BANKSIA INTEGRIFOLIA AS BONSAI
Posted: February 25th, 2009, 8:56 am
Original article written Nov 2005
INTRODUCTION
There are currently 76 known species of Banksia in Australia, most of which are found in Western Australia.16 species grow on the east coast only of Australia and it is from these Banksia that I have drawn my experiences. All Western Australian species have died in my local environment within a short time, even those grafted on east coast understock. I have, however, seen some Western Australian Banksia growing quite happily in Canberra, so it will come down to your own local environment.
Banksia are related to the Protea family of Africa, with which they have many similarities. Banksia are an evergreen tree or shrub, although some prostrate species and cultivars occur as well. They can be a large, single trunk tree with an irregular outline or have a shrubby, multi trunk appearance. The leaves come in a large variety of shapes and sizes and the growth habits are also very varied. Flowers are also variable but are usually numerous on a spike that becomes woody. The flowers set at the end of new growth and take some time to mature. Not all the flowers become seed as there are just too many on each spike.
Some 36 species are fire-tolerant; having thick bark and/or a woody base or lignotuber. These Banksia can take heavy pruning quite well. The fire-sensitive Banksia are thin barked and do not sprout back easily or at all. They respond to light but frequent trimming but not heavy pruning.
The continent of Australia is very old and the soils are very thin and poor in nutrients. The Banksia have evolved over 100 million years to be able to cope quite well with the poor or sandy soils of Australia.
HINTS FOR GROWING NURSERY STOCK
First try whichever Banksia already grow in or near your area, and remember that the larger growing, tree type Banksia will probably be the best for Bonsai. Some of these will have large leaves (up to 6"/150mm) and be quite vigorous growers but with the correct techniques the leaf size can be reduced dramatically.
I have grown Banksia ericifolia (Heath Banksia), B. paludosa (Swamp Banksia), B. marginata (Silver Banksia), B. serrata (Old Man Banksia), and B. integrifolia (Coast Banksia). I hope to try others as well but so far my favorites are Banksia serrata and Banksia integrifolia.
Banksia can be easily grown from seed or cuttings but must be potted up and on quickly; always pot up to the next size and do not over pot! The potting mix should be neither too fine nor too coarse but above all should freely drain. The roots of Banksia are very fine and will fill the pot quickly; in summer you will need to water more often than most other plants in pots.
You can pot up to the next size pot every year while growing the tree on. I use the recommended dose of Native or Standard Osmocote in the potting mix and liquid feed every week or two (except winter) with a mild liquid fertilizer like Maxicrop, Nitrosol, or Charlie Carp etc.
USE FERTILIZERS AT FULL RECOMMENDED STRENGTH UNLESS PLANTS ARE SICK OR NEW TO YOUR COLLECTION!!!
I believe it is better to have healthy, vigorous plants and then deal with the resultant growth in the shaping process, rather than having weak, sickly plants that have been dwarfed by starvation. If you choose to follow a higher fertilizing regime than you have been using or I am recommending you should build up to it gradually.
Banksias are both hungry and thirsty in pots so please give them what they need and they will repay you with many years of pleasure.
DO NOT POT-ON A BANKSIA AT ANY STAGE IF IT IS WEAK, SKINNY OR WOBBLY.
If it is weak or scrawny looking just give it a light trim and put it back; if it is wobbly you should investigate the soil for Curl Grubs. If you find the roots have been severely eaten by the grubs then you give it a hard root prune and put it back in a similar size pot and lightly trim the foliage.
I AVOID POTTING BANKSIA IN WINTER!
Banksia need to be grown in full sun, so except for immediately after repotting I keep my nursery stock and Bonsai in as full sun and wind as they can take. Growing in full sun gives you a healthier, more disease and pest free tree. It also keeps the foliage more compact. Do not sit a Banksia in water unless you are trying to grow on a tree very quickly, and definitely never in winter. Banksia can suffer from root rot so I try to keep the foliage as full as possible to keep sucking the water out of the pot and thereby keeping the roots on the dry side.
