Summer 2019 Watering

July 13th, 2019

After record amounts of rain fall earlier this spring things are drying out. The Chicagoland area saw historic amounts of rainfall in April, May & June. In fact, May 2019 was the wettest May in almost 150 years of record keeping.

In the later part of June it seems that we were having almost daily rainfall. It felt like we were living in a tropical locale like Florida or Hawaii where storms roll in every afternoon and pass through. Fast forward to today, July 13th, 2019 and the its seems that the spigot has been turned off. I’ve noticed that the grass is growing slower and turning brown in some places. I’ve noticed un-mulched beds with 1/8″-1/4″ cracks in the soil. Now, I’m not trying to be an alarmist and we are by no means in a drought or anything remotely close to that, but plants that were “being babied” by the frequent rains are now starting to show some signs of stress. This is especially true on trees and shrubs that were planted within the last 24 months.

I’ve noticed that some seemingly healthy trees are starting to shed what look like perfectly healthy leaves or dropping some yellow leaves. Now there are A LOT of reasons why a tree would drop leaves but I believe that some trees that were so “happy” with all of the rainfall that they got more leaves than they really needed and now that the rainfall is tapering off the trees are shedding some percentage of their leaves to sort of level things out  a bit. A perfect example of this would be River Birch. River Birch will commonly shed 10-20% of their leaves as soon as it starts to get hot and dry. They will drop yellow leaves from an otherwise healthy looking canopy (consequently River Birch are also prone to a nutrient deficiency called Iron Chlorosis which also causes yellow leaves but in this case they stay on the tree and look pale or “anemic”).

So what’s the point?

When a client calls in about a stressed plant or sends me photos of a stressed plant, my first question is always, “How, often have you been watering the plant?”.  I’ve heard the following response from a lot of customers that have called in or sent me photos of stressed plants in recent days, “Well, with all the rain we’ve been getting, I haven’t been watering at all?” The point is, the best way to prevent drought related stress is to start watering the tree or shrub before symptoms start to appear.

It’s Time to Start Watering

How often and how much water should trees and shrubs be getting and what’s the best method (sprinkler, irrigation system, hose, soaker hose) of watering? Well, that’s the million dollar question. Let’s get a few “ground rules” out of the way before we talk about how long and how often to water.

  • Heavy clay soils retain a large amount of water
  • Sandy or rocky soils drain much quicker and have less water holding capacity
  • Some plants have higher or lower water needs than others
  • Watering too much OR too little can have dire consequences for plants
  • Newly planted container grown plants may have more foliage than roots at this time of year and may need more frequent watering
    • This is especially true of Barberry, Dappled Willow, Spirea, Ninebark, Hydrangea, etc.

So with these things in mind, here is my recommended watering schedule  for plants that were installed (planted) this year:

Trees: slow trickling hose placed at the base of the tree. Allow the water to trickle for about 30-45 minutes. Do this one time every 7-10 days.

Shrubs: slow trickling hose placed at the base of the shrub for about 3-5 minutes. Do this one time every 3-5 days.

Perennials: water by hand with a watering wand. 30 seconds per plant is usually good. Do this once every 3-5 days or more frequently if the plants look wilted.

Sod / Grass Seed: Water Daily and do not allow the soil / sod to ever dry out completely.

 

If your plants were installed last season cut the frequency in half – meaning water trees every 14 days instead of once every 7-10 days. For perennials and shrubs planted in 2018 water one time per week.

 

What if it rains, should I still water?

If we receive an 1″ of rainfall, you can count that as a good watering. Anything less than that usually doesn’t soak in well enough to be effective for newly planted trees and shrubs.

Watering of Conifers (Evergreen Trees – Spruce, Pine, Fir, Hemlock, etc.)

Evergreen trees such as Pine and Spruce tend to be very water efficient and do not like to be overwatered. That being said, the shape of the evergreen (being wider at the base of the tree) prevents the root system on recently planted trees from receiving rainfall and / or water from sprinklers. I like to place the hose under the tree, right at the base of the trunk, and let it trickle for 30-45 minutes. Do this once every 2 weeks. This is especially important for Canadian (Eastern) Hemlock which are often planted in the shade of other trees. The surrounding trees often soak up rain water quicker than the newly planted (in the last 1-4 years) Hemlock. I have a handful of Hemlock planted under the canopy of large Oak in my yard. They look amazing and provide some winter screening and a nice home for the birds. I water them religiously during the summer months. They are larger and fairly well established but I still water them once every 3 weeks or so. I will place a hose under the tree and let it trickle for 60-90 minutes. It is important to take note that I only do this once every 3 weeks or so and only during the hot summer months (July, August and September).

– Matt Zerby, Owner

 

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