what are the trade-offs between soil blocks and air-pruning trays?

Question

In the past, I've tried peat pots, the puff-up peat tablets, the cheap flimsy trays for doing starts.

Peat pots don't really let the roots through. The tablet things are a recurring cost (so are the peat pots, but I made the mistake of buying a big case of them)

I want to invest in something that will last.

I see a couple of options:

1. Block makers. I like the idea of easy step-ups.
2. Air pruning trays.
3. Rootmaker, speedling, star shaped (no brand)
4. I'm trying hydroponic pots. They work OK if I cut out the solid circle on the bottom, and enables me to push the seedling out.

What are the trade-offs? The block makers have good reviews in other questions, but I haven't seen much mention of the fancier, air-pruning, trays.

Answer 1

I have used soil blocks for starting transplants since the late 80s. For me, they are close to ideal for the following reasons:

• It is "green" because except for what is used in the manufacturing of the soil block tool, there are no plastic or disposable parts involved.
• I can set up an automatic wicked watering system simply by setting the new blocks on a wicking mat, so they can water themselves for the most part
• There are gaps between the soil blocks which allow for natural root pruning of the seedling growing in it
• I can make and use my own soil block mix, which cuts down on the cost.
• The plant's roots can go directly from growing in the soil block to growing directly in the soil without any of the barriers found in peat pots or pellets. No matter what the manufacturer says, the nets and the pots do not simply disappear into the garden soil in one season and will restrict plant growth in most gardens
• My whole seed starting setup can be easily nested and stored for the next season, without having to find room for tons of small pots and easily broken plastic seed starting trays and pots.

Disadvantages of soil blocks include:

• The soil blocks need to be properly packed into the tool when being created, and that takes a bit of practice to learn to do well
• The blocks can be a bit fragile at first, but within a couple of weeks or so will strengthen up to where you can lift them and move them around without any major catastrophes occurring
• Seed blocks may dry out a bit faster than seedlings in plastic pots, because the air flow is greater on all sides - this is why watering from the bottom and using a wicking mat is a good idea

The root pruning plastic seed starting cells have many of the same advantages as the soil blocks, except they will require storage in between seasons, are subject to tears and cracks if not handled very gently and stored in a protected way, and involve an ongoing use of plastic as they age and need replacement. This means that they will eventually be a more expensive and less "sustainable" option than soil blocks. (As an example, my first soil block maker tool - bought in the 80s - is still going strong.) They may require a bit less watering, because only the tops and bottoms are open, but they will still require more attention than a traditional plastic seedling pot setup.

Answer 2

I recently (within the last year) started using soil blocks for all of my seed starting and I agree that they are a little finicky and take some practice to use. The trade off, which is huge IMO, is that they are a one-time cost (other than the soil) and that my seedlings have never done as well as they do in the soil blocks now! They are robust, healthy, and when planted out, grow super fast.

Answer 3

I used soil blockers for fifteen years in a small commercial greenhouse operation. We did between 3,000 and 5,000 starts a year.

I started off with the hand blockers, and eventually got the big foot-operated one that made three times as many blocks. They are really worth it for production.

To me, nothing beats soil blockers. Yes, you can buy a lot of pots and trays and other single-use things for the price of one blocker, but once you have a blocker, there are no other costs.

The micro-blockers are plastic and crappy. The rest of them are metal, and stood up very well to hard use, often by untrained volunteers.

Their ability to air-prune is fantastic, especially for fiddly starts like cucurbits, which don't do well if they become root-bound.

I only wish the micro-blockers were more durable. Certain tiny seeds did very well with them, but the tools kept coming apart.

On all of these, you have to pay more attention to watering than you do with pots. But it's worth it, in my opinion!

For commercial sales, we potted up from blocks to re-used pots. Our retailers did not like selling the blocks at all! But in the market, we regularly sold the blocks to customers, because we could talk to them and educate them about the process.