Unwanted Plants

Unwanted plants that grow along with the crops are called weeds. They compete for nutrients, sunlight and water with the main crop. The process of removal of weeds is known as weeding.

However, 98 toxic plants also exist in India, Karnataka, Bangalore. These include Aloe vera, Crown of thorns, and Poinsettia. If you see any of these, be sure to keep your distance and protect your family and pets from getting poisoned.

Toxic plants

Spider Lily / Lycoris albiflora / Buttermint 

Lycoris albiflora Buttermint / Spider lily

Red Spider Lily

Spider lilies are considered mildly poisonous, so don't eat them. In Japan, where it is called “Higanbana”, the plant is used to protect the rice paddies since it is toxic to rats and other wild animals. You may find the rice patties lined with these plants creating a striking view when in bloom.

Monkshood / Wolfsbane

                         Monkshood / Wolfsbane

Caution: This plant is poisonous, but with purple flowers this lovely, it's hard to resist. Plant the perennial (also called wolfsbane) in shaded areas — and make sure you wash your hands after handling it. If you have curious kids or pets, you might want to skip this one.

Poinsettia

Poinsettia / Euphorbia pulcherrima

In warm climates the poinsettia grows outdoors as a winter-flowering leggy shrub about 3 metres (10 feet) high; as a potted plant in northern areas it rarely grows beyond 1 metre. What appear to be petals are actually coloured leaf like bracts that surround a central cluster of tiny yellow flowers. A milky latex  in the stems and leaves  can be irritating to persons or animals sensitive to it, but the claim that poinsettias are deadly poisonous is greatly exaggerated.

Jatropha jatropha

Jetropha Jatropha Flower

Jatropha Jatropha / Biofuel / Nettlespurge

Jatropha is a genus  of flowering plants in the spurge  family, Euphorbiaceae. The name is derived from the Greek  (iatros), meaning "physician", and  (trophe), meaning "nutrition", hence the common name physic nut. Another common name is nettlespurge.Most of these are native to the Americas, Plants produce separate  male and female flowers. As with many members of the family Euphorbiaceae, Jatropha contains compounds that are highly toxic. Jatropha species have traditionally been used in basketmaking, tanning and dye production. In the 2000s, one species, Jatropha curcas, generated interest as an oil crop for biodiesel production and also medicinal importance when used as lamp oil; native Mexicans in the Veracruz area developed by selective breeding a Jatropha curcas variant lacking the toxic compounds, yielding a better income when used as source for biodiesel, because of its edible byproduct. Toxicity may return if edible.

Lantana

Lantana

    

Verbena bonariensis

These tiny beauties flower profusely until the first frost, brightening beds, borders and hanging baskets even in part shade. They'll even tolerate the hot, dry summer days in the South leading up to a cooler fall.

These tiny beauties flower profusely until the first frost, brightening beds, borders and hanging baskets even in part shade. They'll even tolerate the hot, dry summer days in the South leading up to a cooler fall.

Green unripe fruits of the plant are toxic to humans. Ingestion of the flowers, fruits, and leaves can cause vomiting, diarrhoea, difficulty breathing, and liver failure, while the leaves can cause contact dermatitis.

Lantana's aromatic flower clusters (called umbels ) are a mix of red, orange, yellow, or blue and white florets. Other colors exist as new varieties are being selected. The flowers typically change color as they mature, resulting in inflorenses that are two- or three-colored.

Some species are invasive, and are considered to be noxious weeds.The spread of lantana is aided by the fact that their leaves are poisonous to most animals and thus avoided by herbivores, while their fruit is a delicacy for many birds, including the yellow fronted white eye of Vanuatu the superb fairy wren  in Australia, the scaly breasted munia, and the Mauritius bulbul in the Mascarenes; these distribute  the seeds and thereby unwittingly contribute to the degradation of their home ecosystem. 

