Sunday, January 27, 2013

Seed starting the Living Low way, part 3

In the first two parts of my series on seed starting, I discussed creating a good environment for starting seeds and purchasing or preparing a good medium for seed-starting. In this, the last part of the series, I’ll discuss containers in which to hold the seeds and growing media and the trays that will keep leaking water from damaging anything. As before, I will stress using what you already have or can make or scrounge for free, and also consider what is best for the scale you are working at (anywhere from raising a few tomato plants up to raising a thousand or so seedlings, scales that I have experience with). Finally, I will briefly consider other aspects of seed starting in which my experience is different from conventional seed starting advice and tell you why I do things differently so you can decide what to do in your own situation.

I’m not going to get into the details of sowing seeds since those have been well treated elsewhere. The best single book on seed-starting, one I recommend to anyone who intends to start at least a few seeds every year, is Nancy Bubel’s The New Seed Starters Handbook. For an online guide to seed-starting, see here.

Let’s suppose you are just beginning to grow from seeds and plan to grow something along the lines of a few tomato or lettuce seedlings. You’ll have to purchase the seed packet (unless someone you trust gives you a few seeds), and if you don’t have any compost or want to avoid “weed” seedling confusion you’ll need to purchase a small amount of a seed-starting mix. But you won’t have to purchase anything else as long as you have on hand or can scrounge a smallish plastic garden pot or similar sized plastic container. If you save plastic containers such as those that, say, onion dip or ricotta cheese or margarine or any number of other processed foods come in, you have excellent containers in which to start and grow on seeds. Any container with a depth of around 2 to 3 inches will work for starting seeds (it needs to be this deep to accommodate the seedling’s root system). I rummaged through our kitchen cabinets and found three such containers of a size to hold about 16 ounces of food. Each is a bit more than 2 inches deep and a little over 4 inches in diameter. Imagine them sectioned into quarters, as if you were dividing them into pie slices, with a seedling growing in about the middle of each section. You could grow four seedlings to transplant size in one container like this. Or you could use a container like this to start a larger number of seeds, later removing each seedling and replanting it into its own container to grow on to transplant size. Gardeners call the removing and replanting pricking out; you can use a repurposed chopstick to carefully tease out each individual seedling (a table knife would also work). You can avoid the pricking out operation by sowing a few seeds into the middle of each of the four quarters of the containers of my example, then thinning to one seedling per quarter and growing the remaining seedlings to transplant size. To remove them, use a knife to section out the quarters of mix and remove each quarter with its seedling; plant the seedling with its quarter of mix clinging to its roots. If you have 8 ounce plastic containers like those used for yogurt, you could plant three to four seeds in each, cut out the weaker seedlings after each seedling has at least 4 leaves, and grow the remaining seedling to transplant size. This size container would grow a fine tomato seedling as well as something like lettuce that has a less-extensive root system.

If you have a gardening hobby and have a collection of various sizes of pots as a result, you can use those pots to start or grow seedlings. You can start a number of seeds in a larger, say 6 inch pot, and prick each out into a 2 to 4 inch pot to grow on to transplant size depending on the size of the seedling when it is transplanted, or start a few seeds in enough of the smaller parts and thin to one seedling per pot. As a general rule, things planted in cool spring weather, like lettuce and cabbage, are usually grown to smaller sizes than tomatoes and others that are planted after the last frost. Smaller-sized plants need less root room and can be grown in smaller pots. You can use terra-cotta or ceramic pots as well as plastic pots; just be aware that the mix in a small terra-cotta pot can dry out rapidly in your heated living quarters or on a warm sunny day on a glassed-in porch.

If you don’t have any of these sorts of things on hand, check with folks you know for extra garden pots or processed food container or save the right size of processed food containers when you purchase such foods. If you live someplace where trash is put out on the curb or in dumpsters in the alleys, check for these in the discards, or ask someone you know who lives in an area with alley dumpsters to look for you. You might think that recycling centers would be a good place to scrounge this sort of thing, but at least around here, you’d be wrong; materials in recycling centers are considered the property of the recycler.

