Container Gardening Secrets: Ideas to Inspiration

Why container gardening?

Container gardens allow anyone with a little bit of space and sunshine to garden almost anywhere and may even lead to an addiction of colourful pots and quirky vessels on your deck or patio. The impact of colourful glazed pots or the whimsical effect of a repurposed washtub lends a personalized aesthetic to landscapes like your own signature.

There are endless choices available to begin your container garden. Cedar boxes, railing baskets, large resin pots, half barrels, storage totes, fish tanks, and even the kitchen sink can be used to grow vegetables in as long as you abide by a few fundamental principles when choosing.

Principles of container gardening

1. Pair plants with a vessel that accommodates their growing root system.
2. Provide a soil mixture appropriate for plant choice.
3. Ensure drainage will be adequate for the variety chosen.

Thanks to their size, container gardens are much more manageable than growing in a ground-level bed. They also allow for greater control of the growing conditions. You can address soil structure, fertilizer, and water needs of specific plants and you can position containers so they are receiving the appropriate sunlight for each variety.

Placing containers in ideal locations will save water and lead to healthier plants that can fight off pests more readily. Used functionally to grow produce in a small space or as an accoutrement to the landscape, container gardens have many benefits to offer.

What can you grow in a container?

There are so many plants that will grow successfully in containers the simpler question may be what can’t you grow? To begin, research the needs of your favorite varieties to determine the space you will need for the root system and the type of soil you will use to ensure a thriving plant.

In the list below you will find a list of the conventional container plants. This serves as a general guide to the pot size and the right soil combination for each. Note that the pot sizes listed are the minimum requirements. Some plants will have to be repotted into larger containers or else they’ll become root bound.

Common Container Gardening Plants and Their Needs

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How to choose the right container

The beauty of the pot is generally how we choose containers, but this is secondary to the function of the pot. Aesthetics and garden design aside, choosing the right container should be determined by the size of the plant/root ball you want to grow and the material the container is made from.

Size of plant/root ball

Plants like vegetables that mature over one season, trees with large root balls, or multiple plantings in a container can become root bound very quickly, causing the container to dry out fast. Avoid an exercise in frustration with a little bit of education on how big a space each will need.

• For annual hanging baskets, a good rule of thumb is one plant per inch of basket diameter. For example, 12 plants per 12-inch basket.
• For bigger plants like geraniums, herbs, and strawberries, use only four plants per 12-inch basket. Planters or large pots are more suitable for multiple plantings of more abundant vegetables, perennials, trees, or shrubs.
• For window boxes, plant two plants for every 12 inches of length. Generally window boxes should be at least 8 inches wide and 8 inches deep to provide enough depth for root growth.

Container material

The container material is also a factor to consider when choosing your vessel. Some of the most common options are highlighted below.

• Plastic or resin is lightweight, inexpensive, and durable. But these materials can also become over saturated, causing root disease. It’s also worth noting that the standard black plastic or resin pot absorbs more heat, so if you are putting a container in a hot, sunny location, choose a lighter colour instead.
• Terra cotta or clay pots are a popular option for those who live in wetter coastal climates. Terra cotta pots dry much quicker than plastic (and smaller pots dry out more quickly than larger ones), which helps control associated moisture diseases. A downside is that they are heavy, breakable, and need to be emptied or protected in locations that freeze in the winter.
• Glazed clay pots offer a wide range of colour and size providing significant impact in any space. However, like the plastic or resin, clay pots can become saturated with water causing root disease and also need to be emptied or protected in winter.
• Eco pots or fibre pots have a high porosity and breathe well, which promotes healthy root growth, particularly for vegetables. These pots can be made from coconut coir, pressed paper or other grain husks, each with its own life span. A primary benefit being that these pots will degrade naturally with little impact on the environment by contributing to the landfill at the end of their lifespan.
• Wood is the most common planter material for raised beds or planter boxes. Mostly constructed with cedar, wood is beautiful, easy to build and can be made to any size or shape. One of the disadvantages for those who live on the coast is that wood can rot, making it more attractive to the pill bug which also likes to feed on plant material.
• Glass or plastic terrariums are meant to provide a moist, humid environment for tropicals and a beautifully unique way to create a lush environment in a small space. The terrarium can be created using an old aquarium, a large vase or clear bottle. Given that drainage cannot be added, over-saturation can be an issue encouraging rot and gnats. Ensure that the base of the vessel has a sufficient layer of coarse gravel and a thin layer of charcoal to alleviate these potential problems.
• Uncommon vessels like metal buckets, washtubs, old boots, boats, baskets, sinks, bathtubs and even toilets can be used to personalise your landscape. With the addition of holes for water drainage, transforming these non-conventional containers to a planter requires little else.

