10.3: Recent introduced plants
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Plants introduced to Hawai‘i after 1778 (post European contact) are known as recent introductions. Starting in the 1800s, different crops were brought in and tested to determine the viability of growing them in the Islands (Table 10.4.1). For example, pineapple and coffee were introduced to the Islands in 1813. Coffee became one of the most important crops, along with pineapple and sugarcane. Although sugarcane was introduced to Hawai‘i by Polynesians before European contact, the first variety for commercial production ('Lāhainā') was introduced in 1854 to Maui (Lincoln, 2017). Pineapples were tested in 1885 in Mānoa, O‘ahu; the starting point for commercial production. Rice was first introduced in 1858. Later trials were conducted to see if it could be grown commercially, and it soon became one of the most commonly grown crops in the 19th century (HDOA, 1998). Today, rice is no longer grown commercially in Hawai‘i, but it is still part of the diet.
| Crop name | Species | Year Introduced |
|---|---|---|
| Orange | Citrus × sinensis | 1792 |
| Coffee | Coffea spp. | 1813 |
| Pineapple | Ananas comosus | 1813 |
| Mango | Mangifera indica | 1824 |
| 'Lāhainā' sugarcane | Saccharum spp. | 1854* |
| Eucalyptus | Eucalyptus spp. | 1870 |
| Macadamia | Macadamia spp. | 1881 |
| Rice | Oryza sativa | 1858 |
| ‘Solo’ Papaya | Carica papaya | 1911 |
| Seed corn (commercial) | Zea mays | 1966 |
Pineapple and sugarcane production drove the plantation era (1850-1980s) in Hawai‘i with many immigrant groups coming to the Islands for work. People from different cultures who arrived brought with them their own staples, and these crops were frequently incorporated into the plants that are grown and consumed in Hawai‘i today (Figure \(\PageIndex{1}\)).
Plantation agriculture changed the way land and water were managed, used, and controlled, and had negative impacts on traditional agriculture (Figure \(\PageIndex{2}\)). Starting with plantations, water was taken from the windward side of islands to the leeward sides to irrigate sugar and pineapple fields, negatively impacting kalo production. Today, plantations have mostly disappeared from Hawai‘i, and seed crops such as corn, as well as diversified agriculture have taken hold (Perroy et al., 2016).
The horticultural trade also brought many ornamental plants to Hawai‘i over the past century. For example, plumeria (Plumeria spp.) and monkeypod (Samanea saman) are introductions from Latin America (Figure \(\PageIndex{3}\)). These plants have become part of life in Hawai‘i since they are abundant in gardens and lowland areas where people live. Many of these introduced species remain in cultivation and do not naturalize (grow and reproduce in wild spaces without human assistance). For example, plumerias do not produce seedlings that can grow without human help. They need to be propagated by cuttings. However, many other horticultural species have become naturalized and have become invasive.
Although some Polynesian introduced plants escaped cultivation and have become naturalized (e.g. kukui), most naturalized species are plants introduced after 1778. The invasive species we have in the Islands are mostly recent introductions. These have escaped cultivation and naturalized in wild habitats. Some of the names used for this group of recent introductions are exotics, aliens, and weeds. There are hundreds of naturalized species in Hawai‘i, and many have negative impacts on native ecosystems. For example, strawberry guava (Psidium cattleianum), from South America, grows in such thick stands that they overcrowd native species, eventually killing them (Figure \(\PageIndex{4}\)).
Another example of an invasive species in Hawai‘i is fountain grass (Pennisetum setaceum) which is native to Africa and southeast Asia. Fountain grass dominates the understory of native dryland forests and competes with native trees. It also creates a fire risk in an environment that did not evolve with the frequent wildfires we see today (Cordell and Sandquist, 2008). On O‘ahu, for example, the introduction of fire-prone grasses has created problems not only to native ecosystems, but also to communities on the west (leeward) side of the Islands. Fires have become far more common in the past decades, and increasingly cause damage to houses and businesses. The fires open dry lowlands to the invasive koa haole (Leucaena leucocephala), from Central America, which, along with fire prone grasses, dominates these areas (Figure \(\PageIndex{5}\)).
The introduction of numerous invasive plant and animal species, along with other factors, has resulted in the decrease of native species, to the point where a significant number of them have become endangered. Hawai‘i has more endangered species (species that have a higher risk of extinction) per square meter than any other place on Earth, and this is linked to habitat loss and invasive species (Czech et al., 2000). Invasive species displace natives species, and a plant community dominated by non-native species does not function the same way as a native-dominated community (Kagawa et al., 2009). For example, water gets absorbed into the soil way less in non-native forests compared to native forests, and during big rain events the water runs towards the ocean instead of recharging the aquifer. This has a direct impact not only on the environment, but on the quality of life for humans as well since we all need freshwater.
Learning about the plants in Hawai‘i can not only be interesting, but it connects us to our environment, to cultural practices, and to food security. We depend on plants for survival in many ways, and plants bring beauty to our lives. Plants bring us together around the table for a good meal, while helping us celebrate cultural traditions through food recipes and as part of life rituals.