Wise Watering

A Guide To Proper Landscape Watering

by Tina Mast // July - August - September 2017

Improper watering is without a doubt the leading cause of plant death in the landscape. One of the reasons that watering is so misunderstood is that it can be difficult to tell someone exactly how much and how often they should be watering. Each watering situation is different and depends on a number of conditions including the soil, weather, sun exposure, mulch, and whether or not the plant is actively growing, as well as the type of plant in question.

It’s important to know the conditions in which your plants are going to best thrive. While some plants actually prefer more extreme conditions such as wet or dry soils, most plants are somewhere in the middle of the spectrum and like soil that is moist but well-drained. This means that if you squeeze together some soil in your hand, it should stick together, but fall apart easily.

Established Trees and Shrubs

Trees and shrubs that have been planted in the landscape for two years or more should be pretty well established and shouldn’t require much supplemental watering. A good rule of thumb for the average plant is that you want it to get approximately one inch of water per week during periods without rain. If you have an irrigation system, you can determine the water output by putting a shallow container such as a cat food or tuna can on the ground to catch the water. It’s better if the plants receive this amount of water in one or two waterings, rather than over several waterings. It will encourage deep root growth and help prevent root rot.

Newly Planted Trees and Shrubs

Trees and shrubs that are newly planted require more attention than established plantings. These plants usually have a small rootball in comparison to the rest of the plant. Plants should always be thoroughly watered at the time of planting. Watering during the first month after planting is especially critical. If we have little rainfall, you may need to water every two to three days during warm weather. The amount you apply should be enough to thoroughly moisten the rootball. Plants with smaller rootballs, such as those in one or three gallon pots, often require more frequent watering than those with larger ones. Don’t be afraid to stick your finger down into the rootball to check for moisture. After the first month, you should be able to decrease watering frequency. Plants planted in the fall have longer to begin establishing a root system before the heat of summer, but they may still require supplemental watering for up to two years after planting. Even though the colder months are still a ways off, be aware that during that timeframe, if we have long periods without rain through winter, you need to check the soil moisture and water when needed. Be wary if forecasters call for extended periods of freezing temperatures and dry conditions which can be a death sentence for many plants.

Annuals and Perennials

Annuals and perennials establish more quickly than shrubs or trees, but may have to be watered more frequently once established. Watering during the first month after planting is similar to that for trees and shrubs – every two to three days, although some plants may need daily watering initially. After that first month, two to three times per week should be enough.

Tips For Watering And For Water Conservation

– Water deeply to encourage deep root growth and promote better drought adaptability. Keep water pressure low so water has time to seep in, rather than run off.
– Provide a 2” to 3” layer of mulch to improve moisture retention and decrease watering (and cut down on weeding). Be sure to keep mulch away from contact with the base of the plant.
– During warm weather, water early in the morning or in the evening to reduce evaporation.
– Choose drought-tolerant plants to reduce water needs.
– Consider using rain barrels to collect runoff from downspouts. Fill watering cans while waiting for shower water to get hot.
– Be mindful of plants that may be getting watered when you irrigate your lawn and make sure they are not staying too moist.
– Know the signs of improper watering. Wilting, brown leaf edges, and stunted growth are signs of underwatering. Wilting that does not recover with watering can be a sign of overwatering. 
– Group plantings by water needs, placing drought-tolerant plants with other ones that like dry conditions and plants that require more water with similar plants. That way you can water each group accordingly. Extra tip: watering chores can be made easier by planting the drought-lovers further away from the house while the plants that need more attention are closer to the house (and the hose).
– Build a watering basin around plants so that water stays in the vicinity of the root zone instead of running along the soil surface away from the plant’s roots. 

Tina Mast

Communications director at Homewood Nursery in Raleigh.