LECA, which stands for Lightweight Expanded Clay Aggregate, is a popular growing medium used by gardeners and horticulturists. It consists of small, lightweight clay pebbles that provide aeration and drainage to plant roots while retaining some moisture.

What is LECA Made Of?

LECA is made by heating clay at high temperatures. This causes the clay to expand and form porous, round-shaped pebbles that resemble rocks or pea gravel. The pebbles are very lightweight due to all the air space within them, making LECA an excellent soilless growing medium.

LECA pebbles are typically about 5-20mm in diameter on average. They have a neutral pH and do not contain any nutrients on their own. The pebbles are inert and simply provide air pockets and space for roots to spread out.

Benefits of Using LECA for Plants

Using LECA as a growing medium offers many advantages for plants:

Excellent Drainage and Aeration

The porous structure and air pockets within LECA pebbles provide excellent drainage and aeration for plant roots. This allows oxygen to easily reach the roots while preventing them from becoming waterlogged. Proper aeration is critical for healthy root growth.

Good Water Retention

While LECA drains well, the pebbles also retain a small amount of moisture on their surfaces. This helps prevent plants from drying out too quickly between waterings. The pebbles hold just enough moisture for plant roots while still draining excess water.

Lightweight and Easy to Handle

LECA is extremely lightweight, making it easier to transport and work with compared to standard potting soil. The pebbles are also clean and do not compress over time. This allows for good aeration and drainage even after using LECA for several seasons.

Resists Compaction

Standard potting mixes can become compacted over time, reducing aeration for plant roots. But LECA’s rigid structure resists compaction, maintaining plenty of air space even after months or years of use.

Minimizes Risk of Root Rot

Excess moisture is one of the leading causes of root rot in houseplants and container gardens. Because LECA provides such excellent drainage, it helps minimize the risk of deadly root rot taking hold due to overwatering.

Allows Flexible Watering

Plants grown in LECA can be watered frequently without risk of overwatering. The pebbles drain so quickly that roots will not sit in soggy conditions. This makes it possible to automate watering with drip irrigation systems.

Reusable and Sustainable

LECA pebbles can be rinsed, sterilized, and reused indefinitely. There is no need to discard them after each growing season. Reusing LECA is more environmentally sustainable than peat-based growing mixes.

Neutral pH

LECA has a near neutral pH around 7. This makes it suitable for most plants without needing pH adjustments. Acid-loving plants may benefit from some pH lowering amendments when using LECA.

Low Environmental Impact

LECA production uses lower firing temperatures than bricks, making it more energy efficient to produce. Mining clay also has a lower habitat impact than harvesting peat bogs in many instances.

How to Use LECA for Houseplants

Using LECA for houseplants is easy. Here are some tips:

• Start with a container that has drainage holes. Plastic pots, cache pots, or wire hanging baskets all work well.
• Place a layer of LECA pebbles at the bottom of the pot for drainage. About 1-2 inches deep is sufficient.
• For smaller plants, fill the rest of the pot with LECA. For larger plants, use LECA in the bottom half of the pot and a well-draining soilless mix for the top half.
• Water enough so that some drips out the bottom drainage holes, then allow to fully drain. The pebbles on top will appear moist while excess water flows through.
• Add some slow release fertilizer beads into the LECA and reapply every 6-8 weeks. Or use liquid fertilizer diluted to half strength with each watering.
• Group plants with similar watering needs together. Plants that like drying out between waterings do best fully planted in LECA. Those that require more moisture do better with LECA on bottom and soil mix up top.
• Monitor plants for signs of underwatering or overwatering and adjust your schedule as needed. LECA takes some trial and error to get the watering frequency right.

Using LECA in Hydroponics Systems

In addition to container gardening, LECA pebbles are also a popular growing media for hydroponic systems. Reasons why LECA works well for hydroponics include:

• Provides excellent anchor for plant roots when using methods like deep water culture (DWC), nutrient film technique (NFT), and drip systems.
• Maintains oxygen flow to roots and allows for rapid drainage compared to other aggregate options.
• Can be reused for multiple crop cycles since LECA does not break down over time.
• LECA is chemically inert and will not alter pH or EC levels in hydro nutrient solutions.
• Very lightweight and easy to work with compared to options like clay pellets or gravel.

