What Can You Grow in the Holes of Cinder Blocks?
You can grow compact herbs, flowers, leafy greens, bush beans, and even peppers in cinder-block holes; use the deeper bed inside the blocks for larger vegetables. The holes work best as small, exposed planting pockets around the edge of a raised bed, not as the main root space for crops that sprawl or grow deep roots. The key is choosing plants that stay reasonably compact and can handle soil that warms and dries faster than the main bed.
Why Cinder Block Holes Work Best for Small Plants
Cinder blocks have hollow cells that can be filled with growing mix. When blocks form the border of a raised bed, those cells create a built-in row of mini planters.
They are useful for herbs and flowers that might otherwise take up valuable bed space. A planted block border can also soften the look of the blocks, attract pollinators, and keep small plants reachable from outside the bed.
Treat the holes as a productive planted border.
The holes can be challenging because they have less soil than a regular garden bed. Their exposed sides also warm quickly, and the mix can dry faster than soil protected inside the bed. That makes plant choice especially important.
How to Plant Cinder Block Holes Successfully
A stable block border, suitable growing mix, and regular watering support herbs, flowers, leafy edibles, beans, and peppers in the holes.
Step 1: Choose the Right Location
Put the block bed where its intended plants will receive the light they need. Tomatoes, peppers, and squash need 6 to 8 hours of full sun daily; check the plant label for the selected crop because varieties can differ.
Use the sunnier side of the block border for peppers, beans, marigolds, and heat-tolerant herbs. Reserve shadier edges for parsley, leafy greens, or other plants that appreciate less intense afternoon exposure.
If the blocks form the edge of a raised bed, make sure you can reach both the holes and the center of the bed without stepping on the soil.
Step 2: Build a Stable Block Border
Set blocks on firm, level ground so they do not rock or settle unevenly after you fill them. If you are stacking blocks into a raised bed wall, keep the wall to 3 rows and stagger the joints between rows.
A three-layer block bed can provide useful root depth in the main growing area. One cinder-block bed built three blocks high held a full 24 inches of soil. That deeper central soil supports a wider range of vegetables.
Fill the center of the bed with garden soil improved with compost. Save the individual block openings for smaller plants that will not compete heavily with your main crop.
Before filling the holes, choose plants based on what you want the border to do.
| Goal for the Block Holes | Good Plant Choices | Best Use |
|---|---|---|
| Kitchen herbs | Chives, thyme, oregano, parsley, basil | Easy-to-reach plants for frequent harvesting |
| Flower border | Marigolds, compact annual flowers, pansies in their season | Color, pollinators, and a softer-looking bed edge |
| Leafy edibles | Leaf lettuce, mustard greens | Small harvests near the outside of the bed |
| Compact vegetables | Bush beans, peppers | Extra edible production without taking central-bed space |
| Trailing ornamentals | Purple heart, tender succulents | Decorative planting on exposed edges or corners |
| Larger vegetables | Tomatoes, squash, sprawling vines | Plant in the main bed, not a single block hole |
Step 3: Fill Each Hole With Growing Mix
Remove weeds, stones, and old roots from each opening. Fill the cavity with a loose growing mix that holds moisture but still drains well. Compost is useful here because the small volume of soil in a block hole needs organic matter to stay workable.
Avoid packing the mix tightly. Water it after filling so it settles, then add more mix if it sinks below the top of the opening.
Plant seeds or transplants at their normal planting depth. Keep the plant crown at the soil surface, and do not bury stems under mulch or extra soil. For bush beans or peppers, leave room for the plant to grow upward.
Cinder-block openings can hold peppers, marigolds, and beans, while unused cavities in a block-bed border are especially useful for small herb plants.
Step 4: Water, Mulch, and Finish the Planting
Water the holes well after planting.
Add a light layer of mulch over bare soil after seedlings are established. Mulch helps shade the mix and reduces splashing, but keep it away from plant stems.
Label herbs and flowers if you are planting several varieties around the bed. Once plants are rooted and growing, harvest herbs regularly, remove spent flowers, and trim anything that begins to shade or crowd neighboring holes.
Best Plants for Cinder Block Holes
Cinder block holes can grow herbs, marigolds, leafy greens, bush beans, and peppers; tender succulents can grow in them in Zone 10.
Herbs
Herbs are usually the easiest use for block openings. Chives, thyme, oregano, parsley, and basil can all make practical border plantings because they are easy to harvest from outside the bed.
Herbs vary in mature size. Thyme and oregano can spread outward over the block edges, which gives the bed a planted, finished look. Chives remain upright and narrow. Parsley stays manageable if harvested often.
Avoid putting long-lived woody herbs in a single hole if they will eventually outgrow it. Rosemary, for example, grows into a larger plant over time.
Flowers
Marigolds are a straightforward choice for block holes because they add color without taking up the central bed. Planting flowers in outer cavities can make a vegetable bed look intentional rather than purely utilitarian.
Compact flowering annuals are useful along the hottest, brightest edge of the bed. In cooler parts of the year, pansies can be another decorative option where they suit the season.
