Seed Starting Mix?

I would be interested to hear what type of seed starting mix has produced the best results for you? Do you buy a commercial brand or mix your own? Do you add any fertilizer?



I have been using Pro Mix bx, or Sunshine® Pro Premium Potting Soil both of which comes in a 3.8 cu ft compressed bail. The supplier nearest me was out of it last yr and I did not want to drive 50 mi to get it at an agricultural outlet so I used a Hydro Farm product called B’Cuzz which is almost the same as Pro Mix without the beneficial soil bacteria, so I added a small amount of Fox Farms Potting mix which has the beneficial bacteria that B’Cuzz does not have. This seems to work extremely well, I lost almost zero seedlings, and I started to fertilize at approx 10-14 days using a diluted fert. The B’cuzz worked well, had maybe 10-25% more perlite per volume than Pro Mix or Sunshine, but other than draining really well, was no problem. I did have to fertilize a little more frequently. I plant sprouting seeds directly out side into the cool temps starting in Dec/Jan. Temps here usually do not go below 30F.

I love Pro Mix bx too. The local suppliers recently changed hand and they do not carry Pro Mix now. There are different formulations of Pro Mix. I bought some 2 cu ft. compressed bales of Pro Mix in the orange plastic from Home Depot recently and potted up some precocious rose germinations. So far it seems like it is working well. This mix seems comparable in peat quality and perlite to the bx mix, just not the beneficials. I try to be really careful with watering to not overwater and encourage root rot. With the difficulty getting Pro Mix bx I think I’ll try this other form of Pro Mix this winter. At Home Depot it is $13.97 per bale. Recently another home supply store that also has it put it on sale for $8.99. I confess I bought more than I probably need. I recently just got in the house with 3 more I bought today. There are 8 of them in the basement and have two more in the garage yet. I’m trying to resist the urge to go back for more. I feel like a squirrel getting ready for winter scurrying things away!

Thanks everyone for the suggestions. After much searching locally I did find an outlet that was selling Sunshine Pro Mix 4. Picked up a bale this week, it was pretty pricey at $49. This business specialized in hydroponic supplies and from the looks of it lots of expensive grow lights for those growing their own marijuana. Hope the added expense of growing medium improves the germination rate. Have new dishpans to use as growing trays and the cinderblock surrounds are ready. Also, this year I am covering the cinderblock surround with window screens. Lost most of my seedlings last year to critters chomping on them. Now, I just need time to check the fridge and see if anything has started to germinate yet.

Joan, I don’t know if you have slugs and snails, but if they are present, use LOTS of snail bait. They LOVE rose seedlings, too. Even large slugs can get in to the tiniest crack, like rats can.

I ALWAYS make my own. It is so much cheaper, and I know what is in it.

Non-Toxic Slug Bait is essential here. Nothing is worse than seeing a years worth of work chowed down on in one night.

I use a combination of half commercial seed-starting mix and half vermiculite. The odd thing is, it seems to need to be made fresh every year. I wonder if once seedlings start growing in it, they produce whatever “nobody germinate except me I was first” hormone and it stays in the soil. I’ve also found that adding some of those water-absorbing polymer beads to the bottom of the box helps a lot.

While I cannot be objective about results since I have done no comparisons and now always make my own, (I’m cheap) I do a mix of perlite, peat, and shredded forest products, with added manures (poultry, mostly), alfalfa meal, blood/bone meal, fish emulsion with other minerals/goodies that seems to work pretty well. I try to mix well in advance to allow microbes to get going.

I don’t know my actual costs, but I’m guessing that For about $20 in ingredients, I pretty much fill a large trash can with this mix. Dunno how that compares to a 3.8 cu.ft bale of Pro Mix.

Anyway, it may be my imagination, but I think the beneficials that come with the natural ingredients seem to reduce damping off and other issues.

You can buy a 50# bag of alfalfa meal or pellets sold as horse feed for about the same price as a 15# bag sold as fertilizer, btw, (c. $12) and it works well amending the beds too.

I really should measure out the ingredients and test a batch to get the balance right. I know that I’m inconsistent, and sometimes out of an ingredient or two, which is not good since I try to avoid chemical fertilizers on the younger plants. (I just think they do better that way. Plants grown on chemical fertilizers, I find, are more delicate and dependent on such.)


When fluffed up the 3.8 cuFt bale is likely enough to fill up a trash can since it is uber compressed. I made my own mix the first two yrs of growing and what I made did not compare to my current results. I do pay between $28 and $36 per bale, but that does go a long way. Since I grow lots of other ‘stuff’ I have some long term plants to compare of other species. They are also happier with the ProMix-type planting mix. As I said above, I do mix in some Fox Farms (variety Happy Frog) mix for the beneficials if I cannot get them in the mix, and I periodically add them to the watering since we have very chlorinated water which is not selective. The pricing on the mixes does vary. I believe I saw it as high as $50+ in a more upscale outlet, but I try to buy when it is on sale or from an ag/landscape supply outlet.