To use LECA in hydroponics, completely submerge the lower portion of the roots in the nutrient solution reservoir while the upper portion sits anchored in the LECA media bed. Make sure light does not reach the reservoir to prevent algae growth.

Popular crops to grow hydroponically with LECA include lettuces, herbs, tomatoes, cucumbers, peppers, and strawberries.

Troubleshooting Common LECA Problems

When making the switch to LECA, there can be a learning curve. Here are some common problems and how to resolve them:

Problem: Plants wilting, leaves drooping, signs of underwatering

Solution: Increase watering frequency. LECA requires more frequent watering than soil or peat mixes. Roots take time to adapt to drying out between waterings.

Problem: Root rot, foul odor, mushy roots

Solution: Allow media to dry out before next watering. Improve drainage by adding more LECA to containers. Reduce watering amount and frequency.

Problem: White mineral deposits on pebbles

Solution: This is normal salt buildup. Rinse pebbles periodically to remove. Use distilled or purified water if deposits become excessive.

Problem: Green algae growth on LECA

Solution: Improve light exposure and air circulation. Let media fully dry between waterings. Scrub off algae growth and sterilize pebbles with bleach solution if needed.

Problem: Plants showing signs of nutrient deficiencies

Solution: Increase fertilization regimen. LECA has no cation exchange capacity to hold onto fertilizers, so nutrients must be supplied frequently.

Problem: pH fluctuations out of optimal range

Solution: Monitor and adjust pH of water/nutrients. Use pH Down or Up amendments as needed to maintain range.

Tips for Reusing and Cleaning LECA

One of the benefits of LECA is that it can be reused for many years. Here are some tips for cleaning and sterilizing LECA between uses:

• Rinse away any debris under running water. Use a colander or mesh screen.
• Soak in a bleach solution (1 part bleach, 9 parts water) for 15-30 minutes to sterilize.
• Rinse thoroughly 3-4 times to remove any bleach residue.
• Air dry pebbles fully before reuse or storage.
• Autoclave or bake LECA at 180°F for 30 minutes to fully sterilize if disinfecting.
• Replace any pebbles that are breaking down or degraded over time.
• Scrub off stubborn mineral deposits with vinegar or biodegradable cleaning agents as needed.

Taking some time to properly clean LECA between uses helps prevent disease transmission and maintains proper aeration.

Is LECA Safe for Pets and Children?

One concern with using LECA is the potential risk if pebbles are ingested by pets or children. Small pebbles could present a minor choking hazard.

However, LECA is considered non-toxic if swallowed. The porous clay pebbles can pass through the digestive system without issue, unlike polymeric growing media. Monitor pets and toddlers to prevent accidental ingestion. Avoid using LECA in open-air gardens accessible to them.

Rinsing LECA to remove any accumulated dust, salts, or fertilizer residue will also help minimize any potential risks. Overall, LECA presents a very low toxicity risk but supervision around pets and kids is still advised.

Is LECA Better Than Soil for Plants?

There is no definitive answer to whether LECA is better than soil across the board. Each growing medium has pros and cons that make it suitable for certain situations.

Some benefits LECA can provide over soil:

• Better drainage and oxygenation for roots
• Lighter weight for hanging baskets and wall gardens
• Reusable for many years compared to single season soil
• Less prone to issues like soil compaction over time
• Allows growing plants with minimal soil medium

Some benefits of soil over LECA:

• Natural cation exchange capacity provides some nutrient retention
• Organic matter offers beneficial microbiome for plants
• Can be more forgiving for inconsistent watering
• Familiar to most gardeners over LECA
• Often cheaper and easier to source than LECA

The ideal growing medium depends on factors like the specific plants, your growing environment, and gardening preferences. Many container gardeners find the best approach is using a blend of LECA and soil-based potting mix to get the benefits of both!

