Chinese Elm - a definitive guide

The Chinese Elm or Ulmus Parvifolia is the most popular tree available on the Bonsai market today. For the beginner it is the ideal choice and is the place where most newcomers find themselves having been tempted or presented with one as a gift. I receive numerous questions regarding the care of these trees and so will try and present the truth regarding this species, warts and all to try and ease the ordeal of trying to keep it alive.
That makes it sound like they are difficult subjects but nothing could be further from the truth. I have never lost one and as long as you adhere to the guidelines offered here then neither will you.

As a species Chinese Elm grows wild in China, Japan, Korea and Taiwan and though usually deciduous can be reluctant to lose its leaves. In areas where they receive enough light and warmth all year round they can be considered evergreen but this can sometimes be misleading.. They are grown commercially mostly in China on a vast scale. They are put into cold storage before export so that they become dormant for the journey and once in the UK are placed in warm green houses to recover.
Pause for thought No.1. - Southern California has enough warmth and light for this. Margaret Billings flat in West London is warm most of the time, except when she's out at work of course and during the night but apart from that the temperatures a constant 75 deg F and the windowsill where she keeps it gets plenty of light even on those short, grey days of November, December, January, February.....

So what can Margaret expect from her tree. Well it is pretty obvious that all other factors aside, there is not enough light and warmth to keep the tree evergreen through the winter. Argue if you wish, many do but California we ain't and no amount of wishful thinking will change that fact. So given our miserable british climate what can we do to get the best out of our Chinese Elm. Move to San Jose? Mmm, nice but not entirely practical. I have quite a few of these trees and some are kept in a cold green house over winter with minimal frost protection and they do just fine. They keep their leaves and continue growing with this minimal protection. Others stay outside in the garden and most go dormant duriing winter and for the most part they behave in a similar way to Oak or beech in that they hold onto the dead leaves in order to protectthe new buds. Depending on the weather they will start sprouting in February. Now I live in quite a mild spot on the North Wales coast. We get frost but it tends to be short-lived and not particularly hard. In colder parts of the country it would be advisable to give a little more protection but there is no need to go overboard.

I digress, lets go back to Margaret with her Christmas present. Bear in mind that the tree has probably been in the country for say 3 to 6 months. It has undergone fresh growth from a dormant state in a nice warm green house before being shipped out to the local supermarket, superstore or market stall where it has received little or nor care in variable temperatures and light levels, has been moved several times, knocked about, wrapped and dressed up with a bow before arriving in it's new home. It is probably, dehydrated, more than a little shocked and highly stressed. (Well wouldn't you be after all that). What does it need now?
There are two ways of looking at it. The right way and the wrong way

The Wrong Way - Oh my God, Aunt Mary must have spent a fortune on this tree, please don't let me kill it. Some of the leaves are looking a bit yellow, I'd better put it somewhere warm, near a radiator perhaps, theres no window nearby but that 100w bulb should give it plenty of light. It looks a bit dry but when I pour water on the surface it just runs off, so I suppose it must mean it's got enough already. I'll give it some fertiliser as well that'll do the trick.....

The Right Way - It's winter and this Chinese Elm being a deciduous tree will naturally want to lose at least some of its leaves in response to reduced light levels. That's why some of them are turning yellow. It obviously needs a rest somewhere cool until spring arrives, when there will be enough light to support fresh growth. It looks a bit dry and since water runs off the surface I will stand it in a bowl of water for 15 minutes to give the rootball a chance to soak up what it needs. Then I'll put it on the windowsill in the kitchen where it can get as much natural light as possible and I will have to check on it every day while I am at the sink. I won't need to feed it until it starts growing again and then I'll ask that nice Mark at Green Dragon Bonsai for advice ;- )

So in this way the tree gets to Spring well rested, recovered from it's pre-Christmas ordeal and in good shape to put all its energy into fresh spring growth. Having said that, given the right circumstances and as much natural light as possible some fresh growth may occur during the winter. The way to treat this is not to expect too much too soon and not to push the tree too hard into a premature spring flush. This means watering just enough and feeding lightly, once every 3-4 weeks.

