Hi, welcome to Taiga Bonzai in this article we discuss some of the many reasons why plants give the appearance of health and vitality one moment, then suddenly show signs of decline. A problem scientists and horticulturists have been trying to solve for eons.

Introduction – there are countless reasons why plants die and to attempt to explain the cause and effect would result in volumes of the written word. Therefore, we look at some of the most common and uncommon. These include the seed or plant, soil medium, water table, pests and disease.

It can be argued that seeds are delicate in their form and their is evidence to support this theory for example. In (commercially grown) vegetables and various fruit species, due to their short ‘shelf life’.

However in the main seeds collected from the wild are robust and hardy, able to withstand high and low temperatures. They can be stored in the right conditions for long periods of time; providing they have not been attacked by pests and disease.

Soil mediums – are prepared to suit the plant be it ericaceous (coniferous) or organic. (deciduous) It should be a composition with good drainage allowing the roots especially feeders to travel in search of nutrients and moisture. (see article 06 – ‘The pH factor (Part I)’ which discusses the acidity/alkaline levels for a range of plants.

A question often asked is “does the soil have to changed on a regular basis” in short the answer is no. Because a teaspoon of soil is estimated to contain up to a billion bacteria cells, that work to maintain the soil condition. Adding a small amount of fertilizer occasionally helps and the plant can survive for years in the same medium.

However, much depends on the type of plant regardless of the species. If growing from seed then the plant will require a soil medium to help the initial growth stage for example, John Innes no. 1 or similar brand.

When the plant has developed sufficiently i.e. a few pairs of true leaves it is re-planted in a soil medium that is more appropriate. This is done to slow the growth rate, otherwise the plant/s become ‘spindly’ tall, or thin. Hence, the result is usually stress and vulnerability to attack because it’s defences have yet to be developed.

Water table – in the main most trees dislike their roots soaking wet nonetheless, there are exceptions to this consensus for example, the following permanently reside in wet conditions.

Pumpkin genus Cucurbita, Ash, Fraxinus profunda Sweetbay Magnolia, Magnolia virginiana Willow, Salix Mangrove, Rhizophora mangle Bald Cypress, Taxodium distichum Water Tupelo, Nyssa aquatica River Birch, Betula nigra and Pin Oak Quercus palustris. The water pH ranges from acidic to saline and plants living in such conditions are able to thrive. Whereas other species cannot tolerate these extremes.

Rain water is always preferable, alternatively if you rely on the household tap, the water condition will depend on the supplier and the chemicals used to treat it for example. Chlorine (CI) a strong disinfectant added to drinking water as a purification technique. Moreover, tap water needs to stand for a couple of days before use.

Pests and disease – the most common of pests and disease derive from insects including: Aphids Aphidoidea, Scale Coccoidea, Mealybug Pseudococcidae, Sawfly Septentrionalis and Red spider mite Tetranychus urticae. The latter difficult to see with the naked eye as it resides in the soil, the only immediate way of detection is via the very fine webs they weave.

The above mentioned pest are just an example and can be dealt with accordingly using horticultural soap not insecticide. Unfortunately the predators that usually protect our plants are disappearing at breakneck speed due to loss of habitat caused by the idiosyncratic lust for urbanisation.

The decline – over the last few decades there has been a decline in the insect population. Disappearing are many helpful predators including, Ladybugs Coccinellidae, Green Lacewings Chrysopidae, Honey Bees genus Apis, Praying Mantis family Mantidae, Spiders family Arachnida, Ground Beetles family Carabidae, Soldier Beetles family Cantharidae, Assassin Bugs family Reduviidae and Robber Flies. Asilidae

These insects are part of the food chain they eradicate unwanted pests including aphids, scale, mealy bugs and saw fly and in turn are the main resources for many birds, small mammals, fish, reptiles and other creatures.

Moreover, they are an important key for human food production because, many crops depend on insects for pollination leading to fruit and seed production. Insects play a very important role in decomposing organic matter allowing nutrients to return to the soil. Therefore, in terms of insect ecological importance, a sharp decline in their abundance is of great concern.

