fertilize transplants or not?

mulberryknobMarch 10, 2013

For years I potted up my small seedlings without fertilizer because I'd read--many years ago--that it was better not too. I pot up into Miracle Gro potting soil that says it feeds plants for six months. But I haven't always had the growth I expect. Sometimes the plants stall for longer than I think they should and sometimes they actually turn a bit yellow or purple. So I've started fertilizing them with Miracle Gro fertilizer mixed at half strength and I think they do better. (I don't fertilize peas because they only spend 2 weeks in the tubes before they go into the ground and I sprinkle bloodmeal to discourage rabbits and that gives them a nitrogen boost.) But I want good sturdy broccoli, tomato and pepper transplants. What do the rest of you do? Fertilize at the time of potting up? After they settle and make a bit of growth?

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Okiedawn OK Zone 7


I have done it every which way. Usually, I pot up into Miracle Grow and do not fertilize until the transplants go into the ground, but that decision is based on how they look. If I think the seedlings color is poor, I will fertilize with some sort of water-soluable fertilizer at 50% strength.That usually helps, but it won't help if they are being exposed to temperatures so cool that it affects their ability to take up nutrients.

The yellow or purple could be that they are just adjusting to being potted up. It could be that the temps are still a little cool for them. It could be that they are hungry and want to be fed. i just try to analyze what the conditions have been like lately and then decide whether to feed them or not.

I agree with you that they seem to do better if given a little booster feeding before they go into the ground. It just is that it can be a slippery slope.....the last thing I want is for them to grow so much that they outgrow whatever containers they're being raised in. I am not a big fan of having to pot up again into larger containers just because I'm having to hold on to the plants and keep them out of the ground a bit longer than I intended.

I really think the sluggish growth is more a function of cold temperatures which can impede nutrient uptake. I noticed sluggish growth on a lot of my cool-season seedlings in the greenhouse week before last.. I never did feed them, but after a few warmer days and nights, they perked up and make wonderful growth last week while I was away a fires for several days. That made be look at them and think "hhmmmm. Must have been the cool air."

I know the conventional wisdom is that you can harm young, delicate plant roots by fertilizing them too early in their life. I won't dispute that because I imagine there is research that backs up the conventional wisdom. What I'll simply say, instead, is that I have fed young seedlings at virtually every stage of their lives at one point or another, and I've never seen any adverse effect from it whatsoever. However, I generally use liquid fish emulsion, liquid seaweed or something else that has fairly low NPK numbers anyway and I still reduce them to 50% of the recommended strength. With Miracle Grow and similar water-soluable fertilizers, at 50% strength I've never seen them harm a seedling either.

I usuallly water in seedlings when transplanted, and then wait a week or two before fertilizing. It depends on the soil though. If they are in one of the more well-enriched beds, I might not fertilize them at all until they've made good growth. If in poorer soil, I might do it a week after transplanting. And it depends on the weather. If I am pushing plants into the ground a bit early, I won't fertilize with anything that will push them to form a lot of foliage that is likely to get damaged on a cold night. I'd rather see the early growth going into developing a good root system.


    Bookmark   March 10, 2013 at 3:26PM
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I cant add much because I dont use seed starting mix. Last year I added some compost to the lc1 sunshine mix I use, this year I also added compost and composted manure and a finer grained potting soil. This is just something I have experimented with, but it seems my plants are growing a little faster than I like. My plants always do better when I can start moving them into natural light.

I have moved some plants into the garden at three weeks of age and have lost some because they had not been conditioned properly and had not had time to develop a strong root system. Harsh weather and transplant shock can be ruff on young plants even when they are growing well.

Until I find a reason to change my mind I will have some kind of feed for young plants that are started inside.

    Bookmark   March 10, 2013 at 6:20PM
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Thanks, Dawn and Larry. I think you might be right, Dawn, about the cool temps. I keep my plants in a plastic-covered plant bench with a soil heating cable but on really cold nights lately it has gotten down in the 40s.
Larry, the Miracle Gro I pot up into is advertised as potting soil, not seed starting mix but I wonder about the feeding-for-six-months claim. I see what I think is pelleted feritlizer in it, but not a lot and I am sure that not every 5 oz cup gets the same amount--I have seen some real difference in the way seedlings of the same variety grow off after they are moved into it. .

    Bookmark   March 10, 2013 at 9:33PM
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Dorothy, I have never bought into that "Feed For Six Mo." idea either. Up until this year I would mix a light MG feeding mix into a spray bottle and give my plants a boost every now and then. Being as cold and wet this year my plants have spent very little time outside. I would like to fix up some kind of small greenhouse for the extra heat because my plants look better and grow better under those conditions. With only the shop lights the plants get too tall, too fast. I think I have some 4 mill and some 6 mill visqueen, so hopefully I can rig up something to make my plants happier. I will pot up this week into paper pots and let my plants grow a little before planting time.

    Bookmark   March 10, 2013 at 11:33PM
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I think light intensity has a profound affect on seedlings, too. As you all know I put up the new light garden this year with T5 tubes and wow! do they make a huge difference! Healthier, greener, faster growth rate and so on.

I don't use but 1/4 strength fertilizer every watering and the plants respond quite well at that ratio. I have always used that dosage since it was suggested to me years ago by a gardening friend. It may not be such a huge deal.

BTW, Dorothy, I used MG seedling mix that I found at Ace, too.


    Bookmark   March 23, 2013 at 2:53PM
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I tried mixing in a little compost and a little composted manure into my potting mix this year. This it the first time I have mixed in the composted manure but it seems to be doing well, but my tomatoes are getting too large for my conditions. They are out growing my lights and I dont have a place to set them if the weather is bad. I just have the cheap t8 lights over them.


    Bookmark   March 23, 2013 at 5:55PM
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