Whichever container material you use, drainage is key in how successful you will be. Standing water or excessive moisture for plants that don’t love wet feet invites diseases, fungus and pests, which will negatively impact your plants. Ensure you have adequate drainage for the plants that you choose. If drainage holes aren’t present or more drainage is necessary, add holes or a layer of coarse gravel at the bottom of the pot to allow moisture to be released.

How do you prepare the soil in your containers?

Preparing your container to plant is simple but requires a little more than filling the pot with potting soil and adding plants. Soil is the bed for your plant and the foundation on which the plant depends to grow. It is the medium in which the plants gain access to moisture, nutrients and oxygen. Not all plants require the same soil, so it’s important to know the soil combination each requires and the function of each material.

• Organic matter (OM) is a dual purpose medium made up of varying sized chunks of material offering porosity to aerate the soil as well as acting like a sponge to hold onto water in the tiny particles of material. The most common organic matter chosen for containers would be peat or coconut coir. Both will help your containers retain moisture.
• Compost is a type of OM that offers the same benefits as well as being rich in nutrients. Compost is generally derived from rotted plant material or manures processed by worms.
• Sand is a fine, granular rock material that contributes to drainage in the container. Every container should have a bit, but too much can dry out a pot too quickly.
• Loam is equal parts clay, silt and sand which gives the benefits of each with few of the disadvantages of each material.

Most often you will fill your containers with seedlings or starts, but you can also seed directly into containers. Sowing direct into containers requires a seeding medium on the top 3” of container soil.

Easy to create, add a 3:1 ratio of peat: vermiculite as the base for your seeds. Water well before seeding and follow up daily with watering to prevent seeds from drying out.

Related:

• 6 Tips for Building Soil for Raised Garden Beds and Planters
• Raised Garden Beds: Soil Depth requirements

Feeding your potted garden

A new container filled with sterile soil or potting mix does not have many nutrients to feed the young plants. Adding food during the soil mixing stage is essential to give them what they need in their first month of growing.

One cup of organic fertilizer mix of 5-3-4, plus a 1/2 cup of bone meal per 10 gallons of soil mixed throughout the pot, will ensure an excellent start for your plants.

All-purpose organic fertilizer provides nutrients for potted plants.

For annuals, throughout the growing season, use 1/4 cup of the same organic fertilizer sprinkled weekly onto the soil surface or an all-purpose liquid fertilizer. Liquid fish emulsion is one helpful choice.

Another option is to use compost tea or tea made from worm castings. This is a simple solution for providing your plants with all the micronutrients they need as well as contributing beneficial microbes to the soil.

Compost teas, if created correctly using well-rotted compost, will not burn and can be used multiple times a week.

Compost Tea Recipe:

Add 2 cups well-rotted compost or worm castings to a 3-gallon bucket of water. Stir vigorously and allow to stand overnight. After 12 hours, stir vigorously again then let particles settle. Pour tea mixture into containers. The remaining sludge can be reused to make another batch of tea or added directly to a container. For more information, read The Best Compost Tea Recipes to Help Your Plants Thrive.

How to choose plants for containers and small space gardens

A visit to the garden centre to purchase starts or plants can be overwhelming if you don’t have a plan before you get there. There are so many options, so it’s easy to get distracted. As you would with your landscape, prepare your design ahead of your shopping trip, so you know exactly what you are looking for. Here are some insights to make the decision process a little easier.

Vegetables are not just limited to the landscape and beds. In fact, some thrive in potted conditions as you can provide exactly the right combination of conditions they are looking for. The top ten choices for your container garden are: tomatoes, peppers, squash, beans, lettuce, bok choi, radishes, spinach, peas and carrots.

