7 Container Gardening Mistakes & How to Avoid Them

Person planting crops in their EarthBox container gardening system

Container gardening continues to soar in popularity. After all, it’s a great way to grow your produce, regardless of how much space you own.

However, like any other type of gardening, container gardening requires a certain level of care and attention to ensure plants grow healthy and strong. Otherwise, you’ll be disappointed in the results, particularly with your yields.

Unfortunately, people make mistakes that cost them those yields. Here are seven common container gardening mistakes. Better still, here’s how you can correct them.

Mistake #1: Selecting the Wrong Gardening Container

Choosing the wrong container size leads to many problems, including poor plant growth, root-bound plants, and dry soil.

For example, the soil dries slowly if your planting box is too large. That leaves your plant roots in wet soil because they can’t absorb all the moisture, making them more susceptible to root rot.

Conversely, the soil dries quickly in gardening containers that are too small. And that leads to you constantly having to water your plants. By the way, clay and terracotta planters have a similar impact. For instance, their porous nature causes the soil to dry more rapidly than a plastic planting box.

You need a planter box that’s both deep and wide enough for plant roots to get sufficient growing space. The more your plant’s roots can spread in the gardening container, the more they can access moisture and essential nutrients from the soil.

Focus on the Depth of Your Container

Ensure your planting box is at least 8 inches deep when growing vegetables. Generally, the deeper your planting box, the larger your reservoir of moist soil. Equally important, the more room your plants will have for root growth.

Eight inches of depth accommodates a variety of vegetables, including garlic, onions, lettuce, brussels sprouts, strawberries, herbs, and radishes.

Sub-irrigated planters are the exception. SIP planters have a water reservoir below the planting area to provide moisture for the plants. For example, EarthBox vegetable planting boxes include this self-watering feature to remove some guesswork from container gardening.

You’ll need an even deeper gardening container (10 inches more) for beets, broccoli, potatoes, beans, sweet corn, peas, squash, eggplants, and carrots.

Bigger is Better When it Comes to Planting Boxes

Regarding the length of your planting box, leave a planting space at least two inches wider than the plant’s diameter. Always err on the side of too large so that your plants have adequate space to spread.

Because plants come in all sizes, you’ll need to determine the mature size of the plant and limit yourself to a number that will fit comfortably in the gardening container.

There are plenty of resources online that provide placement charts for plant spacing. For instance, EarthBox offers placement charts for its planting boxes.

Mistake #2: Failing to Consider Plant Requirements

The reality is that most vegetables grow perfectly fine in gardening containers. Still, knowing which plants grow best in your climate is essential. When in doubt, talk to someone at your local garden center or utilize your local Cooperative Extension. Some container gardening companies also have growing guides to show you what grows best in your climate zone.

Equally important, you’ll need to place your gardening containers in an area that provides at least six hours of sunlight – most vegetables require full sun. Without appropriate sunlight, your yields will suffer.

That said, pay attention during sweltering summer months. Consider moving your plants into a shaded area for part of the day. At the very least, pay close attention to watering needs.

Mistake #3: Overlooking Plant Compatibility

First, don’t overplant. Placing too many plants in a container garden stunts their growth.

Second, you should also pay attention to companion planting. Some plants work well together and benefit each other. Others, not so much.

In some instances, one type of plant may produce biochemicals that hinder the growth of another plant. For example, beans don’t work well with onion family members. However, they do work well with carrots.

In other instances, one plant may become flavored by another plant. For example, herbs like rosemary and basil can impact the flavor of cucumbers.

Garlic also impacts some plants negatively. For example, when planted with lettuce, it produces chemicals that wilt the lettuce.

You can learn more about companion planting here.

Companion planting infographic for EarthBox Original container gardening system

Mistake #4: Over or Underwatering Plants in Your Container Garden

Here’s where many novice gardening enthusiasts mess up. And typically, the results are the same whether you water too much or too little – your plants wilt and die. Or if they survive, your yields are poor.

Underwatering leads to dry soil and stunted growth. Over-watering leads to root rot and other concerns.

Remember that water is lost much faster from gardening containers than from the ground. And, as mentioned, some containers are naturally porous, where moisture evaporates from the sides. By lining terracotta planters or using non-porous planting boxes, you can reduce that concern.

Water also evaporates from the soil surface in containers. So use mulch or gravel to limit the evaporation and minimize your watering requirements.

Checking for Moisture in Your Planting Box

You can check the soil’s moisture by inserting your finger into it. If it feels dry, it’s time to water.