If you repot in winter or don’t leave enough foliage on the tree over winter you may encourage root rot, the tree sort of drowns in the excess soil and water.
BANKSIA AS BONSAI
B. marginata, B. serrata and B. integrifolia all make good Bonsai, but my experiences with B. integrifolia are the most extensive and it is my personal favorite.
Banksia integrifolia, the Coast Banksia, grows in many locations in the wild, from the most exposed, windswept coastal headland where it may grow flat against a cliff or it may be a 25 mtr high tree growing in snowy conditions in the mountains.
Its leaves are large, long and smooth edged, but as a Bonsai the leaves can be small, blunt and toothed. This is because the constant trimming causes the tree to put out a juvenile form of leaf that is most suitable for Bonsai. The leaf is still strong and vigorous and not deformed or delicate in any way.
The frequent potting, fertilizing and trimming gives us a very quick growing, thick trunked tree that buds back on old wood very well.
If you live in Sydney or further north, you may be able to pot-on nursery stock every six months or so to achieve quick growth. If you live in Canberra or cold areas of Victoria or N.S.W, you may need to allow more time in each size pot, say twelve months. Pot in early summer to avoid excessive new growth on the tree going into winter; soft new foliage can be badly damaged by frost and lead to problems with die-back etc.
My reason for avoiding potting in winter or early spring is that the tree just sits and sulks until the warmer weather arrives; there is no advantage in potting early. In fact by sitting in a larger pot in wet conditions for 3-6 months you may encourage root rot, die back or excessive new growth when it is too cold.
Some Australian Natives will grow at any time of year if the conditions are right, but in pots you may accidentally trigger growth at the wrong time of year.
As a Bonsai the B. integrifolia is also very quick growing and is usually my ‘waterweed’. That is, it is usually the first tree to droop if it is in fresh growth.
I usually repot my Banksia Bonsai about every 12-18 months. I wait until the tree shows me that it has used up all its store of fertilizer and fresh potting mix and is not growing as vigorously as it was. I don’t wait until it is absolutely exhausted nor so pot bound that water has trouble penetrating. Letting a Banksia become root bound will introduce you to an interesting aspect of the Banksia; and that is Proteoid Roots.
Proteoid roots are the trees natural response to a lack of nutrients. It puts out a set of roots that are very fine and are able to scavenge very small amounts of food etc from the soil or potting mix. If there is suddenly an abundance of nutrients the tree can take up too much and suffer badly or even die. The Banksia don’t have a feedback mechanism to stop it from taking up too much food, so if you have a tree that is rootbound or very hungry then you must fertilize lightly to start with and then build up to a normal fertilizing regime.
If, when you are repotting you see Proteoid Roots, you can just cut off those roots with no adverse effects for the tree. Proteoid Roots look like the Mycorrhizae you may see on the root system of pines, that is a fine web-like white patch.
As I said I repot about every 12-18 months but I don’t do a heavy repot and trim each time. I will just do a Slip Pot into a larger pot .This involves just a very light root prune or even just a teasing out of the roots and a light tip prune of the foliage. This allows the tree to grow at a good rate in the pot and not slow it down. If you have a tree that is hard to keep the water up to and it is mid summer then the Slip Potting technique is the one to use.
After using the Slip pot technique a few times in a row you can then do a normal repot. With the Banksia I suggest that you repot in early summer using the following sequence. It doesn’t matter if the tree is actively growing because I trim the tree to the shape I want and then leave the tree to start forming its new buds for a week or two. I then give the roots a hard root prune and put it into a smaller pot.
The following years I go back to the Slip pot method. Each time I repot using either method I put Native or Standard Osmocote into the Potting Mix at the suggested rate and continue to fertilize also with Maxicrop or equivalent at the suggested rate.
STYLING A BANKSIA. TO WIRE OR NOT TO WIRE.
Once you come to style your Banksia you must decide on a shaping method. You can just ‘Clip and Grow’ or apply some wire.
