Well I suppose anything is "possible". It all depends on the quality expectations one has and the time and effort they have available for attention. If one is willing to put in all the effort and expense and end up with leggy, lanky weak stemmed seedlings with compromised circulatory systems and compromised nutrient distribution and then hope they will recover once in the garden, fine. But if the goal is best quality, healthy transplants then no, I'd say it really isn't possible to do.

The reason I say that is because I know from decades of experience that it can be difficult to do even in a commercial greenhouse and that we often have to provide supplemental lighting. As you pointed out neither the # hours nor the intensity of the sun's spectrum is sufficient in the northern hemisphere in early spring when most are starting seeds. Further compromise that exposure by putting window materials in the way and it gets worse. Energy efficient windows are even worse. A simple light meter proves that.

So the choice is up to the grower.

Dave

You have made my day. I was also wondering about a light, but budget and inclination had me wary. Thank you for giving support to those of us who don't have mats/lights for whatever reason.

I start peppers, tomatoes, zucchini and the earliest lettuce and beans in a cool porch. Also brassicas - outside the latter get eaten by snails. No lights and no heat. I place the tomatoes and peppers on the top of the boiler until they germinate and then move them to the porch. I think Campanula will agree that grow lights are not widespread amongst domestic gardeners here.

I've started small numbers of transplants using only window light when I was going to be at home a lot. I start them in a warmer place away from the window and move them to the window as soon as I see any sprouts emerging. They start in an east facing window in the morning and are moved to a west facing window in the afternoon...sometimes they move to a south window midday if I'm going away and can't move them with the sun. I'll also tilt the trays so the sunlight hits the surface more directly. For anything more than one tray all the moving gets old real fast. Even with one tray, lights are less work. Add timers and the lights get easier yet.

So yes, it can be done. But you need the right windows and may need to manage plant placement.

Wintersowing methods work for many without indoor space. I've done very little of it, but the wintersowing forum here at GW has lots of info.

I'm crazy enough to have broadcast some seed outside in early December, winter-sown other varieties outside in translucent jugs in January, planted even more inside under grow lights in February/March, and then finally I'll be direct-sowing some more outside in April and May.

Oh, did I mention I really enjoy growing flowers from seed?

Agree with Dave. It's possible, but it's complicated, highly dependent on your location and building, and not a reliable or consistent method. Especially as far north as Boston where light intensity is low in spring, weather is highly variable, where your season is short enough as it is and spring temps are not nice enough for unheated porches or outdoor sowing of most summer veggie crops.

Think of it as an energy cost. You pay it either way, whether it's in lights setup or fussing over moving plants to keep the light and then still risking leggy starts if you have a week of overcast weather. It can be done, I dare say a lot of people get into gardening that first time without any clue and will get decent plants through sheer beginners luck or what not, but then the second time around their results might be highly disappointing. And if you're not lucky enough to have the perfect window or greenhouse and be able to be around all day to fuss over plants, lights go a long way towards increasing your chances of getting healthy plants to put outside when your season starts.

The UK hardly has blue skies and sunshine year round. But very few home gardeners here have any kind of light setup. Gardening writers even do columns around this time of year on how to raise seeds on windowsills. I still think you are making this sound far too complicated. If a person is just raising a few transplants for themselves a bright windowsill will work. I am not a beginner 'without any clue' relying on 'beginners luck.' I've gardened all my life as did my parents and grandparents. None of us ever had any lights. Until I started frequenting Garden Web I had never had any kind of conversation about grow lights with any fellow home gardener. It's just not on our radar. In fact if I were to talk about them, people might suspect I was going to grow pot. I am sure lights work wonderfully but they are absolutely not a sine qua non for producing healthy transplants. I also think that, like the concept of buying in soil, new gardeners are persuaded that they must have light by marketers when outdoor sowing and a sunny windowsill are absolutely fine for domestic purposes, especially when you are starting out. I wonder how many sets of expensive lights are languishing unused in basements and garages around the country?

