Ce calendrier horticole est spécialement conçu pour les zones de rusticité 4 au Canada.
Si vous vous trouvez dans les zones 3, 5, 6, 7 ou 8, certaines tâches devront peut-être être effectuées plus tôt ou plus tard.
Please let me know if you have any suggestions or changes!


A huge thank you to Christopher, a bonsai enthusiast, for allowing me to use much of this horticultural calendar.
Your help is greatly appreciated!


In the fertilizer market, a standard has been established for the display: you'll always find three digits representing nitrogen (N), phosphorus (P) and potash (K).
When I refer to a type of fertilizer, it's not just the numbers that are important, but also the formula to be obtained. For example, if I recommend using a fertilizer rich in nitrogen (e.g. : N.P.K. – 10.5.5), the aim is to find a fertilizer whose first digit is higher than the other two. The same applies to the other formulations.

January

GENERAL

  • Read the articles you didn't read during the season.
  • Organizing your next season.
  • Preparing the substrate for future repotting
  • Plan the final development of your trees by making sketches.

Tropicals

  • Bring extra moisture and light to your indoor bonsai.
  • Fertilize with a complete fertilizer but higher in nitrogen ( Ex.: N.P.K. – 10.5.5)

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Ligating, pruning, sharis and jins on conifers in cold greenhouses.
  • Start your seedlings, put some soil in a ziploc bag (1/4 cup), a little water (1 tablespoon), mix with your seeds and refrigerate.
  • Adjust watering in your cold greenhouse according to substrate humidity.
  • Watering frequency can vary from once a week to once or twice a week, depending on species and substrate.
  • Beware in winter, as the substrate may still be damp on the surface, but completely dry deep down.
  • Do not exceed three weeks without watering.

RUSTICS

February

GENERAL

  • Read the articles you didn't read during the season.
  • Organizing your next season.
  • Preparing the substrate for future repotting
  • Plan the final development of your trees by making sketches.

Tropicals

  • As the days lengthen, some trees are showing signs of regrowth and budding.
  • Fertilize with a complete fertilizer but higher in nitrogen ( Ex.: N.P.K. – 10.5.5). You can halve the dose if you don't want a growth spurt (wilting) due to lack of light or the risk of burning the roots.

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Mid-February: repot very early trees such as elms, cherries, apricots, quince and three-lobed maples if they are already budding.
  • End of February: repot Japanese maples when buds are fully expanded.
  • Watch for budding of early species.
  • Unpack your seedlings from the fridge and sow them.
  • Increase watering frequency slightly if necessary

RUSTICS

March

GENERAL

  • Read the articles you didn't read during the season.
  • Organizing your next season.
  • Preparing the substrate for future repotting
  • Plan the final development of your trees by making sketches.

Tropicals

  • Most trees should have resumed their growth with the longer days. Some species will even go into flower
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Make your air layering.
  • Grafting on pine trees.
  • Slightly increase the frequency of your watering according to the temperature in your greenhouse and the level of activity of your trees.
  • Cuts Japanese maples.
  • Repot conifers in cold greenhouses: junipers, pines, yews, chamaecyparis, cryptomerias, ginkgos.
  • Re-pot other less early deciduous trees: boxwood, beech, etc.
  • Do a thinning pruning to allow light to penetrate the often overcrowded branches.
  • Pinch new shoots on pines, yews and maples.

RUSTICS

April

GENERAL

  • Be careful with all types of bonsai. Outside temperatures are often variable. So make sure it's just right for your bonsai, especially if you've started taking them out of their shelters or your cold greenhouse.

Tropicals

  • Resist the temptation to take your trees outside if the temperature is below 10 degrees Celsius.
  • For developing trees, continue to fertilize flowering trees with a phosphorus-rich fertilizer (e.g. N.P.K. – 5.10.5).
  • For developing trees that do not flower, use a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Make sure you constantly check the temperature inside your greenhouse
  • Make your air layering.
  • Grafting on pine trees.
  • Continue to fertilize developing trees with higher nitrogen fertilizers ( Ex.: N.P.K. – 10.5.5).
  • Fertilize only with chemical fertilizers (take care not to burn your trees' roots by following the manufacturer's recommendations).
  • Delay fertilization of “finished” bonsai to reduce leaf/needle size.
  • Continue pinching pines, yews and maples if necessary, depending on the tree's stage of development.
  • End of April: take the trees out of the cold greenhouse when night-time temperatures are no longer expected to fall below 3°C.
  • Leave them in the shade for around two weeks to avoid burning the foliage and allow them to acclimatize to the new temperature.
  • Treat your trees with insecticide to kill eggs and insects that hibernate in cold greenhouses.
  • Treat your trees with a fungicide (bordo/copper or sulfur-based) to prevent the development of fungal diseases that thrive at cool temperatures.