Kalanchoe

Double white Kalanchoe

Kalanchoe all colors

Kalanchoe

Leaves are fleshy. Flowers are in pink,white, orange and yellow color. These plants are cultivated as ornamental houseplants. Kalanchoe and Euphorbia succulents are two succulents that can be toxic to humans. Still, as a general rule with all house plants, it's important to keep even non-toxic succulents out of reach of children and pets.

Euphorbia / Crown  of Thorns / Christ Thorn

Euphorbia milli

Aloe vera

Aloe vera is a succulent plant species of the genus Aloe. It is widely distributed, and is considered an invasive species in many world regions. An evergreen perennial, it originates from the Arabian Peninsula, but grows wild in tropical, semi-tropical, and arid climates around the world.

Aloe latex, however, can be dangerous. Taking aloe latex orally can lead to cramps and diarrhea, and it could make other oral medications you’re taking less effective, .

Aloe latex can lead to more serious problems, too. A dose of even just 1 gram (g) orally per day for several days could end up causing kidney damage and may even be fatal. It also can lower blood glucose levels, so people with type 2 diabetes need to be careful and talk to their doctor before incorporating aloe latex into their care regimen. Another potential negative for aloe latex: It may have cancer-promoting effects. 

Oleander (Nerium oleander) 

Oleander (Nerium oleander) is a striking evergreen shrub characterized by long, lance-shaped leaves, a resilient disposition and fragrant blooms in shades of reds, pinks, yellow and white. A native of southwestern Europe and East Asia, oleander can be found growing in sunny sites in U.S. Department of Agriculture plant hardiness zones 8 to 11. While the shrub is beautiful and sounds like a gardener's dream, it's also deadly: Ingesting a single leaf can kill an adult. Due to the plant's extreme toxicity, oleander may not be a suitable shrub for households with small children or pets, and the risk may be too great even in an adults-only home.

All parts are toxic. Oleanders contain two extremely toxic cardiac glycosides, oleandroside and nerioside. These toxic components exist in all parts of the plant, from the leaves to the branches, seeds, flowers and even the flower nectar. Toxins are effective whether the plant is fresh or dry, and honey made from the flowers is also poisonous.

Ingesting even a very small piece of the plant may be fatal. People have died from using oleander branches as skewers for meat. Also, children have been poisoned from chewing leaves and sucking nectar from blossoms. Poisoning symptoms may include severe stomach pain, diarrhea, vomiting, nausea, weakness, dizziness and irregular heartbeat. Also, pupils may appear dilated. In the worst case scenario, respiratory paralysis, coma and death occur. 

Devil's Ivy / Golden pathos

Are pathos poisonous? Pothos plants are toxic to cats and dogs4 as well as humans5, but the plant is not lethal if ingested. The roots, leaves, and stems of pothos contain insoluble calcium oxalate crystals, which can irritate the skin, mouth, and digestive tract.

Stinking Passion Flower

Passiflora foetida

 Love-in-a-mist, Bush passion fruit, Running pop, Red-fruit passionflower, Stoneflower, Fit-weed

Stinking passion flower gets its name from the unpleasant odor released from the plant’s stems and leaves. Stinking passion flower is a climbing vine with pink, lavender, or white flowers that attract bees and butterflies. In some locations, it is considered an invasive weed, although the flowers are pretty when trellised.

Invasive Species

Weeds

Olive Tree

As an invasive species

Olive Tree, An invasive weed Adelaide Hills, South Australia

Since its first domestication, O. europaea has been spreading back to the  wild from planted groves. 

In some other parts of the world where it has been introduced, most notably South Australia the olive has become a major woody weed that displaces native vegetation. In South Australia, its seeds are spread by the introduced red fox and by many bird species, including the European starling and the native emu, into woodlands, where they germinate and eventually form a dense canopy that prevents regeneration of native trees. As the climate of South Australia is very dry and bushfire prone, the oil-rich feral olive tree substantially increases the fire hazard of native sclerophyll woodlands.

