We all know when we’re feeling sick, whether it’s a headache, a common cold, or the flu - the symptoms are familiar to everyone. Determining if friends or family members are sick may be harder to spot; and when it comes to spotting the health of a plant, it’s a whole new ballgame. As you gain experience with bonsai tree care, it will get easier for you to determine its health in one glance. Follow these three guidelines to learn what to look for to tell the current health of your plant. Once you understand what to look for, it will become easy to compare the health of your bonsai from year to year.  

1. It’s growing and the new growth is out of control.

New growth and elongation of branch tips on a bonsai are good! In the spring you should see a “spring flush” of fresh new growth begin to elongate on every branch.  If the growth is robust, and elongation happens quickly it’s likely that your tree is happy and doing well.  

Good Growth:

• Fresh spring growth elongates and matures evenly on all the branches.
• The color of the foliage is dark green (or typical for the particular species)
• The size and turgidity of the foliage is consistent and firm

Bad Growth:

• Foliage emerges slowly, or only one or two leaves or needles are produced on many of the branches. But keep in mind some trees do take months to make new foliage (juniper, some pines)
• Foliage emerges, but then wilts or turns brown.  This could be the result of late spring freezes, heat waves, fungal infections or insect attacks.  But if there is no apparent cause it may mean your tree is weak.
• No foliage growth in spring or summer.  If there is no notable foliage elongation in spring and summer, your tree is probably very sick, it’s not the only thing to look for, but it’s a major concern.

2. It’s doing things that trees around you are doing.

If you’re growing temperate climate trees then you should notice that your tree does things similar to the trees that grow around you in the natural environment.  Temperate climate trees are almost anything that grows in North America, Europe, Japan, China, South Africa or Australia. Tropical and semi-tropical trees are those species that do or can grow in constant temperatures like conditions found in Central America, and other places that are typically warm and humid year round.

For temperate-climate species:

1. It’s fall and the leaves of deciduous trees are looking a bit tired, and beginning to change color, then eventually drop off and make a mess out of your clean bonsai bench. 
2. It’s winter and the branches are bare, or the needles are oddly colored.  In winter, deciduous trees are leafless and conifers frequently turn either yellow-green or other colors, an indication that the tree is creating “anti-freeze” to protect itself from cold temperatures.  All bonsai should have their roots protected from temperatures below 28F, (-2C) to avoid damage.  
3. It’s spring and all the new tips are elongating.  Spring is a magical time of abundant growth, if your tree is healthy, it will be making new foliage and branching.  Encourage the new growth, or contain it depending on how mature your tree is.  On trees like maples, the new tips are pinched on mature trees to shorten the growth, while on other trees the spring growth is left to elongate and either cut back or even eliminated later in the season. (check on species specific instructions!) 
4. It’s summer and....   Summer can be an odd time for trees, and depending on your climate they might grow right through, vigorously showing wonderful new growth.  However, if your summer is too cold, or too hot, many trees will go into summer dormancy where new growth is minimal.  They frequently resume growing in early fall for a short time before going dormant again.

For Tropical and Semi-Tropical trees:

• Seasonality can still exist in semi-tropical trees.  Chinese Elms can grow year round in some conditions, while going dormant and deciduous in colder climates. 
• Tropical trees should show regular spurts of growth, but not necessarily constant.  The healthier the tree, the more vigorous the new growth will be.
• If you are growing tropical varieties in a temperate climate, keep in mind that the day length can affect the tree’s ability to grow.  You may only see growth in spring and summer if your day length is not long enough at other times. 

3. The color, shape and texture of the foliage is good.

Good foliage characteristics vary by species, but generally the needles or leaves should be consistently deep green and evenly colored with foliage near the top of the tree slightly larger than the foliage on lower branches.  If the foliage is not looking good, not to worry, many health problems are simply a matter of good cultural practices.  

For Broadleaf Evergreen and Deciduous:

• Leaves that are healthy in shape but yellow, or showing uneven coloration may indicate a nutrient deficiency.
• Leaves that are curled, distorted or damaged may indicate an insect problem.
• Leaves that are spotted, burned at the margin, or distorted, absent indications of insects, may indicate a fungal problem, or a problem with water quality.

For Conifers:

• Needles that are unevenly colored, or uniformly yellow may indicate a nutrient deficiency
• Needles that have a pale, washed out appearance or are dirty in appearance or stunted may indicate an insect problem.
• Needles that show banding, deformation or browning may indicate a fungal or watering problem, or a fungal or insect problem with the roots. 

Hopefully that will give you some good ideas about how healthy your bonsai is!  Check out some of our other blog posts for more bonsai care tips, and visit our Gallery for images of refined, healthy trees from Eric's personal collection!