Sourcing LECA and Purchasing Tips

LECA can be purchased from most hydroponic stores, nurseries, or online retailers. Look for horticultural grades sold as “LECA”, “clay pebbles”, or “expanded clay aggregates”.

When buying LECA, examine the pebbles for:

• Clean, off-white color – avoid grey, dingy batches
• Little dust – excessive dusty residue lowers quality
• Few broken pieces – intact pebbles maintain structure better
• Consistent sizing – different sizes help increase porosity

High quality LECA is often produced in Northern Europe from companies like Leca International. cheaper LECA sold in large bags is typically sourced from Asia and tends to have more variability in quality. Stick to horticultural grades from reputable hydroponic or soilless mix brands for best results.

Conclusion

LECA provides an excellent growing medium that offers great drainage, aeration, and reusable performance. It can take some adjustment from traditional soil mixes but is worth trying for both houseplants and hydroponic systems.

Look for signs of under or overwatering and adjust your watering habits accordingly if transitioning to LECA. With proper care, plants grown in LECA can thrive and develop healthy, vigorous root systems. Its sustainable, inert nature makes it a smart choice for environmentally-conscious gardeners.

Frequently Asked Questions About LECA

What plants grow well in LECA?

Most plants can grow well in LECA as long as you provide adequate water and nutrients. Some types of plants that do exceptionally well in LECA include orchids, bromeliads, herbs, tomatoes, cucumbers, peppers, lettuce, strawberries, and cannabis.

Can you start seeds in LECA?

It is challenging to start seeds directly in LECA because the pebbles provide no moisture retention for sprouting. An easier method is starting seeds in a soilless seed starting mix, then transplanting into LECA once sprouted and established.

Is LECA better than perlite?

LECA and perlite both provide excellent aeration for plant roots. The main differences are that LECA also provides some moisture retention while perlite does not. LECA is also reusable for many years while perlite eventually breaks down. LECA can be used alone as a standalone growing media while perlite cannot.

Does LECA change pH?

LECA has a neutral pH around 7 and does not alter pH up or down. For acid loving plants, it may be necessary to amend LECA with materials like peat or pine bark fines to lower the pH.

Can you mix LECA and soil?

Absolutely! In fact, many container gardeners find the best results by using a blend of LECA and potting soil. The LECA boosts drainage and prevents soil compaction, while the potting mix provides nutrients. Aim for 20-40% LECA mixed into potting mixes.

How do you fertilize plants in LECA?

Since LECA contains no nutrients, plants need consistent fertilizer application. Use a liquid fertilizer with each watering at half strength, or incorporate slow-release fertilizer granules when potting. LECA requires more frequent fertilization than standard potting mixes.

Can LECA go bad or expire?

LECA itself does not really go bad or expire. The pebbles will last for many years if cleaned and stored properly between uses. Always inspect and remove any degraded LECA and Sterilize the pebbles periodically. Avoid cross-contamination between plants by cleaning thoroughly.

Is LECA hydrophobic?

New, unused LECA can be somewhat hydrophobic (repels water) at first. This is easily remedied by rinsing and wetting the pebbles several times before use. Once saturated, LECA will maintain some moisture retention while still draining rapidly.

Can you grow weed in LECA?

Absolutely! In fact, LECA is a very popular cannabis growing medium. The excellent drainage and air flow LECA provides are ideal for healthy cannabis root systems. Many growers use LECA in hydroponic setups or blended into soilless super soils for weed.

Conclusion

LECA is a versatile and environmentally responsible growing medium with many benefits for plants. It retains some moisture while still providing great drainage and aeration. LECA’s lightweight nature makes it ideal for use in containers and hydroponic systems.

With proper irrigation and nutrient management, plants thrive in LECA. While it takes some adjustment from standard soil, LECA is reusable for many years and allows for excellent root growth. Blending LECA with potting mix helps ease the transition away from soil while still gaining benefits.

Look for signs of over or underwatering when first using LECA and adjust your watering frequency accordingly. Provide consistent nutrients to account for LECA’s lack of cation exchange capacity. With a bit of trial and error, LECA can help gardens and hydroponic systems flourish!