Are Cedar Planters Safe? - Plant Care Guide

Yes, cedar planters are generally considered safe for growing most plants, including edibles. Western Red Cedar, a popular choice for planters, contains natural oils that give it resistance to rot, decay, and insect damage without the need for chemical treatments. This makes them a favored, non-toxic option for gardeners seeking a durable and natural material for their containers and raised garden beds.

Why Choose Cedar for Planters and Garden Beds?

Cedar is a highly popular material for planters and raised garden beds among gardeners, and for good reason. Its inherent properties make it well-suited for outdoor use, especially when compared to other wood types. The natural characteristics of cedar offer several significant advantages.

Key reasons to choose cedar:

• Natural Rot and Pest Resistance: This is cedar's standout feature. Cedarwood contains natural compounds, primarily thujaplicins, that act as fungicides and insecticides. This makes it naturally resistant to decay, rot, and insect infestations without the need for chemical preservatives. This inherent resistance is a major factor in its safety for edibles.
• Durability and Longevity: Thanks to its natural resistance, cedar lasts much longer than many other untreated woods when exposed to the elements and moist soil. A well-maintained cedar planter can last for 10-20 years or more.
• Lightweight: Compared to some hardwoods, cedar is relatively lightweight, making it easier to construct and move planters.
• Appearance: Cedar has a beautiful, rich reddish-brown color that weathers gracefully to a soft silvery-gray over time. Its attractive grain adds a natural aesthetic to any garden space.
• Stability: Cedar is known for its dimensional stability, meaning it's less prone to warping, twisting, and shrinking than other woods when exposed to moisture and temperature changes.
• Sustainability: Western Red Cedar, in particular, is often sourced from sustainably managed forests, making it an environmentally friendly choice for many gardeners.

These qualities collectively make cedar planters a robust, attractive, and reliable choice for a wide range of gardening needs.

Are There Any Types of Cedar to Avoid for Planters?

While cedar is generally safe, it's important to understand that "cedar" can refer to several different species of trees. The type of cedar primarily recommended and widely used for garden applications is Western Red Cedar. However, there are other types, and some might not be as ideal or could even raise minor concerns.

Types of cedar to be aware of:

• Western Red Cedar (Thuja plicata): This is the gold standard for safe and durable planters. It's naturally rot-resistant and has no known harmful leachates that would negatively impact plants or human health when growing edibles. This is the cedar you want.
• Eastern Red Cedar (Juniperus virginiana): This is actually a type of juniper, not a true cedar. While it also has good decay resistance and a beautiful reddish color, it's known for its very strong, aromatic scent due to high levels of cedar oil. While generally considered safe, some sources suggest its strong aromatics might potentially influence the taste of very sensitive herbs if planted directly against the wood, though this is rare. Its main use is often for cedar chests and fence posts. It's not typically the preferred choice for raised beds for edibles.
• "Cedar" with Chemical Treatments: This is the most important type to avoid for growing edibles. If lumber is simply labeled "cedar" but also mentions being pressure-treated or having other chemical preservatives, it should not be used for food gardens. These chemicals can leach into the soil and be absorbed by plants, potentially posing health risks. Always look for untreated, natural cedar.

When purchasing wood for your planters, always confirm the species of cedar and ensure it is untreated to guarantee its safety, especially for edible plants.

What Makes Untreated Cedar Planters Safe for Edibles?

The question of safety for edible plants is paramount for any material used in gardening. Untreated cedar planters are considered safe for edibles precisely because of their natural composition and the absence of harmful chemicals.

Why untreated cedar is safe for edibles:

• No Harmful Chemical Additives: Unlike chemically treated lumber (like some pressure-treated wood), natural cedar does not have man-made preservatives infused into its fibers. This means there are no toxic chemicals to leach into your soil and subsequently into your food.
• Natural Compounds Are Non-Toxic to Plants: The thujaplicins and other natural oils responsible for cedar's rot resistance are generally harmless to plants and do not accumulate in a way that would make edibles unsafe for human consumption. These compounds are a natural defense mechanism for the tree, not a synthetic toxin designed to kill.
• Minimal Leachate: While cedar does naturally contain compounds that can leach out over time (which contributes to its resistance and gives it that distinct smell), the amount is very small and typically not concentrated enough to negatively impact plant growth or contaminate the edible parts of plants. The soil itself acts as a buffer.
• pH Neutral: Cedar wood does not significantly alter the soil's pH level in a way that would be detrimental to most plants. This is an important consideration for healthy plant growth.

