Mad About Berries

The Appeal of Metal Containers in Gardening

Gardening is as much about the beauty of plants as it is about the containers they're housed in. In recent years, metal containers have emerged as a trendy and functional choice for many garden enthusiasts.

These pots, with their industrial charm and resilient nature, offer a striking contrast to the soft, organic forms of plants. However, many gardeners wonder if they can plant vegetables and similar plants in metal pots and containers...

Whether you're a city dweller with a balcony garden or someone with a spacious backyard, metal containers can add a touch of modernity and flair to your green space.

Published: October 25, 2023.

celery in metal planter

Types of Metal Containers for Gardening

Selecting the right type of metal container can make all the difference in the success and aesthetics of your gardening project.

Galvanized Steel: A Popular Choice

Galvanized steel containers have risen in popularity due to their rustic yet refined look. "Galvanized" means the steel has been coated with a protective layer of zinc to prevent rusting.

These containers are often used for farmhouse or industrial-style designs and are suitable for a variety of plants. Apart from their aesthetic appeal, they're also known for their durability.

However, it's essential to ensure they have proper drainage to prevent rusting and that they are light-colored, as steel can retain heat and potentially overheat plant roots.

Stainless Steel: Durable and Sleek

When you think of a modern and clean design, stainless steel might come to mind. This material is rust-resistant, making it an excellent choice for outdoor garden spaces where containers might be exposed to rain.

Its sleek surface is easy to clean, and it can reflect sunlight, adding an interesting dynamic to the garden. However, like galvanized steel, stainless steel can get hot, so it's important to consider plant placement and container location.

Aluminum: Lightweight and Rust-Free

If you're seeking a lightweight option that's easy to move around, aluminum containers might be your best bet. They don't rust, making them great for both indoor and outdoor settings. Their lighter shade often gives a contemporary vibe, complementing minimalist garden designs. However, they can dent more easily than steel, so they need to be handled with care.

Copper and Brass: Beautiful but Specific

Copper and brass pots exude a timeless elegance. They can develop a beautiful patina over time, adding character and charm. These metals have natural antibacterial properties, which can be beneficial for plant health.

However, they can react with certain soils and fertilizers, so it's crucial to use them with non-reactive plants or place a barrier between the metal and soil.

Each metal type offers unique benefits and considerations. By understanding their properties, gardeners can make informed choices that suit their gardening goals and aesthetic preferences.

Personally, galvanized steel offers the best ratio of quality and price.

large metal planter

Benefits of Using Galvanized Containers for Plants

Galvanized containers have become a favorite among garden enthusiasts and professionals alike and for good reasons.

  • Durability: One of the most significant advantages of galvanized containers is their resistance to rust. The zinc coating provides a barrier against the elements, making them suitable for outdoor use even in harsh weather conditions.
  • Aesthetic Appeal: With their rustic charm, galvanized containers can serve as a focal point in gardens, patios, or balconies. They blend well with various design aesthetics, from modern to farmhouse styles.
  • Affordability: Compared to other metal containers, galvanized pots are often more cost-effective, offering gardeners a stylish yet budget-friendly option.
  • Versatility: They are available in various sizes and shapes, making them suitable for a wide range of plants, from flowers and herbs to small trees and shrubs.
  • Heat Reflection: The reflective properties of galvanized containers can be beneficial in preventing the soil from overheating, especially in sunny locations.

Safety Concerns When Using Metal Containers

While metal containers bring a unique touch to gardens, it's essential to be aware of certain safety aspects, especially when growing edibles.

Understanding Galvanized Metal and its Safety

The zinc coating on galvanized containers can react with acidic soils or organic fertilizers, potentially releasing trace amounts of zinc into the soil.

While zinc is an essential micronutrient for plants, excessive amounts can be harmful. If growing edibles, it's advisable to use a liner or ensure the pH of the soil is close to neutral.

Note: many areas still use zinc-coated water pipes. Still concerned about zinc from galvanized steel?

Potential Risks with Aluminum Containers

Aluminum is naturally corrosion-resistant, but when exposed to highly acidic or alkaline soils, it can corrode and release aluminum ions.

