The Olive Tree as Bonsai

HEART OF THE MEDITERRANEAN - THE OLIVE TREE

Prior to cheap airfares very few of us in Blighty would have been capable of identifying an olive tree. Today most folk with even a small interest in arboricultural matters will recount tales of being impressed by the ancient olive trees of some exotic sounding Mediterranean destination. Most garden centres now carry a large array of olive plants ranging from small chunky cuttings to massive ancient full size trees. In U.K bonsai circles good quality yamadori olive trees have been practically unobtainable until fairly recently….but who would have the heart to remove a lovely olive tree from its sun kissed home on some romantic foreign shore and bring it back to suffer the rigours of a dark wet English winter??

Silly ideals aside, it is testament to the olive's adaptability and robustness that, in spite of what you may have read, it does grow very well here assuming you start with the right variety and provide for the plant's simple needs. Before going any further please let me point out that what follows is based on my own practical experience of cultivating olive trees as bonsai in the U.K. It is nearly twenty years since I bought my first olive tree and he is still doing well in the hands of a friend of ours. I live on the Norfolk/Suffolk border just four miles from the sea. Here the weather is fairly mild. The spring time is generally a little cooler than many places but the autumn time is warmer. Winter nights are usually a few degrees warmer than further inland thanks to the warming effect of the sea. We are in what's termed a rain shadow area so the climate is perhaps a little drier than much of the U.K on average.

There is a myth in bonsai circles that olive trees are not frost hardy. This seems to be the main concern I have encountered in talking to people about this species and much of the reason for folk avoiding olives. Sadly the internet is awash with mis-information based on hearsay, conjecture and preconceptions. I have seen more than one source stating that olives are not frost hardy but do make ideal Indoor Bonsai. "Google" Olive trees and you will get about 6.6 million hits. It won't take you long to find out that these plants are indeed hardy…very hardy! 

By it's very nature the process of creating bonsai is a stressful one on any plant. A small element of stress is a good thing in life and cultivating plants in pots forces a certain level of restricted growth. Bonsai is the process and skill of directing and managing that growth and few trees lend themselves to the process better than the olive tree. From a bare stump to an exhibition quality bonsai tree in no more than ten years is a feat few other species can boast. I have achieved this feat a number of times now, we never have less than thirty olives on our nursery and all of these are continually being grown and developed as bonsai. As a result I can confidently say that what follows works!

 

Taxonomy - Olea is a genus of about 20 species in the family Oleaceae, native to warm temperate and tropical regions of southern Europe, Africa, southern Asia and Australasia. They are evergreen trees and shrubs, with small, opposite, entire leaves. The fruit is called a drupe. There are literally hundreds of cultivars of olive tree. Much like apples, trees with different fruit characteristics have been developed over hundreds of years. The species is very variable and no two trees ever seem to be quite the same. As far as bonsai is concerned we are going to encounter three main groups where the foliage is the defining characteristic.

Olea oleaster, a wild olive whose cultivar "Olivastro" is used as rootstock for O. europaea; formerly classified as the subspecies O. europaea oleaster. By far the best type for bonsai cultivation. Tiny leaves, vertical growing twigs when mature. Good examples will have spectacular bark and natural deadwood. Generally collected from the wild in costal regions. Unusually for a dwarf foliage type oleaster is extremely vigorous and forgiving. Most expensive but this is the one to buy!

Olea sylvestris, a small-fruited wild olive of the Mediterranean region. Medium size dark green shiny leaves generally more rounded than oleaster. Looser growing habit. More susceptible to fungal problems in very damp conditions than oleaster. Slower growing than oleaster but with care can produce a very impressive bonsai tree.

Olea europaea, the primary type of olive cultivated for fruit production. Most come from old olive groves. Large oblong grey leaves, very loose habit. Tolerant of most conditions. Good quality bark is rare with this type. Big cheap trees are often available in general nurseries and garden centres. In the UK this type is very poor, generally showing weak growth and susceptible to fungal problems like peacock spot and pest infestation particularly scale insect. Very hard to produce dense foliage masses without very strong sustained sunshine. Best avoided for bonsai use in the UK.

