My first bonsai winter

Kisetsu-en Shohin Bonsai Europe FORUM Q&A My first bonsai winter

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    Nancy Hoffman

      Hello – I live in Washington State, USA, in the lovely Pacific NW. Our summers are mild and not too hot, and extremely dry from May to October. Our winters are quite rainy – we get the vast majority of our considerable rainfall from October to April.  And we sometimes get snow and ice as well. We typically have winter temperatures above freezing, but we occasionally get cold periods that can last a few days or a week here because we are at the west end of the Columbia River gorge. East of where I live is Mount Hood, and then further on is high desert – where winters are extremely cold. The Colombia Gorge sometimes acts a a funnel for very cold easterly winds and low temperatures.  I just started my bonsai journey this year in spring. I have dug up some trees and shrubs from my own garden, a few were given to me by friends and neighbors, and I have been able to find other free or inexpensive plants and a few plants from nurseries. Here is my chief concern – since many of my plants were acquired over the summer I chose not to repot them and wait until spring. In September I did carefully move some mugo pines and other small japanese white pines and black pines pines to pond baskets to offer better drainage over the wet winter months. I did this without disturbing the soil, which looks to be mainly pine bark with maybe a bit of pumice mixed in. I also have some japanese maples, and shrubs like pyracantha, cotoneaster, flowering quince and japanese holly in the nursery pots they came in. My plan is to keep everything outside all winter, I do have a pop-up greenhouse where I can put things if it gets too cold for an extended period, or especially for the pines it it gets too wet – which is more likely the issue. Any advice? I want to have as many trees in good health in the spring so I can repot into better substrate and start their early development. Thank you in advance for your help and understanding the concerns of a beginner.


        Sounds like a great start with many species needing different kinds of attention too.

        Your winters seem equal to what we have around here nowadays and therefore I can share what we do here to keep trees well overwintered.

        when it gets cold in shorter periods like one week native and adapted trees will have no problems. Only trees like Gingko and Trident maples that hate cold roots will benefit from being inside a polytunnel or equal to have higher root temperatures during winter.

        Pines hate to be wet, so place these under some sort of shelter in wet periods no matter how well draining the soil is. It can be a simple roof or any other arrangement keeping them from being soaked in rainy periods. Japanese red and black pines are especially prone to root rot if too wet over time.  Temperature wise they love the cold, especially P. mugo.

        By the way, avoid pine bark in the substrate as it breaks down quickly and ruins the overall soil structure, so it isn’t good at all for bonsai. Replace it with Pumice or lava in spring or the next time you need to repot.

        It might demand moving trees around in between so they get the best possible situation. It sounds like you have covered the main aspects and concerns fine. You can bring in most trees in an open polytunnel, pop-up or stationary greenhouse where airflow is keeping fungi out, and then close it if it gets cold for some days. But open the doors as soon as it isn’t to circulate air.

        Also, take care of cold winds, and winds in general if the soil is frozen. Roots can’t take up water when the soil is frozen, and winds will dry them out fast.

        You should be covered if you check your trees regularly and also be sure to water if they dry out. Even when it’s cold, but not freezing, the water will evaporate from the soil, and more trees are damaged during winter from drought rather than cold (as long as the species cope with freezing). Water sparsely though avoiding trees soaking.

        Most trees here stay outside but move in in cold or wet periods in a shelter. We get very wet periods and this is as damaging for the roots as freezing. Hope this helps, but be sure to ask again if there is something not clear. I will take the subject up in the next members’ Live Q&A on Thursday. 

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