High concentrations of aluminum can be toxic to plant roots and might be a concern if they leach into edibles.

Stainless Steel: Is it Safe for Edibles?

Stainless steel is generally considered safe for growing plants, including edibles.

However, it's crucial to ensure the container doesn't have any chromium coatings or treatments, which can leach into the soil and be taken up by plants.

Copper and Brass: Points to Consider

While these metals are stunning, they can react with certain soils and fertilizers. Over time, this can lead to a buildup of toxic levels of metal in the soil.

If using these containers for edibles, it's essential to monitor soil pH and use liners to prevent direct contact between the soil and metal.

While metal containers offer a stylish and durable option for gardening, it's essential to be informed about potential interactions between metals and the soil, especially when cultivating edibles.

Proper precautions and regular monitoring can ensure both plant health and safety for consumption.

copper planter

Is Galvanized Steel Food Safe - Yes or No?

Galvanized steel is steel coated with a layer of zinc to prevent rusting. The primary concern regarding its use with food is the potential for zinc to leach into the food, especially when the food is acidic. But, there are other concerns as well.

  • Zinc Leaching: The primary concern with galvanized steel comes from the potential for zinc to leach into food, especially acidic foods like tomatoes or citrus fruits. When these foods come into contact with the zinc coating, the acid can dissolve small amounts of zinc, and it can then get into the food. While zinc is an essential mineral for human health in small amounts, excessive zinc intake can be harmful.
  • Cadmium Presence: Historically, some galvanizing processes used small amounts of cadmium, which is toxic to humans in even small amounts. Modern galvanizing processes have largely eliminated this risk, but older galvanized items or those of uncertain origin might still pose a risk.
  • Not Suitable for Cooking: Galvanized steel should not be used for cooking or baking. When heated, galvanized steel can off-gas fumes from the zinc coating, which can lead to metal fume fever, a short-term but unpleasant illness.
  • Use in Gardening: When it comes to using galvanized containers for growing food plants, the risk is considered minimal. Still, if you're concerned, you can line the container or use a barrier between the soil and the container.
  • FDA Guidelines: The U.S. Food and Drug Administration (FDA) advises against the use of galvanized containers for acidic foods and beverages.

While galvanized steel can be used for certain food-related applications, it's crucial to be aware of the potential risks. It's best to avoid using it with acidic foods and for cooking and to be cautious with older items where the composition might be uncertain.

If you're unsure about a specific use or item, it's always a good idea to err on the side of caution.

Note: author of this article uses galvanized steel pots for herbs like lavender, rosemary, and similar, which require good drainage (many drainage holes combined with a layer of pebbles on the bottom) and not much water - containers are good even after 20+ years...

rosemary in metal pot

Enameled Metal Pots in Gardening

Enameled metal pots, often made from cast iron or steel coated with a layer of porcelain enamel, are primarily designed for cooking.

However, they can be repurposed for gardening with a few considerations in mind. Here's what you need to know about using enameled pots for gardening, especially for edible plants:

Pros of Using Enameled Metal Pots for Gardening

  • Non-reactive Coating: The enamel coating is non-reactive, which means it won't leach harmful substances into the soil, making it safe for growing edible plants.
  • Aesthetic Appeal: Enameled pots come in various colors and designs, making them attractive options for gardening. Their shiny and vibrant appearance can add a touch of elegance to any space.
  • Durability: Enameled pots are sturdy and can withstand various weather conditions if they remain chip-free.

Cons and Considerations

  • Drainage: Most enameled pots are not designed with drainage holes, which are essential for most plants to prevent overwatering and root rot. If you decide to use one for planting, you may need to drill drainage holes in the bottom, but do so carefully to avoid chipping the enamel.
  • Potential Chipping: If the enamel chips, the underlying metal (often iron or steel) can be exposed and may rust over time, especially when in contact with moist soil. Rust can alter the pH of the soil, potentially affecting plant growth. Ensure the enamel is in good condition and be gentle to prevent further chipping.
  • Heat Conduction: Metal pots, even those with enamel coatings, can conduct heat. In direct sunlight, they might heat up, raising the soil temperature, which might not be ideal for certain plants, especially delicate ones.
  • Weight: Especially if you're considering enameled cast iron pots, they can be quite heavy, making them less suitable for hanging or places where weight could be an issue.
  • Size Limitations: Many enameled pots, being designed for cooking, might be on the smaller side for some plants, especially those with deeper root systems.