If you are repurposing a processed food container, you need to poke drainage holes in it so the mix doesn’t get waterlogged. Poking four holes in the side a quarter to half inch up from the bottom, using a knife or scissors blade, should be sufficient for the size containers mentioned. It’s best to poke holes in the sides rather than the bottom; holes on the bottom that are in direct contact with whatever is holding leaking water often will not allow proper drainage through them.

Unless water leaking out from your containers or pots won’t damage whatever they are sitting on, you’ll need to put them on a non-leaking tray. The pot trays you can buy at garden centers will work, but almost certainly you have something on hand that will work just as well. Pie plates are about the same size and shape as pot trays; you could use the thin aluminum pie plates from commercially-purchased pies as long as you didn’t poke any holes in them while getting the pie out, or if you bake your own pies, you can use glass or metal pie plates you have on hand. Anyone who bakes has a collection of different sized containers (8x8 and 9x13 inches are common sizes); as long as these don’t leak, you can put your seed-starting containers inside them. Similar sized containers you may have on hand for leftovers would work just as well as long as they don’t leak. If you are raising a number of seedings on a tray table in front of a window and you have a cookie sheet with raised sides, put the cookie sheet on the table and your seed starting containers on the cookie sheet. (You could as well put the cookie sheet on your glassed-in porch or under a fluorescent light fixture.)

If you are growing more than one variety of plant, you will need some way to label containers so you know what is in them. Garden centers have materials you can use to make labels. Homemade versions could be writing the variety name on the side of a processed food container with a waterproof marker, cutting similar plastic containers into the size you want and labeling them with the variety name, repurposing a popsicle stick or making a wooden stick from scrap wood and labeling them, or in my case, repurposing the metal slats from discarded venetian blinds (plastic blind slats would work as well) and labeling these. In the last three cases you’ll put the marker next to the seeds of that variety if you have more than one kind of seed in the container. Use a pair of strong scissors or tin snips to cut blinds into smaller pieces. I use a special marking pen that can withstand sunlight because I re-use many of the labels from year to year, so I want the name to be legible for years. You can use an ordinary waterproof marking pen, but the writing will fade over a period of weeks or months when exposed to sunlight. That may not be an issue if you are writing on wood or plastic that itself rots after a period of time. If you want something more permanent and you can scrounge metal or plastic blind slats, a non-fading pen is best to use. Be sure to cap it tightly after each use! A china pen might also make a long-lasting mark; if you have one, try it and see.

If you get to the point where you are starting several tens to a few thousand seedlings of many different types of plants, cell packs and other specialized seed starting equipment will begin to look attractive to you. It’s a lot easier to handle one tray with 36 plants or a single wooden flat with 300 or so onion seedlings than multiple containers with smaller numbers of plants. You could buy these new, but you may be able to scrounge or make some or all of what you need. The four or six packs that garden centers sell seedlings in can be re-used for many years if you take care to not rip them when you remove the plants and you store them under cover when you are not growing plants in them. Even ones with a rip or three from previous rough handling can generally be reused for a few to several years, until the rips get so large that the individual cells no longer hold the seed starting mix. I started with the equivalent of a few hundred seedlings’ worth of different sizes of four and six packs and various sizes of trays to hold them, all scrounged by me or gardening friends who already had enough. I still have about half of the packs, and all of the trays, after several years of re-use and keeping them inside when they don’t have plants in them, some of them with rips they have always had. You probably know someone who buys and plants annuals that are sold in these packs; ask them to save the packs and trays for you if they don’t need them. Those of you who live where there are alley dumpsters should be able to find them in or around the dumpsters during prime annual-planting months (April and May around here). Until I started to collect these, I didn’t realize that six and four packs come in many different sizes, as do the trays that hold them. You may need to mix and match packs and trays that you scrounge.

Now that some of my scrounged packs have deteriorated so much I cannot use them, I have purchased a few sheets of six packs from Fedco as replacements. These should last much longer than the scrounged packs because I am very careful not to rip them and I keep them in the basement until they are pressed into service and upon removal of all plants.

