This month we’re talking a lot about seed starting and we can’t talk about starting seeds without talking about heat and light. Seeds sprout more quickly and efficiently when they’ve got the correct soil temperatures and the easiest way to do this is with a seedling heat mat. It’s not a requirement, though, so we’ll also talk about some ways you can up the ante on the soil temperatures during seed starting without a heat mat.
Once those seeds do sprout and you're nurturing those little seedlings the correct light can make all the difference, and usually even the sunniest window in your house just isn’t going to cut it. That means we need do a little investing in some lights to help our seedlings along. Today on Just Grow Something we'll explore soil heating options and various types of grow lights, including the most economical and even tabletop solutions. Let’s dig in!
*Question of the Month: “What is your most successful crop and why?” This could be a specific variety of something that outproduces all the others, the plant that you love the most, or the crop that grows fantastically well for you without fail every single year. Whatever you consider your most successful crop in whatever way you consider it successful. Send me an email, post it in the Facebook group or send me a DM on Facebook, Instagram, or TikTok… you have until February 29th to get me your answer!
References and Resources:
Full Spectrum LED mini grow light
48" x 20" (four tray) Waterproof Durable Seedling Heat Mat
10” x 20.75” (single tray) Waterproof Seedling Heat Mat
Best Grow Lights for Growing Vegetables Indoors.
Guide to Choosing a Grow Light - Johnny's Selected Seeds.
5 Different Fluorescent Tube Sizes and How to Choose One (thespruce.com)
Just Grow Something Merch Shop
Order from True Leaf Market and support the show!
Just Grow Something Gardening Friends Facebook Group
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This is positively farming media this month.
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We're talking a lot about seed starting, and we can't talk
00:00:08
about starting seeds without talking about heat and light.
00:00:11
Seeds sprout more quickly and efficiently when they've got the
00:00:15
correct soil temperatures, and the easiest way to do this is
00:00:18
with a seedling heat mat. It's not a requirement, though,
00:00:22
so we'll also talk about some ways that you can up the ante on
00:00:25
the soil temperatures during seed starting without a heat
00:00:28
mat. Once those seeds do sprout and
00:00:31
you're nurturing those little seedlings, the correct light can
00:00:35
make all the difference, and usually even the sunniest window
00:00:38
in your house just isn't going to cut it.
00:00:41
That means we need to do a little investing in some lights
00:00:44
to help our seedlings along. Today on Just Grow Something,
00:00:47
we'll explore soil heating options and various types of
00:00:50
grow lights, including the most economical and even tabletop
00:00:54
solutions. Let's dig in.
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Hey, I'm Karen. I started gardening in a small
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corner of my suburban backyard and now 18 years later I've got
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a degree in horticulture and operate a 40 acre market farm.
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I believe there is power in food and that everyone should know
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how to grow at least a. Little bit.
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Of their own on this podcast I share evidence based techniques
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to help you plant, grow, harvest and store all your family's
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favorites. Consider me your.
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Friend in the garden. So grab your garden journal and
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a cup of coffee and get ready to just grow something.
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I am super happy to announce that the merch shop over on Just
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growsomethingpodcast.com has finally reopened if you're
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looking for a great way to. Support the.
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Show while also sporting some cool garden related clothing,
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mugs and more. That's the place.
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To do it, I'm adding more designs every few weeks and I
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just know there is something over there that will fit right
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into your garden personality. Head to just
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growsomethingpodcast.com slash. Shop to check.
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Out all the options and support the podcast with specially
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designed merch from the show. Just
00:02:05
growsomethingpodcast.com/shop. I am going to make this a fairly
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quick episode because if you can't hear it, I am in the
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throes of a major head cold and I can't breathe, so my throat is
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also giving me problems. So we are going to run through
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this fairly quickly. Don't forget to answer the
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February question of the month. What is your most successful
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crop and why? This could be a specific variety
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of something that out produces all the others.
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The plant that you love the most or the crop that grows
00:02:40
fantastically well for you without fail every single year.
00:02:45
Whatever you consider your most successful crop in whatever way
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you consider it successful, nobody has given me their answer
00:02:53
yet, and we've only got a week or so left.
00:02:55
So send me an e-mail, post it in the Facebook group, or send me
00:02:59
Adm on Facebook, Instagram or TikTok.
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You have until February 29th to get me your answer.
