We’ve had a dry summer here in Vancouver, WA. And though it rained just the other day, the photos in this post were made about 10 days ago at a point where we’d had no rain for about 60 days straight. The container in the photo below is on my front porch. It gets exactly the same amount of rain or watering that the rest of the yard gets. We’ve run the sprinkler maybe three times over the past 60 days and gotten no rain.
So, why, given that all of the plants in the photo received the exact same sunlight, weather and watering over the course of 60 days, are the container plants dead while the in-ground plants are very much alive?
It’s because plants in containers need to be watered more than plants in the ground. In the container are (were) orange sedge (Carex testacea, the grass-like plant) and creeping marjoram (Origanum marjorana, an herb). The container’s dead marjoram—vegetation closest to the bottom of the photo—is the same exact same plant as you see in the photo’s upper right corner (in the ground)—all brightly green and very much alive. Interestingly, there is also a bit of black mondo grass (Ophiopogon nigrescens) in the container and though it’s not thriving, it has survived when the other plants are completely dead. A testament to it’s drought-tolerance!
It’s a myth that container gardens are easier—or less work—than in-the-ground gardens. A HUGE myth. People in condos don’t really have a choice if they want plants on their patios/balconies. But if you do have a choice, always choose to plant in-ground or in raised beds vs in a container—unless you are prepared to put forth extra effort to care for the containerized plants. Use containers as accent—jewelry— for your garden, but be prepared to spend more time and effort on that bling.
The extra work consists, first, of refreshing the soil. What is planted in the container will determine how often you will need refresh soil. If it’s annuals or vegetables, you’ll need fresh soil every year, and likely you’ll also need additional fertilizer (please use organic) during the growing season. If the container consists of perennials or woody plants, you might get 1-2 years of growth before the soil’s nutrients are depleted. And of course, it depends on how heavily the plants feed (how much nutrition they require). You can put some good compost on top of the soil for the second year to help provide nutrients. But that only goes so far as compost does it’s magic very slowly.
The other extra work of containerized plants is keeping them watered. In our wet winter season (here in the Pacific Northwest), this isn’t a problem unless the containers are under eaves or a covered patio. But in our hot, dry summers the volume of soil in a container—even fairly large ones—is not sufficient to retain adequate moisture when the weather is hot and dry—even for short durations. Visit your independent garden center on a hot summer day and check out how often they water the plants. Trust me, it is a LOT!
What I Did Wrong
The plants in my container (in the photo above) succumbed due to my lack of attention when it was hot. They had good soil, but it simply dried out due to lack of water. In the garden area at the top of the photo, the surface soil may have dried out, but since I water deeply and infrequently, the surface being dry was not an issue. This good watering practice, however, is not good enough for containerized plants. They will always require more frequent watering than in-ground gardens.
What To Do Right
This deep and infrequent way of watering causes out-in-the-garden plants to send their roots deep into the soil. The soil’s mass, use of mulch to insulation the soil from surface heat and dryness, and sufficient organic matter incorporated into the soil enabled the soil to retain a good amount of moisture. And it keeps the plants alive during drought periods. I keep a 2″ layer of leaf mold mulch on top of the soil in my ornamental beds. All of these things stack up to keep the plants in the ground alive even though they’ve only been watered 3 times in 60 days. This is a testament for using drought-tolerant plants in ornamental beds!
How to Water Correctly
We’ve established that we need to water plants. Most everyone knows this. Even so-called ‘drought-tolerant’ plants need to be watered occasionally. No plant can live with NO water.
I like to design with drought-tolerant plants. I also like to ensure that the soil does as good a job as it can to retain water in a way that is healthy for the plants. Or, I will select plants suited for whatever conditions I find on-site. If I find clay soil, I plant stuff that likes to be in clay. If I find sandy soil, I plant stuff that likes extremely well draining soil. If the client has soil that is inappropriate for the plants they desire, we amend the soil with generous amounts of compost—up to about 10% volume of the area being amended. I’ve seen guides recommending more or less compost by volume, but it truly depends on the situation and what is being planted. In gardening, all ‘rules’ aren’t hard and fast for all situations. This is one of the things that is so frustrating about gardening. It also makes gardening intriguing, mentally challenging. :-)
There are several ways to get water to a plant’s roots. We can let Mother Nature water them in the form of rain. We can use some sort of sprinkler or drip system, either above- or in-ground, or we can water by hand. I’m not going to go into a discussion of the various irrigation methods here because that is not the point of this post. People have their own irrigation preferences. And depending on your soil and what you’ve planted, one watering method may work better for you and your pocketbook. There are many variables that affect irrigation choices.