Because the plastic the packs and trays are made from is processed out of oil, I think it’s imperative to take the best care possible of them and to re-use them as many years as you can. They may seem as if they are cheap and disposable, but in actuality they come at a high cost. Use them in a way that respects that cost.

At the several tens to a few hundred seedlings scale, you may find it easiest to start and grow all of your plants in a motley collection of packs in trays. You can start a few seeds to each cell of the pack, thin to 1 seedling per cell, and put markers in individual cells or packs as needed to distinguish plants from one another. You’ll want to check each tray to see if it has drainage holes or not. Trays come both ways. If you put the trays on top of something that will be damaged by leaking water, be sure that the trays do not have drainage holes. If they do, you’ll have to put the trays on top of something larger that won’t leak. A large cookie sheet might do.

If you are starting several hundred to a few thousand seedlings, as I now do, you will probably want to start the seedlings in flats (boxes in which you start rows of seedlings, like a miniature raised-bed garden; the photo at the top shows one of mine from last February). You may want to start one or more flats with all of the seeds that need cooler temperatures to germinate and grow, and one or more flats with all the seeds that need warm temperatures to germinate and grow. Then you can put the flats in different places that match the environment each seed needs to grow well. As seedlings become crowded in the flat, you can prick them out into individual cells of a pack and keep the packs in trays, moving the trays as needed so the seedlings grow in the right conditions. This is what I do now. I start the flats on the glassed-in porch during winter or early spring. The flats with cool weather seeds like lettuces and cabbage family plants get put on the floor where it is cooler. The flats with tomato, pepper, eggplant, and other seeds needing warmer conditions for germination are put on the heat mat and the heat mat is turned on for the two or three weeks that it takes for all the seeds that will germinate into healthy seedlings to do so. As I prick out plants into cell packs I put the cell packs in their trays into the cold frame, or keep them on the porch if it is too cold in the cold frame. Seedlings that grow too large for the cell packs get potted-on into individual 2 or 3 inch pots. I prick out a few more of each kind of plant than I need in case some of the plants die before it is time to transplant them to the garden; the remainder of the seedlings get eaten if they are edible in that state or composted. Onion and leek seedlings stay in the flat until they are large enough to plant directly into the garden. This system is economical of space and of the various components and it allows me to care for many seedlings easily.

If you want to use wooden flats like the ones in the photo to start seedlings in, as always, you can buy them or make them yourself. The flats you can purchase from Bountiful Gardens are made from repurposed redwood and should last for many years. I have one and like it. Since then Mike has made five more of the half size flat out of scrap wood, and I now start most of my seeds in these flats plus a few smaller wooden and heavy paper flats I purchased some years back. I suggest using the half size flat, about 11x14x3 inches, as larger flats will be very heavy when full of mix and plants. You can make flats from any solid, untreated scrap wood you have lying around. As long as you remove the soil and dry the flat when all the plants have been removed and store it in a dry place, scrap wood flats should last a long time. You need to have a little space between the bottom boards to allow water to drain out of the flat; about 1/4 inch of space is sufficient. Before you put seed starting mix in the flat, line it with paper you would otherwise recycle to keep the mix from falling out the bottom. The paper doesn’t prevent drainage and it will slowly rot away as the seedlings grow. To sow seeds into a flat, you can put a sheet of 1 inch chicken wire on top of the flat and use the wooden end of an unsharpened pencil to make a shallow hole in the mix at the center of each hole in the wire, then remove the chicken wire and plant seeds into the holes, labeling each row as needed. Or use the edge of a thin board to make a shallow depression in the soil of a filled flat and sow your seeds into the depression, again labeling each row as needed with the seeds in the row.