For these reasons, gardeners can feel confident using untreated Western Red Cedar for growing vegetables, herbs, and fruits without worrying about adverse health effects from the planter material.

How Do You Ensure a Cedar Planter Stays Safe Over Time?

Even though cedar planters are naturally safe, proper construction and minimal maintenance can help them last longer and remain effective without compromising their non-toxic nature. Ensuring longevity means continuing to avoid harmful treatments.

Practices to keep your cedar planter safe and durable:

• Start with untreated wood: This is the foundational rule. Never use chemically treated cedar for edibles.
• Ensure good drainage: Proper drainage is critical for both plant health and the longevity of the planter. Excess standing water inside the planter will accelerate wood decay, even for rot-resistant cedar.
  • Drill adequate drainage holes in the bottom.
  • Consider adding a layer of coarse gravel or broken pottery at the bottom of the planter before adding soil, though this is debated and not always necessary if holes are sufficient.
• Use a liner (optional, with caution): A food-safe liner can extend the life of the wood by creating a barrier between the wet soil and the cedar.
  • Choose the right liner: Use heavy-duty, food-grade plastic sheeting (like pond liner or 6-mil polyethylene plastic). Ensure it's BPA-free.
  • Proper installation: Line the bottom and sides, but do not block drainage holes. Cut holes in the liner where your planter's drainage holes are. Also, leave the top edge of the liner a few inches below the rim of the planter to allow for air circulation between the wood and the liner.
• Avoid external chemical treatments: Do not paint or seal the inside of the planter with any wood treatments, as these could leach into the soil. For the exterior, you can use a natural, food-safe sealant (like tung oil or linseed oil) if you wish to maintain the cedar's color and add a layer of protection, but this is entirely optional and not necessary for the wood's inherent resistance.
• Regular inspection: Periodically check your planter for any signs of cracking, excessive rot, or pest damage. Addressing minor issues early can prevent them from becoming major problems.

By following these simple guidelines, your cedar planter will remain a safe and long-lasting home for your plants.

Should You Line Cedar Planters?

The question of whether to line cedar planters is a common one, and there isn't a single definitive answer. It depends on your priorities: extending the life of the planter versus pure natural gardening.

Reasons to consider lining a cedar planter:

• Extends wood longevity: The primary benefit of lining is that it creates a barrier between the constantly wet soil and the cedarwood. This significantly slows down the natural decomposition process of the wood, helping your planter last even longer.
• Prevents soil loss: A liner can help contain finer soil particles, especially in planters with wider gaps between boards.
• Reduces nutrient leaching: While not a major concern for safety, a liner can prevent some nutrients from leaching directly into the wood itself.

Reasons to consider NOT lining a cedar planter:

• Simplicity: No need to purchase or install a liner.
• Breathability: The wood can breathe more freely, which some argue is beneficial for certain plants and soil health.
• Natural aesthetic: Some prefer the purely natural look and feel without a plastic barrier.
• Cedar's natural resistance: Cedar is chosen specifically for its inherent ability to resist rot, so a liner isn't strictly necessary for safe plant growth.

If you choose to line a cedar planter, here’s how to do it safely and effectively:

1. Select the right material: Use a heavy-duty, food-grade plastic sheeting. Options include:
   • Pond liner: Durable and often explicitly labelled food-safe.
   • 6-mil polyethylene plastic: Look for "UV-stabilized" to prevent breakdown from sunlight. Ensure it's BPA-free and phthalate-free.
   • Avoid thin trash bags or non-food-grade plastics, as they can break down and leach chemicals.
2. Ensure drainage: This is paramount. Cut holes in the liner to align with or even be larger than the drainage holes in your planter. You want water to escape freely.
3. Don't seal the top: The liner should not extend above the soil line or be sealed at the top. Leave a few inches of space between the top of the liner and the rim of the planter. This allows for air circulation and helps prevent the liner from acting like a swimming pool, trapping too much moisture directly against the wood.
4. Secure the liner: You can staple the liner to the inside walls of the planter, making sure the staples are above the soil line.