While enameled pots can be safely used for gardening edible plants due to their non-reactive nature, you need to ensure proper drainage and be mindful of potential chipping.

They can be a charming addition to a garden or balcony, but like any container choice, they require some adaptations and care to be suitable for plant growth.

Tips for Successful Gardening in Metal Containers

Metal containers, with their chic industrial aesthetic, can elevate the look of any garden space. But to ensure the plants within them thrive, it's essential to follow some specific gardening guidelines.

Ensuring Proper Drainage

Like any other container gardening, drainage is key. While some metal containers come with pre-drilled holes, others might not.

Inadequate drainage can cause water to pool at the bottom, leading to root rot and other moisture-related diseases. If your container doesn't have drainage holes, consider drilling a few yourself or layering the bottom with coarse gravel or broken pottery pieces.

This will allow excess water to drain out and provide an escape route for any built-up moisture.

Managing Soil Temperature in Metal Pots

Metal, by nature, conducts heat, which means your soil can get hot during sunny days, especially in containers made of darker metals. This can stress plants and dry out the soil rapidly.

To combat this, consider placing your metal containers in partial shade during the hottest parts of the day or insulating the inside of the pot with a layer of bubble wrap or coco coir before adding soil.

Mulching the top layer of soil can also help in retaining moisture and regulating temperature.

Choosing the Right Plants for Metal Containers

Not every plant is suitable for metal containers, especially ones that require consistent moisture levels or have sensitive root systems.

Succulents, drought-tolerant plants, and herbs generally do well in these containers. However, if you're keen on growing plants with higher moisture needs, ensure you're regularly monitoring the soil moisture and temperature.

red metal pot with plant

Do You Need to Line a Metal Planter?

Lining a metal planter can be beneficial for several reasons:

  • Protection for the Plant: A liner can create a barrier between the plant's roots and the metal, which can get very hot in direct sunlight or very cold in freezing temperatures. This can help regulate soil temperature and protect sensitive roots.
  • Prevent Metal Leaching: Certain metals can react with the soil, especially if the soil is acidic or alkaline. A liner prevents any potential leaching of metals into the soil, which is particularly important if you're growing edibles.
  • Enhance Drainage: While metal planters should ideally have drainage holes, if they don't, a liner made of a permeable material can help manage moisture and reduce the risk of waterlogging and root rot.
  • Rust Prevention: Over time, constant contact with wet soil can cause some metal planters, especially those that aren't galvanized, to rust. A liner can reduce this risk.
  • Easier Plant Management: Using a liner, especially one that's removable, can make it easier to change out plants, refresh the soil, or move plants indoors during colder months.
  • Aesthetic Reasons: If the inside of the planter is not as finished or polished as the outside, a liner can hide any imperfections and provide a neater appearance.

While it's not always strictly necessary to line a metal planter, doing so can prolong the life of the planter, make plant management easier, and provide a better growing environment for the plant.

If you opt to use a liner, ensure that it still allows for proper drainage and aeration.

What is the Best Material to Line a Metal Planters?

