when do you use LECA

20251127 Monday 1500 raining afternoon 

While waiting for Tan Chong servicing my Nissan Serena

Here is the simple, clear rule for using LECA in your cloth grow bags:

🌱 When to Use LECA at the Bottom

Use LECA only for plants that:

  • Need very sharp drainage
  • Hate “wet feet”
  • Have woody roots or sensitive taproot
  • Are grown in cloth bags on balconies (risk of water pooling)

These usually include:

✅ Grapes

✓ Very sensitive to root rot
✓ Need fast drainage → 5 cm LECA is correct

❌ Potatoes (no need LECA)

  • Potatoes love moisture
  • Too much drainage = small tubers
  • Soil settling helps tuber growth
    → LECA unnecessary and reduces yield

🍈 Your other vegetables

1. Pumpkin

✓ Big feeder
✓ Loves moisture
✓ Deep roots
→ No LECA needed

2. Winter Melon (冬瓜)

✓ Similar to pumpkin
✓ Loves moist but not soggy
→ No LECA needed
Just ensure pot is at least 40–60 cm deep.

3. Bitter Gourd (苦瓜)

✓ Fast-growing vine
✓ Likes moist soil
✓ Too much drainage = frequent watering
→ No LECA needed

4. Long Beans / String Beans / French Beans

✓ Beans prefer moist, airy soil
✓ Cloth bags already provide good drainage
→ No LECA needed

🧪 Summary Table (Very Clear)

Crop Need LECA? Why
Grapes YES (5 cm) Prevent root rot, woody perennial
Potatoes No Moisture-loving tubers
Pumpkin No Likes moisture, big feeder
Winter Melon No Needs stable moisture
Bitter Gourd No Moist-lover
Long Beans / French Beans No Cloth bag already drains well
Cucumber No But optional 2–3 cm if your water sits

⭐ Only 3 cases you might add LECA for vegetables

Use 2–3 cm LECA only if:

  1. Your balcony floor blocks the bag bottom from dripping freely
  2. Your tray under the bag keeps water
  3. Your bag is very tall (50–60 cm) and holds too much water at the bottom

Otherwise, save your money — soil + compost is enough.


Yes — only grapes need LECA (because grapes are woody perennials and very sensitive to root rot).
For almost all your other vegetables, LECA is optional or usually unnecessary.


🌊 Using the Deep Water Cycle (DWC) hydroponic box

In hydroponics, the LECA role is different.
But for your case:

If you are putting soil in the hydroponic box → then NO LECA needed.

(Soil + water reservoir = not recommended, but if used → still no LECA)


Hydroponic towers

If using it as true hydroponics with net pots → LECA is used only in net pots.

Here is the clear, simple rule for hydroponic tower net cups:

🌿 Hydroponic Tower → Net Cup → LECA + Sponge?

✔ YES, you still use sponge (or rockwool) for germination.

✔ THEN transfer the seedling + sponge into the net cup filled with LECA.

LECA does not replace the sponge for germination.

🌱 Why you still need the sponge

Because:

  • Seeds need high moisture + stability to sprout
  • LECA has big gaps, seeds fall through
  • LECA dries faster → poor germination
  • Sponge holds the seed firmly until roots grow long enough

So your current method (germinating inside sponge cubes) is correct.

🌿 How to use sponge + LECA in a hydroponic tower

  1. Germinate seeds in sponge
    → keep moist, humid, warm

  2. When seedling has
    2 true leaves + roots coming out, then…

  3. Place the entire sponge block into the net cup

  4. Fill the rest of the cup with LECA around the sponge
    → LECA supports the plant
    → Holds the sponge upright
    → Allows water flow and oxygen

  5. Put the net cup into the hydroponic tower

🧪 Simplest Setup

Stage Medium Correct?
Germination Sponge (or rockwool) ✔ YES
Seedling in net cup Sponge + LECA ✔ YES
Root growth in tower Roots hang down in water ✔ YES
Using only LECA No (bad germination) ❌

🌿 When can you skip sponge?

Only for big, easy seeds like:

  • Long bean
  • Cucumber
  • Pumpkin
    But even then, germination is more reliable in sponge.

For leafy greens, herbs, tomatoes, brinjal → always sponge first.


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