If you’re looking for a simple and affordable way to start a garden, you might be surprised by what you can grow in cinder blocks. This article will answer the common question of what plants grow well in cinder blocks, focusing on varieties that thrive in the unique conditions these blocks provide.
Cinder blocks can be repurposed into productive planters, especially for herbs and flowers that prefer excellent drainage. Their hollow cores create perfect individual pockets for plants, and the porous concrete material allows water to escape quickly, preventing soggy roots. This makes them an ideal choice for gardeners dealing with limited space or poor soil.
What Plants Grow Well In Cinder Blocks
The best plants for cinder block gardens are those that prefer dry, well-draining soil and don’t have extensive, deep root systems. The blocks create a warmer microclimate as they absorb heat, which some plants love and others can’t tolerate. Generally, you’ll have the most success with herbs, compact vegetables, succulents, and certain resilient flowers.
When selecting plants, consider the size of the block’s openings. Standard blocks have holes that are roughly 8×8 inches, which is ample space for many small to medium plants. You can also plant in the top cavity of a stacked block wall for a cascading effect.
Herbs That Thrive In Cinder Block Planters
Herbs are arguably the perfect match for cinder block gardening. Most herbs originate from Mediterranean climates where the soil is rocky and dry, making them naturally adapted to the conditions a cinder block provides. Their root systems are typically compact, and many prefer soil that dries out between waterings.
You can create a dedicated culinary herb garden right outside your kitchen door using just a few blocks. Here are the top herbs to plant:
- Rosemary: This woody herb loves full sun and excellent drainage. The heat retained by the cinder blocks mimics its native habitat perfectly.
- Thyme: All varieties of thyme, including creeping thyme planted in top holes, do exceptionally well. It’s drought-tolerant and spreads nicely.
- Oregano: Another Mediterranean staple, oregano will flourish and even become more pungent when grown in the lean, fast-draining soil of a block.
- Lavender: While often grouped with flowers, lavender is an herb that demands perfect drainage. Cinder blocks prevent the root rot that commonly kills lavender in richer soils.
- Sage: Sage’s fuzzy leaves are designed to conserve moisture, making it a great candidate for the drier block environment.
- Chives: These are hardy and will multiply in a block cavity. They tolerate a bit more moisture than some other herbs on this list.
Vegetables Suitable For Cinder Block Gardens
While not all vegetables are suited for the confined space, many compact and shallow-rooted varieties will produce a surprising yeild. The key is to manage soil fertility, as the frequent watering required can wash nutrients away more quickly.
It’s a good idea to refresh the soil with compost at the start of each season and consider a mild, organic fertilizer during the growing period. Here are vegetables that perform well:
- Leaf Lettuce & Spinach: These leafy greens have shallow roots and can be planted densely. They appreciate the cooler soil in the block’s interior during warmer months.
- Radishes: As a fast-growing root vegetable, radishes are ideal. They mature before they can become cramped.
- Green Onions (Scallions): You can succession plant these all season long. They take up very little room.
- Bush Beans: Choose compact “bush” varieties rather than climbing pole beans. A single plant per hole can be very productive.
- Swiss Chard: This colorful, nutritious green is more tolerant of varied conditions than some lettuces and adds visual appeal.
- Compact Peppers: Some smaller chili or ornamental pepper plants can succeed if given just one block cavity each and plenty of sun.
Avoid large, sprawling vegetables like tomatoes (unless a very determinate dwarf variety), corn, squash, or deep-rooted carrots, as they will quickly become stressed and underperform.
Flowers And Ornamental Plants For Cinder Blocks
Cinder block planters can be incredibly decorative. The geometric pattern of the blocks provides a modern, structural backdrop for blooming flowers and trailing plants. The excellent drainage is a boon for many flowers that dislike “wet feet.”
For a vibrant display, mix and match plants of different heights and habits, using the top holes for spillers and the front holes for upright growers.