Lining a metal planter is a great idea to protect both the plants and the planter itself. Here's a rundown of the best materials to use:

  • Landscape Fabric: This is a breathable fabric that's permeable, allowing water to drain while keeping soil in place. It's durable, resistant to decay, and easy to cut and fit to the size of your planter.
  • Coconut Coir or Coco Liners: These are natural, biodegradable liners often used in hanging baskets. They help retain moisture while allowing excess water to drain away. Additionally, they offer a decorative touch to planters.
  • Burlap: Like landscape fabric, burlap is breathable, ensuring that roots receive adequate air. It's a natural material that's also biodegradable. Its rustic look can also add an aesthetic touch if it peeks out slightly from the top of the planter.
  • Plastic or Polythene Sheeting: While they're effective barriers against moisture, they're impermeable, so if you use them, you'll need to ensure the planter has good drainage. If you're using a plastic liner, puncture a few holes in the bottom for water to escape.
  • Pond Liner: This is a heavier-duty liner, often used in larger planters or raised beds. It's durable and effective at preventing soil and water from coming into direct contact with the metal.

pond liner

  • Bubble Wrap: This can be used as an insulating layer, especially in metal planters that might conduct too much heat or cold. It can be placed around the inside walls of the container before adding another liner, like landscape fabric.

When lining a metal planter, ensure you:

  • Ensure Proper Drainage: Whichever liner you choose, make sure that water can drain from the bottom. Stagnant water can lead to root rot and other plant diseases.
  • Trim Excess: If your liner extends above the rim of the planter, trim it for a neat appearance. However, if you like the look of a particular liner, like burlap or coco coir, letting it peek out can add a decorative touch.
  • Replace as Needed: Over time, liners can degrade or become clogged. Check them periodically and replace them when they're no longer effectively serving their purpose.

Choosing the right liner material can extend the life of your metal planter and create a healthier environment for your plants.

Protecting Metal Containers from Rust and Wear

While metal containers, especially galvanized ones, are known for their durability, they aren't invincible. Here's how you can prolong their life and keep them looking their best:

  • Regular Inspection: Keep an eye out for scratches or areas where the protective coating might have worn off. These spots can become potential rust points if left unchecked.
  • Avoid Standing Water: Ensure your containers aren't sitting in water, as this can expedite the rusting process. Using pot feet or stands can help elevate them, ensuring any excess water drains away.
  • Clean with Care: When cleaning your metal containers, avoid abrasive pads or brushes. Instead, use a soft cloth or sponge with mild soapy water. Remember to dry them thoroughly after washing.
  • Use Protective Coatings: If you notice spots where the protective layer has worn off, consider using a clear metal sealant or rust protector to safeguard the container.
  • Indoor Storage: During harsh winters or prolonged rainy seasons, consider moving your metal containers indoors or under a protective cover. This can help in extending their lifespan.

Thanks to these tips and showing a little love, your metal containers can remain both functional and aesthetically pleasing for years to come, even decades.

rusted flower pot

Aesthetic and Design Tips for Metal Container Gardening

When incorporating metal containers into your garden space, it's not just about the plants; it's also about creating a cohesive and appealing design.

  • Play with Heights: Using metal containers of varying heights can create visual interest and depth in your garden. Consider stacking or using stands to elevate some pots while keeping others at ground level.
  • Mix Materials: While the industrial look of metal is captivating, introducing containers made of terracotta, ceramic, or wood can add contrasting textures and warm up the overall design.
  • Add Pops of Color: Brightly colored flowers or foliage can stand out beautifully against the muted tones of metal. Opt for plants like petunias, geraniums, or golden pothos for vivid color and contrast.
  • Use Symmetry: Especially in formal garden settings, the symmetrical placement of metal containers can provide a balanced and harmonious look.
  • Accessorize: Introduce decorative elements like fairy lights, metal trellises, or garden ornaments that complement the industrial vibe of metal containers.
  • Think Beyond Plants: Metal containers can also serve as water features, fire pits, or even storage solutions, becoming multifunctional pieces in your garden design.

Few Final Words: Embracing the Industrial Charm in Gardening

transplanting in metal pot

Metal container gardening is where functionality meets style. These containers, with their robust nature and unique aesthetic, offer gardeners a fresh perspective on traditional gardening norms.

By blending the hard, industrial feel of metal with the soft, organic beauty of plants, a harmonious balance emerges, providing both visual appeal and durability.

Whether you're a seasoned gardener or just starting, embracing the charm of metal containers can add a modern edge to your green haven. Remember, it's all about creativity, adaptation, and finding that perfect blend between nature and industry.

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