Dustin Bajer, Classroom Container Gardening, Potted plants on a patio

Classroom Container Gardening

Start A School Garden With Pots and Containers

One of the easiest ways to introduce gardening to students is through classroom container gardening. A significant obstacle to growing food in the classroom is finding a permanent space, but pots and containers allow any teacher to start small without a fixed garden space. Container gardening can be as simple as a single potted plant on a windowsill. Attractive and portable, gardening in containers is a perfect way to get your hands dirty without breaking the bank or committing to a fixed garden site.

Dustin Bajer, Classroom Container Gardening, Potted plants on a patio
Container Gardening

Growing Leafy Greens and Fruiting Plants in a Classroom Container Garden

With suitable soil, water, and lighting, you can grow almost anything in a container, so when deciding what to grow, consider how you might use the plants in a classroom or school. If you’re hoping to plant and harvest within a single term, fast-growing leafy annual plants might be your best option, but for longer-term projects, consider perennial fruiting plants.

Fastest Growers – Annual Herbs and Leafy Greens

Annual herbs and leafy greens are perfect for growing a harvest within a single semester. Leafy greens like basil, mint, lettuce, and spinach are good choices. 

Medium Growers – Herbaceous Fruiting Plants and Root Vegetables

If you have an entire school year, consider slower-growing fruiting plants like tomatoes, peppers, cucumbers, peas, and beans (yes, these are all fruits). Another good option is root vegetables such as carrots, beets, or potatoes. These plants take longer to mature than leafy greens and require more light but can produce a harvest over a school year.

Some of these plants, like tomatoes and peppers, are technically perennial and can grow and produce for multiple years.

Slowest Growers – Woody Perennial Plants

If you have larger containers and lots of light, consider fruiting plants like tomatoes, peppers, cucumbers, peas, and beans. With even larger containers, consider small trees or shrubs like citrus, figs, and avocados.

For plants kept inside year-round, choose tropical or subtropical plants that evolved without winter. Temperate plants like apples, plums, and cherries require a cold period and will burn themselves out if left indoors.

Growing fig trees in pots
Growing fig trees in pots, Stark Brothers

Choosing Soil For Your Container Garden

Using the right soil is critical. You may be tempted to grab a few shovel scoops of soil from the garden, but resist that urge. While garden soil works well in the backyard, it’s a terrible choice for container gardening as it tends to compact.

Soil is made of organic matter, water, air, and inorganic minerals such as sand, clay, or silt. The inorganic minerals in garden soil make it a brick when used in a pot. Rather than garden soil, choose a soilless potting mix. Soilless potting mixes are chalked full of organic matter, water, and air but lack the inorganic minerals – hence the name “soilless.” Soilless potting mixes are lighter, stay fluffy (air-filled), and don’t easily compact.

Watering Your Container Garden

Generally speaking, potted plants will dry out faster than plants in the ground, so the more significant the pot, the longer you can go between watering.

While each variety of plant has its preference for moisture, the key to container gardening is to find a happy medium between soggy soil and bone dry. Generally speaking, your growing medium should be slightly damp to the touch but not wet. If you squeezed a handful of potting soil and got a single drop of water, you’ve got it right.

How frequently you water will depend on the size of your pot, its location, and the plant you’re growing (some plants, like tomatoes, are thirsty and won’t tolerate drying out).

To prevent overwatering, always use containers with drainage holes at their base. Remember that air is a critical component of healthy soil and that over-watering removes air to the point that the plant’s roots will be unable to breathe.

Lighting Your Container Garden

Like water, each plant has a preference for how much light it wants. While tomatoes and peppers love sunlight, crops like lettuce, spinach, and broccoli are more shade tolerant. Depending on the location of your container and what you’re growing, you may get away with a sunny South-facing window or need to supplement your crop with full-spectrum artificial lights such as compact fluorescent T5s or LEDs. Paired with a timer, I provide 18 hours of daily light for most of my plants.

Choosing The Right Container

Off-The-Shelf-Pots

Off-the-shelf pots vary in height, depth, shape, size, and material. Plastic containers are inexpensive and light but not as durable. In contrast, ceramic pots can be expensive and bulky. The best pot for a school is probably a free pot, so talk to colleagues, big-box stores, and nurseries to see if you can take any old containers they might have lying around. Plastic nursery pots are inexpensive, come in standard sizes, and are a good choice for school; they’re not pretty but durable and abundant.

Self-Watering Pots

Self-watering containers generally have a water reservoir below the soil and a wick to draw water into the container as the soil requires it. Any self-watering pot or automatic watering technique is valuable for schools because it answers the existential question of “who will take care of the plants over the weekend or break?” You can sometimes find self-watering pots at garden supply stores, though they’re not as common.

Earthboxes Containers

An Earthbox is a self-watering container that consists of a grow box, casters (for easy transport), and an organic soil amendment (fertilizers and minerals). Lights can be purchased as an accessory. Sustainable Food Edmonton’s Little Green Thumbs Program uses Earthboxes to grow vegetables and herbs in hundreds of school classrooms here in Edmonton.

Growing strawberries in an earthbox
Strawberries growing in an Earthbox

Earthboxes provide roughly two square feet of growing space on top of a self-watering reservoir; keep the water reservoir topped up, and the innovative Earthbox design wicks up water when needed. I can say from personal experience that growing in Earthboxes is an easy and efficient way to start growing food in the classroom. The only downside of Earthboxes is that they are one of the more expensive options.

Global Buckets

Global Buckets are self-watering and an inexpensive container gardening method for schools.
Global Buckets are self-watering and an inexpensive container gardening method for schools, Farming Outside the Box.

Making Global Buckets might be the perfect option for the DIY class and teacher—the invention of two high school students looking for an inexpensive way to make Earthboxes. Essentially a bucket inside a bucket, you can build a cheap self-watering container for a fraction of the price of an Earthbox. Global Buckets are deep enough to root vegetables like potatoes or grow larger plants like small trees and shrubs.

Wicking Beds

A wicking bed is a large garden box built on a water reservoir. As the soil dries, water is wicked from the reservoir below. Admittedly, wicking beds are verging on the edge of permanent raised beds, but mobile DIY versions exist.

Most wicking beds rely on creating a watertight reservoir filled with gravel, with soil on top. A porous landscape fabric separates the gravel and soil. Wicking beds use the soil’s natural water-wicking action to soak up water as needed.

Dustin Bajer, Jasper Place High School self-watering wicking bed
Self-Watering Wicking Bed at Jasper Place High School

Start Small and Find Success

Container gardening is an excellent way to start growing food in the classroom. Use a light, soilless growing medium in an inexpensive (or free) container. The beauty of this approach is that you can start small and find success and scale up (or down) depending on the needs of your students and your project’s goals.