1. Up to 3 Years After Planting
This is probably the number one misunderstood watering rule: a plant isn't “established” after just a few months of watering. Many trees, shrubs, and perennials take up to three years to grow a strong root system after transplanting. During that time, they rely on supplemental water far more than gardeners realize. Other than cacti or other highly drought-adapted plants, any newly planted plant that isn't getting the equivalent of an inch of rain every week, and more in hot weather, probably needs water (and even new cacti will need a little).
2. While Flowering or Fruiting
Producing flowers, fruit, or foliage takes a lot of energy. Watering plants during those times is essential for keeping those systems running. Think of it like hydration during exercise: when plants are working hard, they need consistent moisture.
This applies not only to fast-growing annual edibles such as tomatoes and basil, but to plants you might forget. Spring-blooming bulbs, for example, benefit from watering while they're building energy before going dormant. Likewise, amaryllis appreciate steady moisture while growing foliage after flowering, both indoors in spring, and outdoors in summer before their fall rest period.
3. During an Extended Drought and Afterwards
Even established trees and shrubs aren't immune to dry periods, and stress from drought doesn't always show up right away. Symptoms such as dieback, leaf drop, or pest problems may appear months later, especially when dry periods last several weeks or occur at unusual times of year. Deep watering during and after droughts helps plants recover and rebuild their reserves.
4. Before a Freeze
Once plants go dormant for the winter, they need less water, but it is key to keep them well-hydrated before that. Watering your outdoor plants before a freeze (when the air temperature drops to 32°F or lower) protects them against cold stress. Water fills air pockets in soil, holding the heat that has been absorbed during the day and releasing it at night. Also, being well-hydrated reduces the risk of dehydration caused by freezing. Water 24 to 48 hours before a freeze, and do it in the morning, aiming the water at the soil, not the foliage.
5. To Prevent Dog Spotting in Lawns
Dogs urinating on a lawn lead to brown spots, which are best addressed immediately. Rinse the area as soon as possible with water to reduce the concentration of salts and nitrogen, minimizing lawn damage before it sets in.
Essential Watering Tips
How much to water: Your plant's water needs change based on its maturity, how quickly the soil drains, seasonal changes, and weather conditions. Start by paying attention to local weather conditions. Smart irrigation sensors can help prevent unnecessary watering after storms.
How to avoid overwatering: Always check the soil before watering both indoor and outdoor plants, so you don't overwater your plants. Stick your finger 1 to 2 inches deep into the soil to check the moisture level. If it feels dry, it's time to water. For mature trees, it's smart to check even deeper, using a trowel to dig 6 to 7 inches.
Measuring the amount of water: It is tricky to eyeball how much water sprinklers are providing your plants. If you don't have electronic irrigation sensors, use a shallow can (anything like an empty cat food can will do) to run a test. Place the shallow can out and run your sprinkler. The can, filled to about 1 inch high, is your benchmark for how long it takes to deliver roughly 1 inch of water.
