Summer care

As the heat builds up the next two months, be considerate of several things…

For one, if you consistently get temperatures into the mid to high nineties and above, this is when some light shade cloth for shohin, companion plants and some of our more sun-sensitive trees such as stewartia and Ezo spruce should be put up. If you rarely get above the high eighties, shade cloth is unnecessary.

Be careful of watering. In an earlier post I wrote about the dangers at this time of year with poorly rooted trees—the ones that now will be exposing themselves with burned leaf tips. In the spring we should have been letting our trees really obviously dry out a bit before watering, which creates as strong, well-ramified fine root system. But in high heat days keep your trees moist. It is not a time to be playing around with letting roots grow out by withholding water—that is only for cooler days.

On very hot days, when the sun is on the horizon in the evening, spray the foliage and pots of your trees in a very light watering that is called hamisu in Japan: leaf watering. This refreshes a tree and cools it down. It is not meant to soak the pot.

Again with temperature, if you live where temperatures rarely get into the nineties, you may continue to fertilize throughout the summer. This is especially true for young bonsai (not necessarily young trees)—trees in development.

Watch your grafts. If you’ve done any juniper veneer grafts last month, be sure to protect even the shielding duct tape over the scion from the hot sun. The tape will reflect much of the sun’s energy, but still the top of the scion can get burned. The addition of shade cloth above grafted trees greatly increases their aftercare success rate. For approach grafts this consideration is not necessary.

Enjoy the summer days ~ One of the odd things about Portland Oregon, where I live, is that there are very few mosquitoes here. I see (or hear) only about three a year. Given all the water it is a surprise. Some people don’t even have screens on their windows…

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  1. Josef says:

    Hi Michael,

    I too have been practicing ‘hamisu’ on my trees, but have a question about the regular watering. Would it be best to soak only the soil at the time of the main watering, or would it be appropriate to soak the top of the tree at that time as well? Thanks!

    • crataegus says:


      Yes, you may water the tops of trees at the same time as general watering. If the tree has a weak branch, however, just water the weak area and not the whole tree. That localized hamisu tends to strengthen weak branches.


  2. Josef says:

    OK, thanks a lot!

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