Flowers in the holes also help separate crops visually. A row of marigolds along one side and herbs along another can make it easier to remember what is planted where.
Leafy Greens and Small Edibles
Leaf lettuce and mustard greens can work in block holes when temperatures are suitable for them. They are best treated as a small bonus harvest, not the main source of greens for the household.
Bush beans can also grow in the openings, especially when you want to use vertical space above the block. Give them support if the variety needs it, and keep neighboring plants from shading the young bean plants.
Peppers are an overlooked edible option for cinder-block holes. A compact pepper plant can use one opening.
Purple Heart and Succulents
Purple heart can grow in a cinder-block hole as an ornamental trailing plant. Its spreading habit lets it drape over the outside of the block border, which is useful for softening hard edges.
Tender succulents can be grown outdoors in block holes in Zone 10. Confirm your local hardiness zone before leaving them outside year-round, since cold damage is often more of a problem than heat for tender succulent plantings.
Use a fast-draining growing mix for succulents, and avoid placing them in a hole that stays wet after rain or irrigation.
Put Large Vegetables in the Main Bed
The block holes are not the best place for tomatoes, squash, large peppers, or sprawling vines. These crops need more root room, more consistent moisture, and better anchoring than one block cavity usually provides.
Plant tomatoes and squash in the deeper soil inside the block border.
You can still make the block border part of a productive vegetable garden. For example, plant basil, parsley, marigolds, or peppers in the holes around the outside. The result is easier to harvest and makes better use of the entire structure.
Handle Heat, Drying, and Crowding
Keep Small Pockets From Drying Out
Do not count on paint on the outside of the blocks to solve drying problems. The more useful approach is to start with a moisture-holding growing mix, mulch bare soil, and inspect the holes often during dry weather.
Place moisture-loving plants such as parsley or greens on the gentler side of the bed. Use the hottest edge for thyme, oregano, marigolds, peppers, or other more heat-tolerant choices.
Prevent Plants From Outgrowing Their Space
A plant may look fine when first planted but become too large as roots and foliage develop. Trim herbs often and deadhead flowering plants as needed.
Watch for roots lifting the growing mix, foliage shading neighboring holes, or plants repeatedly wilting even when watered. Those signs call for an adjustment to the planting.
Concrete can also make these small pockets more challenging for sensitive plants. Fresh, compost-rich growing mix gives roots a better environment than compacted soil left in the holes season after season.
Other Useful Cinder Block Garden Ideas
Cinder blocks are most useful when they do more than hold back soil. A planted block border can become part of the garden design.
- Create an herb border around a raised vegetable bed.
- Plant flowers in outside-facing holes to make the bed more attractive from a patio or walkway.
- Use corner holes for trailing purple heart or oregano.
- Grow a mix of marigolds and herbs around food crops.
- Make a small standalone block planter for herbs near the kitchen.
- Use block holes at the end of a bed for a few peppers or bush beans rather than wasting the space.
Check the Planting as It Grows
A successful cinder-block planting should be easy to maintain, not another garden chore that needs constant rescuing. Check for these signs after planting:
- The growing mix stays in place after watering.
- Plants are not shaded by taller vegetables in the main bed.
- Herbs can be harvested without reaching into the bed.
- Flowers or trailing plants do not block paths or cover nearby crops.
- The growing mix is not staying soggy.
- Plants still have room around their stems as they mature.
Frequently Asked Questions
What Are Cinder Blocks With Holes Called?
They are commonly called cinder blocks. The hollow sections are called cells or cavities, and those cells can be filled with growing mix for small plants.
Can You Grow Purple Heart in Cinder Block Holes?
Yes, purple heart can grow in a cinder-block hole and trail over the outside edge of the block. It is most useful as an ornamental border plant because its foliage softens the hard concrete shape. Protect it from cold conditions that would damage a tender plant.
What Are the Easiest Flowers to Grow in Cinder Block Holes?
Marigolds are among the easiest flowers to use in cinder-block holes because they stay manageable and tolerate bright conditions. Compact seasonal flowers can also work, but avoid varieties that become tall, heavy, or sprawling enough to pull out of the small soil pocket.
Do Plants in Cinder Block Holes Need Extra Watering?
Often, yes. The holes hold less soil than a raised bed, and the exposed concrete can make the growing mix warm and dry faster. Check the moisture below the surface and water when the mix is no longer moist there.
Can You Grow Tomatoes or Squash in a Cinder Block Hole?
Tomatoes and squash are better planted in the main raised bed because they need much more root room than one cavity provides. They also need 6 to 8 hours of full sun daily, so give them the deepest, sunniest part of the bed and use the holes for smaller companion plants.
What Are the Drawbacks of Using Cinder Blocks in a Garden?
The cavities can be challenging because they are tight spaces and can get too hot and dry easily. Use them for plants that stay small.
How do you build a cinder block raised garden bed?
Create the bed perimeter with blocks, then add layers with the seams offset between courses. Stop at three rows to keep the wall within the recommended height. One three-layer example provided 24 inches of soil in the center of the bed.