starting seeds + air pruning - things I've learned

This is our third year gardening, third year of starting plants from seed, and third year of learning. In my first year, we used the regular seed starting trays you see in any store. I hated them. The plastic was flimsy, the plants got root bound, or the roots escaped into the tray below and got mangled during transplanting. The trays lasted for 2-3 uses, and then disintegrated.

In our second year, I used a mix of the surviving trays and toilet paper rolls - save the rolls once you're done with the toilet paper. Then in the spring, fill them tightly with potting mix, water thoroughly, and plant the seeds (like here). Once the time comes to transplant, pop the whole thing in the ground and cover. The cardboard will disintegrate over time. This approach was pretty good for things that don't like their roots disturbed (carrots, peas). However, the rolls got moldy and unpleasant over time, and roots escaped sideways into the tray, resulting in a bit of a struggle during transplanting time.

This year I came across the technique of air pruning, the approach where some of the plant's roots are exposed to air, after which the tips die and the root branches (here's more detail: air pruning). The result is a branched, healthy root system, with no root-bound plants.

There are quite a few different containers and approaches to this, from fabric pots, to planting in shopping bags, to nursery-quality air pruning pots. To start the seeds, I tried two different approaches - one making seed starter pots out of newspaper (instructions here: newspaper pots), and one using net cups, following the advice of the air-pruning guru, Larry Hall (here is his FB page; note that it's a closed group and you'll need to be added by the admin, and his YouTube channel).

I bought 100 cups on Amazon (net cups). They're fairly sturdy, and should last quite a few years, especially if I'm nice to them. I made another 100 or more newspaper cups to accommodate the rest of the starters. Silly of me, I didn't do a proper control, where you would plant the same seeds in the two growing containers, to see which one does best. However, so far most of the net-cup plants did much better than the newspaper ones. I did not expect such a difference (and perhaps that's why I didn't do the control bit). But I know that I will be buying another 100-200 cups for next year's season.

One extremely helpful tip that I read about this spring was to use aluminum foil as a reflective surface between the seedlings and the rooms. When growing seedlings on windowsills, they end up bending towards the light source. To reduce bending, the plants need to be turned once or twice a day, which is a chore if you have quite a few of them. The aluminum foil does two things: 1) it doubles up the amount of light the plants receive, which results in shorter, sturdier plants, and 2) it prevents the plants from bending. As a result, the plants only need to be turned once a week, if that - I haven't turned many of my seedlings in weeks now, and they're only slightly off-center...

Hopefully these help someone out there!
Have a great growing year

I did a similar thing this year, but instead of net pots I used coir blocks. You have to buy the coir blocks every year though, so I shall try the net pots next year! The coir blocks were sterile which stopped mould growing, but they were sterile which meant they weren't loaded with useful bacteria like compost.

I found my plants in the coir blocks did a lot better than the ones I planted in my homemade newspaper/cardboard tube pots as well. Identical varieties in each type of pot:

That's a cool result, neat to see I'm not the only one with the same conclusion...

Oh, forgot to mention that the guy advocating the net cups (Larry Hall) uses this mix for starting and growing plants:

2 five gallon buckets full peat moss
1 five gallon bucket Well rotted horse manure or compost or worm castings
1 and 1/2 cup Garden lime
1 large coffee can full of perlite
1 handful of Epsom salts

And you can add your own rock dust, bone meal, blood meal, etc

I used garden soil instead of manure (and used 2 buckets of soil instead of 1 bucket of manure, to increase volume), since the manure we have on hand had insect eggs, and I wasn't comfortable with it. They tell you to not use 100% soil though, since apparently it won't wick moisture when you water from the bottom...

Great topic and tips. Thanks!
I tried using Gutter Guards (even cheaper at Dollar store) pots I made. However, my biggest problem is moisture. They dry out sooooo quickly. I can't keep them watered enough.
Same with soil cubes btw. I really believe air pruning is the way to go but I can't figure out the water issue.

Did you have that problem? What do you do to keep them soil moist?

It seemed that packing the potting mix right in helped (the more mix, the less air pockets). I did have to add water every 2-3 days, depending on weather. I would just add ~ 1'' of water to the container where the plants sit. It does make traveling difficult - we couldn't leave for more than 2-3 days; 2 days if sunny, 3 days if cloudy, and EVERYTHING got watered thoroughly just before leaving. My plants are all sitting on the windowsills, so sunshine increases evaporation tremendously. You could use larger pots, too, but then you're running into space issues. Plus, I have a fungus gnat infestation at home (yay), so large amounts of moist peaty substrate aren't on the top of the list of my favourite things...