- Marigolds: These hardy annuals bloom reliably all season, love full sun, and their pest-repelling qualities are a bonus in any garden.
- Petunias: Especially cascading or “wave” varieties, are perfect for planting in the top row to spill over the edge.
- Portulaca (Moss Rose): This drought-tolerant succulent thrives on neglect and full sun, producing cheerful flowers all summer.
- Sedum & Hens-and-Chicks: These succulents are virtually foolproof in cinder blocks. They store water in their leaves and adore the gritty, dry conditions.
- Alyssum: Its sweet fragrance and carpet of tiny white or purple flowers make it a lovely border plant for the front of a block bed.
- Zinnias: For a pop of tall color, plant a single zinnia in a back-row block. They are easy to grow from seed directly in the block.
Preparing Your Cinder Blocks For Planting
Proper preparation is crucial for your plants to succeed. You cannot simply fill the holes with garden soil and plant. A few key steps will ensure your cinder block garden is healthy and productive for seasons to come.
Cleaning And Safety Considerations
First, source your blocks. New blocks are fine, but used ones are often free or very cheap. If using used blocks, clean them thoroughly with water and a stiff brush to remove old debris or dirt. A common concern is about the materials in older cinder blocks.
While modern concrete blocks are generally considered safe, very old “cinder” blocks (made with coal ash) could potentially leach minerals. If you are uncertain about the blocks’ age or origin and are growing edibles, a simple precaution is to line the planting holes. Use a heavy-duty plastic landscape fabric or even a double layer of burlap sacks to create a barrier between the soil and the block interior.
Creating The Perfect Soil Mix
The soil mix is the most important factor. Regular garden soil is too dense and will compact in the blocks, leading to poor drainage and root rot. You need a light, airy, and nutrient-rich mix.
A simple and effective recipe is:
- Two parts high-quality potting mix (not garden soil).
- One part coarse compost for nutrients and moisture retention.
- One part perlite or coarse sand to further improve drainage.
Mix these components thoroughly before filling the block cavities. Fill each hole completely, leaving about an inch of space from the top for watering.
Ensuring Proper Drainage
Although cinder blocks are porous, it’s wise to ensure the bottom of the planting hole isn’t blocked if the block is sitting directly on soil or pavement. If placing blocks on a solid surface like a patio, consider propping them up slightly on a couple of small stones to allow water to freely exit the bottom holes.
For a raised bed built with stacked blocks, drainage is usually not an issue if the bottom course is open to the ground below. The natural wicking action of the concrete can dry the soil quickly, so monitor your plants closely, especially in hot weather, as they may need water more frequently than plants in the ground.
Designing And Arranging Your Cinder Block Garden
The layout of your cinder block garden is limited only by your space and imagination. You can arrange blocks in simple rows, stacked tiers, or geometric patterns.
Simple Single-Row Planters
This is the easiest way to start. Place blocks with the holes facing up in a sunny spot along a path, driveway, or fence line. This creates a neat, linear garden perfect for a herb border or a row of marigolds. You can plant in every hole or alternate for a spaced-out look.
Stacked Raised Beds
For a more substantial garden, stack blocks to create a raised bed frame. A two-block-high wall is stable and provides a good depth for most recommended plants. Simply stack them in a staggered pattern like bricks, filling the interior of the bed with your soil mix. You can then plant in the block holes around the perimeter and in the large open bed in the center.
The center bed allows for deeper-rooted plants or more vegetables, while the perimeter blocks are ideal for herbs and flowers. This design maximizes your planting space and creates a defined, tidy garden area.
Vertical And Tiered Gardens
Use the inherent structure of the blocks to build upwards. Create a pyramid by stacking a row of blocks, then a shorter row on top, and maybe a single block on the very top. This tiered design is excellent for creating visual interest and ensuring all plants get sunlight. Plant trailing plants like portulaca or creeping thyme in the top-tier holes so they can cascade down.
