To prevent root disturbance when planting out, I usually sow my sweet corn in peat pots which I then put in the propagator. As soon as the seed germinates, I grow the seedlings on for two to three weeks and, once they are reasonably robust and have hardened off, I plant them out in the pots. This year, I ran out of peat pots and used plastic ones (same size) instead, and the seedlings seemed bigger and stronger than usual. They are now in the open ground and thriving, despite the slight root disturbance they suffered when I removed them from their pots. Is this year's improvement in the seedlings' growth attributable to the quality of the seed (I used a new brand), or do peat pots, perhaps, slow down their development; and are the problems associated with root disturbance a bit of a myth? I would be interested to know if anyone else has had a similar experience.
Three important things about peat pots (and paper pots) to prevent them from hurting your seedlings:
- If the roots aren't burgeoning through the bottom, tear it off
- Tear a line down the side of the pot to let the soil expand in the pot when you water it.
- Bury the sides of the peat pot or tear them off, exposed sides will absorb water out of the soil and rob it from your plants.
(I read this somewhere this year, I'll give credit if I can find the source)
Nothing will grow very tall with a root ball all clumped and it might have taken longer for your seedlings to burst forth.
If the tops of the peat pots stick out above ground level, they have a tendency to wick water up and out of the soil. This will hurt the plants by drying them out, especially where the roots are breaking through the pots.