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Time to start thinking about watering - at last!

Dare I say that spring has finally arrived? With the warmer weather comes the important task of assessing watering needs of your landscape plants. How, when and why you water depend on several things and it's our responsibility as gardeners and plant owners to provide adequate moisture to plants if Mother Nature isn't helping out.

Our Extension webpage Water Wisely provides some great information. Here are a few tips:

Know your plants and their water requirements

How much light will your plants get?
Plants can grow in many conditions when given good care. When it comes to buying a new plant, it's important to know the kind of growing conditions you can provide for it. The growers' plant tags provide a lot of information about the growing needs of plants. 
  • Your zone? Check USDA Cold Hardiness Zones map
  • Planting space available should match size of full grown plant
  • Sun / shade - full sun 6+ hrs, part sun/shade 3-6 hrs, full shade less than 3 hrs
  • Soil type - clay, sand, loam (the best!)

Soil texture matters! 

Soil is literally the foundation of everything we grow. Smooth, sticky clay soil packs down reducing air pores in soil and causes water to pool on / near the surface.

You may have an area of your property that is always damp and water seems to just sit there. It's likely you have clay soil in that area. It's tough for plant roots to grow through compacted clay soil. Compost mixed into clay soil will relieve the compaction, add air spaces and create a much more root-friendly growing environment.

Likewise, compost can help improve sandy soil as well. Sandy soil is coarse and water drains quickly through it, resulting in a dry, nutrient-poor growing environment for plants. Mix compost into sandy soil to improve its ability to hold water and make it available for plant roots to take up.

Not sure what you have? Get in touch with your soil.

Native plants and their cultivars typically
can adapt to different moisture levels.
Try to make a ball out of your soil and break it with your finger.
  • Soil ball crumbles? Loamy soil
  • Soil ball stay intact? Clay soil
  • Can't form a ball with your soil because it falls apart? Sandy soil
Still not sure? It's always a good idea to get a soil test done. Texture is just ONE of the pieces of information you will get from the talented soil scientists there. You can send a soil sample to the University of Minnesota Soil Testing Lab.

Instructions on how to take / send a sample, cost and more can be found here.

UMN Dept. of Soil, Water, Climate
Soil Testing Laboratory
135 Crops Research Building
1902 Dudley Avenue
St. Paul, MN 55108
Office hours: Monday-Friday, 8:00 a.m.- 4:30 p.m.
Ph: 612-625-3101

After planting a new tree in the spring, how much should you water? 

Newly planted trees and shrubs require 1 to 1.5 gallons per inch caliper (the diameter of the main stem) every day for 2 wks after planting, then every 2-3 days for the next 12 weeks, and every week after planting for the next 12 weeks or until the soil freezes.

Don't forget about your current big trees and shrubs. While a healthy, mature tree or shrub has established its root system, they need water too when rainfall is scarce. Water until the top 6-9 inches of soil around the tree's root area is moist. An sprinkler is a good choice for this kind of watering as it can be moved around easily.

Most shrub roots grow under the main branches. Tree roots, on the other hand, spread far beyond their trunk and canopy with most of the roots growing in the top 18-20 inches of soil. Many are right below the surface of the soil. So how do you know where to actually place the sprinkler to reach as many tree roots as possible - by the trunk? Five feet away? Across the yard? You need an idea of how far those roots spread:
  • Measure the diameter or circumference of the tree trunk about 4.5 feet about the ground
  • Check the chart here
  • For example, a tree with a diameter of 10 inches has a root spread of 30-32 feet.

Seedlings and plants in pots need more
watering attention as they dry out quickly.

Rain counts! 

Rain counts when it comes to considering how much water your plants need. Rainfall varies from place to place. There are a number of ways you can determine how much rainfall you have received in your area. Local weather reports and blogs that report the amount of rainfall are good resources. The easiest way to measure rainfall in your backyard is with a simple rain gauge. Rain gauges need to mounted properly and monitored.

Our colleagues at North Dakota State University have a good handout about choosing, locating and mounting a rain gauge:
Measuring Rain at Home

Author: Julie Weisenhorn, Extension Educator - Horticulture

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