Cestrum Nocturnum/ Fragrant Night Blooming Jasmine / The lady of the night/ Night scented jasmine /  night-scented cestrum or poisonberry,

Cassia spectabilis 

Leaves & Flowers

Cestrum nocturnum is an evergreen woody shrub with slender branches growing to 4 m (13 ft) tall. The plant is multi-branched and heavily foliated. The leaves are simple, narrow lanceolate, 6–20 cm (2.4–7.9 in) long and 2–4.5 cm (0.79–1.77 in) broad, smooth and glossy, with an entire margin. Towards the front they are pointed or tapered, the base is rounded or blunt. The leaf stalks are 0.8 to 2 cm long.

Inflorescences

The flowers are greenish-white, with a slender tubular corolla  2–2.5 cm (0.79–0.98 in) long with five acute lobes, 10–13 mm (0.39–0.51 in) diameter when open at night, and are produced in  cymose inflorescences . A powerful, sweet perfume is released at night. The mostly multi-flowered, drooping inflorescences panicles are terminal or axillary. They are clustered, sparsely branched panicles, on the inflorescence axes of which there are herbaceous bracts. The five sepals are fused to form a bell-shaped, approximately 2 mm long calyx and have five pointed tips, which are slightly enlarged, ribbed and acutely pointed on the fruit. The inside and outside of the calyx are finely haired.

The fruit is a white berry 10 millimetres (0.39 in) long by 5 mm (0.20 in) diameter. There is also a variety with yellowish flowers. There are mixed reports regarding the toxicity of foliage and fruit.

Cestrum nocturnum is grown in subtropical regions as an ornamental plant for its flowers that are heavily perfumed at night. 

Toxicity

Ingestion of C. nocturnum has not been well documented, but there is some reason to believe that caution is in order. All members of the family Solanaceae  contain an alkaloid toxin called solanine,  though some members of the family are routinely eaten without ill-effect. The most commonly reported problems associated with C. nocturnum are respiratory problems from the scent, and feverish symptoms following ingestion.

Some people, especially those with respiratory sensitivities or asthma, have reported difficulty breathing, irritation of the nose and throat, headache, nausea, or other symptoms when exposed to the blossom's powerful scent. Some Cestrum species contain chlorogenic acid, and the presence of this potent sensitizer may be responsible for this effect in C. nocturnum.

Some plant guides describe C. nocturnum as "toxic" and warn that ingesting plant parts, especially fruit, may result in elevated temperature, rapid pulse, excess salivation and gastritis. "Ingesting 15 lb of plant material caused a cow to salivate, clamp its jaws, collapse, and eventually die

Plant extracts have shown larvicidal activity against the mosquito Aedes aegypti while showing no toxicity to fish. Plant extracts cause hematological changes in the freshwater fish when exposed to sub lethal concentrations.

Invasive potential

Cestrum nocturnum has become widely naturalized  in tropical and subtropical regions throughout the world, including Australia, New Zealand, South Africa, southern China and the southernmost United States, and is difficult to eradicate. It is classed as a weed in some countries.

In Auckland, New Zealand, it has been reported as a seriously invasive weed

Cassia spectabilis 

  

Cassia spectabilis / Senna spectabilis/ A Weed Tree

Cassia spectabilis / Senna spectabilis

Common Name : Golden Cassia.

Origin : Central America and the Northern regions of South America 

Flowering Season : September - November.

Vernacular Name : None.

Brief Description : This is a Cassia with a spreading canopy. It is also short in stature. The large inflorescences are held above the canopy and are produced when the tree has leaves. The combination of green and yellow is quite spectacular when the tree is in bloom. All these features make it well suited for landscaping and also for planting especially in parks and gardens. 

Common Purslane

Portulaca oleracea/ Little Hogweed

Portulaca Oleracea, commonly known as Purslane or Common Purslane in English, Paruppu Keerai in Tamil and Kulfa Ka Saag in Hindi. It is an annual succulent plant in the botanical family of Portulacaceae.

