Adventures in Soil Blocking

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Deeply Rooted
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Of all of the flowers that I have tried to grow from seed, annual phlox has been the trickiest. They are kind of my nemesis. Phlox has been hard to germinate, and not very easy to grow-on either. Last summer there were only a handful of plants that made it to bloom--but in the end they were gorgeous. I saved about a tablespoon of seed, and I am stunned to report that those seeds sprouted nicely for me after just a few days. I had them under a little piece of damp paper towel in a cup in the fridge for about 24 hours, and then in a dark kitchen drawer for about 5 days (since phlox seeds really need complete darkness to germinate). Today I poked the seeds in to 3/4" soil blocks, and I am cautiously optimistic that they will grow.
 

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Branching Out

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My grow light station is filling up so I may have to pause my seed starting for a bit. I have one more shelf available under lights, so tomorrow I will shuffle things around a bit and move the tall plants like dill up to the top shelf.
 

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flowerbug

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I sometimes top-dress with seed starting soil too- that's a handy technique to use, especially if you just need to sprinkle a light layer of soil to cover the seeds a bit. And like you I enjoy seeing what I can find around the house for seed starting. Good chance that cat litter tray will be purr-fect! ;)

Today I realized that trying to presprout snapdragon seeds is an exercise in frustration; the seeds are like dust, and almost impossible to remove from the paper towel after a few days. Next time I think I will just scatter pinches of snapdragon seed on top of the soil blocks instead.

note, i've not tried this with seeds but it shouldn't take too much to try out. :) we only have really thin singly ply TP so turning it upside down and then watering it will probably work well for keeping seeds lightly covered but also spaced how you'd like.

take squares of TP and dab them with sugar water or perhaps corn syrup with a toothpick and then sprinkle the seeds on and they will only stick where the sugar water is at. pour off the rest. you don't want to stack them together. i would just do them right as i was putting the seeds in the trays because i'm sure they'll wander and fall off if they rub together or as they dry.
 

flowerbug

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Of all of the flowers that I have tried to grow from seed, annual phlox has been the trickiest. They are kind of my nemesis. Phlox has been hard to germinate, and not very easy to grow-on either. Last summer there were only a handful of plants that made it to bloom--but in the end they were gorgeous. I saved about a tablespoon of seed, and I am stunned to report that those seeds sprouted nicely for me after just a few days. I had them under a little piece of damp paper towel in a cup in the fridge for about 24 hours, and then in a dark kitchen drawer for about 5 days (since phlox seeds really need complete darkness to germinate). Today I poked the seeds in to 3/4" soil blocks, and I am cautiously optimistic that they will grow.

i've not had to grow any annual phlox. for sure the perennial kind we grow here doesn't seem to have issues with sprouting and growing. those large seeds are one of the favorites of the goldfinches.
 

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note, i've not tried this with seeds but it shouldn't take too much to try out. :) we only have really thin singly ply TP so turning it upside down and then watering it will probably work well for keeping seeds lightly covered but also spaced how you'd like.

take squares of TP and dab them with sugar water or perhaps corn syrup with a toothpick and then sprinkle the seeds on and they will only stick where the sugar water is at. pour off the rest. you don't want to stack them together. i would just do them right as i was putting the seeds in the trays because i'm sure they'll wander and fall off if they rub together or as they dry.
Good idea- kind of like homemade seed tape! I have a friend who has done this with carrots, and had good success. One bonus with snapdragons is that you can sow the seeds reasonably thickly and then prick them out when the seedlings are small; they don't seem bothered by being moved, as long as it is done in a timely manner. I may need to try a comparison of different germination methods. Having a massive stockpile of home-saved seeds has turned out to be a catalyst for experimentation-- something that would be very expensive to do if the seeds had to be sourced from a seed company.
 

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This morning my husband helped me make a prototype for a simple soil blocking device, using items commonly found around the house. The goal is to create a tool that is cost-free, to encourage people to give this growing technique a try. This tool is made of a hair spray bottle lid and one of those little Barbie-sized tables that are placed in pizza boxes, so when the boxes are stacked the cardboard doesn't contact the pizza.

First, we marked out where the little legs would sit, and then we made holes for them. Initially I used an ice pick but it was too small, so we used a heated awl to make the holes a bit bigger. Next the little white 'table' was place inside the hairspray lid, with its legs pushed all the way through the holes and sticking out the bottom. Then while holding the cup in my hand I filled it with soil starting mix, and then pressed very firmly with a flat spoon to compact the block of soil as much as I could (a bit of water squished out of the holes in the bottom, which was fine). The last photo shows what it looked like when the cup was full.
 

