Bonsai trees in general tend to be quite hardy and will tolerate low temperatures without experiencing harm; it is more often the extended periods of freezing weather that pose threats than shorter temperatures alone.
To protect your trees it is wise to begin winterizing them as early as possible in autumn. There are a variety of methods for doing so and all can help.
Hardiness
Bonsai trees can be exposed to an array of climate conditions. Some require winter protection while others can withstand the chill without issue – it really all depends on where you live and which species of tree is being grown.
There are various methods available to you for protecting outdoor bonsai during winter, with perhaps the easiest one being moving them into protective quarters such as a wooden frame or box. By moving them indoors, bonsai are shielded from wind gusts as well as excessive rainfall or melting snow that might otherwise damage them.
Shelter will protect a tree from predators and pests which might otherwise find itself drawn to it during the cold months, protecting against potential threats such as predators or pests which could become attracted by its warmth during winter. Pests harbored over winter can quickly multiply, leading to irreparable damage when spring arrives again.
If your outdoor bonsai remains exposed, its soil must remain very damp during winter to prevent it drying out and lose vital moisture to plants through their roots, as this water helps meet their needs and dry roots will wreak havoc with hardiness of its trees.
Applying mulch over the soil is an effective way to make sure that trees receive enough moisture and remain warm over the winter. Also be sure to remove any dead leaves before tucking it up for storage for another year.
Bonsai trees must be protected during winter if temperatures dip below -10deg Celsius (15deg Fahrenheit). Although certain junipers can withstand these extreme cold conditions, more delicate species will likely succumb to frost or freezing conditions and be damaged irreparably if left outside without protection; their cells could become permanently damaged from freezing temperatures that damage cell structures permanently.
Temperature
Consider temperature when evaluating how your bonsai will fare over winter. Depending on where you live and which types of trees you own, different protection may be required – though keep in mind that keeping it warm is more important than protecting from extreme cold.
Many temperate bonsai species that are grown outdoors require strict winterization procedures. Once temperatures turn colder, their trees should be relocated indoors for protection due to being in containers rather than soil; their roots cannot absorb as much moisture through containers, leading to their becoming weak or dying altogether.
Bonsai trees that have been exposed to prolonged periods of freezing temperatures often experience dehydration due to soil freezing and drying out, losing vital nutrients from their soil that they need. Furthermore, wind gusts or harsh winter sunlight may exacerbate these issues and accelerate dehydration further.
To combat this, it is advisable to relocate your bonsai into an environment with consistent temperatures throughout winter, such as an unheated basement, garage, cold frame or greenhouse. Furthermore, adding a grow light may allow the tree to receive enough extra moisture.
Tropical and subtropical bonsai require less protection as they’re used to living in warm temperatures all year long, though ideally located close to a window in order to receive maximum sunlight; south-facing windows tend to offer the most solar illumination during their winters.
Water
Water requirements for bonsai trees during the winter will depend on both your local climate and species. To keep the soil from becoming waterlogged, ensure it remains moist but not saturated – overwatering could make roots susceptible to freezing temperatures.
Indoor bonsai should be kept in an environment in which temperatures remain consistent throughout winter, such as an unheated basement or garage. Furthermore, heater vents should be avoided as these can cause temperature variations that cause bonsai trees to fluctuate significantly.
Bonsais should also be kept indoors to protect it from wind damage, which can result in moisture evaporating away from its roots and harming its health. To mitigate this effect, position it in a protected location with plenty of shelter available, covering it with a tarp to shield from raindrops if necessary and use a cover sheet as additional protection from precipitation.
Outdoor bonsai trees should be protected from frost by covering them with a layer of snow, similar to how indoor bonsai are protected with tarps, but care must be taken that the cover does not constrict root growth and limit their development.
If you live in a very cold climate, it is wise to move any outdoor bonsai that may become frost-damaged in an unheated shed, garage, or cold frame during wintertime. This can prevent roots from being affected by frost damage which could prove fatal for the plant itself.
Many novice gardeners mistakenly assume that frost-hardy plants will thrive outdoors without needing protection, which may be true of deciduous bonsai trees as they naturally enter dormancy in wintertime; however, even these could succumb to severe conditions if left alone for too long.
If bringing an outdoor bonsai indoors for the winter, fertilization should stop in late August in order to facilitate its dormant period and prepare it for its dormancy period. Continued growth during this period could compromise its internal clock, leading to poor health in spring.
Light
Many bonsai enthusiasts bring their trees indoors during winter to provide shelter from harsh conditions. Unfortunately, this prevents dormancy and disrupts its natural cycle of growth and rest throughout the year, increasing thawing/refreezing which damages roots; additionally, constant light and warmth encourage continued growth contrary to what would normally occur before dormancy again resumed come spring.
If you live in a mild climate, temperate bonsai may not need extra protection during winter. This includes pines, junipers and deciduous trees which lose their leaves in autumn. Tropical bonsai which have been grown outdoors will require shelter when temperatures drop: this could include providing them with shelter such as greenhouse, unheated garage or cold frame facilities.
Not only can these structures offer a warm environment, they can also protect root systems from frost. Many people add mulch or insulation layers to ensure that soil stays moist and cool – as it should. It is also wise to regularly remove any fertilizer buildup on the surface of soil that might create crusting that makes watering difficult later.
As part of winter tree care, it is vital that trees go into dormancy appropriately in order to survive harsh weather and come back into full health in spring. To do this, remove any dead branches or leaves from trees before placing them in a safe area until spring arrives.
To maintain dormancy in plants, it’s essential to avoid overwatering in fall and apply dormant oil. Furthermore, it may also help to remove leaves from deciduous trees and rake away old brown needles from coniferous trees – this will prepare the plants for winter while helping prevent insects or fungus from overwintering in their roots.