Container Explainer: How to Choose the Right Pots for Your Plants
The right container goes a long way towards keeping plants happy and healthy. How do you choose?
Starting off with the right container, particularly the right size, is key to setting up your potted garden, and getting it to look good and thrive. Large plants in small containers dry out quickly and become pot-bound, while small plants in large pots look odd and can have trouble regulating soil moisture. If you’re new to gardening or looking for a refresher, save this guide to choosing the right container size for your planting combination.
What Size Container Do You Need?
Ornamental plants
How much soil a plant needs, and therefore how big a container it needs, depends on the type of plant and how deep the roots grow. For any container, keep soil quantity proportional to the plant type and size to help balance soil moisture.
Ornamental plants
How much soil a plant needs, and therefore how big a container it needs, depends on the type of plant and how deep the roots grow. For any container, keep soil quantity proportional to the plant type and size to help balance soil moisture.
- Small succulents need shallow soil (less than 15 centimetres).
- Annuals need a soil depth of 30 centimetres.
- Perennials need a soil depth of 30 to 45 centimetres.
- Shrubs need a soil depth of 45 to 60 centimetres.
- Small trees need a soil depth of 60 to 90 centimetres.
These dwarf blueberries can thrive in medium-size containers since the plants stay small.
Edible plants
For most plants grown as crops, the more room in a container you can give them, the better.
Edible plants
For most plants grown as crops, the more room in a container you can give them, the better.
- Herbs planted indoors can grow in soil that’s 15 centimetres deep; outdoors, plant them with a soil depth of 30 inches.
- Shallow-rooting crops such as lettuces, strawberries and radishes can grow in 15 to 30 centimetres of soil.
- Medium-size edibles, including capsicums, eggplants, squashes, melons and corn, require a soil depth of at least 30 to 45 centimetres.
- Give large-scale edible plants, such as tomatoes, potatoes and full-size berry shrubs, at least 45 centimetres or (better yet) 60 centimetres of soil.
- Citrus and other fruit trees need soil that’s 60 to 90 centimetres deep.
Container Shapes
Not only does a container’s size affect how well a plant grows, the container’s shape does too.
Round, square and rectangular
Medium to large round, square and rectangular containers with deep soil reservoirs (30 to 90 centimetres, depending on the plant type) are good options for flowering perennials, shrubs and small trees. Use larger containers for planting combinations of multiple plants so each plant has room to grow.
Not only does a container’s size affect how well a plant grows, the container’s shape does too.
Round, square and rectangular
Medium to large round, square and rectangular containers with deep soil reservoirs (30 to 90 centimetres, depending on the plant type) are good options for flowering perennials, shrubs and small trees. Use larger containers for planting combinations of multiple plants so each plant has room to grow.
Shallow
Low bowls with less than 15 centimetres of soil are perfect for growing small succulents such as stonecrop (Sedum spp.) and hens and chicks (Sempervivum spp.).
Planting stands can raise low containers a little closer to eye level. Shallow containers also work well as toppers for outdoor side tables and dining tables.
Browse edible gardens for inspiration
Low bowls with less than 15 centimetres of soil are perfect for growing small succulents such as stonecrop (Sedum spp.) and hens and chicks (Sempervivum spp.).
Planting stands can raise low containers a little closer to eye level. Shallow containers also work well as toppers for outdoor side tables and dining tables.
Browse edible gardens for inspiration
Vase-shaped
Containers that flare out at the top are good options for mixed combinations of annuals, flowering perennials and an evergreen shrub or small tree.
The wide opening gives plenty of space to put together a combination of plants. Select the depth of the container based on which plant types you’d like to include.
Containers that flare out at the top are good options for mixed combinations of annuals, flowering perennials and an evergreen shrub or small tree.
The wide opening gives plenty of space to put together a combination of plants. Select the depth of the container based on which plant types you’d like to include.
Urn-shaped
Classical-style urns (wide at the bottom with a tight neck and wider opening) are good vessels for annuals and easily removed perennials. Keep in mind that if you plant anything that is deep-rooting, once a root ball forms below the neck of the urn, it can be tough to remove the plant.
If you’re thinking about something deep-rooting like a shrub, vine or small tree, plan to leave it there for its lifetime (size up on the urn at planting time).
Classical-style urns (wide at the bottom with a tight neck and wider opening) are good vessels for annuals and easily removed perennials. Keep in mind that if you plant anything that is deep-rooting, once a root ball forms below the neck of the urn, it can be tough to remove the plant.
If you’re thinking about something deep-rooting like a shrub, vine or small tree, plan to leave it there for its lifetime (size up on the urn at planting time).
Tall and upright
Tall, skinny containers can help elevate small plants, giving them more visual impact. Be careful about pairing a shallow-rooting plant such as a succulent with a tall container (anything over 60 centimetres) filled with soil. It’s easy to overwater and have wet soil collect at the base of the pot beyond the plant roots.
