SEED STARTING WITH SOIL BLOCKS
Starting seedlings indoors is my go-to process for almost everything that I grow in the garden and greenhouse. For the short season here in our high altitude location, this is especially important. It allows a head start on plants that need time to grow, and starting seeds in the warm, protected conditions indoors makes for healthier plants. There are many ways to start seedlings indoors: using soil blocks, divided seed starting trays, peat pots, plugs, newspaper pots, in trays, greenhouse beds, etc. They are usually started in greenhouses, spare rooms or basements under grow lights, on top of warming mats, etc. Everyone has their favorite method, as do I.
I use “SOIL BLOCKS” to start all my seedlings indoors under grow lights. The only seeds I will direct-seed outdoors are peas, carrots & parsnips. Although it is usually recommended to direct-seed beans, beets & corn outside (it is said that they don’t transplant well), but I’ve had great success by starting all of these indoors using this method. The transplant process is easy and good for the plants. With soil blocks there is no need to remove seedlings from small pots or carefully separate them out of seeding trays. My experience with peat pots or newspaper pots are that they work ok, but it still takes time for them to break down for roots to get through, and the soil blocks are much better.
These blocks are not just for getting a head start on the outdoor season. I normally begin all my greenhouse vegetables in the soil blocks also. Although the greenhouse is quite conducive to starting things directly in the beds due to its warmth, the soil blocks not only give the plants a better start, they also allow me to get new plants started while other plants are still filling the beds or allow the soil to rest a bit between plantings. Additionally, since my greenhouse beds are plagued with pill bugs (or roly-polys) which often eat seeds or young seedlings, starting these veggies in soil blocks ensures success.
SOIL BLOCK MAKERS
My soil blocks are made with block makers made by Ladbrooke Soil Blockers. They can be found at several garden supply websites such as GrowOrganic.com or JohnnySeeds.com, along with information about using them. It’s a bit of an investment, but these blockers make great plant starts with a high success rate and the block makers last a long time. I’ve been using mine now since 2009. There are instructions for making your own DIY block makers found on several sites on the internet, but I think the Ladbrooke block makers are well worth the investment.
The soil block makers come in three sizes. The most commonly used is the 2″ mini block. There is also the 4″ maxi, which is made with a hole just the right size to fit the mini block into it after the seedling has grown a bit. The 3/4″ micro size is intended for starting a larger inventory of small seeds with less soil material. I experimented quite a bit with the micro size, but rarely use it anymore. See below.
It’s helpful to read the booklet, “Transplants in Soil Blocks” by David Tresemer. He did a lot of research using this method, and explains which seeds can be started in soil blocks, as well as how many seeds can be planted in each block (for multiplanting), etc.
SOIL USED IN SOIL BLOCKS
Making the blocks takes a little practice and some trial and error, but after a little practice, it’s “as easy as pie” — mud pie, that is. It is important to use a mix that will encourage growth and hold together well. I’ve read about people having difficulty with soil blocks after trying to use purchased potting soil or soil from their gardens, so it’s important to start with a good mix. There are a few soil block recipes available on the internet, including a popular one used by Eliot Coleman, and a few companies will sell a pre-made mix for a price. I use a recipe very similar to Eliot Coleman’s which uses peat moss, perlite, compost, some garden soil, and some various minerals and nutrients. The soil block mix recipe I use can be found here.
2″ MINI BLOCKS
These 2″ blocks, the “mini” blocks, are now what I use exclusively rather than starting with the smaller micro blocks. I simply start the seeds directly in these to transplant later either directly to the garden or to the “maxi” blocks shown below. To start directly in the mini blocks, there are interchangeable pins for these block makers to make different size indentations for the seeds. The photo at the left shows the mini blocks with the micro block placed it its cubed-shaped indention. Normally I use a smaller pin than the cube-size shown here to start seeds directly in the mini blocks. The micro-to-mini block instructions are here fyi.
After the seeds sprout in the micro blocks and appear to be established, they can easily be transferred to blocks slightly larger, where the roots will have more room to grow. This shows the micro blocks placed into the mini blocks. After seeds have begun to grow, they are transplanted into 2″ MINI blocks, The 2″ mini blocks can be made with a cube-shaped hole in the middle just the right size to fit the ¾” micros. The photo here shows how nicely they fit. This gives the seedlings a chance to grow more before being transplanted either outdoors or into MAXI blocks for further growth indoors.