L.R - oleaster-sylvestris-europea leaf comparison.

 

Much like apples growing olive from seed will produce something of a mutt. Just because you took seed from a certain plant with characteristics you liked does not mean that will come true from the seed. The only sure way to get characteristics you like is by using one of the major methods of tissue propagation such as cuttings, layering, division, and budding/grafting. Cuttings involve rooting a severed piece of the parent plant; layering involves rooting a part of the parent and then severing it; and budding and grafting are joining two plant parts from different varieties.

Where bonsai is concerned much of the success required with olive is about selecting a good plant to start with. As a general rule the smaller the leaf the faster the growth rate and the better foliage density you will achieve. If you are starting out with an almost bare stump, good growth rate is important. If an olive has large leaves at the outset, unlike most other broad leaf varieties, it's all but impossible to reduce leaf size over time without severely impairing the growth rate and hence the development as bonsai. So selecting a good strong olive with small leaf and a dense habit at the outset will make one's life much easier in the long run. One of the great characteristics of yamadori olive is the craggy bark quality. Young olives are typically smooth and it's extremely rare that this will begin to improve, even over decades. If you want nice characterful bark buy a tree that has it already or you will be very old before a smooth bark tree starts to develop it. Obviously it goes without saying that you should buy from a reputable source where plants have been lifted with appropriate permissions and have been properly established over a minimum of two or three years prior to sale.

CULTIVATING OLIVES AS BONSAI IN THE U.K 

My experience of growing this tree over decades now has been very rewarding. Olives are a tree that really 'wants' to grow. All we have to do is create suitable conditions. In spite of the difference between it's natural habitat and the U.K it will adapt and settle into life here within a year or two. There are a few little tricks you will need to know in order to get the best from olives here and many of the techniques adopted within the olives natural range simply will not work in Blighty.

Olives & The Cold - The elephant in the room as far as olives and the UK are concerned always seems to be the issue of frost hardiness. As already stated, cold is not our worst enemy. The big problem is the combination of cold AND wet. The effects of which can be just too much for these great trees to handle. As they say 'the secret is in the soil'. Heavy wet cold soil will be the undoing of this species. Travelling across Spain, Italy and as far afield as Cyprus I have seen olives grown in a fibrous medium of peat, perlite, multi-purpose compost and the like. In these areas with scorching summer temperatures this is important. Roots in a pot above ground are subject to much higher temperatures than those planted in the ground. Olives in these areas often need to be watered several times a day to prevent excess drying out and a wet root system will be much cooler than a dry one which largely explains the success of what we in Blighty might consider a very poor quality bonsai soil. In the UK we do not see 'scorching' temperatures but we do see long, cold and miserable dark wet winters and a fibrous soil mix seems to have an ability to transfer cold into a plant with 'chilling' efficiency. Therefore in the UK we need to have an open, very free draining growing medium, summer watering is not really an issue due to an olives drought resistance. But, that free draining mix will help preserve the trees roots over winter. The drier the soil the better the cold resistance. Think of it like this....in the depths of a cold winter lay a big bath towel outside overnight on the concrete and soak it in water. In the morning lay a dry towel on the ground next to the wet one. Next stand on the wet towel in bare feet for a while before moving over to the dry one, both will be cold but which is worse? It's quite reasonable to expect an olive in dry soil to withstand overnight temperatures of minus 10-14 Celsius however an olive in wet soil will suffer badly at just minus 2 Celsius. Obviously, where sustained lows are expected pop an olive in an open, unheated greenhouse or stand it underneath the bench to afford overhead cover but do avoid dark sheds or closed areas such as garages or cloches, olives need GOOD ventilation all the time. Keeping an olive dry in winter not only helps in relation to protecting it against cold but it will also preserve that valuable craggy bark and also any significant deadwood. Trees that are overwintered in the dry will grow much more strongly in summer as the roots will emerge in the spring in significantly better condition. In summary be more concerned about the wet and less about the cold, particularly if your olive is planted in less than ideal soil.

