How to feed your bonsai (Part 2)

Fertilizing:

Most plants in most soils will grow better if additional nutrients are provided b fertilizing.  A soil test will give a complete and accurate measure of the nutrients in the soil.  A general recommendation is that all soils need more nitrogen.  Shallow-rooted plants, such as grass and flowers, need more phosphorus and potassium.  Acid-loving plants, such as rhododendrons, azaleas, camellias, junipers and pin oaks, often need more iron.  Sometimes sandy soils need micronutrients, but rarely clay soils.  Certain micronutrients may be deficient in certain parts of the country.  Boron is sometimes deficient in America's Pacific Northwest (as I was told by a friend).

Many fertilizers are available to supply additional nutrients.  Some fertilizers only supply one nutrient. Many supply N, P and K ONLY!!!. A few fertilizers include all the macronutrients and micronutrients (to review the list of macro and micro nutrients check Part 1 of this series Here!!!) 

The label on the package will indicate which nutrients are included, as well as the sources of the nutrients.  The nutrients are identical, whether they come from organic or synthetic source, but the source will affect how quickly the nutrients are available to the plants.  Ammonia sulfate and water soluble fertilizers release most of their nitrogen in a few days, and may burn plants if too much is applied.  Blood meal releases its nitrogen over a period of months.  Organic fertilizers and specially treated synthetic fertilizers release their nutrients slowly, so they last longer and will not burn.  Deeper-rooted trees and shrubs can be fertilized once a year, but shallow-rooted plants, such as grass and flowers, will need regular fertilizing throughout the growing season.

Water can move nitrogen several centimeters in the soil.  Nitrogen applied in the fall may be carried too deep into the soil by winter rains.  February and March is the best time to feed trees and shrubs.  Phosphorus and potassium hardly move in the soil.  To get them down to tree roots, punch a hole in the soil with a bar, or use a root-feeder and inject them 12 inches (30cm) deep every 24 inches (60cm) in rings from the trunk to twice the length of the branches.  The feeder roots are found throughout the area under and around a tree, not just at the drip line.

Thanks Rod Smith.

Products that contain micronutrients.

Micronutrients are supplied in special micronutrients packages (such as MicroMax, STEM, Apex micronutrient package and others) which bind readily to organic matter if used in conjunction with soilless mixes.

The micronutrient mix is sprinkled on the surface of dry soil and then watered in.  It will increase the acidity of the soil temporarily and is best applied when repotting, or once a year in spring, at bud break.

Back to Basics:

Bonsai will need feeding if you use the single-soil approach as they cannot live on water alone.  Feeding is easy, and here is a breakdown of feeds and the basic regime.

• A high Nitrogen feed makes the leaves grow.
• A low Nitrogen feed makes the branches, roots and cambium (under bark) grow.
• I recommend the low nitrogen feed for maples trees in the early flush of growth as it helps the leaves to become stronger.  Use it in the later part of the year, just prior to Fall or in the winter season in colder climates. Then at the very start of the growing season to encourage the development of branches and roots.
• 0.10.10 or similar is a Zero Nitrogen feed. This is used with most conifers at the beginning of the season and through the early stages of bud or candle development.
• Acid loving plants: Use Miracid or similar (Azaleas, satsukis, ericas and stewartia)

For young trees:

In SPRING use at half-strength when the buds are open 0-10-10. Then builds to full strength in late spring and use High Nitrogen after the first flush of growth.  Feed half-strength through most of the growing season in hotter areas.

In SUMMER if in a hot area, do not fertilize.  If in a cool area, stop in midsummer.  The trees cannot absorb fertilizer at this time: they go to into Semi-dormancy because of the heat and stop growing. (I have learned that after having bad experiences, after leaving 4 years in Miami, FL)

In FALL reduce to half-strength and only use a Low-Nitrogen fertilizer.  This helps the bonsai into the main dormant season in cooler climes.

Brand names varies from country to country or even from city to city or by Nurseries but in general it is fine to use popular houseplant food, but not lawn or grass food because it is far too high in nitrogen and can easily damage the roots.

For Mature trees:

I suggest that surface pellet feeds, such as Rapeseed Cake or Bio Gold are the best option. The direct feeding of liquid fertilizers through the soil should be no more than between two and four times a year when a bonsai is mature.  Too much feeding will generate lush growth.  Adding trace elements is, however, important. In all cases, when dealing with older trees, less is more.

Please, leave your comment, and advise for the next posts. We really appreciate your feedback.