This article was originally written by Oldtimer1 and published in 3rd issue of Overgrow Magazine (in 2000).
I think I should re-post this legendary article here…
Part 1: Making, Maintaining and Renovating Bonsai Mums
This Article was originally published at overgrow.com 27/6/2000. Revised and archived 20/10/03 by Oldtimer1.
Now we will deal with every aspect of the care and maintenance of Mums including root and branch pruning as well as the renovation on an old mother well past her sell by date.
“Tired of huge unwieldy mothers that take up too much space? As I’ve shown before, a fully established bonsai mum only takes 8 inches x 8 inches.”
This bonsai mother, if well fed, produce 10 to 30 good cuttings every 14 days under an HID or every 20 days under fluorescent shop light. This means a 4 ft x 2 ft shoplight with 18 Mums, could produce an output of over 9500 cuttings a year.
Typical Bonsai Mum
We are not talking about intensive production here but it shows just how flexible and efficient the system can be. What it does for the connoisseur is allow them to keep a good selection of varieties in a relatively small space. If you don’t fancy growing one for 6 months or a year it doesn’t matter. All she will need is regular maintenance.
Lets start with Mumming up a plant from a rooted cutting, once again this is simple. You will find that with every batch of cuttings a few will stand out, being sturdier and generally looking better all round, pick one or two of these to make your Mums, not some wimpy left over reject. Remember this mum will provide you with cuttings 4 to 18 times a year for the next 3 to 15 years, so only the best will do. Pick a fully rooted through cutting from the plug tray and pot on into a 2.5 inch square pot. I find square pots much easier to deal with when it comes to root pruning, as you will see later.
Grow it on for a few days so it can start rooting through then trim its top back to leave 3 or 4 side shoots.
These little branches to be will make the main framework of your Mum. Ideally as they grow they should form an open cup shape. The top 2 will grow the fastest and when they get to about 5 inches pinch or snip out their growing tips to just above a leaf node. This will allow the second pair to catch up in a day or so, then pinch them out as well. This will encourage side shoots to form, any that grow into the central cup shaped space pinch out.
You will now have 6 to 8 leading shoots coming up. When they reach 4 to 6 inches they can be taken as your first set of cuttings. You cut them back to just above the first leaf node of the new growth. So after the cuttings have been taken the mum is only a tiny bit larger than the last time she was cut back but the main branches will be starting to get thicker.
Now is the time to move up to the next pot size and a 3 inch sq is ideal. The next set of leading shoots will tend to be 12 to 16, plus there will be others coming up from lower nodes so in total there may be 30 or more. Any really thin ones or any growing into the centre either cut back to one node or remove altogether.
In the picture above from the left:- [one], is the trimmed cutting from above. [two], Has had 2 sets of cuttings taken off and is more than ready to move to a 3 inch pot. As you can see it is a little short of N showing its better to move after only taking one set of cuttings. [three] in a 3 inch pot 12 cuttings have been taken with 2 left on to show where to cut back to. [four] is a five year old Mum that has just had 32 cuttings taken off and could do with some more small twiggy bits removed. She is in a 1 litre pot and has been since she was 3 months old.
Note how all have an open centre, this allows light to both the centre and the outside. It will fill in between taking cuttings but if pruned back to this form, makes better and more even growth giving more good cuttings each time. Water only is used while forming the Mums and no fertiliser. It is not until they are in their final 1 litre pots and a set or two of cuttings have been taken that feeding starts.
The general care and maintenance for fully formed mother plants.
The Mums need just enough fertiliser to keep them healthy. Feed of half strength fertiliser twice a month, using say a 6-2-4 fish mix as about right [its not critical]! This keeps them in good general health but doesn’t over feed them. If you want faster production at any point change to a full strength feed once or twice. Every 2 to 4 weeks a new batch of cuttings are taken even if they are not needed and just put in the worm bin. You can think of it as being like having to mow the lawn and keeps the mum the same size and form for years. Because so much is taken away they can get short of macro nutrients so every month or so give them a foliar spray using maxicrop. Judge this by how the plants are looking not by a time table.
One of the main things that all growers need to learn is regular close observation. To know when they are healthy and need nothing to the first signs of deficiencies appearing. The one thing they may run short of is magnesium even if dolomite lime is used in the compost, this is easily dealt with by one watering plus a foliar spray, using 1 ounce of Epsom salts dissolved in a gallon of water.
They will need root pruning once or twice a year. This depends on how intensively they are fed and how good your water quality is. Despite what is normally quoted it is virtually impossible to flush out salt build up from a root ball. A temporary over fertilisation yes but the gradual crystallisation of salts and carbonate deposits no! If your water supply is heavily contaminated with minerals I recommend a small Reverse-Osmosis filter to clean your water for both your Mums and your production plants.
"Now root pruning and Mum renovation. "
The method of root pruning is the same for routine maintenance or renovation.
Here we are dealing with a 7 year-old mum that hasn’t been root trimmed for nearly a year. I have deliberately neglected her for the last 10 weeks for purposes of showing you the recovery. She has been on a diet of R/O water only, no other feed of any sort. This is to show you how tough Cannabis is and how far you can let things slide and still get a mum back into productivity. Its not a recommended practice and continual abuse like this will eventually kill a mum.
As you can see there is little residual fertiliser left in the compost. It is what we call spent (worn out). The first thing we do is trim back nearly all the top growth back to the main framework branches. Leaving one or two tiny shoots at the tip of each branch to draw sap and keep the branch alive. If all the shoots and buds are removed, 99 times out of a 100 die back sets in-- and once that starts the whole plant usually dies within a month or two. It doesn’t matter if the small shoots are yellow from lacking N, they will soon start to grow and green up as the new roots start forming!
Next the rootball should have 3/4 of an inch cut off each side and an inch off the bottom. This reduces the 4.5 x 4.5 x 4.5 inch rootball to 3 x 3 x 3.5 inches high after the loose compost is scraped from the top. This means that two-thirds of the soil is being replaced. A good full strength organic compost is used when repotting and it only takes a day or two for the roots to really start growing into the new compost.
Set the bottom of the rootball on about 3/4 of an inch of compost then pack out the sides and finally cover the top with a 1/4 to 3/8 of an inch. This means the mum is planted round a 1/4 inch deeper every time root pruning is done about 1/2 an inch a year. In a couple of years from now I will cut down vertically and split the plant in two as the side branch will have a root system of its own. Using this method the roots are constantly being replaced and as well the main trunk replaced slowly. This seems to keep the Mums healthy for many years.
The second mother of our selected “ES” line lasted for just over 15 years using this method. Interestingly if you want to hold a plant long term in a small pot say a 2.5 inch sq this can be root pruned the same as the 1 litre plant but only taking off about 1/4 of an inch all round. I keep Dads in this pot size and some are over 5 years old.
NOTE: it is very important to make sure there are no voids or air gaps left when packing the sides, use a pencil or small dibber, fill slowly and firm lightly.
The last picture is 12 days after the root and top pruning- It tells it’s own story! Already there are enough nice leaders to make 10 good cuttings. I have to admit to putting her under an sodium light to speed up her development and make this Issues deadline. Even so, the recovery wouldn’t have taken much longer in the mum box.
Thats it you should have all the info you need to make and root cuttings in compost the make and maintain bonsai mother plants, its easy, give it a go! .