When you water, focus on saturating the soil. Less frequent waterings where you soak the soil are better than more frequent waterings where you only dampen the soil. Check for water from the drainage holes to know when you’ve saturated the soil.

Speaking of drainage holes, they’re essential. Without drainage holes, water accumulates in the soil. Eventually, it will lead to root rot. If your planting box doesn’t have drainage holes, create some.

You have a couple of solutions if you aren’t sure about when to water or not. One is a moisture meter. The other is a sub-irrigated gardening container.

Water being poured into the water fill tube of an EarthBox planting box

Mistake #5: Using Poor Quality Soil

Feeding your plants properly starts with the soil. You must use quality soil that’s preferably designed for gardening containers.

Some folks grab a shovel, scoop some ground up from somewhere in their yard, and use that for their containers. That’s a disaster. The soil will clump and suffocate your plants.

You want to use soil that drains well while holding nutrients and providing oxygen to your plants. First, it should be light and fluffy. Second, it should include peat moss which helps with water retention. Third, it should consist of perlite or vermiculite, which creates air space.

You can amend the soil with compost, dried manure, slow-release fertilizer, or other essential nutrients to get your plants off to a good start.

You can also save yourself some time by getting a planting kit. For example, EarthBox offers a custom-blended organic potting mix specifically designed for planting boxes. It also includes fertilizer.

Mistake #6: Failing to Feed Your Plants Regularly

Even if you mix something like composted manure into your soil before planting, that fertilizer will last only a few weeks. In addition to your plants consuming the nutrients, some will drain from the container.

Consequently, it’s essential to fertilize your vegetable planting boxes every two to four weeks. Some plants require even more frequent feeding. For example, fruiting plants like tomatoes and peppers benefit from feeding every week. You can even dilute the fertilizer and feed them every day.

Your two best options for fertilizer are granular or liquid fertilizer. The former has slow-release granules that absorb into the soil when you water.

You mix liquid fertilizer with water. Then, you can pour it into the planter. You can also spray some on the plant’s foliage as they will absorb the fertilizer.

A word of caution. If you spray fertilizer on the plant’s leaves, do it in the morning. That way, the plants can dry out before cooler night temperatures hit. Wet foliage invites fungal diseases. That’s why it’s also best to water in the morning.

Don’t Forget These Initials – N, P, K

They stand for nitrogen, phosphorous, and potassium. Each is critical for your plant’s health. When first planting, using a balanced fertilizer with equal parts N-P-K is fine. You’ll often see notation like 10-10-10 to represent the percentage of each nutrient.

After planting, focus on incorporating nutrients essential to your grown vegetables. For example, leafy vegetables like lettuce require nitrogen.

Fruiting plants like tomatoes and peppers like phosphorous, while root crops like carrots and potatoes thrive on potassium.

This is another reason to focus on companion planting. In addition, you’ll benefit by having plants needing the exact fertilizer requirements.

Depending on the gardening container you use, the manufacturer may have specific fertilizer and soil recommendations. Always follow those to avoid guesswork and to guarantee your gardening success.

Mistake #7: Failing to Thin and Support Plants

Keep your plants confined to space requirements. There’s nothing wrong with pruning or thinning plants. However, your plants will grow better and face fewer disease concerns because they’ll have better airflow.

In addition to thinning plants, you’ll also want to ensure you support plants that tend to sprawl or that produce heavy fruits – cucumbers, tomatoes, eggplants, etc. They can quickly take over a space.

Moreover, fruited plants can contact the ground without staking, leading to spoilage or bug concerns. You also run the risk of the plant’s stems cracking.

It’s also best to consider staking when you initially plant. Otherwise, you’ll have to force the plant’s stems to fit the trellis. That leads to breakage, where you can lose budding fruits and cut production.

Tomatoes growing in a green EarthBox container gardening system supported by a 5 foot staking system

EarthBox Helps Avoid Container Gardening Mistakes

One of the best ways to avoid container gardening mistakes is by using EarthBox products. We’ve developed complete gardening systems to help ensure your success. It’s why we’ve been a top-rated and trusted provider since 1994.

Commercial farmers developed our planting boxes. They’re tested and proven in the lab. So you get superior results whether you have a green thumb or not.

Our maintenance-free system controls soil conditions and watering and eliminates the guesswork. As a result, you’ll get double the yields of a conventional garden. So whether you’re planting tomatoes, herbs, vegetables, or strawberries, you’ll get superior yields.

Tomatoes, carrots, and herbs being grown in different EarthBox gardening containers