Most bonsai I've seen are planted in shallow pots, which can require daily watering hot dry weather. Are there successful or failed examples of bonsai in deeper pots? How long can they go without being watered? Does root rot become an issue? Does wind knock them over? What kinds of media are used?
Posted May 1, 2017, 12:15 AM UTC
Cascade style bonsai tend to have taller (and narrower) pots. Also, hello fellow 8a person.
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Normal bonsai soil and a bigger pot theoretically does not have root rot as an issue because normal bonsai soil drains well. A deeper or larger pot also is better at holding more water so it is true they don't need to be watered as often. This is one way in which beginners can kill their trees which often start in small pots.
Hi cacheego, beginner questions should be posted in the weekly beginner question thread that's stickied at the top of the sub. You'll probably get more responses there.
Fun fact: given an equal volume of soil, the shallower pot holds more water longer. Scroll down to the part about the bath sponge and perched water table.
Now, that said, a larger pot with a larger volume of soil can definitely decrease watering demands somewhat. I've often kept trees in larger pots than they technically need over the years because I knew that sometimes I'd need to travel or otherwise have other people taking care of them, and I wanted them to be lower maintenance.
It's not going to buy you a week, though. Maybe just an extra day or two generally. Even still, I try to make sure they get watered every day, especially during the summer. The larger pots (for the things in larger pots) are more of an insurance policy than anything, and over the years I've gotten better at training helpers how to water my trees correctly when I'm not there, so that's becoming less necessary.
I think adding moss might help you reduce evaporation more than a deeper pot. You might also attempt bonsai that look better in deeper pots (cascade or semi-cascade). Root rot should not be an issue if you use inorganic substrate for your bonsai. (soil is discussed in detail in the beginner's wiki of this subreddit). Another option is to keep them in a greenhouse (as long as it does not get too hot in there.) Greenhouse-grown plants have reduced evaporation but might not be suitable for temperate-climate trees.
Thanks for your comment! I work primarily with herbaceous plants in peat-based media. When these plants are well-rooted and have a substantial canopy, I find that most of the water exits through the leaves (transpiration), with evaporation being a minor component. This can still lead to plants drying out in a single day, despite the large water holding capacity and large volume of soil. I found the section of the r/Bonsai wiki that discusses soil, and I'm amazed how coarse some of the inorganic mixes are -- I'd have guessed that a tree planted in Akadama/grit/DE would dry out in a couple hours of hot windy weather, moss or no. Maybe bonsai transpire less due than normal plants, or maybe trees transpire less than the plants I'm used to working with....
And I wanted to make it clear that I meant adding a layer of roadside moss on top of the substrate, which also serves an aesthetic purpose. I did not mean that you should mix sphagnum moss in the soil that you are using.
I doubt that any bonsai would dry in a couple of hours however hot and dry it is (at least in North America). Akadama/turface holds a lot of water. Bonsai are woody plants, not herbaceaous, so maybe they are less prone to quick wilting. I am growing an Ilex verticillata in NAPA/pumice and it does wilt quicker than other plants, but typically I can go a few days to nearly a week without watering. That said, you can reduce the issue of wilting by giving them afternoon shade.
Frequent watering is the price you pay for getting rapid aeration of the roots that a porous soil mix gives, which results in rapid growth and a healthy plant. Here is a very interesting article detailing the difference between planting in a pot and in the earth: https://www.evergreengardenworks.com/earthpot.htm
That's a great article. The sponge demonstration is a great way to get people to understand this. After tilting the sponge, you can touch a wick (strip of cloth, paper towel, whatever) to the bottom, to show the power of hydraulic head.
Some inorganic materials do contain lots of micropores, but with some products the micropores are so small that the water they hold is not available to the plant. I'd love to see a reference table comparing the properties of different types of media. EDIT: Looks like there's a discussion on this happening in this week's beginners' thread.
There are also multiple home-made experiments on this done by the garden/bonsai people at Houzz's garden site. Can't recall what its called.