Pro-Mix Premium Organic Seed Starting Mix, 16 qt.

Item No. SO-PM-USM
PRO-MIX Ultimate Seed Starting Mix is the ideal peat-based growing mix for germinating seeds. This mix is great for germinating, vegetable, flower, herb seeds as well as for starting leaf, stem or root cuttings. Standard Features Formulated with quality horticultural ingredients for growing a wide
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PRO-MIX Ultimate Seed Starting Mix is the ideal peat-based growing mix for germinating seeds. This mix is great for germinating, vegetable, flower, herb seeds as well as for starting leaf, stem or root cuttings.

Standard Features

  • Formulated with quality horticultural ingredients for growing a wide range of plant species.
  • Contains Mycorrhizae, an exclusive biological growth enhancer which promotes plant growth and increases yields.
  • Provides easier plant-care than standard mixes and results in improved seedling performance.
  • Organic fertilizer that gradually feeds plants for up to 3 months.
  • 16 quart loose fill bag
  • NPK: 0.30 - 0.05 - 0.10.


  • Canadian sphagnum peat moss
  • Coir (coco fiber)
  • Perlite
  • Limestone
  • Organic fertilizer
  • Mycorrhizae - PTB297 Technology

Additional Information

LTL Freight Type GROUND
Replenishment System Purchase
Available for Drop Shipment No
Exp. Receipt Date 11/25/2022
Reviews (35)
  • Chunky
    The Pro-Mix Premium Organic "Seed Starting" mix I got was really just potting mix. It had large chunks of bark, twigs and chips of wood products. Something must have gone wrong with the screening process when this was getting mixed and bagged. I did send Greenhouse Megastore a picture and they made it right with me.. Great service.. poor product on this bag . I have purchased a lot of Pro-Mix garden products and this purchase was the only one that didn't meet my expectations. Seed starter mix should not be "chunky".
  • Pro-Mix Premium Organic Seed Starting Mix
    Always have a good result with this product. It does a good job feeding my seedlings for a couple of months until I put them into the ground. It has higher amounts of N-P-K than other similar products that are more available at local hardware stores, garden centers, etc.
  • Very disappointed this year
    I have been using this mix for the past few years. This year, I was only able to buy it at Greenhouse Megastore for TWICE the price I usually pay. I was very disappointed with the quality...a lot of peat clumps, sticks and twigs this year. I sifted them out. After a few weeks I had tons of grass growing in the mix. What the heck happened with this "used to be" fine seed starting mix Pro-Mix? Won't buy again
  • Rough starter
    Had to pick out a lot of hard sticks and quite a few rocks. I expected a seed starting mix to be much more refined.
  • The Best Seed Starting Mix
    Over the years, I have tried a lot of different seed starting mixes, but I have found Pro-Mix Premium Organic Seed Starting Mix is the best I have ever used. The Mycorrhizae, their exclusive biological growth enhancer, promotes excellent growth and root formation. I will use no other.
  • Infested with fungus
    I ordered two bags and liked it while using the first one. Then I opened another bag and found all media surface was covered with yellow ‘grains’ fungus with a strong smell of fungus. Tossed the whole bag. What a waste!
  • To many big chunks
    This had to many twigs and big pieces of wood in it for a seed starting mix. I will try a different seed starting mix.
  • Organic seed starting mix
    I used this soil to repot 13 avocado trees, so far the are doing great. The only reason its not a 5 is because the box was pretty well destroyed when I received it.
  • So far so good!
    I purchased this soil and it seems of good quality, my seeds are all growing in it. Very please so far.Quick delivery each time I purchase my greenhouse products from this company.
  • Dissapointing
    I have used this product in the past with good results. The product I received this year was full of twigs and other large pieces of wood. It really isn't suitable for starting new plants, which is what it is designed for. Sad, I will be looking for an alternate product
  • Excellent
    Used the Pro-Mix Ultimate Seeding Mix to start all of my seeds in 2017. I planted thousands of seeds into 15 200 plug cell flats and germination was near 100% from my seeds purchased from quality vendors. Cheap seed will do what cheap seed does, in my experience its about 50/50. Buy good seed, good starting mix like this one and you will have success. This is an outstanding product. Highly recommend this product. This will be my only seed starting mix in the future.
  • Not Good For Starting Seeds
