If you’ve just planted shrubs along your front walk, or you’ve got an established hedgerow basking in the admiration of your neighbors, you know the importance of watering those shrubs and bushes. But can you water them too much?
You can water shrubs too much, which can make them look sick and susceptible to fungi and rot, or even kill them. Plants can drown just like people, so it’s critical to the success and health of your shrubbery that you know when and how much to water them.
Overzealous plant owners (which is most of us at some point) cause some of the problems, but other issues can result from soil conditions. We’ll look at some watering basics and how you might recognize overwatering in your shrubs.
Why Overwatering Is an Issue
Like every other living thing, plants need oxygen to survive. While there is oxygen in water, plants cannot draw oxygen from that water.
Fish gills can do that, but plants never had reason to evolve such a mechanism.
So when plants are overwatered, they sit in a soup of water and mud. While this can cause many problems, the biggest one concerns oxygen. Oxygen molecules hover around the root system of shrubs, and the roots absorb them there.
But if there is too much water, the plants cannot get those oxygen molecules into their root systems, and the plants can begin to sicken and eventually suffocate. They are actually drowning in your front yard.
Signs That You Are Overwatering
Luckily, we can see that the plants are in trouble before it’s too late if we know what to look for in our shrubs and hedges. The ability to recognize and correct an overwatering problem means your shrubs, no matter how much you’ve overwatered them, still have a chance if they’re not completely dead.
Let’s take a closer look at these signs.
- Wilting leaves indicate too much or too little water. You’ll be able to tell the difference because underwatered plants have wilting leaves that feel somewhat crisp and crunchy, while overwatered leaves will be soft. The first time you see an overwatered leaf will help you recognize the soft wilt immediately in the future.
- Browning leaves reveal overwatering quickly. The tips of overwatered leaves begin to brown soon after overwatering sets in, so cut back on your watering immediately if you notice this.
- Plant edema causes blisters on plant leaves. When excess fluids build up in people, it’s called edema, and the term means the same thing in plants. With too much water flowing into the root systems, those roots can keep pumping water into the cells of your hedges. Eventually, just like a balloon, those cells will pop from the pressure. The resulting injury looks like a blister or a lesion. For the record, this is bad.
- Premature leaf loss happens with too much or too little water. You’ll probably recognize which is the case if you’ve noticed some of the other symptoms, but if leaves are falling off before they should, such as when they are young leaves, overwatering is most likely the issue.
Testing Your Soil
If you’ve planted your shrubs in the last day or two, none of those overwatering symptoms will have shown up yet, but you don’t have to wait for them to manifest to have some idea about the state of your watering frequency.
We can tell much about our plants’ water supplies by looking closely at the soil with a couple of pretty simple tests.
The Touch Test
This test is very simple, and all you need to do is stick your hands in the soil. If you watered 24 hours ago and now find the ground still wet, or even muddy, you used too much. Also, overwatering is definitely an issue if you push down into the soil about 2” (5.08 cm) and still find it very wet.
Moisture Meters
Using a tool to analyze the condition of your soil is more accurate than sticking your finger in the dirt and moving it around.
XLUX on Amazon.com makes a Soil Moisture Meter that doesn’t need batteries or requires you to dig up soil. It’s got one long prong like a meat thermometer, so when you poke it into the ground near the roots of your plants, the probe won’t injure them.
If your soil doesn’t drain well, you might see a bed with dry soil on top but pooling water down at the roots’ level. A soil moisture meter like the XLUX will also alert you to this issue.
A lower-tech version of this meter is to take a screwdriver, jam it into the soil, pull it out, and check to see if it’s wet.
Unscientific, sure, because you can’t be sure if the moisture on the end of it is from the moisture in the lower levels of soil or if it got wet when you pulled it back up through the more moist upper levels. But it doesn’t cost anything, so it’s worth mentioning.
The Squeeze Test
Another soil test involves digging up a small amount of soil and squeezing it to see how much water comes out. You’ll do this test after several hours after you’ve watered, not right after you’ve rolled up the hose.
Here are the steps you should use to complete this test.
- Choose an area just outside the width of the root system and about half its depth.
- Dig a small hole and pull the soil out of it.
- Hold the soil you pulled from the lowest part of the hole in your hand.
- Squeeze it.