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When I first started with indoor seed starting, I put my seed
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trays in a sunny window in our master bedroom where I thought
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they'd get the most warmth and the best light.
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The germination time was definitely much longer than what
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was typical according to the seed packets.
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And then I had the nightmare of trying to rotate my seedlings
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daily as they leaned toward the light coming in from the window,
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and they still got super long and leggy.
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What did survive to go out into the garden just didn't do very
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well, and I knew I had to figure out a better way to start my
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seeds. The next year I invested in a
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seedling heat mat, spending about $40.00 for one that would
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fit 4 full trays of seeds. It was a big investment back
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then for us, but I still use that same heat mat over 15 years
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later, so it was well worth it. I have four more smaller mats
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now too, they're just that effective.
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The other thing I did was hang lights underneath the shelves of
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a metal shelving unit so I can get my seedlings closer to the
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light. We'll talk about the lights
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shortly, but let's dig into the seed mats first.
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The ideal soil temperatures for most vegetable seeds to sprout
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ranges from 60°F up to as high as 95°F, a range of 15 1/2 to 35
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Celsius. For all but the most
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temperamental of seeds, 70 Fahrenheit or 21 Celsius seems
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to be the happy mid range where most seeds will germinate
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readily. Okra and squash are the
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exception to this, preferring temperatures of around 85
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Fahrenheit or 29.4 Celsius. This doesn't mean these seeds
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won't germinate at other than ideal temperature, but
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germination is much more efficient under closer to ideal
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conditions. Not only do heat mats provide
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initial warmth to the growing medium, allowing the seeds to
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sprout faster than at room temperature, but heat mats also
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allow us to maintain a consistent soil temperature.
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This helps us get more uniform germination across all our
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seedlings, which leads to more consistent seedling growth.
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This also means the seedling is expending less of its energy
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pushing out of its seed coat and through the soil, and can save
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that energy for its first few days of growth once germinated.
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Warm soil temperatures provided by a heat map also promote more
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vigorous root development in seedlings because the warmth
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encourages those roots to proliferate the surrounding
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starting medium more efficiently.
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Well developed root systems in the early stages ultimately
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leads to stronger and more resilient plants once they're
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transplanted into the garden. So one other benefit to using a
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heat mat for seed starting is it helps prevent damping off.
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Damping off is a very common fungal disease that affects
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seedlings. Damping off is often triggered
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by cool and damp conditions, and you'll see the stem of the
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ceiling where it meets the soil just collapse in and pinch off,
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which results in the death of the young seedling.
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They just sort of topple over like their little legs have been
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chopped off. Using a heat mat can prevent
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damping off by creating an environment that is less
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conducive to that fungal growth. Now, of course, we don't want to
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keep our seedlings on the heat mat for too long after they've
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sprouted, or it can become too warm at the root zone.
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So after the seedlings have emerged, the ambient air
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temperature in their growing environment actually becomes
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more critical than the soil temperature, and the seedlings
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should be removed from the heat mat relatively quickly.
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Typically within a few days to a week, they should all be
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germinating at around the same rate, so by the time about 75%
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of them have popped up out of the soil, it's time to move them
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off the mat. This is best done gradually if
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you can, to avoid shock and allow some heat retention to
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help the remaining seeds sprout. You can either gradually reduce
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the temperature setting on the heat mat over the course of a
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couple of days, or just move the seedlings to a slightly cooler
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location nearby. Moving the seedlings off the
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heat mat usually cools the soil pretty quickly though, so I like
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to turn down the thermostat. But sometimes I need that mat
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right away to start another set of seeds and I have no choice
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but to move it immediately. Now, there are a couple of
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tricks that you can use if you don't want to invest in a heat
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mat. The one I've used before is once
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you've got your seeds planted, you're going to need to water in
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the seeds or you'll need to moisten that seed started medium
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before you start planting. To do that, use water that is
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heated to about 100°F for that initial watering, and then
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immediately cover the seed tray with plastic wrap or a tray lid
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to trap in that heat. This initial burst of heat will
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help speed up the germination, and then keeping your seed tray
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in an area with ambient air temperatures of around 70
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Fahrenheit or above will also help this process.
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Another option is to put the seedling trays somewhere where
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it's just naturally warmer in your house.
