Boise Bonsai Society
A non-profit organization dedicated to educating our members and the general public in the art and culture of bonsai in the Treasure Valley, since 1996.

Seasonal Tree Care

This section is dedicated to the care of our trees. You can find articles on tree maintenance, protection, fertilization, pests, soils, and seasonal care.


Early-Spring: MAR - APR

* CAUTION: Keep your trees in a protected environment (away from heat, cold, and wind) If Doing any of the following.
  • Bring your trees out of the winter ground protection.
  • Potting - This is the time to trim roots and then pot or repot trees.
    * NOTE: Do not fertilize newly potted trees for 4-6 weeks.
  • Pruning - Prune all deciduous trees. Prune flowering trees after they bloom.
  • Shaping - Now is the time to prune Maples and then pinch back unwanted growth for the next 2 months.
  • Old Wire - Check all wiring from the previous year and remove if needed.
  • You may start wiring now to shape your deciduous trees.
  • Fertilize - Give you Bonsai fertilizer (5-10-10) at least twice a month (see below) to jump start them.
    * Do not fertilize Blooming Plants -Fertilizing causes the flowers to fall off and not last long. Wait until blossoms drop off then fertilize.

Mid-Spring: Late APR - MAY

  • Prune Flowering trees if flowers are gone.
  • Twist off long Pine candles-remove only the strong growth.
    * It is strongly advised to get advanced training/reading of this procedure.
  • Keep pinching back new growth. Hint - Allow 3 leaves or 3 pair of leaves to emerge from bud; pinch back to 1 leaf or 1 pair.
  • Start watering on a regular basis.
  • Rotate your trees.
  • Wire all trees, keeping watch for rapid growth. Do not let your wire become tight and leave scars or the branched.
  • Transplant pine, fir, hemlock and spruce now.
  • Watch for aphids.

Late-Spring: Late MAY

  • Prune Maples on a regular basis.
  • Twist candles on pines.
  • Check wired branches.
  • Tip cascades on their side to promote strong growth on the lower branches (this gives them more sun for growth.)
  • Prune vigorous growth on all trees.
  • Spray for fungus and bugs if needed.
  • Fertilize and water well.


Early-Summer: JUN - Mid JUL

  • Style and do your jin and shari now.
  • Select second growth candles on pines you wish to keep and remove all others.
  • Pinch back growth on conifers.
  • Leaf defoliate on Maple. (Hint - Only do this on finished Bonsai and watch how much water you give it as it needs less without the leaves to take it in.)
  • Prune rhododendrons and azaleas or any spring blooming trees.
  • Pinch back oaks.
  • Do not water during the hot part of the day.
  • Spray for borers, thripes and mites if you have them.
  • Select fruit for display and remove all others.

Mid-Summer: JUL

  • Watch for signs of heat stress-Move Maples to shade.
  • Fertilizing: Water trees first, then fertilize, in morning or evening; not in mid-day heat.
  • Begin transitioning to a 5-10-10 or 0-10-10 fertilizer to prep for seasonal change.
  • Prune flowering trees now for shape. Hint - Try not to remove inner branches as these will flower next spring.
  • Pinch and prune maples

Late-Summer: AUG - SEP

  • Water often and deeply.
  • Fertilize with a 5-10-10 or 0-10-10 fertilizer.
  • Scrub the trunks of elm, birch and zelkova with a diluted solution of lime sulfur to remove any fungus or mold.
  • Protect trees from afternoon sun.
  • Prune to avoid dieback. Rotate your tree on a turntable and if you cannot see through the foliage, then prune so the sun can get in to the inner branches.
  • Cut pine needles in half to promote secondary budding.


Early-Fall: Late SEP - Mid OCT

  • Plant root over rock styles now.
  • Make the last application of fertilizer that contains nitrogen.
  • Start restricting water on deciduous trees for more fall color.
  • Excellent time to collect trees from the wild.
  • Watch for insects.
  • Start preparing for winter storage-Mark which trees (this is very helpful) you will need to repot in spring.

Mid-Late-Fall: OCT - 1st Frost


  • Water only as needed.
  • Check branch wires for tightness and remove if needed.
  • Fertilize with a 0-10-10 fertilizer.

  • Make the first application of lime sulfur. Do not let the lime sulfur get on your soil. Place some kind of cover over the base of your tree to protect the soil.
  • Move trees to winter storage. Usually around the first week of November.
  • Do not wire, fertilize, transplant or prune.


Early-Winter: NOV - DEC

* Do not re-pot any outdoor trees.
  • Prune fall blooming bonsai - This includes magnolia, chrysanthemum, camellia or similar plants. New buds form in the spring so now is the perfect time to trim.
  • Wire any deciduous\junipers\pines at this time. Then when Spring arrives your tree will be in the shape you desire.
  • Remove excess moss in winter harbors insects and disease. Water trees only if they feel/look dry. Always water early in the day as overnight temperature may drop drastically and the water will freeze and may break your pot.
  • Clean pots of mineral residues - You may pull the tree from its pot, wrap the root ball with a wet towel and then clean the pot.
  • Apply lime sulfur to Deciduous trees - early winter before you put your trees to bed spray according to directions on label. Apply now and you will have better success the following year with fungus.
    * Do not let the lime sulfur get on your soil. Place some kind of cover over the base of your tree to protect the soil.
  • Stop fertilizing unless you have a greenhouse then you may use a 0-10-10 fertilizer once a month for root growth. Keep in mind that trees in the ground are dormant and need no additional fertilizer.
  • Rocks - Now is the perfect time, weather permitting to look for rocks for viewing stones, landscapes, and suiseki.
  • Disinfect - Clean all you bonsai stands with a mixture of 1/2 water and 1/2 bleach. Scrub this mixture in and let stand for 1 hour, to kill any disease present, and then wash with water. Be careful this mixture will damage/kill any surrounding plants, grass and trees. Clean up any debris, leaves, and needles from under your stands.
  • Put your trees to bed - This can be anywhere from mid-October to late November depending on the weather. Bury your pots up to the top of the pot/or place in a non-windy location and cover with mulch.

Mid-Winter: DEC - JAN

  • Check to see if bonsai need water.
  • Spray with dormant spray (Neem Oil).
  • Sharpen tools.
  • Read and educate yourself with books.

Late-Winter: JAN - FEB

* CAUTION: If you do any of these procedures listed below for winter you must keep your trees in a controlled weather environment (Non-heated Garage, Cold Room or Greenhouse).
  • Dormant Spray - If we have warm weather and buds begin to swell, spray with dormant spray. Be careful if you have Quince or any early flowering tree and spray early enough as dormant spray will kill the buds if sprayed too late.
  • Train conifers now - The sap in conifers is just starting to flow slowly. This is an ideal time to wire and shape branches. Withhold water, and you should wrap raffia around the branches before wire to protect the bark (very important).
  • Prune early bloom deciduous trees - Prune now for shape and where you want the flowers to appear.
  • Fertilizing - You may apply a light Fertilizer (0-10-10), this will promote root growth.
  • Bare Root Conifers - You may pull your trees out of the ground & pot up. You can trim the roots and appropriate foliage.
  • If sunny weather comes during this time be sure to water your trees.
  • Grafting - Late winter is the best time to graft.