Q. I really want a red bird of paradise in our yard. I killed a new plant last year by over-watering. We have the typical irrigation of watering in the early morning and after 7pm. Other than size of the sprinkler heads we use I don’t know how to water my new plant. Can you help me?
A. This plant died from watering it too often. It may not use a lot of water, but it needs to get watered more often than a desert provides or it will die. It, and its relatives, grow naturally throughout the tropics and subtropics where water is available ideally more often.
Secondly, the only plants that need daily watering in the summer are very shallow rooted lawns (ex. tall fescue), most annual vegetables (e.g. tomatoes, eggplant, peppers, etc.) and annual flowers like petunias and snapdragons. Generally, the larger the plant, the deeper its roots. Woody plants that grow to three feet tall have roots that can grow as much as 12 inches deep; woody plants up to 12 feet tall have roots that can grow as much as 18 inches deep, plants that are 25 feet tall have roots that can grow 24 inches deep, etc.
Water according to the 40-30-20-10 rule. If any sized root (12 inches to three feet) is divided into fourths, the top fourth consumes the most water, next is the second quarter, then the third, etc. When water use is calculated from dead plants, it is found that the top fourth uses about 40% of the water, the next quarter uses about 30%, then 20% and the last approaches 10%. If you want deeper roots, apply water all at once to root depth; let the first quarter use the water and don’t water again until the second quarter is being used. When you water this way, evaporative losses are minimized, and more water gets the roots to grow.
All woody plants (your red bird of paradise is a “woody plant”) need at least one day without any water during the summer. This type of watering allows roots to “breathe” and develops deeper root growth. It improves heat resistance. Ideally these plants should be watered when the soil is no longer moist but starting to dry when the probe is pushed 4 to 6 inches deep.