Arizona summers can be brutal to our trees! By heeding the following sage advice, you should have a garden full of happy trees at the end of the season.
HEAT is coming next, after a delightful spring. Time to make sure your shade screen is in place (or lath framing or both), to help reduce the temperature of your bonsai pots. Those black plastic cans absorb a lot of heat as well. The best summer protection for your trees is, of course, under a shade tree--who'da thunk it? If you're just starting out, and your only plants are still in cans, your watering will be once daily, unless you have a really thirsty species. For bonsai pots, overhead shade is essential, and later in June we may need to apply a layer of sphagnum moss to the top of our root ball, even skirting to reflect heat. Rod covered all this at the last meeting, in case you missed it!
As we hit the 100 degree mark, and go over the top, you should consider watering twice daily, both early morning and mid-to-late afternoon, but not after dark. How would you like to go to bed with wet feet?
Early morning misting of foliage, and again at dusk, is always helpful, simulating dew. We have resumed fertilizing, and you can still use a 10-10-10 or 12-12-12 formula, as our nights are still cool. Once our nighttime lows stay above 70, some of our plants, especially conifers, will slow down to conserve energy and transpiration. At that time, in about two weeks, we can reduce nitrogen to the 5, 6, 8 level. Fish based products are good, such as a combination of fish emulsion and some liquid kelp. Spraying all your foliage once a week with Pro-Tekt helps strengthen the plants against drying winds and heat, and don't forget to add some to your fertilizing or watering. If you can't find it locally, order it through Amazon.
June offers a smorgasbord to spider mites, as we're warm and dry. A good blast of water once a week, with a few drops of liquid soap added, will help to fend them off.
If you spot them, usually by a color change in foliage, spray with a summer or all-season oil, which has a paraffin base, and is not toxic. Check your bonsai every time you water, and you'll head off most of these problems.
We all look forward to our summer rains -- enjoy!