The first ripe tomato is a competitive sport
Nobody admits this out loud, but every vege gardener in New Zealand is quietly racing the neighbours. The first cherry tomato of the season is worth more than the last twenty kilos of them, and it is won or lost in August, on a windowsill, long before anything goes in the ground.
Soil blocking is how you win it. Not because it is fashionable, but because a seedling that has never had its roots torn does not stop and sulk for a fortnight after planting. It just keeps going.
If you want the full theory, the compost recipe and the step by step of pressing a block, our quick guide to soil blocking for cut flowers has all of it and applies exactly the same way to vegetables. This guide is the vege specific part: what to block, what to leave alone, and which size to use.
What to block, and what to sow straight in the ground
This is the bit most guides skip, and it is the bit that saves you the most disappointment.
Block these. Anything that transplants happily and benefits from a head start indoors. Tomatoes, chillies, capsicums and eggplants. The whole brassica family: broccoli, cauliflower, cabbage, kale, brussels sprouts. Lettuce, silverbeet and spinach. Leeks, spring onions and celery. Basil, parsley, coriander and most soft herbs.
These are the crops where six weeks of indoor warmth in August turns into a plant that is fruiting while your neighbour's is still deciding.
Sow these straight where they are to grow. Carrots, parsnips, radishes, swedes and beetroot. Every one of these puts down a taproot almost immediately, and a taproot that gets bent, broken or checked early gives you a forked, stumpy or generally disappointing root at harvest. No amount of careful handling fixes it. Sow them in the ground, thin them, and move on.
Peas and beans are usually direct sown too. They germinate fast and grow vigorously enough that they do not need the head start. The exception is if birds or slugs eat your peas the moment they emerge, in which case blocking a tray and planting out at ten centimetres tall is a perfectly reasonable act of self defence.
The ones that go either way. Cucumbers, courgettes, pumpkins and melons are vigorous enough to direct sow once the soil is warm, and plenty of growers do exactly that. But they also famously resent root disturbance, which is why the usual advice is to start them in something biodegradable if you start them inside at all. A soil block is that something. There is no pot, so there is nothing to disturb. If you want cucumbers earlier than the calendar strictly allows, this is how you do it without paying for it later.
Which block for which crop
The range works as a ladder, and most vege growers only need the first two rungs.
Micro 20, twenty 2cm blocks. Where the season starts. Twenty tiny cubes at a time, which is the right scale for a windowsill rather than a bench. Perfect for tomatoes, chillies, capsicums, brassicas, lettuce and herbs. Small seed goes in here.
Mini 4, four 5cm blocks. The workhorse. It makes four blocks at a time and comes with seed pins as standard, which give you the small indentation to drop a seed into. Sow larger seed straight into these, or use them as the next size up for your Micro 20 seedlings.
The bit that makes the system click. Fit the Cube Inserts to the Mini 4 and instead of a seed indentation it presses a square recess, exactly sized to take a Micro 20 block. Your seedling moves up a size without you ever touching it. No pricking out, no fingers, no snapped root. Worth knowing before you order: the cube inserts fit the Mini 4 and not the Mini 5.
Dowel pins are the other Mini 4 accessory, and they make a deeper, wider hole for larger seed. Useful for cucurbits and beans if you are blocking them.
Maxi 1, one 10cm block. The heavyweight, and honestly more than most home gardeners need. It has a square indentation sized to receive a whole Mini 4 block, so it is the third rung of the ladder for tomatoes you intend to grow enormous, or for anything that has to wait out a cold snap before it can go outside.
The timing, for a New Zealand spring
Tomatoes want to go in six to eight weeks before your last frost, which for most of the country means sowing from late August into early October. Planting out is late October to mid November once the frosts have genuinely finished, and it is roughly eighty to ninety days from transplant to your first ripe fruit.
Do that arithmetic and you can see where the race is won. Sow in early August and plant out in early October, and you are picking a few days either side of Christmas. Wait for Labour Weekend like most of the country and you are eating them in February.
Brassicas and leafy greens are more forgiving and can be sown in blocks from now through spring. Basil is the fussy one: it hates cold, so keep it genuinely warm indoors and do not rush it outside.
Moving up without touching a root
When a Micro 20 seedling has its first pair of true leaves and you can see roots at the edge of the block, it is ready to move up. Press a set of Mini 4 blocks with the cube inserts fitted, drop the small block into the recess, firm it gently, water it in. That is the whole operation, and it takes about four seconds a plant.
A seedling widger is the tool for lifting the small blocks. It is a slim stainless steel scoop that gets underneath without your fingers ever touching the roots. A soil scoop moves the mix into the blocker without half of it on the floor, which is also how you get children usefully involved rather than decoratively involved.
Label as you go. Every gardener believes they will remember which row is Black Krim and which is Sungold. No gardener remembers.
Getting them outside
Blocks dry out faster than pots because there is more surface exposed to the air, so water from below. Sit the tray in a shallow bath of water and let the blocks drink, rather than pouring over the top and eroding them.
Harden off over a week or so: a few hours outside in a sheltered spot, building up. This is where a cloche or tunnel earns its keep, because it lets you get seedlings out of the house a fortnight or three weeks earlier than bare ground would allow, which is exactly the margin that decides whether you are picking in December or February.
The three things that go wrong
Mix that is too dry. A soil block needs mix wet enough to hold together like a wrung out sponge. Too dry and the block crumbles as it comes out of the blocker. This is the single most common reason people give up on soil blocking in the first ten minutes, and it is entirely fixable with more water.
Watering from above. It erodes the blocks and they slump. Bottom water.
Blocking things you should have direct sown. Carrots in a soil block will still germinate. They will just be disappointing in March, and you will have forgotten why.
The kit
- Soil Blocker Micro 20, twenty 2cm blocks, $98.50
- Soil Blocker Mini 4, four 5cm blocks, seed pins included, $108.50
- Cube Insert 4 pack, $19.00
- Dowel Pin Insert 4 pack, $15.00
- Soil Blocker Maxi 1, one 10cm block, $248.00
- Seedling Widger, $19.90
- Soil Scoop set of three, $21.50
- Plant Labels, $20.93
Or start with the whole lot in the Seed Raising & Potting collection.
Buy once. Buy well.