Clip and Grow with Banksia is very similar to deciduous trees; just cut back either to a small branch growing in the direction you want and then let it grow and thicken and then repeat the process; or cut right back very hard to a point on the bare trunk and wait for new growth to emerge. As in the case of root pruning you only cut back hard in the warmer months!
Wiring a Banksia has a few interesting foibles. If you wire a branch down below horizontal it tends to lose vigor, it only thickens at about one third of the rate as a branch wired up then out. If you must for artistic reasons wire a branch down, leave it long and untrimmed and wire the very tip upwards. This allows the branch to stay vigorous as it thickens and when it has set you can unwire the branch and trim back the growing tip. Once the branch is set in the downward position it then allows the side growth to grow and thicken as normal.
If a bud bursts on the trunk and you wish to keep it and turn it into a branch you will probably need to wire it. [Clip and grow won’t work in this situation] Wire the branch very loosely so that it can expand without the wire cutting in. You will be surprised at how quickly the branch thickens and you can take the wire off and rewire in the reverse direction if you have any marks from the wire.
Once the shape of the tree is established you can maintain the foliage in its general outline by frequent tip pruning. If you fertilize well and occasionally cut out stronger growth at the top of the tree then the lower branches will stay in good health. When you cut back all over the tree you may get buds popping and new growth emerging anywhere on the trunk or branches. The growth is strongly upright so you will probably need to trim the vertical growth about three times as frequently as the sideways growth.
I occasionally spray my Banksia with a mixture of Confidor and Pest Oil. This controls Leaf Miner which distorts the foliage and puts a protective sheen on the foliage. Kill borers with a piece of wire if you spot any holes in the trunk or other signs.
The style of tree you create is totally up to you and you can decide whether you try a Japanese looking style or a more southern hemisphere style. The B integrifolia will suit almost any style whereas B serrata will lend itself more to a less formal style.
I hope this helps you with your Banksia; they are certainly a great subject for Bonsai.
Note: Feb 2009. Re Seasol.
So far I have had no known bad reaction to Seasol and I have been including Seasol more regularly in my fertilizing regime.
Maybe just use low doses on Banksia until you build up the vigor of the particular plant.
INTRODUCTION
There are currently 76 known species of Banksia in Australia, most of which are found in Western Australia.16 species grow on the east coast only of Australia and it is from these Banksia that I have drawn my experiences. All Western Australian species have died in my local environment within a short time, even those grafted on east coast understock. I have, however, seen some Western Australian Banksia growing quite happily in Canberra, so it will come down to your own local environment.
Banksia are related to the Protea family of Africa, with which they have many similarities. Banksia are an evergreen tree or shrub, although some prostrate species and cultivars occur as well. They can be a large, single trunk tree with an irregular outline or have a shrubby, multi trunk appearance. The leaves come in a large variety of shapes and sizes and the growth habits are also very varied. Flowers are also variable but are usually numerous on a spike that becomes woody. The flowers set at the end of new growth and take some time to mature. Not all the flowers become seed as there are just too many on each spike.
Some 36 species are fire-tolerant; having thick bark and/or a woody base or lignotuber. These Banksia can take heavy pruning quite well. The fire-sensitive Banksia are thin barked and do not sprout back easily or at all. They respond to light but frequent trimming but not heavy pruning.
The continent of Australia is very old and the soils are very thin and poor in nutrients. The Banksia have evolved over 100 million years to be able to cope quite well with the poor or sandy soils of Australia.
HINTS FOR GROWING NURSERY STOCK
First try whichever Banksia already grow in or near your area, and remember that the larger growing, tree type Banksia will probably be the best for Bonsai. Some of these will have large leaves (up to 6"/150mm) and be quite vigorous growers but with the correct techniques the leaf size can be reduced dramatically.
I have grown Banksia ericifolia (Heath Banksia), B. paludosa (Swamp Banksia), B. marginata (Silver Banksia), B. serrata (Old Man Banksia), and B. integrifolia (Coast Banksia). I hope to try others as well but so far my favorites are Banksia serrata and Banksia integrifolia.