Ultimately, whether to line your cedar planter is a personal choice. For most gardeners, going without a liner is perfectly fine given cedar's natural durability. If you want maximum longevity for your planter, a carefully chosen and installed liner can be a good investment.

Does Cedar Affect Soil pH or Plant Growth?

A common concern among gardeners is whether the wood used in planters might subtly alter the soil's pH level or release compounds that could inhibit plant growth. For untreated cedar planters, these concerns are generally minimal.

Impact on soil pH:

• Minimal effect: Cedar wood, like most organic materials, is slightly acidic. However, when used in a planter, its effect on the overall soil pH is negligible. The large volume of potting mix or garden soil will buffer any minor pH changes from the wood.
• Compost and water have greater impact: Factors like the type of potting mix you use, your water source (e.g., hard water can increase pH), and amendments like compost will have a far more significant impact on your soil's pH than the cedar planter itself.
• Testing is key: If you are concerned about pH for specific acid-loving or alkaline-loving plants, the best approach is to test your soil regularly using a soil pH meter.

Impact on plant growth:

• Generally beneficial or neutral: The natural compounds in cedar that provide rot resistance are usually not harmful to plants. In fact, some might even offer very minor protective qualities.
• Well-drained environment: Cedar's durability means the planter maintains its structural integrity longer, providing a consistent and healthy root environment. Good drainage (which cedar contributes to through its porosity) is crucial for plant growth.
• No known phytotoxicity: There's no scientific evidence to suggest that untreated Western Red Cedar leaches chemicals that are phytotoxic (toxic to plants) at levels found in typical planter use.

So, you can rest assured that your cedar planters are unlikely to negatively impact your soil's pH or inhibit the healthy growth of your beloved plants.

What About the Fasteners and Hardware Used in Cedar Planters?

When constructing or choosing cedar planters, it's not just the wood that matters for safety; the fasteners and hardware used are equally important, especially if you're growing edibles. Rusting metals and certain coated screws can introduce unwanted elements into your soil.

Safe fasteners and hardware options:

• Stainless Steel Screws: This is the best option for longevity and safety. Stainless steel is resistant to rust and corrosion, even in damp soil environments, and will not leach any harmful metals into your soil. Look for stainless steel deck screws.
• Galvanized Screws/Nails: Hot-dipped galvanized fasteners are a good, more economical alternative to stainless steel. The zinc coating provides good rust resistance. While zinc can leach in trace amounts, it's an essential micronutrient for plants, and the levels are usually negligible and non-harmful.
• Brass or Copper Screws/Nails: These are also resistant to corrosion and safe, but can be more expensive.

Fasteners and hardware to avoid for edible planters:

• Plain Steel Screws/Nails: These will rust quickly when exposed to moisture in the soil, potentially weakening the planter's structure and introducing rust (iron oxides) into the soil. While iron is a plant nutrient, excessive rust is not ideal.
• Electro-galvanized Screws: These have a thinner zinc coating than hot-dipped galvanized and will rust more quickly.
• Certain Coated Screws: Some screws have special coatings for exterior use. Unless the manufacturer explicitly states they are safe for contact with soil and edible plants, it's best to avoid them due to potential unknown chemical leaching.

By selecting stainless steel or hot-dipped galvanized fasteners, you ensure that all components of your cedar planter remain safe and durable for growing your edibles.

Are There Any Aesthetic Considerations for Cedar Planters?

Beyond safety and durability, cedar planters offer significant aesthetic appeal that can enhance any garden, patio, or balcony space. Their natural beauty is one of the reasons they are so popular.

Aesthetic qualities of cedar planters:

• Natural Color and Grain: Western Red Cedar starts with a rich, warm reddish-brown hue that has beautiful, straight grain patterns. This natural color adds an inviting and earthy feel to your outdoor decor.
• Graceful Weathering: Over time, if left untreated, cedar will naturally weather to a soft, elegant silvery-gray patina. Many gardeners appreciate this weathered look, as it blends seamlessly with natural landscapes.
• Versatility: Cedar planters come in a wide range of designs, from simple rectangular raised beds to intricate tiered planters and hanging baskets. Its workability allows for various shapes and sizes to fit different garden styles.
• Complements Greenery: The natural tones of cedar provide a beautiful backdrop that makes vibrant green foliage and colorful flowers or vegetables truly pop.
• Aromatic Qualities: While not directly visible, the pleasant, subtle aroma of cedar can be a delightful sensory addition to your garden space.

