While shopping for seed starting supplies this winter, I came across this growing media called, Wonder Soil. Never heard of it, but the reviews on that shopping site were all extremely positive. So, I dug deeper, researching user reviews on any store site that sold the stuff. People were raving about how awesome it was… everywhere.

Okay, now we have to try it out too. But first, shop wisely.

If you buy Wonder Soil from Home Depot – you’re going to pay way too much! Seriously, even with shipping costs included from elsewhere, there’s no discount from the Depot, in fact, it’s highway robbery. A dozen trays, 2 dozen cell-pak liners, and a dozen tall humidity domes, along with 5 1-pound bricks of Wonder Soil cost a total of $9.99. The bricks were only $5 apiece, but HD wants $7 before shipping (it’s an online only product). You can get this media in several sizes and forms, including a 10-pound brick that makes a wheelbarrow full of potting soil – but this was in the dead of winter. Small mixing batches that can be done in the laundry room are more appropriate when it’s -20F outside. That little block gives you 2.5 gallons of seed starting mix, and all you have to do is add water and let it rehydrate. Enough to fill 2.5 trays of cells. FOR $5 BUCKS!

New Seed Starting Mix: Wonder Soil

New Seed Starting Mix: Wonder Soil

What’s In It?

Coir, humus, kelp, mycorrhizae, vermicompost, and moisture-retaining gel granules. That’s why you need to add water, the coir is compressed and dry as a bone. I got a $5 storage tub from the dollar store for a mixing container. This worked out great, but I learned that the amount stated on the label is too much water to add. Use about 7/8 of a gallon of HOT water. Hydration is over in 15 minutes, not an hour like the label states. Scrape the wet off of the outer part of the puffed up block to locate the hard bits left in the center, and stir it around to complete the process. Cold water and too much water was wasteful and saving the floaties in the lake that was left at the bottom was time consuming.

Is It Really Awesome?

For getting seeds germinated fast, it is fantastic. My tomatoes were rising in 3 days, and peppers in 4. That’s record time, especially for hot peppers. Jalapenos are notorious for being slow sprouters, and the hotter varieties commonly take up to 3 weeks to break out of the seed shell. All the seeds that were going to sprout were up in 14 days. I’ve used it to start some annual flowers too.

It continues to be totally wonderful without any further requirements on your part beyond proper light, and not letting the medium dry out. Maintaining the moisture is best done with capillary mats, but you still have to keep an eye on the amount of water inside the reservoir tray. At least for the first few weeks…

Yellowing bottom leaves are probably signs of nutrient deficiency, not drought.

Signs of Nutrient Deficiency… Not Drought

You do need to fertilize your plants after about 3 weeks, and the bigger tomatoes grow – the more nutrients they consume. Wonder Soil being mostly coir means that it’s got no nutritional value for your rapidly expanding seedlings, and the amount of worm castings and kelp it comes with is not sufficient or depleted. If you don’t provide more nutrition fast enough, they will start starving. But you might not identify this as the issue at first. The peppers, which aren’t as heavy feeders as tomatoes, went through this period much better, though they were starting to show slight yellowing on the newest leaves – no where near as pronounced as the tomatoes.

At the onset, the bottom leaves look a bit pale. Maybe some curling here and there. Is it too dry? Next day, bottom leaves yellowing. Some purple on those curling leaves. Hmmm maybe it’s the water pH – this isn’t hydro, it’s garden starter plants. Change the water with neutral pH version. Day 3? Okay, this is definitely plants screaming, FEED ME!

Will they die? Only if you don’t give them instant nutrition. Liquid directly into the growth media, watered in from the top. And you’ll have to keep repeating this every few days, or they’ll start looking peaked again. The smart approach would be hit them with liquid in a balanced analysis, and the next day put slow release fertilizer into the soil of each cell…

But, hindsight is 20-20. I’ll be ahead of this game next year. None of this spoon feeding regime. Don’t ask me why it didn’t occur to me to do this weeks ago, but here we are at planting time. Slow-release is going into the cells at the end of week 4. This setback will slow down food production once they are planted. They will be repair, but the time spent doing that is time lost in such a time-sensitive affair. Still, what I thought were sad looking tomatoes, make the greenhouse alternative look kinda pitiful. Mine are leggier, but much richer green. That’s not enough light for tomatoes this old, but they’ll be basking in real sunlight before Monday with always available nutrients. I’ve grown a good harvest with sorrier looking starter plants in the past. Here they are at 7 weeks after sowing, and it is high time they moved to new quarters – they’ve run out of space on this shelf, and the light can only go up another 2″ at most:

7-Week Tomato Seedlings: Wonder Soil Trial Grow

7-Week Tomato Seedlings: Wonder Soil Trial Grow

The Next Experimental Test

Since I’ve got a brick left, and some already expanded in a bucket, it’s time to test Wonder Soil in outdoor containers mixed with other media. Yep. We’re gonna see what it does mixed with Miracle Gro potting mix, topsoil, and what have you. Plus fertilizer from day one. These won’t be seed containers, but already rooted plants.

Tammy Clayton

Tammy Clayton

Content crafter and Senior Editor at Garden Culture Magazine
Tammy has been immersed in the world of plants and growing since her first job as an assistant weeder at the tender age of 8. Heavily influenced by a former life as a landscape designer and nursery owner, she swears good looking plants follow her home. (Some feel she's got a perennial obsession, others say the problem is tomato plants.)

If you don't find her at the desk - check the gardens. When not writing and weeding, she enjoys a good book, painting junk furniture, and blending the harvest of heirloom tomatoes and chiles into salsas.
Tammy Clayton

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