Successful watering requires that you be observant. You may think you are watering appropriately, but are you? Have you checked to see if the water is penetrating deeply enough? Have you set up your irrigation system so that each zone delivers water appropriate for the plants living there? Conversely, have you planted plants near each other that all have the same watering requirements? Is your system set up to ensure saturation by ‘priming’ the area? If your system is watering more than twice a week, it is likely incorrect for ornamental gardens—and it may be incorrect for turf grass, too.
The Trouble with Watering by Hand
The photos at right were taken the same day as the first photo in this post. It is showing the same garden bed area. You are seeing the leaf mold mulch. In the upper photo, the mulch is wet. I hand-watered it with my hose sprayer for about 10 minutes. The bed is about 4′ x 12′ in size. Ten minutes should provide quite a bit of water, right?
Well, let’s see. The lower photo shows the same spot of mulch as the upper photo, and I’ve lifted up the top about 1/2″ of mulch to reveal that the 10 minutes of hand-watering has moistened barely 1/4″ down into it. There is 1-2″ of mulch on this bed, and after 10 minutes of watering, no water has reached the soil. NONE AT ALL! I later set up the sprinkler and gave the area a long, slow drink (priming first), then checked the mulch and soil again to be sure it received adequate penetration. It was all pleasantly moist. Yay!
These photos perfectly illustrate why we caution gardeners about watering by hand. What seems like a long time stand out there holding the hose simply doesn’t supply enough water to the plants. The only time this method would work is if the soil and mulch are already moistened (primed). If we are irrigating properly by watering infrequently, then we need to slowly supply a large quantity of water over a long period of time so that the mulch and soil—which may have become hydrophobic as they dried out—can have time to moisten. Priming is a great way to moisten hydrophobic soils. Gentle rains are great at doing this. Hard downpours are poor at watering because if the soil is dry, the water will run off rather than be absorbed.
So when you are watering, be aware of how dry your soil and mulch are before you start. Also be prepared to deliver the water to the soil so it can be absorbed. If your soil has gotten overly dry to the point of being hydrophobic, the best way to re-wet it so the water penetrates is to ‘prime’ it. This is done by turning on the sprinkler (be it above- or in-ground) just until the water begins to run off—maybe 5 minutes or less. Then wait maybe 10-20 minutes for that moisture to settle into the soil. You may have to prime a number of times if your soil has become overly dry. Repeat this priming until the water stops running off. Then water gently for long enough so that the water reaches a good 6-12″ or more into the soil. At first you may have to dig holes or use other sorts of probes to learn about how your soil accepts moisture. Understanding understanding these things will help you help your plants.
Sounds like a pain in the butt, right? One reason why in-ground, computer-timed irrigation systems are such a great thing, is that it can be set up to prime the ground before delivering the long, slow drink of water your plants need. If you have, say, 5 watering zones you could set the watering to come on the first time for only 5 minutes. By the time the system gets through the 5th zone, the 1st zone will have rested for 20 minutes. Depending on your soil and watering schedule, you may need to do a second round of this 5-minute priming, after which you can let the zones water as you’ve determined necessary, maybe 20-30 minutes (or more) per zone. And perhaps that longer interval of watering will need to be repeated. The amount and frequency of water to be delivered depends on your soil type and the plants in your garden.
The bottom line: Ornamental beds need to be watered deeply and infrequently so as to keep the soil 4″ and below the surface consistently moist to suit the plants in that bed, while at the same time allowing the top 3-4″ of soil to dry out between watering sessions. Most trees and shrubs can tolerate deeper drying out. Many perennials cannot. Turf grass lawns have different requirements, but that is for another post.
Who Said Gardening Is Easy?
I don’t know who said it, but they were in error. Gardening becomes easier once you learn to do it correctly. Take time to learn the science behind what is happening in your yard. This will help make your gardening easier and more fun.
Get out there! Learn to water correctly. Have a successful garden.