Seed Starting & Soil Blocking Part 1

2022 me is already wondering what 2021 me was thinking when ordering seeds - there’s apparently nothing I wasn’t willing to try!

I attempted a round of soil blocking in January, and it was an epic failure. I didn’t keep the mix wet enough when setting, I let the blocks dry out and I forgot to use humidity domes. To be honest, I was a little scared to try again until earlier this week.

This month I started with cell trays, and once those started germinating (Lisianthus, eucalyptus, snapdragons, lavender and kitchen herbs), I had more confidence to try soil blocking again. I also re-read Cool Flowers, and reading that certain cold hardy annuals are tough to transplant and are therefore great for soil blocks, I figured I’d give it another shot.

This past weekend I grabbed my soil blockers, mixing tray, 10x20 trays and soil mix (I use ProMix from Menards) and went for it. I used my 2” block for sweet peas, and was able to fit 40 in a tray (two trays for these guys, so 80 blocks). I’m doing a trial with sweet peas this year, so 80 seeds went in soil blocks. The rest will go in root trainers. At transplant time some will go on the cordon method and some on a true trellis (this will be a whole separate post). The smaller 3/4” blocks were used for strawflowers, bupleurum, salvia, nigella, bachelor’s buttons, statice, shasta daisy, African daisy, Zulu Prince daisy, geum, bunny tails, hollyhock, sweet annie, mignonette, lupine, bells of ireland, larkspur, snapdragon, clarkia and forget me nots. I used the large soil blocks for cerinthe and calendula.

NOTE: Use the large soil blocks for scabiosa. I used the smaller ones and had to bump them up into the bigger blocks 5 days later! See the picture below of how long that root grew in that short amount of time!

Some soil blocking tips I’m becoming aware of - use more water than you think you’ll need when mixing. I’ve found it’s better for them to be too wet, than not enough, and dry out. Fit as many as you can in a tray, too! I’m able to fit 40 2” blocks in a 10x20 tray, and 300 3/4'“ blocks in a 10x20 tray. I also make all of my blocks, fill the trays, and then sow the seeds. Colored labels have been working well to keep track of what’s in each tray.

Since I do have cell trays still, and feel a bit more comfortable (at this time) with getting them to germinate, I used those for sapiglossis (painted tongue), rudbeckia, yarrow, anchusa, balloon flower, stokesia and Veronica. At the time of this post, I’m seeing germination already from strawflowers, bupleurum, rudbeckia, yarrow and stokesia, salpiglossis, scabiosa, bachelor’s buttons, statice, hollyhock, veronica and salvia.

I’m watching these cold hardy annuals closely in regards to temperature. I have an unheated greenhouse that will be used in a few weeks as part of the gardening off process. Right now all seedlings are in my home office (with the exception of the sweet peas, which are in the basement) which has a temp that ranges from 68-72. I vent the humidity domes and have a fan going to keep the circulation up.

This weekend I’ll be soil blocking more cold hardy annuals - feverfew, goldenrod and fennel. I also gave in and ordered bellflower seeds - which I am so excited to try!

I have pretty high hopes so far for these! I’m also going to DIY a few low tunnels to plant these out in about 6 weeks time. This will be around the 4 week mark before our last frost, so they’ll be covered with a frost cover until we hit the last frost. Hopefully this will give me some spring blooms to share with everyone, so wish me luck!

Supplies:

2” Soil Block - Johnnys Seeds

3/4 Soil Block - The Gardener’s Workshop

1020 trays - Johnny’s Seeds and Menards

Humidity Domes - Menards

Cell Trays - Menards

ProMix - Menards