Watering the Vermont Lawn and Landscape
Summer is upon us here in the Champlain Valley and the mercury is rising, school is out and everyone is rushing out to enjoy the weather and some additional free time. As we do that we notice that our lawns are brown and our landscapes are looking a bit sad. We offer below some helpful watering tips to keep those lawns and landscapes performing with the smartest use of water.
The discussion begins with WHAT we are watering—lawn/turf or landscape planting—specifically what type of planting—tree, shrub, perennial, annual, or even vegetable garden. Knowing WHAT we are watering will determine WHEN we should water and HOW we should water.
Beginning with lawns/turf as this is where we can typically see drought stress first. In northern Vermont our lawns are predominantly a blend of Kentucky bluegrass varieties, fine fescue varieties, some perennial ryegrass varieties, and some tall fescue varieties. All of these varieties are cool season turfs meaning they stop actively growing in temperatures above ~80 +/- degrees F. Cool season grasses lose most of their water to a process called evapotranspiration (ET) where water is lost through the leaves of the plant (transpiration) and then evaporated into the environment. Evapotranspiration occurs most rapidly under hotter temperatures and low relative humidity. This means that your lawn will require more water under hot weather conditions or conditions with exceptionally low relative humidity. The first is easy to track, but most of us when the temps are in the 60’s and 70’s don’t particularly track the humidity and this is where we miss the most watering. The spring of 2015 saw huge ET losses to low relative humidity and lack of rainfall—many lawns were damaged because it happened early and irrigation systems weren’t on yet and it seemed to early to lug hoses and water lawns. Evapotranspiration (ET) rates can also be changed by rooting depth—the more deeply a plant is rooted the more access to soil water it has and can replace water lost to ET. Grass roots more deeply when the top (leaves) are cut at heights higher than 3”. Dry weather conditions as well as ET water loss releases hormones in the grass and causes the elongation of fine root hairs (note here that heat stress can be good for further root development). Water management for cool season turf then takes on a more holistic approach that includes mowing and fertility. The goal of a summer water program should not be to push growth in cool season turf (unless under an athletic field program) but rather to simply replace water lost to ET and to keep grass crowns and rhizomes from drying out and dying. To do this we recommend increasing mowing height to 3”-3.5”, mow with a sharp blade, and provide ample fertility–2 to 4 lbs of actual nitrogen per 1000 ft^2 split in four to five applications through the season. This nitrogen should be >50% slow release. Then, adherence to the mantra, water as deeply as possible as infrequently as possible, is key for building a great turf root system as well as developing healthy, well adapted, cool season turf grass. The actual amount of water needed varies from site to site based on how exposure and soils affect the ET rates of the grass. We would be happy to help you perform a site irrigation audit to assist you in developing a great watering program. All watering of turf should begin at about 4 AM and should be wrapped up by 8:30 AM to 9:00 AM. It is best to not keep blades of grass wet after dark particularly during hot weather. Sprinklers installed with an appropriately designed irrigation system have the best, most even, and most efficient delivery of water to the turf. We work with two irrigation companies in the area and would be happy to refer you based on your needs.
The how and when of watering landscape elements—trees, shrubs, and perennials is very different from turf watering practices. Landscape plants still lose water through ET, but because they have larger and deeper root systems than turf, these plants have access to more water stored in the soil. Because of the deeper root system it is important to not over water these plants as it will stunt root zone development—remember not all stress is bad. In fact, unless just being established properly located (right plant in the right place) landscape plants should require almost no supplemental water post establishment. We strongly discourage irrigation systems in landscape plantings except in a very limited number of circumstances. We also in these circumstances prefer drip systems due to the timing of establishment watering. Establishment watering of new landscapes is key. Plants that get put in the ground during a new installation are growing on limited root systems either established in the ground and then cut or established in a pot and constrained. In all circumstances, nursery stock must remain watered multiple times per day to keep the foliage growing well on its limited roots. When transplanted into the new landscape the roots can now grow into the soil, but they must have some of the old watering habits to nurse the landscape plants through this process. Upon installation we suggest daily watering in the morning and the evening simply using the open end of a garden hose. Thoroughly soak the root zone of the plant with a good volume of water making sure to soak the transplanted root system as well as the surrounding soil. Depending on soil type you might have to water each plant in short bursts you may flood to a run-off point before you have thoroughly soaked into the soil profile. Having a trowel or soil probe to poke down into the soil to check for moisture at depth is key. After a few days of morning and evening we suggest backing off to evenings only depending on weather. In the evening check the plants—if the sun has gone down and things are cooling off and the plants are wilting—provide ample soaking. If the plants are not wilting and the soil tests dry, water deeply just as you water the wilting plant. If the plant is not wilting and the soil is damp, pass on watering. Check the next night. The idea of this process is a slow weaning of the plant off of the regular watering. Note that hotter days will require more attention as will days with a heavy breeze and low relative humidity. As we get ample rainfall stretch the distance between watering and only water if absolutely dry and wilting. When plants work for their water under stress conditions (within reason) they release hormones that allow for further root hair growth and become more suited to their environment and require less input from us the landscape managers. This makes the plants more resistant to drought, disease, and insects.
The keys to a good turf and landscape watering program are
-Proper plant selection and proper turfgrass variety selection is key in reducing the need for water.
-A calibrated and consistent method for delivering water to the plants/turf in need delivers the best results without wasting water.
-More does not make enough better—plants and turf that work for water (not overwork) become better suited to their environment and in the long term require less input.
-Observation is key—follow the plant and turf cues for watering. In plants wilting leaves even after the cool of the evening and in turf loss of color.
Do you feel your landscape requires too much water? Are you struggling to provide enough water to keep things looking sharp? Is your new landscape installation struggling to adapt to its new home? We would love to meet with you to discuss how we can renovate and maintain your lawn and landscape to give you the most performance with the least amount of watering input.