Banksia can be easily grown from seed or cuttings but must be potted up and on quickly; always pot up to the next size and do not over pot! The potting mix should be neither too fine nor too coarse but above all should freely drain. The roots of Banksia are very fine and will fill the pot quickly; in summer you will need to water more often than most other plants in pots.
You can pot up to the next size pot every year while growing the tree on. I use the recommended dose of Native or Standard Osmocote in the potting mix and liquid feed every week or two (except winter) with a mild liquid fertilizer like Maxicrop, Nitrosol, or Charlie Carp etc.
USE FERTILIZERS AT FULL RECOMMENDED STRENGTH UNLESS PLANTS ARE SICK OR NEW TO YOUR COLLECTION!!!
I believe it is better to have healthy, vigorous plants and then deal with the resultant growth in the shaping process, rather than having weak, sickly plants that have been dwarfed by starvation. If you choose to follow a higher fertilizing regime than you have been using or I am recommending you should build up to it gradually.
Banksias are both hungry and thirsty in pots so please give them what they need and they will repay you with many years of pleasure.
DO NOT POT-ON A BANKSIA AT ANY STAGE IF IT IS WEAK, SKINNY OR WOBBLY.
If it is weak or scrawny looking just give it a light trim and put it back; if it is wobbly you should investigate the soil for Curl Grubs. If you find the roots have been severely eaten by the grubs then you give it a hard root prune and put it back in a similar size pot and lightly trim the foliage.
I AVOID POTTING BANKSIA IN WINTER!
Banksia need to be grown in full sun, so except for immediately after repotting I keep my nursery stock and Bonsai in as full sun and wind as they can take. Growing in full sun gives you a healthier, more disease and pest free tree. It also keeps the foliage more compact. Do not sit a Banksia in water unless you are trying to grow on a tree very quickly, and definitely never in winter. Banksia can suffer from root rot so I try to keep the foliage as full as possible to keep sucking the water out of the pot and thereby keeping the roots on the dry side.
If you repot in winter or don’t leave enough foliage on the tree over winter you may encourage root rot, the tree sort of drowns in the excess soil and water.
BANKSIA AS BONSAI
B. marginata, B. serrata and B. integrifolia all make good Bonsai, but my experiences with B. integrifolia are the most extensive and it is my personal favorite.
Banksia integrifolia, the Coast Banksia, grows in many locations in the wild, from the most exposed, windswept coastal headland where it may grow flat against a cliff or it may be a 25 mtr high tree growing in snowy conditions in the mountains.
Its leaves are large, long and smooth edged, but as a Bonsai the leaves can be small, blunt and toothed. This is because the constant trimming causes the tree to put out a juvenile form of leaf that is most suitable for Bonsai. The leaf is still strong and vigorous and not deformed or delicate in any way.
The frequent potting, fertilizing and trimming gives us a very quick growing, thick trunked tree that buds back on old wood very well.
If you live in Sydney or further north, you may be able to pot-on nursery stock every six months or so to achieve quick growth. If you live in Canberra or cold areas of Victoria or N.S.W, you may need to allow more time in each size pot, say twelve months. Pot in early summer to avoid excessive new growth on the tree going into winter; soft new foliage can be badly damaged by frost and lead to problems with die-back etc.
My reason for avoiding potting in winter or early spring is that the tree just sits and sulks until the warmer weather arrives; there is no advantage in potting early. In fact by sitting in a larger pot in wet conditions for 3-6 months you may encourage root rot, die back or excessive new growth when it is too cold.
Some Australian Natives will grow at any time of year if the conditions are right, but in pots you may accidentally trigger growth at the wrong time of year.
As a Bonsai the B. integrifolia is also very quick growing and is usually my ‘waterweed’. That is, it is usually the first tree to droop if it is in fresh growth.
I usually repot my Banksia Bonsai about every 12-18 months. I wait until the tree shows me that it has used up all its store of fertilizer and fresh potting mix and is not growing as vigorously as it was. I don’t wait until it is absolutely exhausted nor so pot bound that water has trouble penetrating. Letting a Banksia become root bound will introduce you to an interesting aspect of the Banksia; and that is Proteoid Roots.