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If you've got a refrigerator that stays warm up top, put them
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up there. If you have a sunroom that gets
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really warm during the day, put them in there and if that area
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cools down at night, cover the seedlings in the evening to trap
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that heat in once the sun starts to go down to help maintain that
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warmer soil temperature. I've seen people use heating
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pads like what we use for like our own aches and pains, but I
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would caution against this. Number one, you have no way to
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know just how hot that thing gets and it may be too warm for
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seed starting. And #2.
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Most of those have automatic shut offs which means you'll
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have to keep coming back to turn it back on again.
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And also if your seedlings are leaking water from the bottom,
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it could be a fire hazard. Seedling heat mats are water
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resistant and they're meant to be used with seedlings.
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Where your heat mat for your back, Yeah, it might be
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questionable. So safety first, please.
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For over three years we have seen pandemic driven cost
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increases from seed suppliers due to seed.
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Shortages. Crazy freight.
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Costs and high inflation. But finally, things are
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normalizing and true leaf market has just been able to lower
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their prices across the board. Hundreds of varieties are now
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priced 10 to 15% lower than they were last year, while other
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varieties are 30 to 50% lower. I just got my most recent order
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of Champion Radishes, Danvers, Carrots and Georgia Southern
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Collards. You can get your own lower
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priced seeds and get free shipping on orders over $75
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while supporting this podcast by going to
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justgrowsomethingpodcast.com/seeds to place your order from True
00:10:01
Leaf Market. OK, So what about lights?
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As soon as those seedlings start to sprout, they're going to need
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light. The type of light that you
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choose should be based on what you're growing, how long you're
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growing it for, and of course your budget.
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Different stages of growth require different spectrums of
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light. This is called the color
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temperature. We're mainly concerned about the
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early growth stages for seed starting, but it's worth
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reviewing all of them just so we know what to look for.
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Light is electromagnetic energy measured in wavelengths, and
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this includes infrared radiation and ultraviolet rays.
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What we're concerned with is visible light, and the color of
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this light varies, ranging from blue and green to yellow and
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red. Plants primarily absorb red and
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blue light for photosynthesis. The color temperature of a light
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source like a light bulb is measured in Kelvin.
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The Kelvin scale ranges from 1000, which is the warm or red
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end, to 10, which is the cool or blue end.
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Different colors affect plant growth in different ways.
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Blue light is needed for vegetative growth.
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Red light promotes flowering and fruit production.
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Now, light bulbs often sit on one end of the spectrum or the
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other, but some lights are full spectrum, emitting light across
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the entire range. For seedlings, clones or any
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plant in its vegetative stage, we want to aim for a range of
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5000 to 7500 Kelvin. This is generally referred to as
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a daylight bulb, flowering and fruiting stage.
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You might consider a color temperature in the red range
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3500 to 4500 Kelvin. This promotes flowering and
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fruiting and this is generally only a consideration when we
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intend to grow plants indoors for extended periods of time.
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These would be considered cool light bulbs.
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So does this mean you need to run out and get grow lights
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specifically? Not at all.
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There are plenty of lights available right off the shelf at
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the hardware store that meet our needs without breaking the bank.
00:12:17
Fluorescent tubes have long been a popular choice for indoor seed
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starting, and this is because they're affordable and they are
00:12:24
effective. So they come in two main types
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that are typically used for seed starting we're talking T fives
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and T eights. E5 bulbs are more energy
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efficient and they produce a brighter light, which makes them
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ideal for seedlings. They are also the smaller of the
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two, and they're usually used in like large office buildings and
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warehouses. T8 bulbs are slightly less
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efficient, but they still provide plenty of good light for
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starting seeds, and they are often the most common ones that
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we find. There are also T12 bulbs, but
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those are like the old school fluorescents that many of us
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grew up with blinking overhead in our classrooms, and those are
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being phased out. And there are T2 fluorescent
00:13:05
bulbs. These are tubes that are only
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about 1/4 inch in diameter. This is the size that's often
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used for those compact fluorescent light bulbs, the
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ones that kind of twist around themselves that are configured
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to sit into like a standard light fixture or a lamp.
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But there are also straight T2 tubes, and those are usually
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used for like tabletop lamps. You know, things that you would
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use for like crafting or sewing, but there's no reason you
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couldn't use AT2 if it's in the right color temperature.