Growing Media & Re-potting Olives as Bonsai -  As already noted, in order to be successful with olive we are going to have to structure our soil correctly and in the U.K this is going to be entirely different from what may be required in warmer climes. Over years I have experimented with everything commonly available and I DO mean everything. I know everyone in bonsai likes to do their own thing and a lot of effort is expended in constantly 'reinventing the wheel'. Save yourself the trouble, heartache and expense, what works is extremely simple and we have proven it works over literally hundreds of olives over nearly twenty years.

Olives have a relatively poor root system but whilst there may be few roots what there is are extremely efficient at doing the job. Olives produce root from just about any live tissue that touches the soil but unlike many varieties used in bonsai it's rare to see an olive in a pot bound condition. Over time the rootball may appear to become compacted but this is most likely to be because of growing media degradation as it is excess root growth. Because of this re-potting does not need to be particularly frequent. Re-potting is more likely to be needed in order to obtain a suitable growing environment for roots, removing unsuitable growing media and field soil where yamadori is concerned. However just because a soil is less than ideal does not mean we need to change it. Where a tree is in less than fighting fit condition changing soil may well cause more of a problem than we hoped it would fix. In that case much better to manage the soil carefully and leave the olive in situ until it's health improves.

Deciding WHEN to re-pot an olive is much like every other bonsai tree, it's not done based on a calendar or preferred time frame but is relative to the trees growth and health over preceding seasons. Much like all bonsai, olives look great in a small bonsai pots however a small bonsai pot is pretty much designed to slow down growth rate in order to enable creation of beautiful refinement. Putting a tree in a bonsai pot does NOT make it a bonsai tree. Olives will resent being trapped in a small pot and assuming you are in the process of developing material towards the end goal of creating a bonsai tree save the little pots for later, MUCH later. Keeping olives in larger deeper pots will significantly improve their growth rate and hence development. In large pots with more soil volume and larger root masses re-potting can often be left for five or even ten years. So long as the tree is producing good growth which shows no sign of slowing down season to season don't even consider re-potting.

If you do have to re-pot an olive the ONLY time to do this is mid-summer. I know that flies in the face of almost everything ever written about bonsai but it works. I have found olives re-potted in spring tend to produce poor subsequent growth in that year and then return to normal in the following year. Why waste a years growth? We typically choose a hot period between mid June and mid July. In the south this may need moving forward a week and in the north you might have to wait a little longer. At this time of year it's easy to dry the soil out a little which makes the task a lot easier. So long as the tree has made significant growth re-potting can be done. Don't prune growth prior to re-potting the tree needs all the leaf mass it can get. Rake out the soil but only prune roots if there are just too many to get back in the pot, as I said olives rarely produce huge masses of root. We do not wash the root system of trees any more, just work slowly and pick out the old soil with a spike. Once the tree is returned to the pot with your new growing media water thoroughly and place the tree out of the wind in FULL SUN. Expect soft shoots to wilt for a couple of days before picking up and growing away like nothing happened. Once these soft shoots pick up the tree is developing new roots and can be put back in it's normal spot. NEVER put re-potted bonsai in the shade but DO shelter from wind. Plants get the energy they need from the sun, shade will impair recovery. Incorporating Green Dream Soil Source into your growing media will significantly improve recovery after re-potting.

As to what soil, or growing media, to use the choice is fairly simple. Before getting into specifics an example of what happens when you get this wrong may be of value......

Offering picture from 2013

2017 finally back on track

 

I bought this olive in Spain in 2013. When the tree arrived it was planted in straight Akadama. Well rooted the tree had obviously been in a pot for some time and so my plan was to leave it in situ and just work with the new growth as it emerged. The following summer the tree dropped a lot of old leaf and failed to produce any significant growth. I put this down to the change of scenery, continued giving the tree the care it needed and expected things to improve the following year which they failed to do. I have had olives go to sleep like this before and don't really have an answer as to why. So by now the tree was looking a lot worse than what I had bought, with very few leaves and a lot of twig die back. By mid-summer 2016 everything was getting worse so in July I pulled the tree out of it's pot, it was planted in a very fine soft akadama which was obviously too dense and wet not to mention too acidic for good nutrient uptake. I thoroughly cleaned away this old soil. There was very little root so what there was I returned to the pot along with a mix our Medium Pumice and a tiny amount of Medium Moler. The tree was then treated exacly as detailed above. Within four weeks I had 10" of new growth. By summers end my olive had produced over two feet of new growth with profuse budding everywhere. The same growth rate continued throughout summer 2017 and now, finally, the tree is back on course. Getting an olives root system and soil right is important for success in bonsai.

