Monthly Bonsai Care Guide
Month-by-month care tips for the Northeast US climate, adapted from 17 years of GSBS newsletters and decades of member experience.
Month-by-month care tips for the Northeast US climate, adapted from 17 years of GSBS newsletters and decades of member experience.
Full Year at a Glance
Protect & Plan
1 Protect trees from extreme cold - check that soil hasn't dried out under snow cover.
2 Excellent month for heavy pruning, new design work, carving, and needle plucking on pines.
3 Plan your spring repotting schedule and order supplies.
4 Check stored trees weekly for moisture and pest issues.
5 Study deciduous tree structure while bare - perfect for evaluating branch placement.
6 Remove trees from glazed containers if possible - glazed pottery tends to crack and spall (shed outer surfaces) in freeze-thaw cycles.
7 Watch out for rodents girdling bark on dormant trees - use mothballs or hardware cloth around pots.
Watering
Minimal - check weekly
Fertilizing
None - trees are dormant
Pruning
Heavy structural pruning OK
Repotting
Wait until spring
Deciduous
Evaluate branch structure. Prune for shape while dormant. Keep roots from freezing solid.
Conifers
Needle pluck pines. Wire junipers and spruces. Protect from wind dehydration.
Tropical
Keep indoors near bright window. Reduce watering but maintain humidity. Watch for spider mites.
Prepare & Compost
1 Prepare bonsai compost: peat, garden compost, sand/grit with slow-release fertilizer.
2 In mild spells, begin repotting and wiring deciduous trees.
3 Branch pruning can be done on most trees except Japanese maples and pines.
4 Check wire on evergreens - branches may swell as sap begins to rise.
5 Late winter is a good time to take hardwood cuttings for propagation - and remember: if in doubt about repotting, wait another year.
6 Start seeds indoors for species you want to grow from scratch.
Watering
Minimal - check weekly
Fertilizing
None - trees are dormant
Pruning
Heavy structural pruning OK
Repotting
Wait until spring
Deciduous
Begin repotting elms and hornbeams in late February if buds are swelling. Avoid maples until March.
Conifers
Continue wiring. Hold off on repotting until March. Check for winter damage.
Tropical
Increase watering slightly as days lengthen. Begin light fertilizing.
Repot & Collect
1 Prime repotting season - root-prune and repot most species this month.
2 Gradually bring trees out of winter shelter as frost risk decreases.
3 Spray for fungus and insects on warm days before buds open.
4 Good month for collecting trees from the wild (yamadori) - dig before leaves emerge.
5 Begin light fertilizing as growth starts.
6 Repotting frequency varies by age: young trees every 1–2 years, mature trees every 3–5 years.
7 When using insecticides or fungicides on container-grown trees, apply at half the label strength to avoid root burn.
Watering
Increase as growth begins
Fertilizing
Begin as buds open
Pruning
Light pruning as needed
Repotting
Peak repotting season
Deciduous
Repot maples, elms, beeches. Root prune up to 1/3. Use well-draining soil mix.
Conifers
Repot pines, junipers, spruces. Be conservative with root pruning on pines.
Tropical
Move outdoors once night temps stay above 50°F consistently. Repot ficus and schefflera.
Feed & Pinch
1 Begin feeding, pinching, watering, and pruning in earnest.
2 Still a decent month for root-pruning and collecting trees from field or yard.
3 Be mindful of late cold snaps - protect tender new growth that could freeze in the next inevitable cold snap.
4 Start air layering projects on healthy, vigorous trees.
5 Watch for aphids on new growth - treat early.
6 Consider pelleted surface fertilizer (e.g., Osmocote) that releases nutrients gradually with each watering - a reliable hands-off approach recommended by veteran GSBS members.
Watering
Increase as growth begins
Fertilizing
Begin as buds open
Pruning
Light pruning as needed
Repotting
Peak repotting season
Deciduous
Pinch new growth to maintain shape. Begin regular fertilizing. Last chance to repot most species.
Conifers
Begin candle pinching on pines. Wire new growth on junipers.
Tropical
Full outdoor season begins. Increase watering and fertilizing.
Water & Watch
1 Daily watering begins - check soil moisture morning and evening.
2 Take softwood cuttings and continue air-layering projects.
3 Watch wired branches carefully - deciduous trees expand quickly in May and June.
4 Remove wire before it bites into bark on fast-growing species.
5 Defoliate strong trees if needed for ramification.
6 Consider softwood cuttings of Chinese elm, zelkova, Japanese maple, and trident maple - they typically root within 3–4 weeks under good conditions and can be individually potted by July.
