Irrigating Trees Properly and Seasonal Adjustments (Arizona)
Proper irrigation is essential for maintaining the health and productivity of trees, particularly fruit trees. However, irrigation schedules and techniques must adapt to seasonal changes, soil types, and tree species to maximize effectiveness. In this article, we’ll explore how to adjust irrigation with the seasons, how soil properties influence water retention and drainage, and the impact these factors have on your irrigation practices. If needed, consider hiring a professional for installation or evaluation of your existing system.
The Importance of Seasonal Irrigation Adjustments
Trees require varying amounts of water depending on their growth stage and the season. Understanding these seasonal needs ensures healthy root development, better fruit production, and overall tree vitality.
Spring: Awakening and Growth
What Happens: Trees break dormancy, and fruit trees begin flowering and fruiting. This is a high-demand period for water.
Irrigation Tips: Gradually increase irrigation frequency as temperatures rise and the tree's water needs grow. Ensure water reaches the deeper roots, encouraging strong root development. Avoid watering foliage to reduce the risk of fungal diseases.
Summer: Peak Demand
What Happens: Hot temperatures increase water evaporation, and trees are in full growth or fruiting stages.
Irrigation Tips: Deep-water trees every 7–10 days, depending on soil type and tree species. Water early in the morning or late in the evening to minimize evaporation. For fruit trees, ensure consistent moisture to prevent fruit drop or splitting.
Not only does soil water evaporate faster in summer heat, but trees also Transpire water through their leaves at a rapid rate to stay cool as well. These two factors have an exponential increase on the need for water. In some severe cases, such as this summer (2024 Arizona) watering even established trees was as frequent as two to three times weekly. This is why, even with an irrigation schedule you must routinely assess the needs of your trees. Many people who just stuck to their pre-determined schedule lost trees due to drought, despite having a dedicated drip irrigation system installed and operating.
Autumn: Preparing for Dormancy
What Happens: Growth slows, and trees prepare for dormancy. Fruit trees may still be producing late-season harvests.
Irrigation Tips: Reduce irrigation frequency as temperatures cool, but ensure adequate water to support root activity. Avoid overwatering, as excess moisture can lead to root rot.
Winter: Dormancy
What Happens: Deciduous trees lose their leaves and enter a low-maintenance state, while evergreens still require some moisture.
Irrigation Tips: Water infrequently, only when soil is dry or during extended dry periods. Focus on providing moisture to the root zone before hard freezes.
This helpful chart serves as a base guideline for your irrigation needs, the rates listed are for established plants that will require less water than newly planted. Once a tree or plant has a well established root system, it is considered “established”.
A drip system or slow dispersal of water over a long period of time is the best method to achieve the depth required to fully water most trees and some small plants. This is called “deep watering”. In order to measure water depth, use a ground stake, rebar, etc. and press it into the moist soil. You should clearly be able to see how deeply the water has reached upon visual inspection.
Avoid pipe systems or under ground delivery methods of irrigation. While this seems intuitively designed, it is actually not ideal for the tree. By depositing water directly into the ground (foregoing absorption and drainage from surface) you bypass all the processes that enrich soil and microbiota, facilitating the exchange of nutrients from environment to organism. Soil is supposed to get wet frequently, this promotes healthy soil living organisms such as fungi and bacteria to be present. These organisms aid in the decomposition process of organic matter, which most trees will produce over time. Through the breakdown of living matter, the microbes excrete nutrients as well as attract other organisms such as earth worms. If a healthy ecosystem can thrive underneath your tree, you would theoretically never need fertilizer to keep it thriving.
When I try to explain this concept to someone, I always ask them to think about the forest floor. Often times, it is covered in several inches or layers of decomposing leaves, needles, bark, etc. And underneath that thick blanket is a very rich soil just teeming with life. These ecosystems have sat undisturbed by man, and we should do everything we can to replicate these results. For most trees, this is their ideal environment. So stop raking up those leaves and let them collect around the base of the tree. Better yet, you can mulch them into smaller pieces and speed up the decomposition process. By having a mulch layer that is several inches thick around the tree, moisture can be retained, and ground temperature lowered in the brutal sun, thus greatly enhancing the efficiency of your irrigation schedule.
Understanding Soil Types and Their Influence on Irrigation
Soil type plays a critical role in determining how often and how much you should water your trees. Here’s a breakdown of common soil types and their properties:
1. Sandy Soil
Properties: Drains quickly. Poor water and nutrient retention.
Irrigation Implications: Water more frequently but in smaller amounts to prevent leaching. Consider adding organic matter to improve water retention.
Sand particles are large and will settle into low spots, facilitating drainage of water from soil. I often add sand to clay rich soils when backfilling a newly planted tree.
2. Loamy Soil
Properties: Ideal balance of drainage and water retention. Supports healthy root growth and nutrient uptake.
Irrigation Implications: Deep-water less frequently, allowing moisture to reach the root zone. Check soil moisture regularly to prevent over- or under-watering.
Loam is a medium sized particle, sitting between sand and clay and will usually retain water in a mostly “ideal” fashion; not too long, and not too short. Drainage in Loam is adequate for most plants and nutrients can be retained better due to less leaching.
3. Clay Soil
Properties: Retains water but drains slowly. Prone to compaction and waterlogging.
Irrigation Implications: Water deeply but less often, giving time for water to infiltrate. Use a slow-drip system to avoid water pooling on the surface.
Clay is the smallest particle size of the three soil types, it will fill every space available; even the small spots between grains of sand. Due to this ability to pack into tight places, compaction is very common in clay rich soils. This makes clay the hardest soil to grow in, but it is still viable if you understand how to irrigate properly for clay. Water runoff is very common in clay, and sometimes a hardscape solution can be implemented to assist with water retention. This can be a berm, well, dike, retaining wall, etc. Something to prevent water from flowing freely away from the targeted irrigation zone.
Adjusting Irrigation Flow Rates for Different Soils
Understanding how water moves through soil is crucial for setting the correct flow rates. Here’s how soil types influence irrigation:
Sandy Soil: Use a higher flow rate for shorter durations to saturate the root zone effectively.
Loamy Soil: Opt for moderate flow rates with deeper watering sessions to balance drainage and retention.
Clay Soil: Use a low flow rate and extend watering time to avoid runoff and allow water to percolate slowly.
Tips for Optimizing Irrigation
Use Mulch: Apply 2–4 inches of mulch around the tree’s base to reduce evaporation and regulate soil temperature. Keep mulch away from the trunk to prevent rot.
Monitor Soil Moisture: Use a soil moisture meter or dig a small hole to check moisture at the root zone (6–12 inches deep).
Implement Drip Irrigation: Drip systems provide consistent, deep watering and are ideal for all soil types. Position emitters at the tree’s dripline to ensure water reaches the active roots.
Water Based on Tree Age: Young Trees: Require more frequent watering as they establish roots. Mature Trees: Require deeper, less frequent watering to support larger root systems.
Key Takeaways
Adjusting your irrigation schedule based on seasonal needs and soil type ensures your trees receive the right amount of water at the right time. By understanding your soil’s drainage properties, using efficient irrigation methods, and monitoring conditions, you can promote healthy, thriving trees year-round.
Whether you’re caring for ornamental trees or cultivating a productive fruit orchard, tailoring your approach to seasonal and soil considerations will safeguard your investment and enhance your landscape's vitality.