- Note what the soil does under pressure.
If water oozes out of the soil and from between your fingers, the soil is too wet. Again, though, if you do this immediately after watering, oozing water won’t mean anything. Make sure to wait a few hours before completing the test.
Incidentally, if no water comes out and the soil crumbles when you let off the pressure, there’s not enough water down in the ground.
Watering Basics
Now that you know what not to do, let’s talk about what you can do. You’ll want to follow a few rules of thumb when it comes to watering new shrubs and established growth, as well.
New Shrubs
Your new shrubs are most in danger of being overwatered right after you plant them because you know that sufficient watering is very important with newly planted shrubs. Often, our good intentions get us into trouble and lead us into overwatering, so we need to know how much water our shrubs need and how much water our watering system delivers.
Most new plants (not just shrubbery) need about 1” (2.54 cm) worth of rainfall every week.
There are very few places in the world that get that amount of rain consistently, so we need to water, so the plants get what they need. Also, if it’s exceptionally hot and dry, your new shrubs might need more watering than usual, in which case you will have to check your soil regularly.
The best way to do this is by trickle watering, which is just what it sounds like.
Rather than take your garden hose out with its sprayer attachment and squirt your shrubs for a little while, you can better serve your new plants with slow, thorough watering.
In general, you should water your newly planted hedges:
- Every day for the first ten to 14 days after they’re planted.
- Every two or three days, depending on the soil and weather conditions where you and your plants live, for the next three months.
- Weekly from 12 weeks and on.
After your shrubs establish mature root systems, they’re no longer newly planted plants. This process can take up to two years, depending on the specific plants you’ve chosen.
Mature Hedges
Once your hedges are mature, you’ll water them once a week or as needed. By this point, though, you’ll be familiar enough with the plants (since you’ve been very attentive to them for the last two years) to recognize any signs of under-or overwatering, and you’ll know your soil well enough not to have to dig around much in it if you’re unsure.
How To Properly Water Your Shrubs
Your plants—very literally—would be better off not getting watered daily.
Note: If you water established plants fairly infrequently, their roots grow deeper and stronger. If the plant learns to ration its water, it will develop its root system accordingly because evolution is so freaking cool.
But you also have to water deeply, which means a lot of water trickling down to at least 4” (10.16 cm) below the surface. Without deep watering, your shrubs’ roots will not grow deep into the ground, making them less able to get water when they need it, such as in a drought.
They also become less stable in the ground, which means that a storm could uproot them easier.
There are three great ways to water deeply, and none of them involve shk-shk-shk-shk, ticka-ticka-ticka-ticka sprinklers. Those are okay for your lawn, but not great. For your shrubs, they are inappropriate.
Let’s take a look at what actually works.
Soaker Hose
Porous material makes up a soaker hose like this LINEX Garden Soaker Hose 1/2 inch x 25 ft that are available on Amazon.com in different lengths, even over 100 ft (30.48 m).
One end hooks to the water spigot and the other end is capped. As water flows into the hose, pressure builds, and the water extrudes out along the length of the hose. No torrent of water disturbs your soil, and you get the equivalent of a nice, gentle rain.
Soaker hoses also bring convenience to your watering because you can thread them around and through the trunks of your shrubs and leave them there for the whole growing season.
If you use mulch, you can even put mulch over the hose if hiding it is your jam.
You can get even fancier with a timer like the Orbit 62061Z Single-Outlet Hose Watering Timer on Amazon.com and never have that “Oh, no, I think I left the water on all weekend” moment again.
Slow Drip
If you don’t want to buy a new hose when you’ve already got a perfectly good garden hose that you’ve had for 25 years, you can use a regular hose much like a soaker hose. Just lay it next to your shrubs, turn the water on very low, and let it drip slowly.
Okay, not exactly drip, but a trickle, I suppose.
We’ll talk more in a bit about measuring how much water you’re putting out there at a time, which will affect how long you let the hose drip. One downside is that if you’ve got a long row of bushes, this method may require you to move the hose several times.
There’s a Hole in My Bucket
A sure-fire way to know exactly how much water you’ve put in the soil at one time is a decidedly low-tech method, but let’s be honest—low-tech means less chance that it will break down. Take something like Seachoice’s Five-Gallon Plastic Bucket on Amazon.com, drill some small holes in the bottom, fill it, and set it next to your shrubs.