I ended up watering everything every day! (Twice a day for the stuff in the heated propagator like the chilli plants). All my stuff starts off indoors though, under lights- so I didn't have to go far to water things. Wouldn't like to do it if plants were in the greenhouse or something though!

I have them outdoors (windy and dry climate) but even twice a day wasn't enough water. I might have to come up with something else. More vermiculite maybe?

If you have them in large enough trays, you could try to go the self-watering route, modifying the kiddie pool approach (sorry if it sounds crazy, here's an article with pictures kiddie pool setup) for full-size plants - have a tray with a flow valve in it, hooked up to a tap. As the container dries, the valves opens and adds water... You'd have to play with level of pots vs. level of water, so that the plants don't constantly have wet feet, but with a large enough number of plants, it could be less work than manual daily watering.

S Usvy wrote:If you have them in large enough trays, you could try to go the self-watering route, modifying the kiddie pool approach (sorry if it sounds crazy, here's an article with pictures kiddie pool setup) for full-size plants - have a tray with a flow valve in it, hooked up to a tap. As the container dries, the valves opens and adds water... You'd have to play with level of pots vs. level of water, so that the plants don't constantly have wet feet, but with a large enough number of plants, it could be less work than manual daily watering.

Cool thanks for the link. Kidie pool doesn't sound crazy. I have one already. I am just manually controlling the water which is a pain!

I bet! Manual anything can be a problem, doesn't allow you to leave for any amount of time. Here's the google search for how to set up the self-watering deal. People swear by them, saying that you can leave them alone and walk away for however long.
self watering containers

Reading through this post, and the discussion of watering issues, has anyone tried using a
"watering reservoir"?  I am thinking of something like for watering your dog/cat/chickens for
extended periods that release water as needed, as the water is used... like when your dog
takes a drink... lowers the water level, which allows some air to enter the bottle and results
in some release of water, until the water closes the air gap and stops the release.
Theoretically this could be scaled up to almost any size.  Just a thought.

I have used Larry Hall's self-wicking setup before and it works well, so long as the plant roots are deep enough. I have 3 rain barrels, 1 under each downspout. There is a hose outlet off each and they are all connected to each other, so the barrels will self level with each other.

The joined lines lead to a single line a few inches lower in elevation, and attaches to a rain gutter. There is a small float valve attached (imagine a 2 inch long toilet float, cheap on Amazon)that will close the line when the gutter fills up, so the gutter remained full all the time. I attached the gutter to a pair of 2x4 boards for support and there was a cap on each end to make it water tight.

Next you cover the gutter with something you can cut into, to minimize mosquito access to the standing water and keep sunlight from growing algae. Then you either use a bucket or cloth bag for each plant: cut a small hole in the bottom, slide a small net cup in the bottom (should be tight enough to not come out), and then place another pieces of fabric in the cup to keep soil from falling out.

Fill each bag with potting mix (must be mix or something that wicks water upwards just as well) and pack it tight into that cup so there's no air pockets. Then pour water in from the top so the soil is soaked, which will start the wicking as the top dries out. When you place the bag on the gutter, the net cup hangs down into the water so it stays totally saturated.

Plant deep enough so there's maybe 6 inches between the bottom of the roots and the bottom of the bag. I tried higher but the mix was too dry and the plants would fail. Your mileage may vary. I tried Walmart cloth bags for 50 cents each, and after 1 year in the sun they were brittle but still fine as long as you don't move them. As tiny root tips grow out to the fabric and go through they self-prune rather than wrap around and around.

Each plant is kept watered this way, without intervention. Once every couple weeks I would top off the barrels since we get very little rain (just 3 inches from April 1 2017 to May 1 2018 ). You could attach a garden hose instead of barrels but the risk of a leak leading to a ton of wasted water isn't worth it to me.

You can attach as many gutters as you like, and they all could lead to a single bucket with a single float in it which is self leveling. Then feed that from a water source big enough to meet your watering needs.

Make those air pruning pots hugel style and it can help even out moisture issues.