I have seeds of hundreds of different tomatoes, and every year I decide on about 100 in a different category each year (tastiest? earliest? multiflora? unusual colour etc). I start them inside in pots of Sunshine 4 which comes in a giant black plastic bag.
When I transplant them into the garden, they go into my natural soil.
This year, the seedlings did not grow well at all. I don't have big tomato plants out in the garden.
I was puzzled and then I remembered that I bought a different kind of Sungro this year - not Sunshine 4, but Sunshine 5. I can't remember why - I guess the store was out of 4.
I decided to run a test - the same tomato seeds, in green pots of Sunshine 4, and blue pots of Sunshine 5. What a difference! The plants in the green pots are about four times the size of the ones in blue. They were all sown at the same time and have the same conditions under a growlight.
Hi Diane,
https://www.sungro.com/retail-product/sunshine-mix-4/
https://www.sungro.com/fr-ca/professional-product/sunshine-mix-5/
Sunshine 4 il more draining than sunshine 5.
Sunshine 5 is probably better for old plants.
You can mixed 1 bloc of coco peat or a draining potting soil at sunshine 5 for get a better result with the seedlings.
i was got greats results to mixed 1/4 of biobizz worm humus at universal potting soil.