10 Common Container Gardening Mistakes

Flowers planted in large pots as container gardens

The Spruce / Adrienne Legault

This article is part of our Mulch Madness series. Mulch Madness is The Spruce's gardening "full court press"—a curation of our very best tips and product recommendations to help you create a truly trophy-worthy lawn and garden.

What could be a more cheerful addition to an outdoor space than containers filled with colorful flowering and foliage plants? Not many types of décor are easier to create. Whether you are a new or experienced gardener, everyone can enjoy learning a new trick or two.

Here are some tips to avoid ten of the most common container gardening mistakes.

Moving a Heavy Container

Have you ever had to lift and move a large garden container that you just filled with potting soil and plants? It can be overwhelmingly heavy, especially if it has been watered. When you are filling and planting a large container, place your pot in its final location and then fill it, avoiding a backache later!

Plant caddies on wheels can also come in incredibly handy if you have to move a heavy pot into partial shade during the hottest part of a hot afternoon.

Container garden in large barrels next to bench

The Spruce / Adrienne Legault

Purchasing Plants That Don't Have the Same Requirements

Choose plants that play well together. For a container garden to thrive, all plants must share the same requirements for sunlight, soil, moisture, and fertilizer. Do your research before purchasing plants, and be sure to read signs posted at the garden center, plant labels, and seed packets for specific instructions about plant requirements.

Small succulent plants in clay container closeup

The Spruce / Adrienne Legault

Underfeeding Your Plants

Most potting mixes initially contain fertilizer that will meet most plants' basic needs. However, nutrients are quickly absorbed by the plants root system and are leached out of the container with every watering. To keep container plants well-fed, you have to provide supplemental food and organic matter once any fertilizer once-present in the potting soil is gone.

Many fertilizer products are available on the market; so be sure to choose one based on the type of plants you are feeding. For example, flowering plants have different needs (such as more phosphorus for blooming) than do shrubs, vegetables, and herbs.

To keep plants properly nourished, fertilize container gardens on a regular basis. Start with a slow-release fertilizer mixed in with the potting soil. Throughout the growing season, apply diluted, liquid fertilizer, such as fish emulsion, every two weeks. Organic or all-natural fertilizers improve the soil, because they break down easily and don't build up chemicals or salts in the container.

Overwatering Your Plants

To avoid overwatering your container gardens, the container must have drainage holes for excess water to drain from the bottom. Sometimes several drainage holes are required for large containers. Understand the moisture requirements for your plants so that you give them the amount of water they need. Some plants like to be constantly moist, and others prefer to dry out between waterings. Be aware that container soil dries out more quickly than soil in a garden bed.

Before you water a container, determine if the soil is dry. You can do this by sticking your finger into the soil at least up to your second knuckle. If the soil at your fingertip feels dry, the container needs to be watered.

If you overwater a container, plants might turn yellow, leaves might drop, and your plants might look wilted and limp. If that's the case, you might have to remove drowned plants and replace them with fresh ones.

If container soil is too wet but the plants still look healthy, move the container to a dry, breezy spot until the soil dries out. If you have the room, you can move the container garden into a garage or sheltered spot to dry out, particularly if the weather conditions are wet

Underwatering Your Plants

Most container gardens must be watered at least once a day in the heat of the summer. It's often best to do so in the morning so that plants stay hydrated all day and foliage has time to dry off before nightfall.

Many containers, especially hanging baskets, window boxes, and small containers under ten inches in diameter, might need more frequent watering because they contain less soil to hold moisture.

When you water, water deeply to soak the soil–a shallow watering does more harm than good because water can't reach the root systems. Apply water until you see it draining from the drainage holes.

Many gardeners add synthetic water crystals to potting soil. The crystals absorb water and then slowly release it when soil dries out. Water crystals are expensive. More than one study has shown that water crystals aren't effective in maintaining moisture, so using them in containers is not recommended.

If plants dry out completely, don’t despair; even the most pathetic, limp plant might revive with a good drink. If the container is small enough, submerge the container into a bucket of water or a water-filled sink until the air bubbles subside. For a large container, use a skewer or stick to gently poke holes deep into the soil to allow water to reach plant roots. Then, water generously.

Underwater plants in clay pot container

The Spruce / Adrienne Legault

Designing an Awkward Plant-to-Pot Ratio

Consider the proportions of your plants to the container size. A large container filled only with low-growing plants can appear to be stunted and out of proportion. A rule of (green) thumb is to have at least one plant that is just as tall as the container (a thriller), surrounded by mid-sized filler plants (plants with a full, mounded growing habit). To complete a balanced look, include low-growing or vining plants that spill over the sides of the container to soften its edges. This design concept is called "thriller, filler, and spiller".

Don't overcrowd your containers. Those small young plants can grow rapidly during the growing season, so consider mature size when designing a container. In small containers, plant growth might be stunted because root systems don't have enough room to fully develop.

Buying Sick or Weak Plants

Buying plants at a reputable local nursery is a good place to start in your quest for healthy plants. You have a greater chance of purchasing well-cared-for plants that are disease- and pest-free at a local nursery that grows their own plants. At a local nursery, you can obtain a wealth of information and advice from knowledgeable staff. Don't be afraid to ask someone to help you select a suitable and healthy plant.

Purchasing plants at a big box store that brings in plants from distributors is a bit more risky. If you can’t resist the prices at a big box store, buy their plants on or close to the day they’re delivered. Ask an employee to tell you which day of the week new plant stock arrives. Delivery day is usually the same every week.​

Make notes about where you purchase your plants. In the event that you buy a tomato plant infected with blight, you can remove that plant and the others that came from the same vendor, hopefully before the disease seriously affects other plants.

Failing to Prune Leggy Plants

When the plants in your container garden become leggy, sparse, or spindly, don’t be afraid to cut them back, shear, or prune them. You might want to move the container to an out-of-the-way spot until the plants rebound, but chances are the plants will re-grow healthier and happier with a good haircut.

Leggy plants in container with green and purple leaves

The Spruce / Adrienne Legault

Living With Ick

After you’ve tried everything and a plant still looks dreadful, cut your losses and toss it on the compost pile or in the trash. If a plant in a container garden doesn't thrive, remove and replace it for an instant visual improvement to the container garden.

Setting Unrealistic Expectations

Before you design and plant a container garden, evaluate the time you have available for proper care and maintenance. Do you travel a lot during the summer? If so, either use self-watering containers, an automatic drip irrigation system, enlist someone to keep your plants healthy and alive while you’re gone, or purchase plants that don't require a lot of water.

Garden how you live. Are you casual or formal? Some people like neat, well-planned, formal containers. Others enjoy plants that spill and sprawl over the edges in a multitude of colors rather than having a particular design scheme.

Container gardens are a low-risk outdoor décor technique—and there’s a lot of room for error but also room to experiment with what you like best. If you choose plants that complement each other and grab your attention, you have freedom to try different combinations and colors that please your sense of style. Whatever your lifestyle or personality, you can design container gardens that give you joy and bring beauty to your surroundings.

Dead plants in red clay container

The Spruce / Adrienne Legault