Article 74 – ‘Quarantine!’

Hi welcome to Taiga Bonzai, today’s post was intended to be a discussion on the infamous Tanuki design. This will be postponed till a later date as the question of quarantine is more appropriate given the time of year when bonsai enthusiasts are looking to add to their collection/s albeit purchased from a nursery, the wild, by air layering, cuttings or grown from seed.

Introduction – is quarantine really necessary, is it just a myth an urban legend – a supposed truth which is actually spurious or a superstition. From the knowledge gained via continuous research in horticulture, we have found that there is a need for plant isolation. Why is this – with spring now upon us growth is rapidly returning above and below the soil line and there are measures that have to be taken to ensure the health and vitality of the plant.

Soil microbiology – all soil mediums regardless of their origin contain bacteria, a teaspoon of productive soil can contain between 100 million and 1 billion bacteria. Some of these bacteria are beneficial including Bacillus, Arthrobacter, Pseudomonas, Agrobacterium, Alcaligenes, Clostridium, Flavobacterium, Corynebacterium, Micrococcus, Xanthomonas and Mycobacterium. But also within the soil structure are viruses which are obligate parasites of bacteria that can destroy a plant’s cellular structure often causing disease resulting in a plants demise.

For example, plant parasitic nematodes also known as eelworms a diverse animal phylum inhabiting a broad range of environments. Taxonomically, they are classified along with insects and other moulting animals in the clade Ecdysozoa and unlike flatworms, have tubular digestive systems with openings at both ends. The following image shows one of the most destructive of these worm-like creatures of which there are many.

Caenorhabditis elegans nematode. Credit Wikipedia

Foliage infestation – there are many pests and disease that attack plant foliage, some are visible to the naked eye but there are many that are too small to see. Nursery plants are notorious for harbouring pests and disease and should be inspected thoroughly prior to purchase. Arguably the question is how does this infestation spread? – In short it is via cross contamination, because the vendor has not taken the necessary precautions to prevent this.

For example, a shipment from mainland Europe to Scandinavia is being fulfilled and depending on the order, the vehicle will probably have more that one stop before the consignment is complete. The plants many different varieties tightly packed on moveable racks floor to ceiling remain in the dark till the load is full, then the journey commences till the destination is reached. It is during this time period when foliage of different plants brush together and contamination begins due to the vehicle’s movement moreover, pests have ample time to roam around moving from plant to plant feeding, laying eggs and spreading pathogens.

We know this to be fact because we were victims of vendor’s sub-standard attention to detail. A few years ago we purchased some Japanese maples including one that was infected with red spider mite Tetranychus urticae. Although the plant was inspected prior to purchase there was no visible sign of the insect on the foliage, the only other possibility is that it was hidden in the soil medium as they are apt to do. It has taken years to eradicate this pest, but due to its resilience it can hide undetected, until the time is right for them to reemerge and continue their destruction. Red spider mites are about 0.5 mm (about 0.02 inch) in length, hence they are difficult to see.

Red spider mite Tetranychus urticae

Taking into consideration what has been discussed thus far, there is no way of knowing what is concealed within the soil, in most cases the composition will be fine; but there is always the possibility that it is not. Indication that problems are looming is when the plant emits signs of ill health, via fungal infection which can include, mildew, rust, blackspot and other forms of blight; these can be treated by using synthetic fungicides. Pests including Scale, Sawfly, Pine knot-horn larva, Mealybugs, Carpenter Ants and Red spider mite will attack causing irreparable damage.

Collecting from the wild – can be enjoyable to some extent, but it is also hard work because much depends on the terrain for example. Derelict building sites if left untouched contain a multitude of species both coniferous and deciduous, these grow in cavities within the walls and in cracked concrete floors. Such places are considered hazardous especially if the structure’s stability is not known, hence when excavating plants one has to be extremely careful in order not to cause unnecessary damage.

If taken from the forest, the area around the plant has to be investigated to ascertain the size of the root spread which can vary considerably depending on the terrain. Should the area be strewn with rocks chances are that the roots will have developed under them in their search for nutrients and because of this, the plant cannot be harvested; which often the case. In this situation discretion is the better part of valour, replace the soil and tidy up the area giving the impression that it has not been disturbed.

Plants harvested from the wild are usually the best option because you know from whence they came, their health condition and surrounding soil medium which should be pH tested. In this case quarantine is not mandatory but advisable, because the plant needs a favourable location to recover from its ordeal. Conifers take longer to recover opposed to deciduous. For more information on this topic see Article 12 ‘Selecting material for bonsai part II’.

Air layering – is a simple but efficient way to clone one plant from its parent, plants use DNA in much the same way that other living beings including humans do. The cells in the clone contain a copy of the donor’s genome, that is translated into proteins and enzymes, which make the biochemistry creating more cells and growth. The cloned plant having a healthy root ball, can be removed from the donor, but should be potted in the same soil type as the parent plant; this ensures the continuity of nutrient supply. Cloned plants do not require quarantine, but isolation is advisable in order for them to develop.

Cuttings – usually from deciduous species can be dipped into rooting hormone powder and planted in a seed compost medium, alternatively they can be placed in a jar of water which after a few weeks will develop roots systems. The cuttings should be placed in reasonably sized pots to encourage further root development and isolated until they are established. Two good examples that are relatively easy to grow are the Ficus ginseng and the Sea buckthorn ‎Hippophae rhamnoides that are quite resilient and vigorous in their growth.

Seeds – are an inexpensive way of producing plants, but not all will germinate because (a) they have not gone through the stratification process and (b) they are sterile. An interesting experiment on testing a seed’s ability to germinate is via store purchased fruit, most varieties including plum, damson, peach, pear and apple seeds require stratification otherwise germination will not take place. Alternatively, mango, pomegranate and citrus varieties will germinate without the need for stratification and can develop into healthy plants. However, these varieties are temperate and cannot tolerate low temperatures in addition, their defence systems are rather poor when attacked by pests and disease. For more information on this topic see Article 12 ‘Selecting material for bonsai part I’ and Article 21 – ‘The Stratification of seeds’

In addition, Information on pests and disease can be found by referring to articles 20 ‘Pests and Diseases‘, ‘Unseen enemies’ series articles 62 to 66 and 56 ‘Bug apocalypse’.

Arguably purchasing plants from nurseries does reduce the time frame to some degree when trying to produce a potential bonsai specimen because they are established and can be shaped accordingly. Nonetheless, being aware of the factors involved that we have described can eradicate unwanted problems regardless of the species one opts for. ‘But what if a plant is inspected to the best of our ability only to find out later that there is an infection – what kind of redress is there?

Unfortunately not a lot, because of the following factors (a) you have removed the plant from the vendor’s premises, (b) it could be argued that cross contamination has occured from one of your other plants, (c) the plant has not been given the proper location as stated on the label i.e. full sun, part sun and shade or shade. Moreover, if the plant develops chlorosis (yellowing of the leaves) or wilt these are signs of overwatering or lack thereof therefore, your viewpoint although justified cannot be proven. A sympathetic vendor may give you a replacement plant if the discussion is amenable but that is the sum total.

If you are contemplating a purchase from a garden centre, nursery or department store make sure to be thorough in your inspection, it is also advisable to wear rubber gloves especially when handling such specimens as, Water Hemlock Cicuta maculata, Oleander Nerium oleander, Yew Taxus baccata and Box Buxus as all are extremely toxic. It is your responsibility to ascertain the plants welfare and condition – if in any doubt walk away. This discussion has given clear reason why the need for quarantine is justified; until next time, BW, Nik.

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