If and when to fertilize pre-fertilized potting soil
May 8, 2016 2:48 PM   Subscribe

I've planted a few vegetables in containers outside (I'm in NY if that matters). I used sta-green potting soil, which claims to have up to 9 months of slow release fertilizer. I bought some miracle-gro liquid fertilizer, but I'm not sure if that would be too much in addition to what's in the potting mix? If not, when would you suggest to start adding the miracle gro?

I'm a complete gardening novice so feel free to explain it to me like I'm five!
posted by theshire to Home & Garden (5 answers total)
Over fertilizing is as bad if not worse as not fertilizing at all, so I would skip the Miracle Grow this year. Maybe use it next year if you are using the same soil. But hopefully you will love gardening so much you will want to start exploring the magical world of composting and compost tea. Natural fertilizers are so much healthier for your plants and for you. Composting isn't hard and doesn't have to take up much space (certain types of composting can be done right under your kitchen sink).
posted by WalkerWestridge at 3:32 PM on May 8, 2016 [2 favorites]

Agree with WalkerWestridge. Too much nitrogen (first number in fertilizer numbers like 10-10-10) burns/kills plants, especially young ones. Fun fact, it's the same reason dog pee leaves dead spots on lawns - too much nitrogen. So no need for the MG this year.
posted by cecic at 3:54 PM on May 8, 2016 [1 favorite]

Nthing putting away the Miracle Gro this year. Use it next year on this soil.
posted by lester at 8:10 PM on May 8, 2016

Nitrogen (likely the first nutrient you'll run out of) is a mobile nutrient. The plant will cannibalise older leaves to keep newer ones in nitrogen. So the first of nitrogen deficiency will be lower leaves turning a lighter shade of green, while new growth is still dark. You'll probably see it in tomatoes first, they're pretty hungry.
posted by Leon at 3:29 PM on May 9, 2016

Hold up, while I agree that you don't need to bust out the Miracle Gro for the time being, container gardening is a little different than in-the-ground gardening in terms of water and fertilizer schedules.

That "9 months" of slow-release isn't going to last 9 months in containers. You need to water a LOT more frequently in containers because there's limited earth (so to speak) for the roots to draw upon for moisture, and the extra water being poured through the pots means that fertilizers wash out faster. (Mind you, you don't want to over-fertilizing in pots and burn your plants in the short term, because, again, your plants are in a constrained amount of potting mix.)

Later in the summer (maybe end of July-ish) when your plants are busting forth with ripening vegetables and everything is humming along like crazy, you'll probably need to start supplementing fertilizer again to keep your plants happy. Just take it easy, don't overdose 'em, dilute your Miracle-Gro a little more than the package instructions say.
posted by desuetude at 10:41 PM on May 9, 2016

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