Clear plastic cups not ideal for early pepper growth

back in 2017, i had beginner’s luck when i got the itch to grow peppers. seedling foliage spanned two or three times the diameter of their small yogurt cup starter homes. my seedlings looked like the healthy pepper seedlings i’ve seen on this forum and

but in the last few years, my pepper starts have been anemic. once transplanted into their final planters, the plants did OK, but the starts were nothing like my early efforts.

and the problem might be due to the use of clear plastic cups, which seem to be associated with quite a bit of algae growth.

yesterday, i had my duh moment—it finally occurred to me that the algae in clear plastic cups was being fed by sunlight and the nutrients that should be going to the pepper plant. also, the clear cups were admitting direct sunlight to where the roots should be, and pepper roots apparently don’t appreciate that kind of attention.

no wonder so many pepper enthusiasts grow in solo cups. no wonder commercial growers sell young plants (not just peppers) in opaque containers.

from now on, i’m going to either use opaque cups alone or ensconce clear plastic cups in solo cups. the latter option will allow the capture of water drainage from the primary cup.

here are my seedlings from 2017, which look way healthier than any of my 2021 seedlings. and yup, most of the cups were opaque.

It looks like one of your 2017 seedlings is in a clear cup and doing fine. I suspect overwatering is the culprit, if it’s staying moist enough for algae to grow. I know I struggle with overwatering; it’s so easy to do.


One mans healthy is another’s sickly.
My current seedlings

1 Like

Peppers love light, and hate to be too wet. I lift containers to tell how wet. I saturate when I water and pretty much let them go bone dry before I water again. I started these later as I had poor germination with my hatch chili peppers. I went back another year (Seed saved for 8 years). I had a bad batch of saved seed. But they are catching up to my other seedlings. Well they are behind as the first batch are planted out in containers and starting to set fruit. Fairly happy with peppers this year. Not a bad start for a cold spring.
I grow in ground and containers
Yellow Monster this lovely cool morning.

I keep about 10 different peppers only now and grow out seed year after year. I am going to add one more I have wanted to grow. I grow mostly hatch peppers. No super hots anymore, I don’t have need for many. I like a milder heat. I grow Orange tree habanero and the Fish pepper for heat. Neither needed this year. I still have plenty dried. I also like to grow banana peppers and pickle them for sandwiches.

Bell peppers are hard to grow. I have only had luck with Yellow Monster and Spanish Mammoth. Above I had to pick green as it was the end of the year. I didn’t feel like bringing them under lights which works fairly well to ripen.
Yellow and Spanish Zone 6a


that’s possible, JC.

but one thing i did differently back then was keeping all cups, including the clear cup, bunched together inside a rectangular planter. not much light reached the sides of the cups.

1 Like

not many plants like sun on their roots. i made the same mistake 4 yrs ago.

True, not the best practice, although I never had any problems. I use white cups, and they do reflect light. All light, why they are white. I guess not the same as actual sunlight. or lamp light. I had many more problems with watering then anything else.
Well switch and see how it works out.

1 Like

white is probably the best as it reflects the suns heat also. peppers are hard to grow well here also. too much rain for them so i grow them in pots in the greenhouse. they appreciate the extra heat in there.