If you prefer to maintain the original reddish-brown color, you can apply an exterior UV-protective sealant or stain to the exterior surfaces of the planter. Make sure these are appropriate for outdoor use and clearly state they are safe for garden environments. Avoid painting the interior as discussed earlier.

How to Extend the Life of Your Cedar Planter Even Further?

While cedar is inherently durable, there are proactive steps you can take to maximize the lifespan of your cedar planter, ensuring it remains a beautiful and functional part of your garden for many years.

Tips for extending cedar planter life:

• Elevate the planter: If your planter sits directly on soil, concrete, or pavers, it can trap moisture underneath, leading to faster rot at the base. Placing small "feet" or cedar blocks underneath the planter to lift it slightly will allow for better airflow and drainage.
• Avoid constant soil contact (if possible): As mentioned, using a food-grade liner can protect the wood from direct, constant contact with wet soil, significantly reducing internal decay.
• Proper irrigation: While plants need water, avoid excessive overhead watering that keeps the wood constantly saturated. Drip irrigation or careful hand-watering directly to the soil minimizes water splashing onto the wood.
• Regular cleaning: Periodically clean the exterior of your planter to remove dirt, algae, or mildew buildup. A soft brush and water are usually sufficient. For stubborn spots, a mild solution of oxygen bleach (eco-friendly and non-toxic) and water can be used, followed by a thorough rinse.
• Winter protection: In areas with harsh winters, consider covering your empty planters or moving smaller ones to a sheltered location (like a garage or shed) during the coldest, wettest months. If plants remain, ensure proper winter care.
• Seal exterior (optional): If you like the original cedar color and want to maintain it, applying an exterior wood sealant or stain specifically designed for garden use (and labeled as non-toxic for plants) can protect the wood from UV damage and moisture. This typically needs reapplication every few years.

By implementing these care strategies, your cedar planters will not only remain safe for your edibles but will also continue to provide a beautiful and lasting home for your garden for a very long time.

Cedar Planters vs. Other Wood Types: A Comparison

When deciding on materials for your garden, understanding how cedar planters stack up against other common wood types can help you make an informed choice. Each wood has its own pros and cons in terms of cost, durability, and safety.

Key takeaways from the comparison:

• For natural safety and good durability for edibles, untreated cedar is hard to beat.
• Newer pressure-treated wood is considered safer than older versions (which contained arsenic, CCA), but if you're risk-averse, particularly for direct-contact edibles, cedar is a clearer choice.
• Untreated pine/fir is cheap but will rot very quickly unless constantly replaced or treated (which brings up safety concerns for edibles).
• Recycled plastic lumber is extremely durable and safe but lacks the natural aesthetics of wood and comes at a higher price point.

Ultimately, cedar planters strike a fantastic balance between natural safety, excellent durability, and appealing aesthetics, making them a top choice for conscientious gardeners.

Are There Any Special Considerations for Growing Specific Plants in Cedar Planters?

While cedar planters are safe for most plants, there are minor considerations, not due to toxicity, but due to the natural properties of the wood or the plant's specific needs.

Considerations for specific plants:

• Acid-loving plants: Plants that prefer very acidic soil (like blueberries or azaleas) might benefit from having their soil pH monitored, though, as mentioned, cedar's impact is usually minimal. You might need to add acidifying amendments to the soil regardless of the planter material.
• Sensitive herbs: Some very delicate herbs with subtle flavors might theoretically pick up a very faint cedar note if planted directly against the wood in very close proximity, though this is rare and not a common complaint. This is more of a speculative aesthetic concern than a safety one.
• Moisture-loving plants: Cedar is porous and helps with drainage. For plants that absolutely need consistently moist soil, you'll need to ensure your watering schedule is diligent, especially if you haven't lined the planter. Using a soil moisture meter can help maintain optimal moisture levels.
• Heavy feeders: Cedar's durability means it won't break down quickly and add significant organic matter to your soil. This is a good thing for stability, but remember to provide your heavy feeder plants with adequate nutrients through good quality potting mix and regular fertilization.

In summary, cedar planters are highly versatile and safe for a vast array of plants, including all your favorite edibles. Any "special considerations" are generally minor, related to common gardening practices, and easily managed, rather than concerns about the inherent safety of the cedar itself.