The arguments – here are the points view from others whom are mindful of this issue. Will de Freitas asks if we are facing insect Armageddon he states that, “A recent study found that German nature reserves have seen a 75% reduction in flying insects over the last 27 years.”

The researchers involved made stark warnings that this indicated a wider collapse of the general insect population that would bring about an ecological catastrophe if left unchecked. (article – October 25, 2017 – The Conversation)

Damian Carrington Environment editor for ‘The Guardian’ in his article (10th February 2019) argues that “The world’s insects are hurtling down the path to extinction, threatening a catastrophic collapse of nature’s ecosystems.” “More than 40% of insect species are declining and a third are endangered. “The rate of extinction is eight times faster than that of mammals, birds and reptiles; the total mass of insects is falling by a precipitous 2.5% a year, according to the best data available.”

In the February 2020 journal ‘Biological Conservation’ no, 242 (a leading international body of scientists in the discipline of conservation science) Editor in chief Vincent Devictor of the Institut des Sciences de L’Evolution de Montpellier, France stated that.

“We are causing insect extinctions by driving habitat loss, degradation, and fragmentation, use of polluting and harmful substances, the spread of invasive species, global climate change, direct over exploitation and co-extinction of species dependent on other species.”

Devictor goes on to say that “With insect extinctions, we lose much more than species. We lose abundance and biomass of insects, diversity across space and time with consequent homogenisation, large parts of the tree of life, unique ecological functions and traits and fundamental parts of extensive networks of biotic interactions. “Such losses lead to the decline of key ecosystem services on which humanity depends.”

The blame game – these are but a few of the arguments from scientists and conservationists from the many we have researched and from these points of view, it appears we have a major situation on our hands.

There are many theories as to the decline in insect populations they include, habitat destruction by intensive farming and urbanisation, pesticide use, introduced species, climate change, eutrophication from fertilisers, pollution and artificial lighting; the latter used in huge polyethylene tunnels for intensive crop production.

Yet, despite the scientific evidence provided, globally our performance in instigating effective insect conservation is below par, we need to realise this fact and act accordingly.

This would involve more inclusive education, better decisions with land managers and government officials in maintaining unique habitats, across the globe. To have more expansive sustainable agriculture and forestry, improved regulation and prevention of environmental risks and greater recognition of protected landscapes.

Insects are a major component of the tapestry of life and failure to protect them will have dire consequences. Because without them a void will appear allowing unwanted pests to multiply to plague proportions.

As we go through our discussions on ‘Plant husbandry’, we reveal more facts that have disastrous effects on horticulture including bonsai. Until next time, BW, Nik.

Hi welcome to Taiga Bonzai, we continue our discussion albeit alphabetically through the list of shrubs and trees that have defence attributes.

Introduction – some of these defensive toxins are harmful to domestic pets and also to humans. Consuming any part the of tree/shrub can cause severe ailments for example, Rhubarb in the family Polygonaceae.

The use of rhubarb stalks as food is a relatively recent innovation first recorded in 18th to 19th-century. However, the leaves of the plant are poisonous as they contain such substances including, oxalic acid, a nephrotoxin. Yet the stalks are widely used for making pies, tarts, crumbles and in wine production.

Oak – Quercus. family Fagaceae. A deciduous and evergreen tree with a variety of species that include, white oak Quercus alba and stone oak Lithocarpus. Oak leaves and acorns are poisonous as they contain tannic acid, which can cause kidney damage, gastroenteritis and diarrhoea in livestock for example.

Sheep, goats, horses and cattle, but it has little effect on the domestic pig. It is said humans are not affected providing the tannins have been removed nonetheless, those with sensitive digestion systems should avoid consumption.

Oleander – family Apocynaceae. A small tree or shrub having approximately 400 different varieties in the genus Nerium, can be found in many temperate zones throughout the world. It is widely cultivated as an ornamental plant for parks and gardens reaching heights of 2 to 6.5m. (19ft) Although there now exist many dwarf varieties, which only grow to 26cm (10 ins) and these can be found in some bonsai collections.

Oleander when mature has grey bark, with dark green thick leaves arranged in pairs that are relatively narrow in shape. The flowers from white to pink to red are highly scented although much depends on the variety and fruit in a long pod.