Larger seeds, or seeds that grow very quickly, such as tomatoes, peppers, beets, squash, and even corn & beans can be started directly in the 2″ mini block, which can be made with a ½” or 1″ dimple in which to place the seeds. With this method I even start my corn and beans in blocks, although most garden resources indicate they should not be started indoors and that they don’t transplant well. In our short growing season it gives them a nice head start, and when transplanted outside I have nice, even rows of things that have all germinated–no empty spaces from sprouting failures. I also use aluminum cake pans for these, with 20 blocks per tray, loosely covered with the plastic lids that come with the trays, until seedlings are too large for the lid. Many seedlings can stay in this size block until being planted in the garden, others may need to be transplanted again, into larger blocks.
After plants begin to outgrow the 2” mini blocks but need to remain indoors for more growth, they can be transplanted into the 4″ maxi block until they are ready to be transplanted outside. These blocks are made with a 2″ cube indentation, just about the right size to fit the 2″ blocks.
I feel that the cube indentation is a bit short for many of the seedlings, such as tomatoes, which can be buried more deeply up the stem. To make more space I will dig about 1/4-1/2″ of the soil out with a kitchen fork from the bottom of each block’s indentation. After putting the smaller block into the larger, I add some soil at the top and bury the stem just a little more.
Update: For some time I started many seedlings in these “micro” blocks shown here, but over time I’ve abandoned this method mostly because I am growing fewer things at a time and find it just as easy to start directly in the “mini” blocks. I’m leaving my thoughts about the micro blocks here FYI.
Germination can start for many of the smaller size seeds (flowers, herbs, etc.) in the 3/4″ MICRO blocks shown here. This gives them a chance to start in a cozy, warm, small space, with very little soil. The Ladbrooke blocker to make these makes 20 small blocks at a time. I put them in these inexpensive cake pans, or other plastic containers saved from frozen meals. The seeds start more quickly in these small blocks and nutrient-rich soil than they would outside. One benefit of starting seeds this way is that when seeds don’t sprout, you haven’t wasted much space or material. It’s important to keep these small seeds & seedlings moist, but not too wet while in these blocks. I usually keep a sprayer handy and spray them a couple of times a day, with some extra water in the tray for bottom watering. Until the seedlings emerge, I keep a lid on loosely, and keep the trays on TOP of my grow lights, to allow for bottom warmth. Once they emerge, they go under the lights, which are kept about 2” above the seedlings. If they do get too dry, not to worry, they’ll usually perk up just fine after some water is applied.
SOIL BLOCKS GROW WELL UNDER LIGHTS OR IN A SUNNY WINDOW
The seedlings grow fast under lights. See how healthy they are after being started and transplanted to the maxi blocks under lights! These tomatoes (2013) were started at 8 weeks before the last frost, and were ready to go outside, but the outside wasn’t quite ready for them. They got a bit taller than I’d like prior to planting out. They don’t really gain much by being started too soon before going outside. I believe 6-7 weeks is plenty of time for tomatoes to get a good start, and if the weather should be too nasty for them to be planted out, another week inside won’t cause any harm. See how nice and leafy these plants are?
Many plants started indoors or in greenhouses in small pots get too tall and leggy. At the right is a photo of my first year’s tomato plants, before I began to use the soil blocks. They required staking in these pots to keep them upright, and although they survived outdoors after transplant, it would have been better to send them out as a shorter, stockier plant. A good way to keep them from getting too tall indoors is to keep the lights just a couple of inches above the top of the plants. It’s also helpful to put a fan on them a portion of each day, or to wiggle them with your hands a bit, to strengthen the stems. This is particularly helpful if your location is windy—they need to get ready to withstand that wind outside!
Below is a photo of one of my tomatoes in its maxi block, just prior to planting. It is not too tall, it’s a nice dark green, and it should grow well after being planted outside.
KEEPING TRACK OF SEEDLINGS IN BLOCKS
When using these micro and mini blocks it can be difficult to know which blocks are which seeds! There is no container to mark on the side, and no room for a name-stake. The aluminum cake pans I use as shown here will hold 20 mini-blocks, or 120 micro-blocks. I have made up sheets I can use to pencil in the seeds I have planted, shown at the left. Each sheet shows 3 trays of seeds. I mark the side of each tray with the date and tray # so I know which side is up. I’ve also made up some similar sheets for the 10×20″ trays I sometimes use, which will hold 50 mini blocks.