RUSTICS

  • Keep your shelters under snow as long as possible to avoid premature budding.
  • If your trees have come out of their winter protection, leave them in the shade for about two weeks to avoid burning the buds and allow them to acclimatize to the new temperature.
  • Start fertilizing rustic trees with slow-decomposing fertilizer granules.
  • End of April, repot all rustic trees once the danger of frost has passed.

May

GENERAL

  • You should therefore start moving your trees out of their shelters and cold greenhouses. However, leave them in the shade for about two weeks to allow them to acclimatize gently.

Tropicals

  • Resist the temptation to take your trees outside if the temperature is below 10 degrees Celsius.
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC

Trees that cannot tolerate temperatures below
to 0 degrees Celsius.

  • Continue to fertilize developing trees with higher nitrogen fertilizers ( Ex.: N.P.K. – 10.5.5).
  • Use only chemical fertilizers (be careful not to burn the roots of your trees).
  • Delay fertilization of “finished” bonsai to reduce leaf/needle size.
  • Continue pinching pines, yews and maples if necessary, depending on the tree's stage of development.
  • Take the trees out of the cold greenhouse when night-time temperatures are no longer expected to fall below 5°C.
  • Place them in the shade to avoid burning the foliage.
  • Treat your trees with insecticide to kill eggs and insects that hibernate in cold greenhouses.
  • Treat your trees with a fungicide (bordo/copper or sulfur-based) to prevent the development of fungal diseases that thrive at cool temperatures.

RUSTICS

  • Remove the trees from their winter protection. Place them in the shade for a few days to avoid burning the growing stems.
  • Start fertilizing rustics with slow-decomposing fertilizer granules for 4 months. For pines, wait until the candles have developed and been pruned.
  • Re-pot all rustic trees once the danger of frost has passed.

June

GENERAL

  • All your trees, including tropical trees, should be placed outside to give them maximum energy during the summer.
  • Frequent fertilization with chemical or organic fertilizers.
  • Water once or twice a day, depending on criteria such as exposure to wind and sun, substrate type, species and pot size.
  • Watch out for aphid and other insect infestations. Treat as needed.
  • Watch out for fungal diseases that may develop in cool, rainy weather.

Tropicals

  • If you haven't already done so, take the tropical trees outside, but make sure the night-time temperature doesn't drop below 10°C. If it does, bring the trees in for the night.
  • In warm weather, start repotting.
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC

Trees that cannot tolerate temperatures below
to 0 degrees Celsius.

  • Defoliate trilobate and palmate maples.
  • Remove spent flowers from azaleas to prevent seeds from developing.
  • Early June: finish repotting azaleas.
  • Mid-June: Deciduous tree cuttings on branches that have begun to harden.
  • Partially defoliate deciduous trees (maples, fruit trees, etc.) and cut them up when the first growth spurt is over.
  • Pinch the candles on Japanese pines.

RUSTICS

  • All rustic trees should be outdoors.
  • Pinch candles on native pines and larches.

July

GENERAL

  • All your trees, including tropical trees, should be placed outside to give them maximum energy during the summer.
  • Frequent fertilization with chemical or organic fertilizers.
  • Water once or twice a day, depending on criteria such as exposure to wind and sun, substrate type, species and pot size.
  • Watch out for aphid and other insect infestations. Treat as needed.
  • Watch out for fungal diseases that may develop in cool, rainy weather.
  • Place some varieties of tree, such as Japanese maples, in partial shade or under an shade structures to avoid damage to foliage from too much sun.

Tropicals

  • With the warm weather, it's an excellent time for repotting, which guarantees a good recovery.
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC

Trees that cannot tolerate temperatures below
to 0 degrees Celsius.

  • Be careful with watering frequencies, as heat, dry weather and winds can quickly dry out your trees.
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

RUSTICS

  • Be careful with watering frequencies, as heat, dry weather and winds can quickly dry out your trees.
  • Offer maximum sun exposure to conifers such as pine, larch and spruce.
  • Fertilize flowering trees with a high phosphorus fertilizer (e.g. N.P.K. – 5.10.5).
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

August

GENERAL

  • Mid-August: Switch to a fertilizer richer in potash (e.g. N.P.K. – 5.5.10) to optimize bud formation for the following spring and strengthen your trees' resistance for the coming winter.
  • Adapt watering to the temperature, which can vary at this time of year.

Tropicals

  • With the warm weather, it's an excellent time for repotting, which guarantees a good recovery.
  • Prune trees that have thrived during the season.
  • Be aware of night-time temperatures: some tree species have difficulty with temperatures below 10 degrees Celsius. If this is the case, bring your trees indoors for the night.
  • Continue to fertilize trees that are not flowering with a nitrogen-rich fertilizer (e.g. : N.P.K. – 10.5.5).