Suitable growing media for olive bonsai in the UK - Any growing media should be alkaline, olives naturally grow on limestone. Large volumes of Moler / cat litter or akadama are a definite no-no. It's always important to have a clay element in any growing media in order to have a good cation exchange capacity (CEC), that is, the soils ability to bind nutrients for the plant. However too much clay means less drainage and many clay products tend to be on the acidic side, especially Japanese volcanic products. Use Moler, it's got a very high CEC and is frost proof and will not degrade over time. I have used Chipped Pine Bark in small amounts, this is good for promoting fungal and bacterial activity. By far the most important element in an olives soil composition is pumice. This has to be limestone Pumice which should be carefully graded with similar particle size throughout typically 3-8mm for smaller pots and Coarse Pumice in the 7-13mm range being ideal. Very small pots may need a slightly smaller particle size to avoid excess drying beteen watering in summer.

What we have now settled upon is - Soil fomulation for UK olive bonsai cultivation

80% graded Pumice - 10% Moler clay - 10% clean chipped pine bark. Finally add a good handfull of Green Dream Soil Source.

 

 
Our olive bonsai soil in situ.

 

Fertilisers for Olive Bonsai Trees  - There is more old cobblers talked about fertilisers or 'feeding' in bonsai circles than almost any other aspect of cultivating bonsai. The term 'feeding' is, at best, a misnomer. Created by greedy marketing men it leads us to the conclusion that a plant consumes food just like a pet would and how cruel would we be to withhold food from our pets. It also suggests that in order to grow well a plant needs plenty of food and that a plant not growing well needs a good feed. The issue is that this leads to a very serious mis-understanding of the role of fertilisers in bonsai. PLANTS DO NOT EAT FOOD. Plants are the ONLY organism on earth that makes their own food from sunlight, water and carbon dioxide. All life on earth is entirely dependant upon plants for energy. All energy on earth comes from the sun but only plants can harness that and turn it into an energy source. Oil and coal store the energy locked up by plants long ago, no plants equals no oil, no plants equals no herbivores and no Big Macs. In order to create energy from sunlight plants use carbon dioxide, water and ultra violet light to create carbohydrates. This is achieved in a little molecule we call chlorophyll, which is green and absorbs light very efficiently. Chlorophyll molecules are arranged within a photosystem whose ultimate function is charge separation, leading to biosynthesis *1. In order to maintain that structure plants need some elements they cannot manufacture in the form of elements like nitrogen, phosphorus and iron.  Where a plant is growing in a restricted soil volume some form of artificial nutrient replenishment is required in order to ensure sustained strong growth. If nutrients are restricted chlorophyll starts to lose it's green colour which typically appears as yellowing of the leaf. Chlorophyll in this state does not produce energy in an efficient way and our plant will become weak if the situation is not addressed and that's where fertiliser comes in to play.

In spite of growing on impoverished soil in the wild, olive trees in cultivation appreciate a regular programme of fertilising. If using the soil mix detailed above it's important to use some organic fertiliser both for the tree and the bacterial and fungal elements within the soil. I now no longer use chemical fertilisers on our nursery, not because of some silly notion of doing good for the environment or other PC nonsense but because I understand how a healthy rhizosphere works and whilst chemicals provide the basics of what a plant might need they do nothing for everyone else who lives there.

Forget what you may have read, fertilising bonsai trees and olives in particular is simplicity itself. You can use any high quality organic fertiliser so long as it incorporates multiple nutrient sources. A product like Rapeseed Pellets are a single source nutrient. These are good for the big numbers (N.P.K) but are light on micronutrients and these are the ones that are most often lacking in bonsai cultivation. The ONLY fertiliser product we now use on ALL of our trees from raw material to decades old bonsai trees is Green Dream Original Organic Bonsai Fertiliser. Pioneered by Colin Lewis thirty years ago this product is literally all you need and application takes just a few seconds every year. Use as instructed and don't look back.

