island arc in the South Pacific Ocean northeast of New Zealand * Kermadec Plate, a long narrow tectonic plate located west of the Kermadec Trench * Kermadec Trench, ...
and
Chatham Islands The Chatham Islands ( ; Moriori language, Moriori: , 'Misty Sun'; ) are an archipelago in the Pacific Ocean about east of New Zealand's South Island, administered as part of New Zealand, and consisting of about 10 islands within an approxima ...
. This species has naturally spread through bird dispersal throughout New Zealand and is now a reasonably common
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in the
South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...
, Chatham and Stewart Islands. Because this species wasn’t endemic to the South Island it is now considered an urban weed. It has been widely dispersed by exotic and indigenous birds.


Habitat

Karo can be found in a variety of habitats including forest margins, cliff faces, streamside and rocky areas. The tomentum on the leaf undersides allow for this species to thrive in coastal conditions because the fine hairs help reduce salt damage and prevent moisture loss. Because karo are mainly found in coastal areas and near the
sea A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...
, they have been referred to as the most tolerant species of New Zealand's tree pittosporums of coastal conditions.


Ecology


Life cycle/phenology

The karo produces dark red
flowers Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
with a fragrant smell from August to October. Towards the end of the flowering period, this species produces green capsules which develop into seedpods with black seeds within. In September, when the fruit is ripe, the capsule splits into three or four valves which have an orange colouring on the inside. These fruits are then consumed by many different species including
rats Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), '' Bandicota'' (bandicoot ...
and
possums Possum may refer to: Animals * Didelphimorphia, or (o)possums, an order of marsupials native to the Americas ** Didelphis, a genus of marsupials within Didelphimorphia *** Common opossum, native to Central and South America *** Virginia opossum, ...
. The ripe seed is on the shrub for approximately six months and ripens in winter which allows plenty of time for dispersal via birds and other animals. During spring, this species produces pale green leaves with white tomentum, which creates contrast against the old foliage with the dark leaves and red flowers.


Growth habit

Karo prefer to be planted in dry and free draining
soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
. This species is happy in sun or shade; however, the height of this species will depend on its exposure to sunlight. When planted in shade karo will stretch to try and find light; however, in a full sun position it tends to have a compacted habit. When in sun, this species can grow up to 3m tall; meaning in a more sheltered environment it can grow up to 6m tall. Although this species isn’t fussy about the soil type, if a karo is in waterlogged soil it can lose its leaves and it will become weakened. Karo are also frost sensitive whilst juvenile; however, they are able to tolerate frost and snowfalls once mature. In order for this species to thrive and have optimal plant growth and health, it should be pruned back to the
leaf node In computer science, a tree is a widely used abstract data type that represents a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be conn ...
at least once a year.


Predators, parasites and diseases

Karo is a tolerant plant that is mainly pest free. It can be susceptible to psyllids, but this only causes aesthetic damage to the plant. However, karo does attract many animals and insects that eat the leaves and fruits. The ITIS has found that some of the main predators are;
tūī The tūī (''Prosthemadera novaeseelandiae'') is a medium-sized bird native to New Zealand. It is blue, green, and bronze coloured with a distinctive white throat tuft (poi). It is an endemism, endemic passerine bird of New Zealand, and the on ...
(''Prosthemadera novaeseelandiae''),
silvereye The silvereye or wax-eye (''Zosterops lateralis''), also known by its Māori name tauhou, is a very small omnivorous passerine bird of the south-west Pacific. In Australia and New Zealand its common name is sometimes white-eye, but this name is ...
(''Zosterops lateralis''),
western honey bee The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for 'bee', and ''mellifera'' is the Latin for 'honey-bearing' or 'honey-carrying', ...
(''Apis mellifera''),
common brushtail possum The common brushtail possum (''Trichosurus vulpecula'', from the Ancient Greek, Greek for "furry tailed" and the Latin for "little fox", previously in the genus ''Phalangista'') is a nocturnal, semiarboreal marsupial of the family Phalangeridae ...
(''Trichosurus vulpecula''), black tailed bumblebee (''Bombus melanopygus'') and the
New Zealand bellbird The New Zealand bellbird (''Anthornis melanura''), also known by its Māori language names korimako, makomako and kōmako, is a medium-sized species of honeyeater Endemism in birds, endemic to New Zealand. It has been the only living member of ...
(''Anthornis melanura''). A study has also been conducted into a new
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
found on ''Pittosporum crassifolium''. This parasite was identified as ''Zeatylenchus pittosporum'' and it was identified on the species due to the distinct yellow and brown discolouration on the leaves of the karo.


Additional information

Although karo can be considered a pest, this species can be planted as a specimen tree and is also useful planted as a
hedge A hedge or hedgerow is a line of closely spaced (3 feet or closer) shrubs and sometimes trees, planted and trained to form a barrier or to mark the boundary of an area, such as between neighbouring properties. Hedges that are used to separate ...
or as a
windbreak A windbreak (shelterbelt) is a planting usually made up of one or more rows of trees or shrubs planted in such a manner as to provide shelter from the wind and to protect soil from erosion. They are commonly planted in hedgerows around the ed ...
. Karo are often mistaken for a
feijoa ''Feijoa sellowiana'' also known as ''Acca sellowiana'' (O.Berg) Burret, is a species of flowering plant in the myrtle family, Myrtaceae. It is native mainly to the highlands of Colombia, southern Brazil and the hills of northeast Uruguay, but i ...
when they are juvenile. This is because they have a very similar form when they are first putting out new growth as the plant appears almost completely grey. ''Pittosporum crassifolium'' is considered to be a "weed in cultivation" in
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, where this species is being kept under observation to ensure it does not become invasive. A study in 2021 tested ''Pittosporum crassifolium'' for
antimicrobial An antimicrobial is an agent that kills microorganisms (microbicide) or stops their growth (bacteriostatic agent). Antimicrobial medicines can be grouped according to the microorganisms they are used to treat. For example, antibiotics are used aga ...
potential and it was found that it can be used as a traditional remedy.


References


External links


Jepson Manual TreatmentPhoto gallery
{{Taxonbar, from=Q15589244 crassifolium Trees of New Zealand