Conifer Bonsai Care: Planting, Repotting, and Fertilizing

Learn how to care for your conifer bonsai in the garden.

Many ACS members today have shown great interest in making bonsai part of their garden decor. Few of us have the room or property to expand our collection of conifers to accommodate all the cultivars available. That’s where “trees in pots”, bonsai, allow us to expand our collections.

Recently, a fellow bonsai club member and I were asked to find an appropriate Chamaecyparis obtusa (hinoki cypress) specimen for our bonsai club’s demonstration tree for this year’s show. We ended up at a conifer nursery north of us which has the best selection of conifers in Northern California.

We did find that special tree for our demonstration. However, as usual, we came home with an additional seven trees apiece that we just couldn’t turn down once we saw them! Sound familiar? In addition, my conifer garden space is getting smaller each year as the trees grow. I cannot add any new trees to my garden unless I’m willing to take out some of my existing plants. Many of these trees are very dear to me, and I want to see them continue growing to maturity.

Pairing Rocks with your Conifer Bonsai

So, where are these additional plants I purchased going? This fall, once the weather cools, I will plant Cedrus atlantica ‘Hillier’s HB’ in a training pot as a cascade bonsai. The other six trees are going to make up a “forest planting”, a grouping of trees of like specimens. I will plant this grouping on a broad, flat rock I purchased a few years ago.

The rock I’ll be using is fantastic. I found it at a local rockery, and it is perfect for the planting I envision. The center area is concave for plenty of root depth and soil material. The trees I purchased for the forest planting are last year’s ACS plant of the year Thuja occidentalis ‘IslPrim’/PRIMO™.

When I first saw these little gallon-sized plants, my heart almost stopped. They are perfect for such a grouping with their narrow, chiseled-like growth pattern. I’m going to have to wait until this fall to put it all together, but I’m finally getting a chance to use this rock.

Conifer Bonsai Styles

It’s interesting to see how many of these unique conifers are available to us. Members can, with very little experience, transform trees quite easily into very nice bonsai. I am personally very fond of the bonsai style called cascade, a waterfall-like transformation of a plant that flows with a downward motion, curving and dropping with downward steps. Plants that are perfect for this style and training are cedars, junipers, and various pines. This is a great style of bonsai for beginners.

In professional bonsai, trees are often times hundreds of years old when they are taken from the local mountains and then styled over many years of training. Conifers are some of the best plants available for training and wiring since most keep their foliage year-round.

Many dwarf and miniature conifers already have a natural, tree-like structure. If you’re very selective in purchasing your trees, you will come away with a good starter plant. This is where the trained eye is so important. Some trees have physical faults built into them, some of which make it impossible to create pleasing bonsai, even over an extended time.

Finding Beginner-Friendly Bonsai

Here are some tips for picking a good starter bonsai:

• Since most trees we can purchase are cultivars, first check for the graft union. This is a good place to start. Does the graft union make a smooth and even transition?
• Avoid plants that have a wagon wheel type of branching, a spiral of branches that all attach around a central area of the main trunk. You want branches to be attached progressively, all the way up the trunk if possible.
• Look for a good flare at the base of the trunk, as branches transition to the surface roots. This adds good visual tree stability.
  
• At the main trunk-line, is there movement upwards that adds interest and variation? Does the tree’s main
  trunk-line slowly taper from the ground to the top?

Don’t be disappointed if you don’t find a plant that has all of these good features. Some bad features can be changed with time and know-how.

Ask how long the plant has been at the nursery. Soil quality will often break down in older containers.

Repotting your Conifer Bonsai

If the season is appropriate, start to repot your selected tree into a bonsai type soil mixture as soon as possible. Healthy-looking plants are a good clue that all is well internally within the container, but this can change rather quickly.

When repotting, never eliminate all the original soil around the roots the first time, proceed gradually and try to untangle unruly roots carefully. For the first repotting, don’t think that your tree must go directly into a shallow bonsai pot. A sizable pot with good soil will keep it safe and healthy for the first year after repotting.

Good health for the tree is very important since your plant will eventually be trained by cutting back unwanted branches and wiring others that will control branch placement. This can be very stressful for plants, but a healthy plant will almost always bounce back.

Medium Type for your Conifer Bonsai

What about the type of soil for bonsai?

True bonsai soils rarely have organic additives like wood chips in their mixture. Some conifers prefer slightly acidic soils. One way to get that is to add fir bark or redwood chips. However, be careful! These chips can eventually break down and create poor soil drainage.

Most conifers prefer a good drainage base that allows for a fair amount of water absorption with equal amounts of air retention. This can only be accomplished by using a good substrate made up of equal parts of volcanic lava, clay particles called akadama, and pumice.

This mixture may catch you by surprise, as it initially did me. This medium makes it difficult to overwater, but it also requires daily watering during the heat of summer. For cooler climate conifers like Abies or Picea, you could substitute fir bark in place of the akadama clay.

Conifer Bonsai Fertilizing and Troubleshooting

Does my newly potted bonsai require fertilization?

Once warmer spring days come around and you see signs of the tree starting new growth, you can begin fertilizing. Organic fertilizers are often times preferred, but I have experienced great results by using fish emulsion along with a healthy dose of Miracle Gro mixed together in a watering can. By feeding the leaves along with the surface soil area every 10 days, I have been able to extend the growing season. I also use a commercial fertilizer called Apex, which I apply to the soil once every year.

Despite all of my experience and care, some of my plants have just died without my knowing what went wrong. ACS members have reported the same results. “I did everything right, but it still died!” Well, yes. It could have had faulty roots, or rotted roots from a blocked container.

The possible causes are endless. I’m convinced that fungal issues may be one of the culprits. Ever since I started a regular summer fungus spraying regimen, my plants have been healthier and have experienced tremendous growth. I use products called Cleries 3336 and Daconil, sprayed every two weeks. They really work!

I hope this article will encourage many members to start enjoying conifers more by selecting bonsai as an addition to in-ground planting. This hobby allows your creative ideas to intertwine with your bonsai development decisions. The result will be your own personal living tree art form. I have been creating bonsai for over eight years and still have much to learn.

As I mentioned in my previous article (Summer CQ), there is no substitute for joining your local bonsai club, which will give you the needed hands-on experience and training. I will write follow-up articles that will delve even further into the development process of your bonsai trees. Remember, you’re working with a living art form, and patience will go a long way to achieving best results. A great book to get is Bonsai by Peter Warren, published by DK. Good plant hunting and bonsai-creating!

Photographs by Jack Christiansen.

Jack is an ACS member, an avid bonsai-enthusiast and bonsai-creator. His garden is an excellent example of creative design and the integration of bonsai into the garden. His knowledge and photographic skills are well-known and widely appreciated. He lives in San Jose, California. Over the years, Jack has been a valued contributor to the CQ.

This article was originally published in the Fall 2018 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.