Answer: I'm assuming you planted it recently in October and by orchid tree you are referring to Bauhinia lunarioides. This a low-water-use tree, but it is on the higher end of the low-water-use continuum, so it may need slightly more frequent watering than a native tree. How often to water depends on soil type, weather conditions and other factors, but as a guideline for desert-adapted plants, in fall, water every 3-4 days for weeks 1-2 (after planting); every 6-7 days for weeks 3-4, every 7-10 days for weeks 5-6 and every 10-14 days for weeks 7-8. Thereafter, gradually extend the time between waterings to every 14-30 days until spring. When temperatures heat up in summer, water as often as every 7 to 21 dayy. Water should soak deeply through the entire rootball with each watering.
Use the 1-2-3 Rule as an easy method to figure out how much water to apply. Small plants with shallow root systems, such as perennials, veggies, herbs, cacti, succulents have roots that reach about 1 foot deep, so water needs to penetrate that far. When the top 1 inch of soil dries out, it's usually time to water again. Shrubs have root systems that are 2 feet deep so water needs to soak 2 feet deep. When the top 2 inches of soil dries out, it's time to water. Trees are 3 feet, etc. As plants establish root systems, the time between waterings can be lengthened, but it is always essential to water to the same depth. So you are applying the same amount of water with each irrigation regardless of the time of year, but the frequency changes. As warm weather arrives, you need to water more frequently than during winter.
As plants mature, emitters (or hose or whatever irrigation system used) must be moved outward to keep pace with the expanding root system. Feeder roots that absorb water are spreading out past the dripline (canopy edge), so apply water just beyond that. Add a layer of organic mulch around the base of your orchid tree to help maintain moisture and reduce soil temperatures. Don't let the mulch touch the trunk. I hope this info helps!
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