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Seedlings are yellowing--need some help ; (

Posted by pitt IN-Zone5 (My Page) on
Mon, Mar 24, 08 at 6:37

I am a grower in Indiana, Zone 5. I have about 4000 seedlings under fluorescent lights (one warm/one cool). Lights are 3 inches from seedlings. Here is the scenario so far.
1. We planted in Pro-Mix with biofungicide this year because we lost so many to damping off last year.
2. A ceiling fan is continually moving in the grow area.
3. At about 3 weeks I started fertilizing with 1/2 strengh -- used Miracle Gro.
4. Seedlings that are yellowing are Amazon dianthus --also some damping off so pulling the flats and replanting.
5. Cramer's Celosia damping off and yellowing.
6. We have really tried to monitor the watering so that we do not overwater.
7. Blue Horizon and Blue Planet ageratum, snaps, etc. seem to be fine so far.
8. Temperature runs about 75.

Just getting a little nervous again, because we lost so much last year. Any help as to what we need to do at this point? Thank you in advance, from anyone who has the time to respond! ; ) pitt

Follow-Up Postings:

RE: Seedlings are yellowing--need some help ; (

What kind of containers are you using and how dense is the planting?
How do you water?
What is the temperature in the room?

I grow under lights and have not had problems with damping off (knock on wood - I'm afraid to even write that!). What you're doing sounds similar to what I do but these things may be different:

I use Fafard Germinating Mix. I use plastic liners and plug trays, mostly 100 cell plugs and 72 liners, a few 200 cell plugs. If I re-use liners or plug trays I scrub them with bleach before reusing them. I bottom water everything. I don't top water anything until it is outside and hardened off. I fertilize with VERY dilute fish emulsion.

Hope this helps,

RE: Seedlings are yellowing--need some help ; (

  • Posted by pitt IN-Zone5 (My Page) on
    Tue, Mar 25, 08 at 5:02

Kirk: Thanks for the reply. The temperature is 75 degrees in the grow area. All the flats are in 100's. At end of season we wash and bleach all flats before we store them away so, hopefully, we are not carrying anything over from last season. I bottom water when I fertilize, but have top watered sporatically with sprayer. I'll stop that! Julia

RE: Seedlings are yellowing--need some help ; (

Hi Julia
IMHO lights should be about 1" above top of plants at all times. That's how I keep mine during winter sowing. Yellowing sounds like possible potassium deficiency. I really like Scott's Peat-Lite 20-10-20. I use a little of it with every dunking.
If you're getting alot of damping off then it sounds like you may be over-watering. Bottom watering is best without drowning the soil.
Trial and error is the name of the game
Cheers - Kim
Billabong Fresh Flower Farm

RE: Seedlings are yellowing--need some help ; (

Does a steady temp of 75 F seem a little warm to others. It does to me. Altho you've been watching the watering, some combination of factors is creating a too moist situation.

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