Peter's Bonsai Blog 

Hawthorns

As well known indigenous species, Hawthorns (Crataegus Monogyna) can be found everywhere in Scotland.  From craggy old specimen trees in a field, to the more ornamental types in a park or private gardens.  Most commonly they have been used as hedging plants particularly in the countryside.  Because the farmers have cut them back annually they can be found as compact little trees, lined up with their foliage interwoven to form a compact (and prickly) hedge.They back bud profusly, give us flowers in Spring time and Berries in the Autum. They make great  Bonsai.

Here's an example that I collected in 2008.

The following group was collected in March 2009, and potted up in this wooden box.  The original attraction was the curved trunk on the right hand side. Unfortunately it died.  I then reappraised my options and came up with a computer image of what this group might look like.

In 2012, I reduced the trunk on the left and the following year did some carving.  By May 2014, the trees were growing well and so I put it in a proper pot.  The new foliage was popping out all over the two live trunks and had to be chopped back.  I did some initial wiring  for the picture.  

The image below was taken in Sept 2014 - so far, its going according to plan.- fingers crossed.

By August 2015 the foliage has filled out quite a bit and  the tree is heading towards the original computer image.  But by 2018 the tree had filled out enough to be a part of the SBA display at Gardening Scotland.

In the spring of 2020 I decided to re-pot this group of trees.  They had been in this pot for 6 years and I felt that the roots had filled the pot and  the soil wasn't draining well enough.  Unfortunately the dead tree on the right simply had no roots at all and as I tried to  take the trees out of the pot, the group simply fell apart.  I tried to keep the  left hand and middle trees by putting them in separate pots but regretably the middle tree did not survive.

I'm now left with one tree from the group.  Although nicely carved it only has two branches.  How on earth do I get a bonsai image out of this?

There are two main varieties (Crataegus Monogyna) which has a white flower and Crataegus laevigata  Paul Scarlet which has a red flower.  Here are some good examples.

It is quite rare to see a convincing Paul Scarlet as a bonsai.  Because the flowers appear on last years growth, if you want lots of flowers, do not trim off all of  the current seasons growth.  Although this species is popular for farm hedges, you seldom see much  flower on a hedge simply because the farmer will have trimmed the hedge at the end of the growing season and removed the current years growth.

Sources of Material

Hawthorns can be developed from cuttings;  purchased as whips in a garden centre; or collected from the wild.  The quickest shortcut to creating substantial bonsai is obviously by collecting from the wild. Most Hawthorns in the Scottish countryside will be seen in the hedgerows, although this is a native species and they can be found  almost anywhere. My favourite locations for collecting are in old Railway embankments or on the edge of moorland where the new growth has been nibbled by sheep, causing the tree to back bud and develop a dense canopy.  Such trees are often  very low and compact, but with substantial trunks.

Collecting Technique

I had been sufficiently impressed with this species for use as a bonsai, that in February 2015, I attended a presentation by Mr Tony Tickle all about how he collects and grows his Hawthorn Bonsai.

I was particularly interested in  how he goes about collecting, or more importantly how he keeps his collected trees alive.   Tony described the following technique;-

Collect Hawthorns just before the new buds are about to break. In Scotland this is usually March / April but you need to monitor the tree closly as the precise date will vary dependant upon the mico climate that the tree is growing in.

Both the foliage and the root ball are cut back to a manageable size.  The trees are bare rooted, planted into a free draining mix, within as small a container as you can get away with.  Then cover the top of the pot with some fresh spagnum moss. It is expected that the tree will stay in this container for several years and so it makes sense to put it into a smallish  container from the outset.  

The whole assembly is then placed into a very large black plastic bag (a wheelie bin liner) and placed onto a heated bed within a greenhouse.  The bin liner has to be a fairly thin gauge to let some light through, (I got some from B&Q). Terry advised that it is also important to open the bag and mist spray the tree every day.  This process would encourage the development of new roots and  green shoots from the collected material.  The objective of the whole process is to get the collected material established as quickly as possible, I.E, it needs to have a good root system and plenty of foliage.

I don't have a greenhouse or polytunnel and so I decided to adapt the technique to my circumstances.

Having placed the collected tree in a free draining mix, in a small container (I chose a 12" dia terracota bulb pot).  The tree and the pot were placed inside a bin liner. Fresh Spagnum moss was  placed on top of the pot.   This assembly was then positioned onto a propagator heat mat like the one below.  It cost £18 on the internet including delivery.

The heat mat was positioned on top of a sheet of polystyrene insulation and the whole thing taken into my garage. As I was concerned about the possibility of the pot getting too dry, I placed a piece of horticultural capillary matting inside the bin liner and directly under the pot.  I then soaked everything inside the bag using a watering can.  The heat pad is rated at 15W and was left on 24/7.

The following picture shows the arrangement, with the bin liner temporarily taken down for the picture.

and  what it looks like, when the tree is bagged up and closed.

The idea of keeping the assembly in the garage was, to minimise heat lost by keeping  it out of the wind, and in recognition that, until there were some new shoots, the tree didn't need any daylight anyway.  The idea was to cause the tree to sweat, and to produce new roots and  foliage shoots within a warm moist environment.  As I understand it, this is a fairly standard horticultural propagation technique.

The results so far have been astounding.  The inside of the bag was very quickly "sweating" as water condensed on the inside of the bag.  Within two weeks the first sign of new roots appeared, popping out of the trunk and lower branches.  These were then followed by new buds.  The new roots are white in colour and  pointed at their tips, whereas the new shoots are green and round.

As the season progressed more and more shoots appeared, and by the 1st April (approximately 4 weeks after I collected the tree) I decided that  the whole assembly should be relocated outdoors.  I chose a sheltered spot adjacent to the house.  The heat mat was plugged in again, and runs continuously.  I spray the foliage every day and ensure that the capillary mat below the pot and the spagnum moss on top of it remain moist. The new roots which had appeared, on the trunk and lower branches quickly died off as the tree was exposed to the light, whereas the tender young shoots took on a darker colour of green, even though they were still inside the bag.

The following pictures show the number of buds that have been created around the cut branches.

And even popping out of the  main trunk...........

At this stage the technique looks to be very successful and I have purchased more heat pads.

However, by the middle of May I felt that the tree had developed enough that I could remove it from the heat pad and the black bag.  The tree was left in a sheltered position and treated like all my other trees.

By the end of June the picture was less encouraging.  Several of the new shoots were dieing back. This was occuring extensivily over the tree, in the areas where new growth had been generated around the ends of cut branches.  However other parts of the tree were growing as normal.  It was almost as though the tree had used its residual energy to develop the new shoots, but their connection to the root system was inadequate.  The followng pictures show the nature of the problem.

I decided to place the tree back inside a bin bag, but without the heat pad.  This is intended to create a humid atmosphere  to help protect the new growth.  We shall see what happens.

PS. I recently attended a demonstration by Ryan Neil, and he was advocating the use of bottom heat to encourage root growth when we repot our trees.  As I have said it seems to be a standard horticultural technique, and it makes sense to me.

Please watch this space for updates.............

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