Do You Need to Add Seeds to Potting Soil?

by Mike Lieberman · 20 comments

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On the surface this question is gonna seem stupid, but I think it has just caused to be asked – Do you need to add seeds to potting soil in order for something to grow?

A few weeks back I wrote about mysterious sprouts growing my containers. I thought I had solved the mystery and that they were old seeds that never sprouted.

Since that time I’ve planted four new containers. They were started using brand new bags of potting soil and the same sprouts are emerging.

When I planted the seeds in the containers, I definitely did not spill the seeds into the containers nor reuse potting soil.

I’m using Whole Foods store made potting soil. Not sure if they have seeds already in there. I think I’m gonna make a new container, not put any seeds in it, water it and see what happens.

Has this happened to anyone else? Does potting soil always sprout like this?


  • Malchus

    Most bought soil is partially made out of compost, which is made out of the green waste that people bring to the recycling facilities. Normally these “piles of greens” need heat in order to compost down well and fast. The heat should also kill all seeds in this compost pile, but most times this is not the case. And then this compost-soil is packed in small bags and sold for alot of money in stores ;)

    Also, within a very short time seeds get into the soil (through wind, birds, etc), and these do sprout very fast as well, so if a container is outdoors, this can be the case as well.

    At least this is what i know about it, of course i might be wrong ;)

  • Mike Lieberman

    Thanks for the info. Makes total sense. It’s a bit odd that all of the sprouts appear to be exactly the same even though multiple bags have been used.

  • nan

    Seeds blow in from other places and plant themselves in your containers. Or a bird could drop a seed in it. You water, they sprout. That’s been my experience with container growing. Then I have weed seeds in the greenhouse when I bring them in for winter. lol

  • Anonymous

    I addition to what others have already said seeds can get into the soil anywhere along the manufacturing or transportation route where it is exposed prior to bagging. Soil bought from places that store it outside also tends to contain bugs or bug eggs. In this area it is not uncommon to dump a potted plant and find centipedes in it. Some people like to heat their soil in the oven before using it to avoid random sprouts and bugs.

  • Mike Lieberman

    the interesting thing is that they are all look like the same kind of seeds.

  • Mike Lieberman

    Not a bad idea. Does heating it harm the health of the soil?

  • Anonymous

    It shouldn’t. As Malchus mentioned compost heats up during the composting proccess if done correctly, effectivley cooking itself.

    If it’s commercial potting soil and contains a lot of other additives the heating might cause some chemical breakdown and degradation. But a lot of people do it with Miracle Grow, which has plenty of additives, and they don’t report any problems.

  • Wendy

    Hi Mike: Love your blog, BTW. I used Miracle Gro’s Potting Mix from Home Depot this year for my containers, and haven’t ever seen stuff sprouting from it–other than what I planted.

  • Mike Lieberman

    Thanks Wendy. Personally I stay away from all Mircale-Gro products. Lots of “stuff” in there that I don’t want in or near my food.

  • Anonymous

    How strange! That has never happened to me. The closest thing is that I get a lot of mushrooms popping up out of organic potting and compost mix, but that is supposed to be due to it either being made from composted mushrooms or the high nutrient content.

    Why don’t you shoot an email to the producer of the soil just to see what they say?

    or the gardening gods are screwing with you :)

  • Mike Lieberman

    Yup. I’m getting screwed with.

  • Junglemn

    i would add seeds to a potting soil garden soil or top soil mix just becaus of the one fact that all seed containe 3 things essential to plants to start growin 1) a baby stem with leaves 2) i baby root which wont start growing until number 3 is activated which is 3) homones and enymes designed for plant growth… so if you add the warm water(not hot) and the E&H leek into the soil you have a soil enriched with more and more growing power which will be absorbed by other plant seed its a symbiosis(two organisms producig each others nutrition) think of it as the same breathing relationship between plants and animals animal breath out CO2 plants breath it in and breathe out O2 which animals breath in and return CO2 into the atmosphere need i say more?

  • Mike Lieberman

    Makes sense…I thinks.

  • http://greenadventuresofacitygirl.blogspot.com/ Heather Mccarl

    Definitely possible. I bought organic compost this year – a different brand than last year and used to fill in 3 new raised beds, and top off 2 old raised beds in my backyard. And lo and behold there were weeds growing in ALL FIVE of them that I have never seen before in my life!!!! My conclusion is that it came from the compost. Especially because the raised beds in my front yard had plywood bottoms (to avoid utilizing potentially contaminated soil) so there would have been no other possible source of the weeds other than from the soil I put in.

  • Mike Lieberman

    Looks like I needs to do some thinning.

  • Wendy

    I’m sure you’re right about the Miracle-Gro. I’m kind of a newbie at this, and didn’t think about it at the time. I will definitely go organic next year.

  • lisa

    Pull them & add them to the compost. I’d say it’s a good sign that you have fertile, organic soil :)

    I love composting & this is an annoying aspect, that we’ve grown to love. Last year we made 2 composting piles, one which would be kept for ‘normal use’ & one which we left to sprout :) We got cucumbers, Sunflowers, Pumpkins galore &…… An Avocado plant!!! We live in NY so that soon died but it’s a fun way to get the whole family interested in garden.

  • http://www.CanarsieBK.com Mike Lieberman

    Yea those native NY avocadoes are a tricky one.

  • http://twitter.com/GreenSoil Manure Tea Gardening

    to me Mike, it sounds like the compost used to make the potting soil was not aged properly and did not reach the right temperature to kill the weed seeds! Further reason for us all to know your “soil source” whenever possible or look for the Mulch and Soil Council stamp of approval not just the words Organic. Here is a link that I think you’ll find interesting http://bit.ly/d0bJDF the bottom paragraph referrers to green waste/compost and is extremely important to know when raising edibles in containers, raised beds, etc. That not all organic matter is toxic free…

  • http://www.UrbanOrganicGardener.com Mike Lieberman

    I ate some of the matured sprouts and they tasted like tatsoi or a similar spicy green. Where I get my soil from is something that I’ve been struggling with. I’m all knowing my soil source, but not sure where to start looking locally.

    I was buying my potting soil from Whole Foods, but I’m not shopping their anymore, so need to find somewhere else.