How to Make Plants Healthier So They Can Handle More Heat

Q. I wrote to you before about my plants and you said to move them to a cooler location. You also said that if they were healthy, they can take a hotter location. I don’t want to move these plants so can I improve their health and not move them? What about a different irrigation strategy?

Add compost to the native soil so that it has more organics in it

 This raises the organic content of desert soils.

When you are done adding compost  to the soil to raise its organics, lay organic mulch on top of the soil surface to continue to "feed" the soil organics over time.

A. The relationship between plant health and how much heat stress it can take is tricky. The most common reasons for poor plant health is its location in the landscape, soil improvement or lack of it and irrigation. It’s very helpful to know where a plant originates. The plants origin tells you it’s best location in the landscape, how much soil improvement is needed and its irrigation requirement. This prior attention to details reduces your involvement in the landscape.

If the plant originates from cooler climates but can handle the heat, it performs best if it’s planted in the cooler parts of a landscape. It performs best planted on the east side of the landscape so it gets shade from the hotter late afternoon sun.

Add Organics to the Soil Like Compost

All plants benefit from some amount of structural amendment (think compost) added to the soil at planting time. The amount of amendment should vary from 10 to 30% (one in ten shovels full vs. one in three). Desert plants from the Southwest benefit from the 10% soil improvement but plants that originate from non-desert countries benefit from 30%. Throw in a couple handfuls of high phosphorus fertilizer as well.

More Water?

As far as irrigation goes, what size was the container at planting time? Plants bought in 5-gallon containers should receive five or 6 gallons of water at each irrigation. Plants growing in 15-gallon containers should receive 15 or 16 gallons of water. When irrigating new plants larger than this at least half of the volume of its container should be used to judge how much water to apply when first planted. How often to apply this water depends on the time of year or season. This is what is changed seasonally on the irrigation clock.