Watering
Increase as growth begins
Fertilizing
Begin as buds open
Pruning
Light pruning as needed
Repotting
Peak repotting season
Deciduous
Pinch constantly. Remove wire that's cutting in. Defoliate strong maples for smaller leaves.
Conifers
Complete candle pinching on black pines. Begin needle pulling on white pines.
Tropical
Peak growth period. Fertilize weekly with dilute solution. Prune aggressively.
Pinch & Spray
1 Pinch terminal buds on deciduous trees, leaving one pair of leaves.
2 Candle-pinching for pines should be winding down by mid-June.
3 Watch closely for insect pests - scale, spider mites, and caterpillars.
4 Move trees to partial shade if temperatures exceed 95°F.
5 Continue regular fertilizing on all species.
6 Chinese junipers are the only trees to safely repot this month - provided they are shielded from drying wind and full sun. If a tree has outgrown its pot, move it to a larger container without disturbing roots.
7 Early morning or evening is best for misting foliage - water left on leaves in full sun causes leaf burn.
Watering
Daily, possibly twice in heat
Fertilizing
Regular - reduce nitrogen in late summer
Pruning
Maintenance pinching and trimming
Repotting
Only tropicals if needed
Deciduous
Second flush of growth - continue pinching. Watch for powdery mildew.
Conifers
Cut back juniper shoots to 2-3 clusters. Final pine candle work.
Tropical
Heavy growth period. Can do major styling work. Water twice daily in heat.
Maintain & Pluck
1 Feeding, pinching, and pruning in full swing.
2 Keep plucking terminal buds off junipers and cedars for dense pads.
3 Spray in shade if using pest chemicals - avoid leaf burn.
4 Mulch soil surface to retain moisture in extreme heat.
5 Provide afternoon shade for sensitive species.
6 Vigorous growth from spring may slow mid-month before a second surge at the tips of earlier shoots - continue pinching as new growth appears.
7 Shari (deadwood on trunk) can be created now while the sap is still flowing and the bark is easier to loosen and remove.
Watering
Daily, possibly twice in heat
Fertilizing
Regular - reduce nitrogen in late summer
Pruning
Maintenance pinching and trimming
Repotting
Only tropicals if needed
Deciduous
Continue maintenance pruning. Reduce fertilizer if trees are stressed by heat.
Conifers
Pluck junipers and cedars. Hold off on heavy work - save for fall.
Tropical
Peak season. Can repot if needed. Watch for root-bound conditions.
Hydrate & Harden
1 Water every day, possibly twice in hot weather.
2 Reduce nitrogen - increase potassium and phosphorus to harden growth.
3 Loosen wire that's biting into branches before it scars.
4 Begin hardening trees for fall - reduce pinching frequency.
5 Last chance for air layering - layers need time to root before fall.
6 Next year's buds, leaves, and flowers are already being set this month - heavy pruning now may trigger new growth that won't harden before winter.
7 Stop leaf pruning of deciduous trees by the end of August.
8 Eliminate nitrogen fertilizer entirely by month's end - switch to a high-potassium formulation.
Watering
Daily, possibly twice in heat
Fertilizing
Regular - reduce nitrogen in late summer
Pruning
Maintenance pinching and trimming
Repotting
Only tropicals if needed
Deciduous
Shift to low-nitrogen fertilizer. Allow growth to harden. Final defoliation window.
Conifers
Needle pull pines if not done. Wire junipers - fall wiring season begins.
Tropical
Continue normal care. Begin reducing fertilizer late in month.
Harden & Cut
1 Begin hardening-off for winter in earnest - avoid drastic pruning, collecting, or repotting.
2 Apply low-nitrogen fertilizer (higher in potassium and phosphorus) after leaves fall but before November to promote bud formation and strengthen roots.
3 Take hardwood cuttings for propagation. This is the last opportunity to pot up air layerings before winter.
4 Plan and prepare winter storage area - an unheated shed or garage that stays above 35°F is ideal.
5 Remove wire from branches that have set properly. Be aware of thickening branches on wired pines.
6 Enjoy autumn color - photograph your trees at their peak.
7 This is the last opportunity for Jin and Shari work while sap is still flowing - bark becomes much harder to loosen after temperatures drop.
