tomato seedling fertilizer

[Greenhousesalsa]

I am getting conflicting information about fertilizing tomato seedlings.
I have read that after the first true leaves appear, to use fish emulsion.
Other sights say they don't need fertilizer until they go into the ground.
I am growing these in a lighted greenhouse fixture, in my home. Not thrilled with using fish fertilizer in the house.
I found some "de-scented" fertilizer on line, but when I try to find it at the local garden depts. I get looked at like I have a third eye!
Do I need to fertilize these plants and what would be the best to use, not smelly fish?
I started them in Jiffy seed starting mix. Growing like crazy and I still have 2 months before I can put them in my real greenhouse outside.
Thanks in advance for any advice.

[Peter1142]

Pot them up into an enriched potting mix, there are organic options with compost, no need to fertilize at all. Otherwise they should get a good liquid fertilizer in an unenriched seed starting mix. Not an expert on those, there is the fish for organic and Miracle Gro for no. I'm sure other posters will have other options for that.

[PaulF]

For potting mix I use MIracle-Gro or its equivalent, whichever is cheapest at the time, with the time release fertilizer. The kind with moisture control is not a good choice, in my opinion. The fertilizer content is so low it does not burn seedlings, does not add so much nitrogen to make the seedlings get leggy, but does fertilize just enough to give them what they need for healthy growth.

If you use a non-fertilized seed starter, when it comes time to pot up after the true leaf stage, I would suggest adding a liquid fertilizer in a diluted form. Fish emulsion is just one type of product you could use with nutrients to assist tomato plant growth. Just don't overdo it. After the tomatoes are planted in the ground I would suggest very little fertilization, especially with high nitrogen content. A soil test will indicate what your soil needs for a balanced growing season. High N in the soil will cause excessive plant growth with little fruit production.

[applestar]

Jiffy Seed Starting Mix doesn't contain any fertilizer at all, I think. I'm not sure why your seedlings are "growing like crazy" and I'd like to be sure it's not insufficient light and spindly growth.

I guess I'll describe my seed starter as well -- I prefer to start seeds in 2:2:1 mix of good quality organic potting mix : coir: all purpose sand/sand size DE/PBRH (Parboiled rice hulls). This way they have some nutrients to start with and is exposed early to symbiotic mycos and other soil microbes.

For first uppotting, I use same mix with added dolomitic lime and vermicompost/earthworm castings, UCG (used coffee grounds) rehydrated alfalfa pellets, bran, and some kind of larger drainage material like perlite, pumice gravel, gravel size DE, PBRH. Not necessarily all of them together, and I don't have a specific formula/recipe.

If another uppotting is needed, then I might use commercial organic fertilizer like Tomato Tone but by then they are mostly outside unless freeze threatens or it stays in the 40's for daytime high for several days. I use clear tubs, low tunnel, etc. to protect them for the most part.

[imafan26]

If you are using a potting mix with slow release fertilizer like Miracle grow potting mix -- it will contain enough slow release fertilizer for about 3 months. You don't have to fertilize until after you have planted out or the seedlings are around 4 inches tall. Phosphorus deficiency will show up as purple tinge to leaves and stems and will be corrected when planted out or fertilized.

If you are using a homemade mix and you do not add slow release fertilizer- then you will have to fertilize.

Most organic mixes are very slow release and if you want to stay organic, you will need to fertilize with something
Organic also is not that easy to do in pots.

If you are using an organic mix like sunshine no. 1 or no. 4, it does not contain enough fertilizer by itself and will require additional fertilizer.

If you are not organic and you do not add slow release fertilizer like osmocote to your planting mix, then once you have a couple of sets of true leaves, you should consider planting them out. If you up pot or keep them in the starter pots more than a month then start fertilizing them with miracle grow 1/4-1/2 strength (if you don't have to be organic) or fish emusion if you are organic.

Some plants like tomatoes are very heavy feeders and even in a potting mix that contains slow release fertilizer like osmocote, they will need to either be in the ground in two or three weeks or they will need supplemental fertilizer and up potting. Phosphorus deficiency usually shows up first as a purplish color to the underside of the leaves and is easily corrected by planting out or a complete liquid fertilizer. Other seedlings may not draw as heavily on the nutrients so do better longer.

[AnnaIkona]

I agree with Peter...most seedlings don't need to be fertelized if you use a high-quality potting mix. Later on, though, when you're ready to transplant the seedling outside you way wanna use some Miracle-Gro.

[Peter1142]

FWIW, I grew very nice tomato transplants (6 weeks grow time) with Nature's Care Potting Mix last year and did not fertilize in the pots once. If anything they grew too big and fast.

[Vanisle_BC]

I'm interested in the comment that "Phosphorus deficiency will show up as purple tinge to leaves and stems." In the past I recall the leaves of my tomato plants - mature & growing, not seedlings - having pronounced purple undersides. In retrospect I'm not aware the plants were unhealthy. My question then is, if this indicates a phosphorus deficiency, what are its other effects on plant and fruit?