When the bucket is empty, guess what? You know you just dropped five gallons. As with the slow drip, you’ll need to move the bucket often or get a bunch of buckets.
How Much Water
Whatever your watering method, measure, measure, measure.
If you have a timer or other meter on your water spigot, it may have a feature allowing you to set it for a flow of a certain amount of water per hour.
Also, your soaker hoses distribute a specific gallons-per-hour amount. If you’re running a slow drip, run it into a bucket for an hour, then measure how much water ended up in the bucket.
To get the soil nice and soaked 6” (15.24 cm) below the surface, you’ll need the equivalent of 1-2” (2.54 to 5.08 cm) of surface water. That translates to about two-thirds of a gallon of water per sq ft (0.09 sq m).
These numbers vary depending on the plants, weather, and soil, which brings us back to all that talk about paying attention to your plants and the soil, so you don’t overwater.
When To Water Your Shrubs
We’ve talked about overwatering and how much to water, but there are still gardeners who wonder when to water—not just like, “When do my plants need more water?” but more along the lines of, “What time of day should I do this?”
People have their opinions, wrong though many of them may be, so let’s spend a moment getting this straight.
Water your shrubs between dawn and 9:00 am. That’s really all there is to it.
Watering after dark means water standing on your plants’ leaves for extended periods, opening the door for mildew, mold, or fungal growth. Watering in the heat of the day means more evaporation, which means less water for your plants.
And here is as good a place as any to say this: don’t just water the tops of your shrubs. Spraying water over them means you run the risk of not having enough water getting down to the ground and into it.
What this does not do is harm your plants, by the way.
The myth that watering your plants in bright sunlight will somehow focus the sunlight into a plant-searing death ray is wholly false and entirely unsupported by science. Water in the afternoon if you want, but your plants will lose more water to evaporation than they would if you water in the morning.
Making the Most of the Water
Two things can help your shrubs do well when they’re new and better when they’re more mature: mulching and stopping water theft. Let’s talk about the one that’s worded in a less interesting manner first.
Mulch
Newly planted shrubs need mulch more than older ones, but that does not mean that older shrubs do not need it at all.
Mulch does many things for your shrubs (and everything in your garden), such as helping prevent other plants like weeds from taking root and insulating the soil from extreme temperatures. When it comes to water matters, mulch:
- Cuts down on water evaporation.
- Prevents water run-off if your soil isn’t the most absorbent it can be.
- Decomposes over time when exposed to water, thereby adding nutrients to the soil.
Perhaps this goes without saying, but do not use rock mulch. Rock mulch does none of the things listed above, it will hold in excess heat that will harm your plants, and it’s actually bad for your soil.
Organic mulch only, please.
Stopping Water Theft
You planted your shrubs and started watering them faithfully. Then some weeds show up. Those weeds are thieves.
You are giving water to your hedges, and the weeds are helping themselves to it.
But it doesn’t belong to them. So stop water theft by mulching to discourage weeds from taking root. When you see a weed or errant sapling that just sprouted or a volunteer begonia from last year, pull it up. It is stealing from your shrubs, and it must face the consequences.
Sources
- Alwerdts Gardens: Watering Guidelines
- Brightview: 4 Signs You are Overwatering Your Plants
- Brightview: How to Rescue Overwatered Plants
- Clemson University: Watering Shrubs and Trees
- Gardening Know-How: Signs Of Plants Affected By Too Much Water
- HGTV: The Proper Way to Water Your Garden | Watering Plants the Right Way
- Iowa State University: When is the best time to water the garden?
- Kansas State University: Watering Newly Planted and Young Trees and Shrubs
- Love Your Landscape: How much water do shrubs need?
- North Dakota State University: Mulch Madness — Yard & Garden Report
- Oklahoma State University: Planting Trees and Shrubs
- Smart Garden Guide: What’s The Best Time Of Day To Water Plants? (The Facts)
- Star Nursery: HOW MUCH SHOULD YOU WATER YOUR SHRUBS and TREES?
- Tree Montgomery: Watering
- University of Minnesota Extension: Watering newly planted trees and shrubs
- Washington State University: The Myth of Hot-Weather Watering