Many seed starting directions say you should cover the container with plastic after you sow the seeds, then remove the plastic once you see tiny plants emerging. I don’t cover the containers, however, except for those on the heat mat. The very humid conditions on the surface of the mix in covered containers will encourage molds or diseases that can kill seedlings. The only reason I cover the flats on the heat mat is because the added heat dries them out faster, but this year I am planning to try growing them uncovered and monitoring the moisture level more closely as I sometimes have trouble with seedlings in these flats dying from disease. Most seeds should be planted with something like 1/8 inch of mix over them to keep them moist (and dark if needed). Some seeds, mostly the very small ones and often those in the aster family (lettuces) and the mint family (basil), germinate better in sunlight. These should be covered, if at all, with the thinnest layer of mix you can manage. Check with the seed retailer or garden books like the one I linked to above for more information on the needs of the seeds you want to grow.

As for watering, you want the mix to be moist but not soaking wet. Using a watering can to water your carefully planted containers risks dislodging the seeds, a serious problem if you have planted multiple kinds of seeds in a single container and depend on their staying where you put them to know what they are. It’s much better to water your containers from the bottom. Just put them in a larger, water-holding container (a stoppered sink is convenient) and add water carefully, avoiding getting it into the container with the seeds, till the water level is just below the top of the mix. You may need to hold down the container with the seeds while you add water as dry mix will be less dense than water so the container will float. Once the mix has absorbed enough water so that the top surface of the mix is moist, remove the container and let it drain in a safe place; in a sink you can remove the stopper and let the container drain. After the seedlings appear and grow a couple of leaves, they will be well enough rooted that you can water from the top with a watering can if you prefer. The bigger the seedlings grow, the more often you’ll need to water.

Finally, many garden books and sites say that if you are re-using containers from year to year, you should soak them in a mild bleach solution to kill “germs” that might harm your seedlings. I never do this. Chlorine bleach is very energy-intensive to prepare and ship, and the gaseous chlorine from which it is made is extremely hazardous. If you are worried about carrying over “germs” on the containers, try washing them in soap and water and letting them dry in sunlight. I don’t even do that much, however, and I don’t have excessive problems with seedlings dying. Generally I sow enough extra seeds to make up for any seedlings that die. The best prevention for “germs” and disease is not to over-water the containers and not to cover them.

This completes my series on starting seeds. Happy growing!


  1. i have had occasional problems with what seems to be damping off of young seedlings. i assume that is from using non-sterile garden soil in the mix. short of cooking the garden soil, which i think would kill "critters" i want to have in the soil, have you a suggestion? i do cover the seedlings on mats. as soon as they have real leaves they graduate to unheated, open containers. any ideas?

    1. I always have a few seedlings that damp off. I don't think it is necessarily because of non-sterile garden soil in the mix because I had problems with it when I used the purchased soil-less mixes which should be sterile. The damping off organism can carry over from mix left on the sides of containers on on garden tools; this is why most garden writers suggest sterilizing re-used containers and tools in a weak bleach solution. But I suspect the damping off organism can infect the soil mix after it's prepared and sowed even if it wasn't present to start, perhaps through air currents that carry it onto the surface of the mix.

      I don't think sterilizing your garden soil by heating it in the oven as is sometimes suggested in gardening publications is the best solution - it's energy intensive, kills off the good critters as well as the bad, and from what I have heard it stinks up your living quarters as well. You could try a small scientific experiment: take two containers and treat them identically except that you heat the soil mix that goes in one but you don't heat the mix that goes in the other. Then see if you notice a difference in damping off between the two containers. I haven't tried the experiment myself.

      What you are already doing (getting your seedlings into unheated, open containers ASAP) and which I do as well is a better solution because it reduces the dampness that seems to be one of the necessary conditions for infection. You could try washing the containers and garden tools with soap and water and then drying them off in sunlight before you use them. Bright sunlight is a mild germicidal and might lessen the degree of infection even if it doesn't prevent it. If you are not already sowing a few extra seeds to account for any that might damp off, I suggest doing that. I sometimes have to re-sow certain seeds in a different container if damping-off is bad enough (a good reason to begin a batch of seeds as early as is reasonable, so you have a window of time to re-sow if needed).

      Finally, Organic Gardening magazine has suggested that compost added to seed-starting mix helps to populate the mix with beneficial organisms that can reduce problems with disease. Maybe cover your seeds with a thin layer of straight compost rather than soil, what I have been doing recently, and see if that helps. I'm not certain it does however.