SEMI-RUSTIC

Trees that cannot tolerate temperatures below
to 0 degrees Celsius.

  • Early August: graft junipers with this year's shoots. Protect with sphagnum moss and a ziploc bag.
  • Mid-August: second growth, resume fertilization.
  • Protect fruit trees from squirrels and birds.
  • Remove pine needles in the appropriate way to obtain
    lateral buds next spring.

RUSTICS

  • Mid-August: Switch to a fertilizer richer in potash (e.g. N.P.K. – 5.5.10).

September

GENERAL

  • Frequent fertilization with chemical or organic fertilizers.
  • Choose a formula rich in potash: (e.g. N.P.K. – 5.5.10)
  • Water once or twice a day, depending on criteria such as exposure to wind and sun, substrate type, species and pot size.
  • Watch carefully for infestations of aphids and other insects, and treat if necessary.
  • Apply a fungicide treatment if cool, rainy conditions are forecast.

Tropicals

  • Move your tropical trees inside as soon as the night-time temperature drops below 10 degrees Celsius.
  • Treat them against insects before installing them indoors.
  • Don't worry if your trees lose a few leaves after moving indoors: they need time to acclimatize to their new environment.

SEMI-RUSTIC

Trees that cannot tolerate temperatures below
to 0 degrees Celsius.

  • Possibility of repotting conifers intended to be placed in a cold greenhouse (i.e. without exposure to frost). 
  • Mid-September: cut back sacrificial branches to give the tree time to heal before winter.

RUSTICS

  • Stop pruning your trees to allow them to heal before winter arrives.
  • It's the ideal time for collecting trees in the wild. (Yamadori)

October

GENERAL

  • Tropical trees must be brought indoors.
  • Adapt your bonsai's watering to temperature variations.
  • Watch carefully for insect infestations and fungal diseases.

Tropicals

  • Tropical trees placed indoors experience a reduction in activity and may lose their leaves.
  • Adapt your watering and avoid positioning your bonsai near heat sources.
  • Keep an eye out for insect infestations.
  • Stop fertilizing your tropicals.

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Apply a fungicide treatment to prevent fungal diseases that develop in cold, damp weather.
  • Continue fall fertilization until the end of October (e.g. N.P.K. – 5.5.10).
  • Remove two-year-old and three-year-old needles from pine trees.
  • Remove moss to allow roots to breathe over winter.
  • Early October :
  • Protect shohins sensitive to cold.
  • Prepare insulation and clean greenhouses before placing trees.
  • Carry out two treatments with horticultural oil (2% dilution) before returning the trees to the greenhouse, with a one-week interval between each treatment.
  • From mid- to late-October, bring in semi-rustic trees, depending on weather conditions.
  • Adjust watering when entering the cold greenhouse.

RUSTICS

November

GENERAL

  • Read the articles you didn't read during the season.
  • Organizing your next season.
  • Preparing the substrate for future repotting
  • Plan the final development of your trees by making sketches.

Tropicals

  • Tropical trees placed indoors experience a reduction in activity and may lose their leaves.
  • Bring extra moisture and light to your indoor bonsai.
  • Adapt your watering and avoid positioning your bonsai near heat sources.
  • Keep an eye out for insect infestations.
  • Stop fertilizing your tropicals.

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Transfer all your semi-rustic bonsai to a cold greenhouse.
  • Remove leaves from maples and other deciduous trees.
  • Ligature, if necessary, deciduous trees that have lost their leaves.
  • Adjust the watering of trees in cold greenhouses.
  • Clean trunks and apply preventive antifungal treatments.
  • Remove moss and weeds from the substrate.

RUSTICS

December

GENERAL

  • Read the articles you didn't read during the season.
  • Organizing your next season.
  • Preparing the substrate for future repotting
  • Plan the final development of your trees by making sketches.

Tropicals

  • Tropical trees placed indoors experience a reduction in activity and may lose their leaves.
  • Bring extra moisture and light to your indoor bonsai.
  • Adapt your watering and avoid positioning your bonsai near heat sources.
  • Keep an eye out for insect infestations.
  • Stop fertilizing your tropicals.

SEMI-RUSTIC (cold greenhouse)


Temperature between 2 and 5 degrees Celsius

  • Water semi-rustic plants once a week to once every two weeks, depending on the climate of your greenhouse, the level of activity of your trees and the size of the pots.
  • Keep a close eye on the watering of your trees. Substrate can appear wet on the surface when it's dry inside, which is often the main cause of tree loss in cold greenhouses.

RUSTICS