17 Vegetable Container Gardening Mistakes to Avoid

Are you creating a container garden for your vegetables this season? Don't fall victim to some of the most common mistakes you can make when vegetable gardening in containers. In this article, gardening expert and former organic farmer Sarah Hyde walks through the most common mistakes container gardeners make with their vegetables.

container gardening mistakes

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All gardeners make mistakes. Mistakes are naturally part of the learning process but can be discouraging for any gardener. This is especially true when it comes to container gardening with your vegetables. Certain veggies can be picky about their growing conditions, especially when grown in containers.

So, what mistakes should you be looking out for this season when planting your container gardens full of vegetables?

We’ve put together a comprehensive list of things to avoid this season when planting your vegetable container gardens. If you steer clear of these common mistakes, you’ll be well on your way to a successful vegetable crop in the summer!

Using ContainersThat Are Too Small  

Gardener Planting Herbs in Small Containers. They are planting dill, and other green garden herbs in the containers.
These herbs will quickly outgrow the pots they have been planted into.

This common container gardening mistake tops the list because most people misjudge the size of the mature plant. It is hard to believe the tomato plant tag that says it will grow into a 5-foot-tall behemoth when it is only a cute, 6-inch-tall seedling. 

Use the largest container you can, since it will provide the plant with space for more root growth. Many plants have greater root mass than they do leaves, an adaptation that has been millennia in the making.

A larger container holds more soil, more water, and more nutrients that your plant needs to thrive. Also, large containers retain water for longer since their mass does not heat as quickly and evaporate water as it does in small pots.  

Allowing Plants to Become Root-Bound

Potted Plant That Has Become Rootbound. The roots have grown together which can cause disease. The plant sits on a wooden table.
A plant becomes rootbound when it has been in a small pot for far too long.

Similar to choosing a container that is allowing your plant to become root-bound (aka pot-bound) or purchasing a transplant that is already root-bound. A plant is considered root bound when the roots circle the bottom of the plant. In severe cases of root-bound plants, the entire potting area will be a compacted mass of roots. 

Root-bound plants lose the healthy white root color and visible root hairs. They become less effective at taking up nutrients and water and the plant’s overall health will suffer. Choosing a large container is the best bet against your plants becoming root bound during the growing season.  

Also, be sure to check the roots of any plant that you purchase from a nursery. Especially if you plan to pot it up into a larger container, choose the healthiest roots that are still actively growing downwards and are relatively straight.

Avoid any plants that are a mass of circling, brown roots at the bottom of the pot. A small amount of root circling is not a deal-breaker, since most plants will come out of it, as long as the roots still look white and healthy.  

Not Cleaning the Container After Prior Use  

Gardener Cleaning a Flower Pot. They are wiping the side of a terra cotta pot, using a purple cloth to clean the dirt and debris off the pot.
It is very important to thoroughly clean the pot you will use for your container garden.

It is best practice to wash your container prior to planting. Using a dirty container can introduce unwanted plant pathogens to your container garden. Especially if you have recycled the container, you never know what plant diseases or fungi could be present.  

If there is heavily caked-on dirt and grime, scrub first using soap and water to loosen the crud. Follow with a sanitizer. You can also use a 10% bleach solution to sanitize the container prior to planting or Lysol-type products.

Be sure to read any labels and follow directions carefully. Make sure the product you are using is safe for your container’s material. Let the container dry fully before planting.  

Choosing the Wrong Variety of Plant 

Gardener Selecting Seeds to Plant in a Container. They are holding in their hands different vegetable seed packages to grow in their garden.
Many plants have a dwarf variety or one that is better for growing in containers.

Many gardeners make the mistake of choosing the wrong variety that is not best suited for container growing. It is an easy mistake when you are surrounded by a bevy of choices at a garden center or plant sale.  

Do your homework before shopping and find varieties that indicate they are good for containers or dwarf varieties. Carefully read the labels of any plants you purchase at a nursery, ask the farmer who grew them, or read the seed catalog description to find the most well-suited varieties for containers. 

Plant breeders have made great strides in breeding container-specific or dwarf varieties of most plants. Tomatoes, for example, maybe listed on the tag as “good for container growing” – choose these varieties if you find them. Other container compatible varieties include carrots with short roots, round-rooted crops like beets, radishes, and most herbs. 

Some crops, such as lettuce or arugula, naturally do well in containers and will most likely not be specifically stated as bred for containers. However, lettuce is bred for performance in hydroponic growing.

Using a Container Without Drainage

Vegetables grown in container garden. There is green kale and red lettuce.
Using a pot without drainage will cause problems.

You find a super cute pot that goes great with your decor. The only problem is there is no drain hole in it! Using a pot without a drain hole in the bottom is a huge mistake. Water will not drain from the pot and the soil will become saturated.

Plant roots need a balance of oxygen and water in the pore space between soil particles to stay healthy. Saturated soil does not allow the plant to breathe, effectively drowning the roots. Without soil oxygen, the plant will eventually die.  