8 Remove leaf litter and debris from soil surface to prevent disease from taking hold. Dead moss should also be cleared away.
9 Moss planted in September will grow through warm autumn spells and establish well by spring - limit it to areas around roots, as too much harbors pests.
Watering
Reduce as growth slows
Fertilizing
Low-nitrogen, stop by November
Pruning
Final structural pruning
Repotting
Wait until spring
Deciduous
Final pruning for shape before dormancy. Heavy feeding with 0-10-10.
Conifers
Wire pines and junipers. Heavy fall feeding to build strength for winter.
Tropical
Begin transitioning indoors in late September. Reduce fertilizer.
Prune & Prepare
1 Growth drawing to a close - stop fertilizing most species.
2 Heavy branch pruning on pines - wounds seal slowly in fall, reducing sap bleed.
3 Prepare winter storage area - cold frame, garage, or unheated room.
4 Many evergreens can be wire-trained in autumn.
5 Clean and oil tools for winter storage.
6 October is prime time to scout garden centers - many discount trees and shrubs up to 50%. Look in the back for stock with broken tops or low crooked branches that normal shoppers pass over - perfect bonsai candidates.
7 Remove any wire that is beginning to dig into branches. Snip carefully with a wire cutter rather than unwinding - unwinding can snap set branches. Avoid re-wiring now; wait until spring.
8 Keep an eye out for plants to dig and pot for next year's training - hardwood cuttings and hard-shelled seeds can be planted outdoors now.
Watering
Reduce as growth slows
Fertilizing
Low-nitrogen, stop by November
Pruning
Final structural pruning
Repotting
Wait until spring
Deciduous
Stop feeding. Allow natural leaf drop. Clean fallen leaves from soil surface.
Conifers
Final wiring opportunity. Cut back junipers. Stop feeding by month's end.
Tropical
Move indoors before first frost. Set up grow lights if needed.
Store & Protect
1 Trees can remain outdoors until month's end in most NJ locations.
2 Check for insects and spray before moving to winter storage.
3 Remove dead leaves and branches - clean up for winter.
4 Tropical bonsai should already be indoors with supplemental lighting.
5 Reduce watering frequency but don't let roots dry out completely.
6 Protect container trees from winter rodents: wrap hardware cloth around pots or move trees into a cold frame.
7 Only rough pruning of raw material should be attempted now - leave short stubs that can be refined to shape in spring. Well-sealed wounds may still die back around edges if winter is severe.
8 Spray trees with a non-systemic fungicide before storage - gives the material time to work before trees return in spring. Clean display areas and spray with fungicide and pesticide to eliminate overwintering pests.
9 You may have luck with hardwood cuttings taken now - some species root reliably from November cuttings.
Watering
Reduce as growth slows
Fertilizing
Low-nitrogen, stop by November
Pruning
Final structural pruning
Repotting
Wait until spring
Deciduous
Move to winter protection after hard frost. Water lightly.
Conifers
Hardy outdoors but protect from drying winds. Water on warm days.
Tropical
Indoor care: bright light, humidity tray, reduced watering. Watch for pests.
Assess & Design
1 Assess deciduous tree design while bare - the true structure is revealed.
2 Wire evergreens (not deciduous - branches too brittle when frozen).
3 Plan repotting schedule for spring and order soil components.
4 Mix soil, clean and sharpen tools, organize supplies.
5 Prevent soil freeze-thaw cycles and wind dehydration in storage.
6 A cold frame - an unheated structure that stays just above freezing - protects trees from desiccating winter winds while preserving natural dormancy.
7 Hardy species can be dug and potted into large containers or growing beds now. Large fully-hardy deciduous trees can be repotted if roots can be protected from hard frost all winter.
8 Inspect conifers for scale, galls, and spider mite - spray on dry, sunny days when temperatures are above freezing.
9 If any tree failed to show growth by mid-season, inspect carefully both above and below ground to understand the cause - this knowledge helps prevent future losses.
Watering
Minimal - check weekly
Fertilizing
None - trees are dormant
Pruning
Heavy structural pruning OK
Repotting
Wait until spring
Deciduous
Study structure. Sketch design plans. Keep roots from freezing solid.
Conifers
Wire freely. Jin and shari work can be done. Keep soil barely moist.
Tropical
Maintain indoor conditions. Reduce fertilizer to monthly. Watch humidity levels.
Our members have decades of experience with bonsai care in the Northeast climate. Join us any second Tuesday to learn hands-on.