Answer: Plants in containers are at risk because the pots can overheat in the sunshine and literally bake the roots. A second problem is that soil in containers can develop air pockets and even though you are watering thoroughly, the water can simply pour out the drainage holes without moistening the soil. The way to overcome this is to set the pot in a larger container of water and let it soak for about 30 minutes, then remove and allow to drain. Don't water again until the top inch of soil is dry. At that time, water throughly and allow to drain. Every 3-4 weeks give the pot the immersion watering to drive out any air pockets.
As for absorbed sunshine, you can either set the pot in a larger decorative pot lined with insulation, or group your containers together so they help shade one another. A third option is to set the pot where an existing shrub will shade the pot from afternoon sunshine.
Finally, be careful with fertilizer. It's easy to overfertilize and burn the roots of containerized plants; use a half-strength dilution of liquid fertilizer to ensure you're not overfeeding.
Best wishes with your guava trees!
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