Proteoid roots are the trees natural response to a lack of nutrients. It puts out a set of roots that are very fine and are able to scavenge very small amounts of food etc from the soil or potting mix. If there is suddenly an abundance of nutrients the tree can take up too much and suffer badly or even die. The Banksia don’t have a feedback mechanism to stop it from taking up too much food, so if you have a tree that is rootbound or very hungry then you must fertilize lightly to start with and then build up to a normal fertilizing regime.
If, when you are repotting you see Proteoid Roots, you can just cut off those roots with no adverse effects for the tree. Proteoid Roots look like the Mycorrhizae you may see on the root system of pines, that is a fine web-like white patch.
As I said I repot about every 12-18 months but I don’t do a heavy repot and trim each time. I will just do a Slip Pot into a larger pot .This involves just a very light root prune or even just a teasing out of the roots and a light tip prune of the foliage. This allows the tree to grow at a good rate in the pot and not slow it down. If you have a tree that is hard to keep the water up to and it is mid summer then the Slip Potting technique is the one to use.
After using the Slip pot technique a few times in a row you can then do a normal repot. With the Banksia I suggest that you repot in early summer using the following sequence. It doesn’t matter if the tree is actively growing because I trim the tree to the shape I want and then leave the tree to start forming its new buds for a week or two. I then give the roots a hard root prune and put it into a smaller pot.
The following years I go back to the Slip pot method. Each time I repot using either method I put Native or Standard Osmocote into the Potting Mix at the suggested rate and continue to fertilize also with Maxicrop or equivalent at the suggested rate.
STYLING A BANKSIA. TO WIRE OR NOT TO WIRE.
Once you come to style your Banksia you must decide on a shaping method. You can just ‘Clip and Grow’ or apply some wire.
Clip and Grow with Banksia is very similar to deciduous trees; just cut back either to a small branch growing in the direction you want and then let it grow and thicken and then repeat the process; or cut right back very hard to a point on the bare trunk and wait for new growth to emerge. As in the case of root pruning you only cut back hard in the warmer months!
Wiring a Banksia has a few interesting foibles. If you wire a branch down below horizontal it tends to lose vigor, it only thickens at about one third of the rate as a branch wired up then out. If you must for artistic reasons wire a branch down, leave it long and untrimmed and wire the very tip upwards. This allows the branch to stay vigorous as it thickens and when it has set you can unwire the branch and trim back the growing tip. Once the branch is set in the downward position it then allows the side growth to grow and thicken as normal.
If a bud bursts on the trunk and you wish to keep it and turn it into a branch you will probably need to wire it. [Clip and grow won’t work in this situation] Wire the branch very loosely so that it can expand without the wire cutting in. You will be surprised at how quickly the branch thickens and you can take the wire off and rewire in the reverse direction if you have any marks from the wire.
Once the shape of the tree is established you can maintain the foliage in its general outline by frequent tip pruning. If you fertilize well and occasionally cut out stronger growth at the top of the tree then the lower branches will stay in good health. When you cut back all over the tree you may get buds popping and new growth emerging anywhere on the trunk or branches. The growth is strongly upright so you will probably need to trim the vertical growth about three times as frequently as the sideways growth.
I occasionally spray my Banksia with a mixture of Confidor and Pest Oil. This controls Leaf Miner which distorts the foliage and puts a protective sheen on the foliage. Kill borers with a piece of wire if you spot any holes in the trunk or other signs.
The style of tree you create is totally up to you and you can decide whether you try a Japanese looking style or a more southern hemisphere style. The B integrifolia will suit almost any style whereas B serrata will lend itself more to a less formal style.
I hope this helps you with your Banksia; they are certainly a great subject for Bonsai.
Note: Feb 2009. Re Seasol.
So far I have had no known bad reaction to Seasol and I have been including Seasol more regularly in my fertilizing regime.
Maybe just use low doses on Banksia until you build up the vigor of the particular plant.