Caring for a Container Garden

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Giving your container gardens the best care will help them grow and prevent pest problems.
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From time to time outdoor plants will begin growing mushrooms out of the containers, which indicates your potting soil is being broken down into plant-available nutrients.
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Fertilizer is an essential element for successful, exuberant container gardens.
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“Practical Organic Gardening” by Mark Highland provides readers with a modern perspective to organic practices, methods, and products that any home gardener can enjoy.

Practical Organic Gardening: The No-Nonsense Guide to Growing Naturally(Cool Springs Press, 2017), by Mark Highland is a modern visual guide to growing organically. The book provides step-by-step photography and how-to projects so readers can take a hands-on look at updated popular gardening techniques. The following excerpt is from Chapter 10, “Organic Container Gardens.”

Prevent pest problems and grow big beautiful container gardens by giving them the best care.


The easiest way to check whether your plants need water is by using your finger to test for moisture. Stick a finger into the soil. If you only get one knuckle deep and feel moisture, you can wait to water. If you get two knuckles deep and still don’t feel moisture, it’s time to water. Make sure to fill in where you poked the soil.

When rechecking in a day or two, check in a different spot. Soon you’ll get a feel for how often to water, though this can change based on weather or environmental conditions. Hotter weather or sun exposure means more frequent watering is needed.

You can also test the moisture content of a pot by lifting it from the pot edge. Heavier pots contain more water. Lighter pots will tip easily when lifted without too much effort. It’s a quick trick that’s not quite as accurate, but with experience you’ll soon learn how to know if the pot needs water by weight.


We’ve talked about soil and water, but fertilizer is the last essential element for successful, exuberant containers. All plants need fertilizer to grow and container gardens are no exception. Container gardens are an enclosed system, which means that everything the plant roots need to grow will have to be already inside the container or added as fertilizer.

The easiest way to fertilize containers is to add a measured dose of an all-purpose fertilizer at planting time. If planting flowering plants, look for fertilizers with a high phosphorus number (the middle number in the three-number sequence; in a 4-6-4 fertilizer, the 6 represents the phosphorus ratio). If the plants are all foliage, then nitrogen (the first number in the three-number sequence) is the most important. Follow the instructions on the label when determining how often to reapply fertilizer throughout the season for best results and optimum growth. Make sure to use organic fertilizers!


Help! There are mushrooms growing out of my containers!

Relax. Potting soil is made of organic material, and fungi eat organic material. Under some circumstances, you may see mushrooms growing out of even an indoor container. Don’t fret, as mushrooms are part of a natural organic soil and garden. However, if they bother you, start by removing the mushrooms as soon as they are visible.

To prevent future outbreaks, take the plant outside and remove the rootball from the pot. Gently remove as much soil as possible, taking care not to damage the roots too much. Plants are tough and can handle a little root loss during a repot. Discard all the removed soil in a garden bed. After this is done, give the roots a little soak in a fresh container full of water (mix in a little liquid kelp or some worm castings for an extra boost). A 10- to 15-minute soak is all you need. Then repot in a new pot with fresh potting soil. Save the old pot and let it sit outside for a bit to air out and get washed by rain. You can use the old pot again after it has been outside for a couple of weeks.

Although rare, this mushroom problem also happens with outdoor containers from time to time. Outside, the plants can be left alone: the mushrooms will run their course and recede after a week or two. The presence of mushrooms is actually a good thing, as it indicates your potting soil is being broken down into plant-available nutrients by the fungi that spawned the mushrooms. If the mushrooms bother you, though, simply remove and compost them. If they come back and you feel you must remove them, follow the process described above to replace all the potting soil in the container and around the rootball.

Yearly Maintenance

Do you need to replace the potting soil every year? That depends. Some potting soils are more reusable than others. Potting soil for outdoor containers should automatically be discarded if plants grown in it died due to plant diseases. If the potting soil grew beautiful plants all season and the plants only died because winter’s frost arrived, then you can reuse the entire container of potting soil the following season.

Potting soils made with compost and aged pine bark last longer than peat-based potting soils, as compost and aged pine bark have already undergone a managed decomposition process and are more resistant to breaking down. If you need to remove the soil to protect a ceramic pot, you can place the soil in plastic bags for the winter. Leave the bags open so the soil can breathe. Place the potting soil back in the container when night temperatures are consistently above freezing (above 32 degrees Fahrenheit).

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Excerpted with permission fromPractical Organic Gardening, by Mark Highland. Published by Cool Springs Press, © 2017.

Mother Earth Gardener
Mother Earth Gardener
Expert advice on all aspects of growing.