Before you attempt to drill a hole into a beautiful ceramic pot, use an inside plastic liner pot instead. Find one that fits snugly into your decorative pot, but that allows you to remove it easily if needed. If possible, remove the plant and inside liner entirely when watering so that you can observe when the water is finished draining out of the bottom.  

Overwatering 

Gardener Watering Vegetable Garden. There are onions and kale growing in the container on the ground.
Too much water in the container garden can cause a number of problems for your plants.

Overwatering is a very common mistake container gardeners make. Many container newbies are so deathly afraid of underwatering their plants that they end up overwatering them while trying to do the right thing!

Unfortunately, the signs of over and under watering are very similar. This includes wilted leaves that do not perk up after watering, yellowing leaves, and ultimately plant death.  

Always test the soil for moisture before watering. Poke your finger into the soil and if it feels dry up to your first knuckle, go ahead and water. Soil hydrometers can be used in containers for gardeners who prefer to keep clean hands.

When it is time to water, water thoroughly until water drains out of the bottom of the pot. A well-draining potting mix will help ensure water drains out properly.

Underwatering 

Broccoli Growing in Container is dry and has not been watered enough. It grows in a black plastic pot with dry, dark soil.
If the soil is too dry, it will pull away from the edges of the container.

Underwatering usually occurs when gardeners give potted plants light, frequent splashes of water, rather than deep soaking drinks. Overly dry soil in a container will pull away from the sides of the pot. Eventually, the soil will become hydrophilic and not retain any water at all.  

If your container soil has gotten super dry, and your plant is not totally dead, you have a chance to rescue it – try bottom watering. Place the pot in a tray large enough to hold it, fill the tray with water, and allow the water to soak up into the soil.

Be patient, since it may take a while to fully rehydrate the soil. Remove the container from the bottom water once it is fully saturated and allow excess water to drain from the bottom holes.  

Not Providing Adequate Sunlight 

Tomato Plants in Containers Next to a House. There are three plants growing in terra cotta pots.
Be sure the plants in your container garden receive at least eight hours of sunlight each day.

Many container gardens are placed on patios. Make sure you observe how much sunlight the plant receives during the day. Most vegetable plants need full sun, which is 8+ hours a day.  

Some vegetables or herbs will still grow with only 6 hours of sunlight per day. Anything less than that will challenge your plant’s health since it is lacking a primary ingredient for photosynthesis, the sun! Move your potted plants if necessary to give them the sun they need. 

Adding Garden Soil to Your Container 

Gardener Adding Garden Soil to Container. Gardener is wearing blue glove and putting soil in a white ceramic pot.
Soil should never be added to containers for gardening, as a potting mix is more favorable for your plants.

It may be tempting to use the soil in your garden to fill your pots. It is free and grows beautiful plants in your yard! Do not do it! 

Adding garden soil, bagged topsoil, or unfinished compost to your containers will turn them into buckets of compacted, poorly draining, heavy pots with unhappy plants. Using any of these also introduces the potential to add thousands of weed seeds to your containers, and possibly soil pathogens.  

If you are able to effectively sterilize the soil, you may be able to use it as a part of a potting mix. However, sterilizing soil is time-consuming and a laborious task, which negates the “free” aspect of using garden soil.  

Instead, use a soilless potting media that is well-draining. Well-draining potting media will commonly have one or more of these ingredients: peat moss, sand, coconut coir, and perlite. Buy a premade mix or mix your own! 

Not Fertilizing, Regularly, or Ever! 

Zucchini Growing in Container of Fertilized Soil. There is one bright green zucchini growing over the side of the pot.
In order for most plants to grow healthy, they need a good feeding in the growing months.

Not feeding your container plants is a common mistake. Assume your potting soil does not include fertilizer if it is not specified on the bag. If it is stated on the bag that fertilizer is included, be sure to read the label and make sure it is appropriate for your needs.   

If there is no fertilizer added, or if you are making your own potting soil, add a balanced fruit and vegetable fertilizer to your potting mix before planting. Compost can be a fine addition to your potting mix in small quantities.

Using small amounts helps avoid the soil compaction and drainage issues described in mistake 9. Incorporate the fertilizer well and follow the directions on the fertilizer packaging to determine the correct amount.  

Adding Too Much Fertilizer 

Gardener Adding Fertilizer to Container Plant. There is fertilizer on the bottom of the dark, rich colored soil.
Too much fertilizer can cause problems for your plants, so it is best to use a balanced amount.

New gardeners may mistakenly believe more fertilizer = a bigger, healthier plant. Trust the application rate on the bag – adding more is not necessarily better, or safe.

Too much fertilizer will cause a “burn” where the edges of the leaves turn yellow and dry, or the whole plant can suffer and die. Using more fertilizer than the plant can take up also can cause fertilizer runoff, leading to water and soil pollution. 

Most readily available fertilizers will indicate if they are good for vegetables, flowers, cacti, or other plants. Use a balanced fertilizer for most vegetables; choose organic or conventional based on your preference. Follow the directions on the packaging to determine how often you need to reapply fertilizer to your potted plant.  