This potted pair hits the sweet spot from a design and healthy soil perspective. The vertical shape of the containers elevates the plants, but the soil reservoir isn’t so deep that it would be at risk for becoming soggy.
Tall, skinny containers can help elevate small plants, giving them more visual impact. Be careful about pairing a shallow-rooting plant such as a succulent with a tall container (anything over 60 centimetres) filled with soil. It’s easy to overwater and have wet soil collect at the base of the pot beyond the plant roots.
This potted pair hits the sweet spot from a design and healthy soil perspective. The vertical shape of the containers elevates the plants, but the soil reservoir isn’t so deep that it would be at risk for becoming soggy.
Choosing Your Container
Given that a container’s size and shape affect how well a plant grows, it’s a good idea to choose plants and vessels at the same time. Otherwise, play matchmaker between containers you already have and the plants you intend to pot up.
When you’re choosing a container based on a plant, don’t rely on the plant’s initial size when estimating the size of container you will need. Instead, look up the mature size of the plant (often found on the back of the plant label) and which category it falls into (succulent, annual, perennial, shrub or tree). Be sure to choose a container that allows enough room for the plant to grow and a soil depth that will provide plenty of root space.
Given that a container’s size and shape affect how well a plant grows, it’s a good idea to choose plants and vessels at the same time. Otherwise, play matchmaker between containers you already have and the plants you intend to pot up.
When you’re choosing a container based on a plant, don’t rely on the plant’s initial size when estimating the size of container you will need. Instead, look up the mature size of the plant (often found on the back of the plant label) and which category it falls into (succulent, annual, perennial, shrub or tree). Be sure to choose a container that allows enough room for the plant to grow and a soil depth that will provide plenty of root space.
Special considerations for edibles
As previously mentioned, err on the side of giving more container space to any crops grown in containers. (Reference the list of ballpark soil depth per type of edible plant above). If crops such as tomato, capsicum, zucchini and eggplant are grown in a crowded container, they compete with one another for nutrients and sun exposure, which can lead to smaller harvests.
As previously mentioned, err on the side of giving more container space to any crops grown in containers. (Reference the list of ballpark soil depth per type of edible plant above). If crops such as tomato, capsicum, zucchini and eggplant are grown in a crowded container, they compete with one another for nutrients and sun exposure, which can lead to smaller harvests.
In general, it’s best to give each medium- or large-size edible plant its own container — possibly tucking herbs or pollinator-friendly plants like marigolds around the base if there’s excess room. Lettuces and smaller plants like radishes and strawberries can be planted with multiple plants per container.
Container-grown edibles are big ‘feeders’, meaning they take a lot of soil nutrients to grow quickly and produce well. Fertilise with a well-balanced organic fertiliser according to package instructions.
The Ways Australians are Reworking the Outdoors
Container-grown edibles are big ‘feeders’, meaning they take a lot of soil nutrients to grow quickly and produce well. Fertilise with a well-balanced organic fertiliser according to package instructions.
The Ways Australians are Reworking the Outdoors
When to Repot
Plants aren’t happy if they’re left in a container they’ve outgrown. Here are three signs that container plants need repotting.
Plants aren’t happy if they’re left in a container they’ve outgrown. Here are three signs that container plants need repotting.
- Plants look overgrown and are no longer proportional to the pot.
- Water quickly runs out of the pot, indicating that roots, rather than water-absorbing soil, are taking up most of the space.
- Plants show signs of stress, such as yellowing leaves, dieback or stunted growth.
How to Repot
- Choose a container that’s at least 5 to 10 centimetres larger (width and depth) than the original container.
- Remove plants from the old container by digging down 10 centimetres or deeper to loosen the roots and then gently tugging the plant free, using a hand trowel if needed for leverage. Keep as much of the root ball intact as possible.
- Fill the new container with fresh potting soil and immediately plant transplants.
- Water well, soaking the potting soil.
Exuberant displays of warm-season annuals and perennials can look as though they’ve outgrown their container by the end of the season, but it’s completely natural and doesn’t necessarily mean they need repotting. Flowers going to seed, dieback and yellowing leaves are just part of the life cycles of the plants.
Pull out annuals at the end of the season and cut back flowering perennials after frost. If the plants seem root-bound after one or two seasons, divide any remaining perennials and plant them in other containers or out into garden beds.
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Pull out annuals at the end of the season and cut back flowering perennials after frost. If the plants seem root-bound after one or two seasons, divide any remaining perennials and plant them in other containers or out into garden beds.
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Read more garden stories for tips and inspiration
A plant needs to be in a container that has enough room for it to grow, but isn’t too big for the plant’s size. If a plant is in a pot that’s too small, its growth will be stunted, roots will become pot-bound and the soil will dry out quickly.
Conversely, a small plant potted up in a large container can be thrown off by the moisture balance in the soil. If plant roots can’t reach the bottom of the pot and drainage holes are at all obstructed, excess moisture will collect at the bottom of the container, forming a mass of soggy soil. This can lead to root rot, an extra-heavy container and a funky wet-soil smell.