Yes, you just have to be patient. They take longer to germinate if at all without a heat mat, or placing in a really warm location. Once germinated they will be leggy (taller than under optimal lighting conditions) if the natural light is not great. They will display their phototropic response growing towards the light source/window, you will need to rotate the tray/pots frequently to keep them growing straight up. You will need to pay close attention to watering as in lower light/heat they tend to not dry out and can develop root rot. You will need to pay close attention to these details. I find lights easier, yet you end up watering more frequently as they dry out faster. This can be more of a PITA than natural light. I did not use lights for years and years. With lights I find it faster, more reliable, and generates bigger leafier healthy plants. But without light is most definitely possible.

I don't think anyone is disputing your success floral - I'm certainly not. But the point is what works for you in your particular environs, with your particular windows, will not work for everyone and the results can be quite inconsistent.

Using lights is easier, faster, and provides more consistent and higher quality results in most situations. If you were to try it I think you would find that to be true but as long as you are happy with the transplants you are currently getting that is all that matters.

Dave

Just in from a few hours on the allotment. One of the jobs was planting out some window grown favas and sweet peas.

I am not going to try lights, Dave. There's no reason for me to do so. I find them unsightly, I don't have the space, I don't want the expense of buying the lamps and using more electricity and I don't have any need. I raise all the plants I want without them. I just wanted to make it clear that the answer to the OP's original question "Starting seeds indoors without grow lights - is it really possible?" is "Yes, it is really possible."

Even though the UK is on the same latitude as Alaska, lights are rarely used in any amateur operation. In fact, my sole experience of requiring lights was in order to grow giant onions (started into growth in late November) while at college. Heated propagators and bench coils are far more common...but still unnecessary in practically all growing methods. The use of lights is garden orthodoxy in the US...so much so, that growing without lights was regarded as revolutionary and given a special name (winter sowing)...as opposed to simply 'sowing' as has been practiced in the UK (and everywhere else) since time immemorial. While control and consistency may indeed be an advantage of growing under artificial conditions..(and the spectrum of lightwaves has a definite effect on vegetative or flowering growth, allowing further control), the downsides, to my mind, far outweigh the convenience of human controlled plant husbandry. Cost, complexity and mostly, the need to continue once a plant has been artificially triggered into growth or germination, is much more of a nuisance than the time-honoured method of sowing seed when ripe and allowing nature to guide the process.

Before I had a greenhouse, I used simple cold-frames and a cardboard box with a reflective foil surface to maximise sunlight. Sowing later removes the likelihood of etiolation...since both heat and light are naturally in sync...and often, seeds sown in May will overtake seeds sown in March/April.

campanula_uk, I so enjoyed reading your note here. What a pleasure to have started this discussion and see it develop like this.

Yes, I grew up in the US garden orthodoxy where grow lights are considered the standard. And of course for millenia most of the world has grown seed -- even in cold areas like mine -- without recourse to these techno-gadgets. So I would be very interested to get a better grasp of how the rest of the world does ornamental gardening. You mention the time-honored method of sowing seed "when ripe." I understand that you're saying that you generally sow seed directly in the garden and not either under grow lights OR a window -- but are you also saying that you typically do it in the fall rather than the spring?

I sow seed when I get it...and that is mostly in autumn, from saved, swapped or collected seed. Some seeds, such as primula, are best sown while still fresh and green - they have not entered dormancy and will germinate easily and quickly...while many umbellifers will only grow from very fresh seed, losing viability in weeks. I sow in 4inch pots rather than direct (although I do sow straight into the soil with hardy annuals and a few perennials if seed is plentiful). I do have to make some effort to protect the seed pots (from blackbirds and mice) but in general, I try to follow a natural sowing method and get the seeds in soil to either stratify over winter or germinate and possibly lose the top-growth until spring (I have gentians doing exactly that...and shrubs such as styrax, schisandra and symplocos). I have never used gibberellins, peroxide, citric acids etc...nor do I stratify in the fridge. OTOH, keeping it simple also means accepting fails...especially tricksy things (like styrax) which go into deep double dormancy and require specific germination triggers. My solution to that is to be as profligate as nature and sow loads (for a typically 70% success rate). The fails are actually a relief, particularly since I invariably fail to consider the huge number of pots, soil and space needed once the pricking out and potting up gets going...although the greatest losses occur over the first summer (I plant in autumn too as I have no access to irrigation).