Providing drinks of fish and/or kelp emulsion mixed with water can be a good way to provide nitrogen during the growing season. (Note: tomatoes do not need extra nitrogen, too much will cause the tomato plant to be all leaf and few fruits, and lead to fruit cracking.) 

Adding Rocks to the Bottom of Your Pot 

Rocks at the Bottom of Flower Pot. There is a yellow flower pot with a plant pulled outside of it. There are rocks at the bottom of the pot.
Using rocks or a similar medium at the bottom of a pot does not equate to proper drainage and can actually harm your plants.

Someone, somewhere once told someone else to add rocks to the bottom of their pot to increase drainage. Many unfortunate gardeners heard the rumor and have been following the same erroneous advice.

Rocks only take up space that could be used by roots, effectively making your planting pot smaller! Plus, rocks make your container pot even more heavy and difficult to move! Skip the rocks, sticks, or anything else that is not potting soil. 

Not Thinning the Plants 

A pair of scissors is used to trim back the leaves of a tomato plant. The plant sits on a windowsill in the sun.
Thinning out plants is very important for the small spaces of a container garden.

Tossing seeds into a container is an easy way to grow direct-seeded crops like lettuce, carrots, arugula, or spinach. Even plants growing in pots need as much space between each other as those you would grow in the ground.  

Always thin your seedlings down to the spacing recommendations provided in the seed catalog or on the seed packet. The remaining plants will grow more quickly, stronger, and with less disease since they have better airflow. They may look sparse temporarily, but you will be rewarded with a fine crop. 

Not Providing a Trellis or Support 

Rhubarb Drooping Out of Container, over the sides. The containers are made of wood and the plants are growing with green foliage.
Not providing support can cause plants to flop over in the container.

Heavy fruited crops – cucumbers, tomatoes, peppers, eggplant, and even petite melons – can make great container-grown plants. They all can be prolific in a small space.

One problem is their stems and vines will sprawl over the sides – not quite the “spill” effect container plant designers mean when they say “fill, spill, and thrill.” Don’t make the mistake of neglecting to install support! 

All heavy-fruited crops grown in containers will need some support to keep their fruit off the potting soil and the ground. Plus, without support, the weight of the fruit risks cracking the plant’s stems.

A simple tomato cage can be placed in the pot at planting time when the plant is still small. Bamboo sticks, wooden sticks, and vinyl-coated rebar are also great options to support potted plants. 

Waiting Too Long to Trellis  

Young Tomato Plant With Support Stick growing in a terra cotta pot and dark rich soil.
It is best to provide a trellis or support as early as possible.

The best time to install a trellis or support is on the day you plant it into the container. The worst mistake is to wait until the plant is setting fruit to try and finagle a trellis under heavy branches.

Do not put this task off! Your future self will thank you when pruning and harvesting is easy and enjoyable with a trellis. Your plants will be happier and stronger when they can grow into the trellis, rather than being squashed into once when they are large. 

Even tall flowers can benefit from growing into a simple sisal twine and bamboo stake support. Not only will your flowers stay out of the dirt, but the stems will also be long, straight, and much better for cutting.    

Setting Out Potted Plants Too Early in the Spring 

Rosemary in Pot Set Outdoors in Spring. The pot is made of terra cotta and the rosemary is young.
Set your container garden out once the final frost has passed.

The first touch of spring weather and a hint of the sun gives many gardeners (especially in northern latitudes) spring fever. The excitement of seeing green again clouds your better judgment.

Many people hurriedly plant containers when the air temperatures have warmed but before the ground has thawed. Either their plants will freeze to death, or they will be out in their jammies tossing sheets over everything. 

Be judicious and do not set your tender plants out until all threat of frost has passed. Check night temperatures regularly, especially if you choose to set plants out early in spring. If you absolutely cannot wait, you will have to be the sheet-tossing gardener. Cover them if the forecast predicts even near-freezing temperatures.  

Planting Single Plants

Carrots Growing in Container. They are planting one set of carrots which are orange and resting in a pot with soil.
Add multiple plants to the container to they can grow more effectively by using each other.

Plants love company. Have you ever seen a natural environment where there is one. single. plant.? No! Plants have grown amongst each other for eons and have adapted to live with other plants nearby.

Plants thrive off each other’s humidity, and by planting more than one container plant near each other, you are creating a little microclimate. Many plants have established symbiotic relationships with others, and some have developed a superpower of nitrogen fixation that benefits all neighboring plants. 

Another reason to plant more than one container plant is to spread your risk. Many adverse things can happen during a growing season – a big windstorm blows down your tomato plant, cracking the stem; a friendly squirrel uses your container for nuts and uproots your plants; one plant dies of disease a month after planting.  

Planting more than one gives you the best chance of having something to harvest. If you have extra, it is fun to share your bounty with your friends or donate it to a food shelf. Plus, once you see the magic of growing your own tomatoes, flowers, or succulents, how can you have just one? 

Final Thoughts 

Gardners make mistakes, and that is okay! It is how we learn. Vegetables grown in containers require special care to ensure they achieve their full potential. Avoid these common container gardening mistakes with your vegetables, and you will hopefully have a bit less heartache and a lot more fun growing! 

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