Does fertilizer make plants grow faster?

[Bruce W.1]

Say you plant your plant in rich and fertile soil. Is there really any point to fertilizing it? Would fertilizer make the plants grow faster?

Thanks for your help.

[Doug Kanter]

Without a soil analysis, "rich and fertile" don't mean much. But, even if the nutrient balance was perfect for a given plant, you'd still need to continue adding to the soil over a period of time. This could mean adding compost, or mulches which contribute nutrients as they decompose. The soil is not a static environment.

[Bruce W.1]

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Fair enough. Then maybe a better question would be how long does it take a plant to deplete the nutrients in the soil?

Take for instance some fast growing house plant, in a pot, and with new potting soil. This plant gets plenty of sun. How long before it needs fertilizer? Without specifics and details it's probably difficult to say. But in general, how long before the soil needs fertilizer? Weeks, months, years?

Thanks.

[Doug Kanter]

I'm not trying to give you a hard time, but it all depends!

1) Potting soil: Not always fortified with plant food. But, let's assume it is for the moment.

2) Size of the pot relative to the type of plant and how long it's been in that pot. Why? Because some plants will become root-bound faster than others, and water will pass right through rather than be absorbed by the soil. So, you now have a situation where nutrients are being washed right out the bottom of the pot. With a freshly potted plant, the soil will be depleted less quickly than the same plant that's become root-bound.

3) Depends on the type of plant, of course. To confuse the issue further, a house plant that flowers only at certain times of year may need to be fed every few weeks during that season, and less often or not at all when it's just making leaves. Others may only need food once or twice a year.

I don't always have the time to adjust to the various plants in the house, so I compromise. I use Miracle Gro liquid, diluted 1/4 of what they recommend (4 times more water, in other words), and use it with almost every watering. Works for most of the plants, with the occasional exception, like the cyclamen I abused horribly over the past couple of months.

If you really are concerned with house plants, I'd recommend you pick up a copy of "Crockett's Indoor Garden". It's out of print, but you can get used copies CHEAP at

[Warren]

Is your question "how long before I need to replenish some nutrients?", or is it "how long before I need to add fertilizer?" Those are two different questions. The second is far narrower than the first, and the answer to the second often can be "never".

It's like asking how long before a person needs to take a vitamin pill. Some people live long lives without ever taking a vitamin pill. And a vitamin pill doesn't necessarily mean that someone in need of nutrition will get what they need.

Fertilizers are the vitamin pill of the plant world. There are situations that are so foreign to the normal culture of a plant that the only way they'll get nutrition is with fertilizer, but even if fertilizer is the only way to get then the nutrients they need, it would still be possible to overdose them.

There are so many variables, and you can't just start plugging values into the equation, and solve it like it's a math problem. And even if you could reduce the needs of a particular plant down to a theoretical number, that doesn't address the delivery method. Fertilizer may not be the right way to deliver those nutrients. Maybe compost is. Maybe repotting is. Maybe different watering methods will allow nature to resolve the problem.

[Doug Kanter]

These are the things that make me scratch my head when people say gardening helps them maintain their sanity. I find just the opposite, but it's a very enjoyable form of insanity. :)

[Travis]

Commercial potting soil probably has zero nutrients.

[Doug Kanter]

Some contains fertilizer, actually. Doesn't mean it's as wonderful as you've paid attention to outdoors until it's teeming with life, however.

[Bruce W.1]

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That helps. I thought fertilizer was like the meat and potatoes of a plant's diet, rather than just a vitamin.

[Doug Kanter]

That's what the lawn service and fertilizer companies would have you believe. Sometimes you do have to introduce some synthetic fertilizer, but it's not the total solution it's made out to be. Neither is weed removal, incidentally.