Having briefly touched on the subject of yellow leaves, now would seem a good time to expand on what is the most frequently raised point about this species. At certain times throughout the year some leaves will show sign of yellowing, usually with black spots appearing followed by varying shades of brown. These leaves will drop off during the growing season as the new growth pushes it off but in winter will stay to protect the new bud at the base. With Chinese Elm, some leaves may be discarded. at any time of the year as conditions change but the main time is during Autumn and Winter when it is adjusting its green area to the light levels. Another time of change occurs in late spring/summer especially if your tree is enjoying some time outdoors when having put out as much new growth as possible will shed some of the older leaves in favour of the fresh new ones and may lose some of the new shoots as it decides that it has put on enough for this year and settles down to enjoy the sun.
Whatever the case, yellow leaves should not be seen as a signal to increase water or feed and should not be confused with brown crinkly leaves that turn quickly as this is a sign of lack of water.
Soft and yellow - no problem.
Dry and crinkly - more water required

Most imported trees will need re-potting in their first spring. This strikes fear into most beginners and there are a couple of things to watch out for. The soil that imported trees arrve in tends to be little short of solid balls of clay and this needs removing and replacing with something more suitable such as a 50/50 mix of potting compost and fine grit. Solid soil masses can be removed with a hosepipe but plenty of water and patience is the best way to go about it. If the soil is of a better quality already then it will be a simpler task of combing out about a third of the root ball all the way round, removing any roots growing down from the underside of the root ball and then trimming any long roots around the perimeter. Don't get carried away, especially if this is your first attempt. Young vigorous trees may need a succession of larger pots over the years as trying to maintain a tree in a pot that is too small for it is a highly specialised area that can cause undue stress. It is often worth considering a new pot, maybe slightly larger which will give some more room for growth, will lessen the need for heavy root pruning and will undoubtedly be of better quality than the imported growers pot. A larger pot will be the order of the day if repotting at other times of year with minimum root and an avoidance of root pruning. Trust your instincts about what the correct pot size is and if in doubt seek advice sooner rather than later!

Once lighter days arrive, new buds will appear and fresh leaves will begin to emerge from just about anywhere on a Chinese Elm and feeding should begin. This can be either a liquid feed or granules. Granules have the advantage of being applied once to the surface and then a weak feed is given every time the tree is watered. They have the disadvantage of looking slightly unsightly, some may attract mould and dosage is a little hit and miss. Liquid feed can be given in more exact amounts on a weekly or fortnightly basis dependent on how much growth is taking place. Rather than stick to rigid time intervals I try and balance feeding with the amount of watering needed. ie More watering will wash away nutrients quicker and feeding frequency will need to be greater.

So we now have a healthy Chinese Elm putting out loads of new growth so you will need to know how to prune it.

The shape your tree takes from here on in is entirely up to you and pruning is almost as simple as removing what you don't want. Having said that, Chinese Elm has this strange system whereby if you cut a branch beyond a certain point the tree will give up on it and put its energy elsewhere. For this reason when trimming new growth, allow the new shoots to put out at least 5 leaves before trimming back to 1 or 2 depending on which direction you wish the next set of new growth to take. This process is then repeated throughout the growing season and in this way vigour is maintained.

It is a myth that Bonsai growth processes are somehow suspended. Nothing could be further from the truth. It is the constant renewal and redirection of fresh growth that produces the fine branch structures that symbolise the best Bonsai. Liken it if you will to a golf course. Divots and pitch marks soon take their toll on the grass andit is the constant regrowth that repairs this wear and tear. Imagine the mess if grass growth was slowed down!!

Well there you have it, everything you need to know about Chinese Elm. I am sure that I have not covered everything so if you have any further questions then please feel free to drop me a line.

Mark Kennerley updated April 2008