In general, it is often considered an exotic weed, All parts of purslane are edible raw or cooked. The seeds can be eaten raw or used to make flour.  It has a slightly sour and salty taste and is eaten throughout much of Europe, North Africa, the Middle East, Asia,

Sphagneticola trilobata

Sphagneticola trilobata / Singapore Daisy / Creeping oxeye / Bay Biscayne/ Invasive specie

Invasive specie: Creeping Oxeye can be used as a thick, rapidly growing groundcover, but you must take great care to prevent its spread. This perennial herb is a member of the Composite flower family Asteraceae and hails from: Central America, The Caribbean, Mexico. The trailing vines of individual plants grow to be a couple of feet long.There is no limit to the potential spread of the plant. It will reproduce, grow and spread wherever there is space. Leaves are fleshy and 2” and 4” inches in length. They range from 1” inch width to 5” inches, and they have irregularly toothed margins. The foliage has rounded stems. Flowering : Bay Biscayne’s pretty, daisy-like flowers are yellowish orange and have hairy stems. There are between 8 and 13 florettes on each stem. The yellowish orange, 1” inch wide flowers grow on stems rising above the dense mat of greenery. In a tropical setting, Trilobata will bloom year-round.

This invasive plant thrives in part shade to full sun.Trailing Daisy prefers moist conditions. But, this weedy plant grows well in almost any soil.  It is not an edible plant and should not be eaten by pets, livestock or children.  It is invasive and is recognized as a weed throughout. This plant is a real threat to agricultural areas, and it spreads rapidly over disturbed ground, abandoned sites, trails, roadsides, ditches and streams. To get rid of Bay Biscayne, you must uproot it carefully and thoroughly. Be sure to remove all rhizomes and roots

Jacaranda

Introduction

Jacaranda Tree 

Bignoniaceae family

Common Names : 

Black poui, blue jacaranda, Neeli Gulmohor, Fern Tree, Exam Tree. जकरंदा 

Jacaranda trees are also called the Exam tree because it flowers during the March (exam time) 

The jacaranda tree (Jacaranda mimosifolia) is a beautiful tropical  tree that produces clusters of fragrant purple panicle-shaped blooms. Jacaranda branches are arched, forming a canopy shaped like an upturned umbrella. The jacaranda tree makes an excellent shade (or street) tree with its fern-like leaves that can grow up to 20 inches in length. It is a fast-growing tree in a tropical environment, gaining about ten feet a year in its first years of life. Its growth rate varies depending on where it's grown, slowing down to a moderate growth rate outside its ideal tropical environment.

Typically planted between fall and early spring, the jacaranda tree can be considered semi-evergreen or deciduous, depending on where it lives. Only mature jacaranda— eight years or older—will flower, blooming in late spring to early summer (though in warmer areas, the tree can flower at any time). Native to South America, it is an invasive species in several parts of the world.

Jacarandas are large growing deciduous tropical trees with asymmetric open canopies. Between April and June, mature trees explode in masses of bright violet lavender clusters flowers.

The jacaranda tree has an invasive growth habit in the tropical zones of Hawaii, Queensland, Australia, Chile’s Juan Fernandez Islands, Kenya, Tanzania, South Africa, and Zambia.

 It is deep-rooted, competes with other plant life, and few plants can grow beneath it. It can form thickets of seedlings and decrease biodiversity in an area. 

Jacaranda roots are aggressive and will crack nearby foundation.

Allergy Producing Plants / Polluting Trees

Saptaparni / Polluting Tree / Alstonia scholaris

Alstonia scholaris/ Blackboard tree/ Milkwood/Devil tree/सप्तपर्णी

Goldenrod 

Goldenrod is a striking weed-like plant that favors full sun and soil that's well drained. But beware if you suffer from allergies, as their pollen can cause a runny nose and itchy eyes.

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