Ongoing Care And Maintenance
Caring for a cinder block garden is straightforward but has a few unique points compared to in-ground gardening. The primary differences stem from the limited soil volume and the porous nature of the container.
Watering Guidelines
This is the most critical maintenance task. The soil in cinder blocks will dry out faster than ground soil, especially during hot, windy weather. You will likely need to water more frequently. However, the goal is still deep, thorough watering, not frequent sprinkling.
Check soil moisture by sticking your finger about an inch into the soil. If it feels dry, water slowly until you see moisture begin to seep out of the bottom pores of the block. Early morning is the best time to water, reducing evaporation and allowing foliage to dry, which helps prevent disease.
Fertilizing Your Plants
Nutrients can be flushed out of the well-draining soil mix with each watering. To keep your plants vigorous, feed them regularly with a balanced, water-soluble organic fertilizer. Follow the label instructions, but you may want to use a half-strength solution every two to three weeks during the peak growing season for vegetables and heavy-flowering plants. Herbs typically require less fertilizer; a light feeding at the start of the season is often sufficient.
Managing Weeds And Pests
Weeding is minimal in a cinder block garden, as there is little exposed soil for weed seeds to germinate. Any weeds that do appear in the block holes are easy to pluck out. For pests, practice general garden vigilance. The diversity of planting herbs with flowers and vegetables can actually help deter some pests naturally.
If aphids or other insects appear, a strong spray of water from the hose or an application of insecticidal soap is usually effective. The elevated nature of the blocks can also make them slightly less accessible to some ground-dwelling pests like slugs, though not immune.
Seasonal Tips And Long-Term Use
Your cinder block garden can be productive across multiple seasons with a little planning. In cooler climates, the blocks’ ability to absorb and radiate heat can be used to your advantage in early spring and late fall, creating a slightly warmer microclimate that can extend your growing season.
At the end of the growing season, remove spent annual plants and add them to your compost pile. You can refresh the soil in the blocks by removing the top few inches and mixing in fresh compost. Perennial herbs like rosemary, thyme, and sage can be left in place if they are healthy; they may even survive the winter in the blocks in milder climates, especially if given a light mulch for root protection.
If you live in a region with freezing winters, the soil in the blocks will expand and contract. It’s best to empty the blocks of soil if you are not overwintering plants to prevent the concrete from cracking over time. Store the soil in a bin to reuse the following spring.
Frequently Asked Questions
Are Cinder Blocks Safe For Growing Vegetables?
Yes, modern concrete blocks are generally considered safe for growing vegetables. If you have concerns about older blocks, you can line the planting holes with a barrier like landscape fabric. The primary risk with any container gardening is ensuring the soil mix is clean and free of contaminants, which you control.
Do I Need To Drill Drainage Holes In The Blocks?
No, you typically do not need to drill additional holes. The porous nature of the concrete and the open bottom of the block cavity provide sufficient drainage. In fact, drainage is often almost too effective, leading to the need for frequent watering.
How Do I Stop Soil From Washing Out Of The Blocks?
Using a soil mix with plenty of organic matter (compost) will help it bind together. Over time, plant roots will also hold the soil in place. If erosion is a problem when watering, place a small stone or a piece of broken pottery over the drainage hole inside the block before adding soil; this slows the water exit without blocking it.
Can I Paint Or Seal My Cinder Block Planters?
You can paint the exterior of the blocks with a breathable, outdoor masonry paint for a decorative look. However, avoid painting or sealing the interior of the planting holes, as this will compromise the drainage and breathability that makes cinder blocks work so well for plants.
What Is The Best Way To Start Seeds In Cinder Blocks?
You can sow seeds directly into the prepared soil in the blocks once the danger of frost has passed. Follow the seed packet instructions for depth and spacing. Since the soil warms quickly in the blocks, germination can be quite fast. Keep the soil consistently moist but not soggy until seedlings are established. For a head start, you can also transplant young seedlings from indoor pots into the blocks.