Wednesday, June 13, 2012

A 'How to Water' Primer

Last night the weather man told everyone to "go out and wash their cars. Anything to bring rain."  This is our friendly reminder--it is time to water those new plants! (I am sure as I post this the clouds will start to build.) The untimely rains this year along with heat and wind have been really tough on new plants.

There is no formula for watering. Like any horticultural task there is an art and a science involved.  There are many factors that can influence when, how much, and how to water. Plant type, plant age (newly planted or not), soil type, micro-climate, lawn irrigation, type of watering method to be used etc. Below is not an all-inclusive guide, but hopefully can get you started down the right path. 

Keys to watering properly:
1. Always check to see if your plants need water.  Dig down a few inches and see if the soil is moist.  A long screw driver, a survey stake, or cut off piece of rebar with a point works well. If resistance is felt when inserting the screw drive it is time to water. Plants that were in containers and haven't rooted out yet will need more frequent watering because the soil-less mix can dry out quickly. 
2. Water in the morning or evening to conserve water. That said, watering when you have time is better than not watering at all.
3. Water DEEPLY.  Most people make the mistake of seeing the top of the soil become moist and assuming they have watered enough. In general, a hose (not a sprinkler) running normally for 2 minutes will apply 10 gallons of water.  If you are watering 10 seconds per shrub less than a gallon of water is being put on. If you are hand watering stand at each shrub for a minute or two.  I tend to water everything and then start over and do it all again.  Deep, infrequent waterings are much better for the health and establishment of your plants. 
4. If you are using a sprinkler spend 15 minutes at the start of the season to calibrate it to know how long it will need to run to put on 1" of water. For directions how.
4. You can test how deep you have watered by using a soil probe (long screw driver, or rebar) an hour after watering. Push the probe into the soil. It will go through moist soil easily but become difficult to push once it hits dry soil.
5. Soil types do affect watering.  If you have a very sandy soil you will have to water more frequently. A clay soil you will have to apply more water but less frequently.
5. Trees are best watered by putting a hose on trickle and leaving it there for several hours. Tree gators or five gallon buckets with holes also work as they slowly release water over a period of time.
Tree gator

6. MULCH, but not too much. 2-3 inches of shredded hardwood mulch conserves moisture, slows evaporation, cools the soil and adds organic matter as the mulch decomposes. A hardwood mulch works best. Don't get mulch happy and bury your plants.

Proper Mulch depth
Improper Mulch depth.

7. Don't assume that because it is 'Native' or 'Drought-tolerant' it doesn't need to be watered during establishment (first year or two).  We see this assumption the most with perennials and grasses. Remember that plants are grown in very light-weight potting soil that does not mimic natural soils. This soil drys out very quickly. In nature, native perennials and grass seedlings extend their roots down deeply before putting on much top growth. When we plant them in the landscape it will take a little while for the roots to extend beyond the potting soil and make their way into the native soils. Finding the balance between not watering enough and over-watering can be tricky. Signs of under watering: leaves wilt and curl; older leaves turn yellow or brown; leaves drop; stems and branches die back.

Newly planted plugs of native grasses and perennials
Same landscape, well cared for, two years later.

8. Don't OVER water. Many plants are killed from too much love or ignoring automatic turf irrigation systems. Be especially careful not to over water if these systems are spraying on to trees and landscape irrigation beds. When soil is water logged plant roots are starved of oxygen. Symptoms of over watering look similar to a dry plant. Leaves turn light green or yellow; leaves wilt; young shoots wilt.  
9. Use a rain gauge. If you get 1 inch of rain in a week you won't need to water.  Adjust watering depending on the amount of rain you get.
10. When indicator plants like gooseneck loostrife, heleopsis, monarda and rubdeckia are wilting it is time to water.

Lawn Irrigation Tips:
  • Water deeply and infrequently to encourage deeper-rooting and resiliency
  • Water early in the day to avoid loss from wind and evaporation and limit potential fungal problems
  • Water efficiently (don’t water pavement, make sure any automatic system is working properly, use rain sensor to avoid watering after rain, etc.)
  • Allow summer dormancy of cool season grasses. Fescue cannot go dormant so some watering is required to keep it alive.
  • Lawns should feel firm when you walk across them. If your lawn is squishy you may be over watering.

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