Herbs love the confines of a container, especially the Mediterranean varieties. Rosemary, oregano, thyme, parsley and anything in the mint family will do well in a container filled with well-drained soil placed in a sunny location. Furthermore, a container will prevent some of the more aggressive varieties like those of the mint family from spreading into areas you don’t want them.

Perennials and shrubs planted in eye-catching containers make very attractive additions to a landscape. Ornamental grasses do as well. Keep in mind that plants should be sized to the pots and the pots sized to space. If foliage is the element, choose ornate pots for an ideal focal point. If plants produce many flowers, a more subtle container is in order. Also consider if the container will be a focal point or an accent to an entrance. The selection of perennials and shrubs are more specific, so it’s essential to do some research before choosing. A good horticulturist at your local nursery will be your best resource for the your location.

Annuals are the best for adding instant colour and flair to the landscape. In your designing stage consider the “thriller, spiller and filler” technique of planting, which incorporates multiple varieties in one pot—the thriller being the focal upright, the spiller to cascade over the pot and the filler to take up the spaces in between.

• Thrillers – Alocasia esculenta, dahlia, cosmos, salvia, snapdragons.
• Spillers – Lobelia, bacopa, nasturtiums, petunia, allysum
• Fillers – Coleus, Heliotrope, Lantana, amaranth, violets, geraniums

Cacti and succulents are one of the easiest to grow in a container as they happily tolerate drier conditions, so terra cotta is one of the best containers to choose for this application. Succulents are also not limited in color, so consider a few of these varieties to plant singly or in a collection:

• Echeveria
• Opuntia
• Crassula
• Senecio
• Sedum
• Snake plant
• Aloe vera

Containers can host multiple plants and types as long as you ensure they have the same moisture and food requirements and enough room to grow. A lovely combination for drier conditions would be African daisies mixed with sedum, senecio, and echeveria. If it is a shady area, you would like to make lush consider a combination of caladium, fuschia and ferns. If space is limited, but the food is your priority, mix greens with cucumber and a tomato plant in a half barrel to provide salad fixings for the summer. Abide by the rules, and you will be happy with the outcome.

Don’t forget to acclimatize your plants before planting. If starts are coming from a lovely warm greenhouse or nursery, they will need some time to adjust to the outdoor temperature. Bring them outside daily and inside at night to harden off and accustom to their new environment for a minimum of 3 days.

How to care for containers after planting

Once you have your containers planted, they will need a bit of care. Place containers in a location where they will receive adequate sunlight and temperature for the variety. Monitor the moisture and water as necessary.

Use a natural-based slow release fertilizer of 5-3-4 every week or water with a compost tea 2-3 times per week. Support peas, beans, wisteria and other vines with a trellis to give them the support and stake tomatoes and peppers before they fall over.

If plants are struggling to grow, they are susceptible to pests and diseases. Give them what they need and avoid the risk.

Things that might go wrong

Too much or too little moisture is the most common problem for container planting. This leads to stressed plants which lead to pests. Let your pots dry a bit between watering and only water until it runs out the bottom.

If the soil has become too dry and plants have wilted in full sun, add small amounts of water throughout a day until the soil is saturated again. Stressful conditions attract pests so do your best to avoid overcrowding or mixing non-like varieties. Pests like aphids and whitefly are the most common of culprits but if caught early can be controlled with a pure soap and water mixture. For more information, read our guide about Natural Garden Pest Control.

Container plants draw attention so you will want to keep up with deadheading, removing exhausted plants and cleaning up brown or tattered leaves. Varieties that have passed their prime should be replaced with something similar or something that will bloom in the near future. Remember to empty clay and terra cotta pots if you live in freezing climes and prune in the fall to put your perennials to bed.

Creative containers for a well-rounded garden

Adding containers to your garden or balcony design offers the opportunity to create seasonal themes, creative dimension or functional purpose. It is an inexpensive way to satisfy the gardener in you and provides an additional habitat for the beneficial bugs and birds that live in your landscape. Let your imagination guide you.