Green Dream The ONLY fertilser you need for bonsai and (contains) NO SHIT! 

 

Maintenance of Olive Tree Bonsai - Olives grow quickly in late spring and summer, in the UK expect to see growth starting in June and ending around the end of August. Because this growth period is short it's important to make the most of it.  New growth photosynthesizes very efficiently and so excess pruning will, over time, weaken an olive. Because we have relitively little bright sunlight here it's important to allow new growth to stay on the tree as long as is possible. In a good warm summer the initial flush of growth should be allowed to extend as far as it will. A light prune in early August should then trigger a second flush assuming the weather plays ball. In a cold summer leave growth untrimmed until early September. Olives have opposite leaves, when pruning, shorten back to a suitable point with a clean cut, any strong shoot will then produce two new shoots from the base of each leaf that remains just below the cut. This way an olive will develop lots of dense twigging as each branch forks two into four into eight and so on. When pruning an olive to build ramification it is important to cut all new shoots at the same time even if that means only removing the very tip. Shoots left unpruned will continue to grow whilst pruned shoots may not extend. If you need to thicken a particular branch take advantage of this by pruning everything except the branch you need to bulk up. Don't cut anything on that branch until it is thick enough.

24" of growth in 4 weeks

Olives have stout shoots

Olive shoots divide readily after pruning

 

Olives have a very strong angular growth habit with stout small branches. In order to shape these for bonsai some degree of shaping with wire will be required. Wiring done in summer at the same time as the first prune should fix in position in just a few weeks. Olives are also very happy to be wired in early autumn after growth stops but before frost, ideally in September. Olives wired at this time of year should be fixed in position by August of the following year. Assuming you can provide winter protection in a cold greenhouse wiring up until Christmas is entirely safe.

Olives have an angular growth habit, some wiring will be required

With correct pruning olives become dense.

 

Keep the bark of olives clean, algae and moss will quickly destroy the beautiful white colour and decay craggy bark. This is a simple matter of spraying the bark, and deadwood, with Bonsai Bark Cleaner & Algae Remover, just spray and walk away. In winter keep olives dry, this will preserve the bark and deadwood quliaty indefinately and also help avoid fungal problems.

 

Keep bark and deadwood of olives clean and dry in winter.

 

Sighting of Olive Tree Bonsai - Always keep olives in full sun and a well aired or windy spot in the garden. Many folk have assumed olives need heat in order to grow but this is significantly less important than bright light. Olives will not grow well in a poly tunnel because the covering reduces light intensity. An olive placed in full sun outside will grow significantly more both in terms of extension and density than a tree placed in a poly tunnel despite the temperature difference. Olives will do very well in a glasshouse providing the glass is clean and clear. Where an olive is failing to produce good growth, bearing in mind the notes above about soil, the most likely reason is a lack of fierce sunlight and UV exposure. Olives are absolutely impervious to windy conditions in fact, it seems the more exposed they are the happier they will be. The number 1 priority for cultivating olives in the UK is SUNLIGHT, SUNLIGHT SUNLIGHT.

Pest and Disease Problems of Olive Trees - Assuming olives are kept in full sun with good air circulation and overwintered correctly it will be very unlikely that pest problems will be encountered. Because of our wet climate the most common issues are likely to be fungal. Over winter don't allow olive leaves to remain wet in an enclosed space, this is asking for trouble. At the end of September every year we put olives into their winter quarters with overhead cover. We always wash the storage area down with a solution of Jeyes fluid and before the trees are bought in the pots are cleaned, weeds pulled and any dead leaves cleaned from amongst the branches and over the soil surface. We then give the whole tree including trunk, bark, deadwood, branches and foliage a thorough wash with Rose Clear Ultra a super efficient systemic fungicide and pesticide. In late spring as the trees are returned to their summer positions we do the same. Following this course of action pretty much guarantees a P&D free season.

Peacock spot on Olea Europea.

