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I am new to bonsai in fact, I have no bonsai tree's over the age of about 1 month. Funny, in my attempt to grow a Japanese Katsura from seed I had left one of my seeding pots outside. I came out to bring it back inside and saw a load of cotton seed stuck to it as the stuff was very prevalent in the wind that day. I picked it all off (or thought I did) and about 2 days later I noticed a little sprout. I almost pulled it but then I thought... what the heck, and I transplanted it into its own container.

So, now I have a little cottonwood tree sprout growing and I think I want to try and make it into a bonsai. So my question is:

Has anyone here made a cottonwood bonsai before and if so, any tips? Also, how long should I wait to plant this outside and how long should it stay there growing?

Some info:

USDA growing zone: 4b-5a

The Köppen Climate Classification subtype for this climate is "Dfb". (Warm Summer Continental Climate).

The average temperature for the year in Bozeman is 41.0°F (5°C). The warmest month, on average, is July with an average temperature of 65.0°F (18.3°C). The coolest month on average is January, with an average temperature of 15.0°F (-9.4°C).

The highest recorded temperature in Bozeman is 100.0°F (37.8°C), which was recorded in July. The lowest recorded temperature in Bozeman is -46.0°F (-43.3°C), which was recorded in January.

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You'll need a lot of patience growing bonsai from seed. I never had cottonwood as starting material (is that Populus? is that native to your region?). But I have experience with Acer, Ulmus, Quercus, and Aesculus. How you usually grow (deciduous) bonsai from seed, is to grow it for 5-7 years in a large container. Trim and prune the plant so that it will fit your container. After these 5-7 years trim it into a bonsai in a real bonsai pot. Try to save your plants from hard frost (around -10C or lower), maybe keep it during the frost period in a cool place such as a cellar or garage.

See here for some starting tips. Good luck with your project.

  • Yes it is; specifically, Populus balsamifera ssp. trichocarpa or Black Cottonwood is native along the rivers from Alaska to California, and east to Montana and up into Canada. It is a beautiful tree when full grown and it produces hardy wood. In fact, I believe Lewis and Clark used it to make wheels, axles and frames for their portages. Unfortunately, I have a slight allergy to the cotton it produces so I have a love/hate relationship with the tree but thanks for the info! – Rob Jul 31 '18 at 20:12
  • To use trees native to your region is always a good idea! Then you know it is in the right climate. – benn Jul 31 '18 at 20:20

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