How to up-pot seedlings and harden them off. 

Let’s learn how to up-pot seedlings. You sewed your seeds and they sprouted!  You now have a tray of strong seedlings that have outgrown their tiny cells.  They are ready to get their new accommodations before heading out into the world.  What are your next steps?

When to up-pot

• It is more than likely your seedlings will need to be upgraded to bigger pots before they are ready to be transplanted out in the garden.   
  • If you recall from the seed starting blog, the seed starting mix does not have any nutrients in it.  Without nutrients, your seedlings will start to struggle and may die. 
  • At this point, you will switch to potting soil, which typically contains enough nutrients to feed your plants for up to 3 months. 
• You can transplant to a bigger pot (2.5 inch) when your seedlings have their second set of true leaves.  
  • At this point, seedlings are established enough to survive any transplant shock.  
• Fill up your 2.5 inch pots with your choice of potting soil (something with the least amount of large chunks will be best). 
• Carefully tease apart your seedlings if you have multiple in one cell. 
• Transplant to their new home.  
• It is at this point that you will need more of the bottom water trays for your 2.5 inch pots.  Sourcing the tray itself can be a bit tricky if you are on a budget.  You might want to buy more kits or see about ordering online.  Rohrers carries these trays in store for under $2.00 a tray.

Should you fertilize seedlings?

• Some gardeners will add fertilizer after they up-pot their seedlings.  
  • I prefer to avoid this because fertilizing seedlings is a delicate matter.  They need much less fertilizer than full sized plants and it can be easy to damage your seedlings. 
  • If I see that my seedlings are struggling, then I will consider adding a small amount of water soluble organic fertilizer based on the nutrient deficiency they appear to be showing.

Hardening off your seedlings

Before seedlings can go outside, they have to be hardened off.  They have been babied and protected inside for the past few months.  Seedlings are not ready to be exposed to the outside elements for an entire day.  

• Start this process by placing them out in the sun for 1 hour the first day, 2 hours the next day, 4 hours the next day, 6 hours the next day, 8 hours the next day, and then they can be left outside all day.  
• Do this leading up to your transplant to garden date or sooner, just be sure to always bring in seedlings before nightfall while temps are still below 40 degrees.  
• This might be a hard schedule to follow for someone working out of the home without any help, a greenhouse outside may help remedy this situation.

When can seedlings be moved outside?

• This is going to be based on your estimated last frost date.  Every state has multiple growing zones and different frost dates.  You can Google this to see when it is for your specific location. 
• Remember, this is just an estimate. This is not an absolute date. 
• It is best to check your 10-day forecast leading up to your estimated frost date.  If it is consistently over 40 degrees all the way up to your frost date and for the following 10 days after as well, it is likely you are safe to proceed with planting. 
  • There is always a risk of planting your seedlings out no matter what the forecast says.  Mother Nature can throw in a snow day a week after the last frost. Use your best judgment and check to see when others are planting in your community. 

You Made It!

Take a moment to appreciate that you have made it from seed to transplant!  You did a great job and your plants are ready for their permanent home outside for the growing season. A beautiful bounty awaits you.