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Branching Out

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Once the cup was full making the block was easy. All I had to do was invert the cup on a tray, and then press firmly on the bottom of the little legs while gently easing the cup upwards with my other hand. The round plastic 'table top' remained pressed against the top of the soil block until I could lift the cup off. In no time I had made several round 'blocks', and when I was finished it was very easy to rinse the dirt off of the plastic cup for storage. It took less than five minutes to make this contraption and it works great. I encourage anyone who is interested in trying soil blocking to have a look around their house to see what can be used to make your own blocking tool-- and if you invent one please share the details with us. I suspect that those who only anticipate making a few hundred blocks per season may be able to make do with a homemade device instead of purchasing one-- but for those like me who make thousands of them a metal soil blocking tool remains the best choice.

A benefit of making large soil blocks is that you can get away without sifting the potting mix (just pick out any large pieces of wood that you come across). Once you add water to hydrate the mix give the soil a good stir, and then once it is well-mixed it's important to press down firmly to completely level the surface-- kind of like smoothing cake batter in a pan. Firmly compacting the mixture and then letting the soil sit for several hours before using it will give you a well-hydrated mixture with a moist--but not soaking wet-- consistency.
 

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Branching Out

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i've not had to grow any annual phlox. for sure the perennial kind we grow here doesn't seem to have issues with sprouting and growing. those large seeds are one of the favorites of the goldfinches.
We have a few perennial phlox here too. They are quite nice, but they only bloom for a short time and are prone to fungal issues in our climate (powdery mildew I think). Annual phlox blooms all summer, is seldom bothered by deer, and can be used as a cut flower for bouquets. From what I understand annual phlox is native to Texas (phlox Drummondii-- maybe Baymule has it growing in her area??) and is supposedly an 'easy' flower to grow. It is one of those flowers that draws you in with its beauty, so I sincerely hope I can figure out how to make it thrive in my garden. I would love for it to self-sow and come back each year as a volunteer. Yesterday I found half a packet of Phlox Brilliant Seeds so I have those hydrating in the darkness of my kitchen drawer. I note that the instructions on the package state that phlox needs light to sprout, but I don't think that is correct. I think annual phlox seeds need complete and total darkness to germinate. https://thekokorogarden.com/blog/20...mel-for-flower-farmers-and-the-cutting-garden

I ordered more phlox seeds as well, for Twinkles Dwarf Mix https://www.rareseeds.com/phlox-twinkles-dwarf-mix
There is free shipping at the moment, and if you order $10 worth they throw in a free pack of seeds as a gift. All of the reviews for this particular variety were just glowing! 🌸
 
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heirloomgal

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My grow light station is filling up so I may have to pause my seed starting for a bit. I have one more shelf available under lights, so tomorrow I will shuffle things around a bit and move the tall plants like dill up to the top shelf.
I'm amazed at your energy to plant all year round!!
 

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Yesterday I tried my hand at creating a really big soil block for bumping up lettuce that had been in 1 1/2" blocks for far too long (4-6 weeks). They were completely root bound, so much so that the roots of the lettuce blocks were spreading out and attaching themselves to the tray, kind of like ivy. To make the blocks I used at 3" square purple pot, and set a smaller square red plastic pot upside down, inside the purple container (the red container being just slightly larger than my 1 1/2" lettuce blocks). Then I packed in a bunch of moist peat moss, filling the purple container to within about an inch of the top. Once inverted on the tray I poked a long pick through the holes in the bottom to release the block, and then carefully removed the small red plastic pot.

The top edges of the block were higher that necessary and the bottom of the block was a tad thin-- so I trimmed the sides down a bit, and used the trimmings to beef up the bottom of the block. After that it was easy to insert the lettuce plants into the holes in the blocks, and then I firmed the soil in around the blocks with my hands. Once they were all tucked in like Christmas Puddings I watered the tray from the bottom (watering them from the top would have washed all the dirt away). This was a little fiddly, but I am very curious to see how they grow now that their roots will have room to spread out. I spaced the blocks out on the tray, so where initially I had a dozen lettuce plants now I have just six. That means that they will take up a lot of space under lights-- but whenever the weather is above freezing I will be able to move them outdoors.
 

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