You know you'll have to make your own blocking mix in order for your blocks to be perfect and professional. You know your main ingredient is peat moss. Your next ingredient is the water absorbing, retaining and aerating medium known as the fluff or the fill. It puffs up the peat which will be saturated with water. Yet peat would dry out too fast if it wasn't for the fluff. Typically, this material has been known as perlite. And, just as peat moss was the only way to make blocks until coco peat came along, perlite was the only way to hydrate and aerate your blocks. Not so anymore. There are now two more exciting mediums to consider, if you have access to them. The first is pumice stone. By far the cheapest ingredient to add to your soil block mix if you can get it local. Pumice stone can absorb and release anywhere from 45-65% of water back to the plant roots. Perlite can absorb and release only 35% of available water, still too low to prevent drying out in case you skip watering for a few days. But with pumice, you have less to worry about, and it is not dusty and irritating to the lungs, which is one drawback to perlite when mixing your own. Pumice is common out in the west, I get it 25 miles away at 50.00 bucks a ton! Cheap! You may have to screen it down to 1/4" before mixing, as it might plug up your blocker. Pumice is the best replacement for perlite when budget is a concern.
The next ingredient of monumental importance to our potting soil industry is diatomite rock. A mined substance from ancient sea bed dwelling creatures, diatomite rock is diatomateous earth before it is pulverized. The new king in organic water retention, it has the ability to hold 150% of it's own weight in water and slowly release it back for absorption by the plant roots. Not only that, it is less dusty and contains numerous micro minerals and nutrients. It is also very colorful in all shades of pastels. Makes a very pretty potting soil! It is a little more expensive than perlite, but well worth the cost, if you forget to water in the heat of the summer. It will not dry out for many days, whereas perlite would be spent of its water and the plant will be dead. Diatomite rock is as lightweight as perlite, too, yet breaks down in your garden soil even more slowly, releasing valuable trace minerals.
And, of course, those seeking a fool proof addition to the blocking mix and any of the three aerators mentioned, Zeba Quench will be mentioned again and again by myself and other commercial farmers. Zeba Quench is an all natural, starch-based biodegradable super absorbent soil amendment that improves soil moisture retention and water supply to plants. It can deliver up to 400%! of its weight in water back to the plant. And, Zeba Quench releases 95% of its stored water to the roots when they need it most. Not only can it do all that, it can do it over and over for hundreds of times hydrating and re hydrating the plant roots all year long. Decreases your watering by 50%, which is a lot of time spent frolicking somewhere else in the summer, not slaving over transplants. It is the ideal soil block amendment, and it comes recommended for no other reason than the assurance factor of having reliable transplants in all seasons.
Many people are reluctant to buy Zeba as an added expense to what should be a virtually free act of gardening: starting and transplanting seedlings in soil blocks. I understand. But, Zeba is most helpful for beginners, busy careers, moms and busy housewives, and professionals in the nursery business. Why? Because if your not always right there tending your soil blocks, they will soon out grow everything around them and be searching for more water, not more space. In a moment's notice, the hot summer sun could kill thousands or even just one precious transplant. If you know you can't be there all the time to monitor soil block growth, which, literally grows before your eyes, than hire someone that will. That help, my friend, is Zeba Quench.
But remember, you can always skip soil blocking and keep your plants in a stunted state of existence called: Plastic pots!
Good day and welcome to spring, the Potting Block Guru is here to dispel the darkness of winter blues! Stay tuned, onions are coming up!