Typically the larger the leaf an olive has the more likely it is to suffer with fungal problems. Olean Europea is particularly susceptible to Peacock Spot (Spilocaea oleaginea). Although not fatal to the tree Peacock Spot will result in an increase in leaf drop and reduced vitality. The disease is carried in rain and is easily recognisable by small dark spots with a pale ring around them on the leaves. The normal solution is to spray with a copper based fungicide but these products normal produce blue discolouration. We have found Rose Clear Ultra controls this problem cleanly and quickly. Healthy tree well sighted should not be bothered by Peacock spot. 

Sooty mildew is another fungal problem we have seen and again is easily cleared up following the described treatment above. Any fungal issue can almost always be traced back to poor sighting of the plant and insufficient air circulation and sun exposure.

As far as pests are concerned the only things we have ever encountered are scale insects and woolly aphid. Scale can be difficult to spot, these live in little brown shells and can typically be found on the underside of branches and leaves. Woolly aphid is pretty obvious and both can very easilt be eradicated using Rose Clear Ultra.

Apart from that just enjoy keeping these fascinating trees, they make beautiful bonsai trees. 

 

 

Folklore and History of Olive Trees - The olive tree has been the symbol of wisdom and peace. The olive tree was the sacred tree of goddess Athena and Athens, the capital of Greece, took its name from the goddess. Zeus had decreed that the city should be given to the god who offered the most useful gift to the people. Poseidon gave them the horse. Athena struck the bare soil with her spear and caused an olive tree to spring up. The people were so delighted with the olive that Zeus gave the city to Athena and named it after her. Athena is often shown with an olive branch, a symbol of peace and plenty.

At the Ancient Olympic Games, winners were presented with a simple olive tree branch which was cut with a gold-handled knife from a wild olive tree. The Greeks believed that the vitality of the sacred tree was transmitted to the recipient through the branch.

Olive oil is still being used for medical purposes and religious purposes and it has been proved to be an essential ingredient of a healthy diet. As a mono saturated fatty acid, olive oil does not have the same cholesterol-raising effect of saturated fats. Olive oil is also a good source of antioxidants. Olive oil, unlike seed oils, remains stable in its chemical structure at relatively high temperatures because of its antioxidant and high oleic acid content. 

  

• - First olive press in the world was found on the island of Crete around 1600 B.C.
• - Homer in the "Odyssey" refers to olive oil as "liquid gold"
• - Solon's Olive protection Law during the Athenian democracy (600 B.C.), in the first written legislation of the world, prohibited the cutting down of olive trees
• - Olympic games winners in ancient Greece were crowned with olive branches
• - Greek Orthodox rituals such as christenings & blessings use olive oil
• - In Genesis, a dove released from the Ark by Noah, returned with an olive branch to show that the flood had receded.
• - Hercules was protected by wearing a wreath of olive leaves upon his head
• - For bravery in battle, Roman soldiers were rewarded with crowns of olive
• - Nobel prize winner Greek poet Odysseas Elytis wrote "Greece is a vine, an olive tree and a boat"
• - Thomas Jefferson wrote: "The olive tree is surely the richest gift of Heaven 
• - Aldous Huxley wrote: "…I like them all, but especially the olive. For what it symbolises, first of all, peace with its leaves and joy with its golden oil."
• - Federico Garcia Lorca wrote: "Angels with long braids and hearts of olive oil."
• - Lawrence Durrell wrote in Prospero's Cell, "The entire Mediterranean seems to rise out of the sour, pungent taste of black olives between the teeth. A taste older than meat or wine, a taste as old as cold water. Only the sea itself seems as ancient a part of the region as the olive and its oil, that like no other products of nature, have shaped civilizations from remotest antiquity to the present."

   

*1 - Biosynthesis (also called anabolism) is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined together to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides.

The prerequisite elements for biosynthesis include: precursor compounds, chemical energy (e.g. ATP), and catalytic enzymes which may require coenzymes (e.g.NADH, NADPH). These elements create monomers, the building blocks for macromolecules. Some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, and DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.

Graham Potter.
© Kaizen Bonsai Ltd 12/2017