These when ripe open to reveal large amounts of seed. Oleander although a very attractive plant, is considered extremely poisonous as it contains the toxins oleandrin and oleanrigenin that are referred to as cardiac glycosides.

Ingesting any part of an Oleander can cause serious gastrointestinal problems; nausea, vomiting, excess salivation, abdominal pain and diarrhoea. Other reactions to Oleander glycosides include cardiac and central nervous system effects. An irregular or erratic heart rate and drowsiness, muscle tremors, seizures and collapse that can have fatal consequences.

Olive – Olea europaea. family Oleaceae. Olive trees are not toxic and ingesting the fruit has no known side effects. However, olive tree pollen is extremely allergenic and according to the Ogren Plant Allergy Scale. A rating system for plants measuring their potential to cause allergic reactions in humans, it has a rating of 10 out of 10. As the olive tree is wind-pollinated and the pollen if inhaled, can cause headache, blocked sinuses, breathing difficulties and serious asthma attacks.

Orange jasmine – Murraya paniculata. family Rutaceae. A tropical evergreen tree or shrub from Asia is a common specimen for bonsai. It has glossy leaves and white scented fragrant flowers that can remain throughout the growing season and fruit ranging from orange to red, resembling the kumquat.

The orange jasmine has no known toxins harmful to humans, but the flowers are highly allergenic and can cause headache, blocked sinuses and breathing difficulties and in some instances severe asthma.

Plum – Prunus Spp. family Rosaceae. Is a diverse group having many species between 19 and 40 according to taxonomists. Arguably the most common plum trees used in bonsai are the European plum Prunus domestica and the Japanese plum Prunus salicina. The flowers are fragrant and vary from white to cream, to various shades of pink.

The fruits are usually globose to oval between 2cm to 6cm in size with firm flesh surrounding a hard seed pod. Plum seeds contain the toxin cyanogenic glycosides including amygdalin that decompose into a sugar molecule. Resulting in the production of Hydrogen cyanide gas, which is extremely poisonous and flammable.

Podocarpus – Podocarpus neriifolius. family Podocarpaceae. There are approximately 97 to 107 species in the genus that are related to conifers and can be found in bonsai collections. Podocarpus are evergreen with cones forming a brightly coloured fleshy, berry-like receptacles inviting birds to feed and in so doing the seeds are dispersed through their digestive tracts.

Podocarpus are also related to yews, thus their leaves, stems, bark and pollen are cytoxic. In spring and early summer, the male Podocarpus blooms and releases the cytotoxic pollen. Exposure to this can create an effect mimicking the cytotoxic side effects of chemotherapy, where blood cells or bone marrow are most at risk of developing serious infections.

Privet­ – Ligustrum vulgare, family Oleaceae. A species native to Europe, Australia, Africa and Asia is commonly used in bonsai. Species include the Japanese privet Ligustrum japonicum, Chinese privet Ligustrum quihoui, which are mainly used for ornamental plants and Ligustrum ovalfolium for hedging purposes.

The latter if managed regularly is quite decorative, but if left to its own devices will become unruly. Privet leaves and bark have bitter properties, which in China are used for making herbal teas. However, privet species that yield fruit should not be ingested as they are toxic. Symptoms include nausea, headache, abdominal pains, vomiting, diarrhoea, low blood pressure and weakness.

Quince – Cydonia oblonga family Rosaceae. Include such species as Chaenomeles japonica and Pseudocydonia sinensis that are small deciduous fruit and flowering trees. The flowers borne in clusters vary according to the species from pale pink to red and both species bear fruit in the form of a pome.

This pome is bright golden-yellow at maturity and although the fruit is edible, it is astringent and can cause a shrinking or constriction of the body tissues for example. A dry puckering of the mouth due to the tannins present. The quince has been used for both culinary and medicinal purposes. But it is poisonous as the seeds contain nitriles, that if ingested will be hydrolysed by the stomach acid producing hydrogen cyanide.

It is strange to think that many plants used for both medical and culinary purpose are quite toxic. Yet if they are prepared correctly they are made safe to consume. In the next article on this subject we continue the discussion beginning with the letter ‘R’ onwards, until next time, BW, Nik.