    I made a fairly large purchase of ProMix Potting Mix and this Seed Starting Mix Spring of 2017. I actually paid more money for the Seed Starting Mix. The products were identical. I would have saved money by just ordering the potting mix to start my seeds in. This is not a fine loose product, but a chunky potting mix ..... it was full of wood, sticks, debris. Will never purchase again, especially since no one returned my phone call from the company.
  • Native Plant nursery owner
    Light, fluffy, sterile. Easy to grow in.
  • Good Mix, but has to many sticks.
    This is a good mix, my plants grow well in it. It could have better water retention and less large debris. If you start in small containers, this may not be for you. I use 2.5 and it fits my needs.
  • Seed starting mix
    I was amazed the first time I used this mix. I planted ground cover type seed which I have used previously in other mediums (several) and the results with this mix were dramatically different and better!! I thought seeds had been doing OK before, but now WOW!
  • Seed starting mix
    Starting mix had to many small sticks in it. It was used for starting seedlings. was just average.
  • Excellent soil
    I buy a lot of stuff for my garden,i have tried everything out there.This soil is the best!! and i will be buying more.
  • to many sticks and debri
    After struggling with unwanted bits of trash when using this stuff for filling a tray, I screened it for my second batch, which was quite laborious.Also it may be too rich, my seedlings are quite leggy, all of them.
  • Shouldn't be labeled for seed starting.
    I have to agree with Richard, this mix was so coarse, I had to triple sift it before I could begin to use it. Twigs, pebbles, and chunks of wood were prevalent in all the five bags I purchased. Never again.
  • grower
    great product for Greenhouse germination
  • Great seed starter
    Really like this seed starter. It's moist, light, and easy to use. Even this tiniest seeds germinate in it. Used it for the first time this season and can't find anything wrong with it. Good price, great quality.
  • Great Product
    This is the best starting mix I have found to date.
  • Not Happy
    Unfortunately I have to agree with the review below. Further I lost three flats of seedlings to what appears to be fertilizer burn or some kind of chemical contamination. Seedlings withered just as or after the seedlings got their true leaves. I have been gardening since I was 6 and am now 51 and have never seen anything like this before and did nothing different than previous seasons.
  • Ultimate Organic Seeding Mix
    The mixture is not really suitable for small seed starting. The mixture is extremely coarse with numerous twigs.
  • Amazing Seed Starting Mix
    I blended this seed starting mix which was just the right combination of ingredients (low compacting) with Espoma Organic Potting Mix in a 3:2 ratio and achieved tomato seed germination in 2 days and eggplant germination 3 days in combination with the Garland Propagator and Seeding Heat Mat. The 2 parts Espoma Potting Mix helped boost the Mycorrhizae and other essential fungi in a high humidity warm temperature environment
  • Pro Mix Seed Starting Mix
    This product performs very well as a seed starter. I blend it 50/50 with a coir based product and enjoy very good germination rates.
  • good
    I have heard good things about this seed mix. Just used it for first time and have some thyme seeds already . I placed my order and the next day i had my soil. But the shipping is expensive of course.
  • kathy
    Love the seed growing mix. i will always use it. The seed trays are a good buy. Thank you so much
  • Christy
    Started many seeds, nice texture. Easy to grow in
  • Like a Charm
    I would use this product again.
  • Growing African Violet seeds
    Tried another seeding mix for African Violet seeds and none grew.With your ultimate seeding mix my African Violet seeds are growing like wildfire. your shipping was fast. Thank you
  • Best starting seeding mix I have found yet!
    This starting seeding mix is the best I have found so far! 90% germination rate- much better than other brands used.
  • Nice fluffy mix
    The ultimate seeding mix is very fluffy and uniform. I got excellent germination results this year, and the tomato and bean seedlings germinated earlier than usual. I bought it mostly for the mycorrhizae inoculant, which will be beneficial throughout the plant's lifetime. Pro-Mix in general is quality stuff, you wont be disappointed.
  • excellent product
    This is excellent growing medium for seeds and small plants. The mailing service was excellent, arriving in just a few day. The product was moist and in good condition.
    This is a quality, uniform mix. Perfect for starting seeds in plug flats (I use 128 flats) or in larger cell packs.