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Now fluorescence do tend to put off a little bit of a heat, not
00:13:36
as much as the T12's used to, but still some, which can either
00:13:40
be a help if you're starting seeds in a cool area or could
00:13:43
actually prove to dry out your seedlings a little more quickly
00:13:45
in the early stages when we're trying to keep those lights
00:13:48
really close to the seedlings. So the pros to using
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fluorescence is they do have an affordable initial cost, they
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are widely available and they are a good light spectrum for
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seedling growth. The cons to them are those bulbs
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need to be replaced periodically.
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They are not as energy efficient as LED lights and the bulbs are
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going to degrade over time which is going to reduce the light
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output. Ask me how I know I have a
00:14:14
plenty of fluorescent lights in my ceiling room right now that
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need to be replaced because they are just kind of dim now.
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I closed second behind fluorescent lights and the one
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that I actually prefer now is LED lights.
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Light Emitting Diode lights have gained popularity for seeds
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starting in recent years, mostly because they are very energy
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efficient. So they may have a higher
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initial cost compared to fluorescent lights, but they are
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more energy efficient and they have a much longer lifespan.
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I have been slowly switching all of my lights over to LED and
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there are plenty of very very affordable options out there
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now. I just saw some 24 inch LED shop
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lights selling for $10 and they would be perfect for an indoor
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seed starting set up and they will last you for years.
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Now the pros to the LE DS, energy efficiency, long
00:15:08
lifespan, which is going to reduce the need for having to
00:15:10
frequently replace them like the fluorescence and they have a low
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heat output so this is going to minimize the risk of heat damage
00:15:17
to those seedlings. Cost to this, Yes they are a
00:15:21
higher initial cost compared to fluorescence, but those prices
00:15:24
are rapidly coming down. Some models may have a limited
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coverage area so it might require you to have multiple
00:15:33
fixtures for a larger seed starting set up or just make
00:15:36
sure that you have fixtures that have reflectors attached to them
00:15:40
to sort of spread that light out.
00:15:43
And then of course just like anything else, the quality on
00:15:45
the LED lights is going to vary, you know based on the brand.
00:15:49
So you might want to do a little bit of research and just make
00:15:52
sure that you're getting a reliable product.
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The LED option that I've chosen are 4 foot shop lights.
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Most of them have a reflector, but the ones I got super cheap
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don't have reflectors. And that's OK because they were
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so cheap that it was very economical to just add one more
00:16:10
light to each shelf instead of using a reflector.
00:16:12
And I will say that the LE DS are much brighter than my
00:16:16
fluorescents were even when they were brand new.
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And like I said, the rest of those fluorescents are in
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desperate need of being replaced this year.
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Now what I've been referring to is basically shop lights, but of
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course both the fluorescent and the LED options are available
00:16:30
specifically as grow lights as well.
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When they are marketed as grow lights, they typically have a
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more narrow Kelvin spectrum or they are marketed as broad
00:16:42
spectrum to cover all plant requirements.
00:16:45
So LE DS, actually a lot of them now have customizable spectrum
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options if you want to be very, very specific.
00:16:52
Of course, they also often come with a much larger price tag
00:16:56
just because they say they are grow lights.
00:16:59
And most of these lights that are specifically grow lights are
00:17:02
intended for a much longer time frame of use in terms of the
00:17:07
plant growth, or they're intended to be switched out at
00:17:10
various stages of plant growth. So none of this is necessary for
00:17:15
simple indoor seed starting. Just be sure whatever option you
00:17:19
choose is rated at 5000 Kelvin or above for that vegetative
00:17:24
growth and you'll be just fine. You can also find very small
00:17:29
grow lights online that are meant as additional lighting for
00:17:34
indoor plants, but these can totally work for a small seed
00:17:38
starting area too. These are often little clip on
00:17:41
lights or lights that fan out in multiple directions that stand
00:17:45
on a tabletop. If you're only starting a
00:17:48
handful of seeds, put those trays near a sunny window and
00:17:51
simply add one of these little inexpensive grow lights and your
00:17:54
seedlings will have enough light to get them through until
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they're ready to move outside. Now there are also ready made
00:18:01
systems for starting your seedlings and doors that have
00:18:04
the lights built in and generally have some sort of
00:18:08
adjustable shelf to be able to raise and lower the plants or a
00:18:11
pulley system to raise and lower the lights.
00:18:13
There are single and multi tier systems designed to sit on a
00:18:17
table. These are specifically for like
00:18:20
small scale indoor gardening, which make them perfect for home
00:18:23
gardeners that have limited space or are only starting seeds
00:18:26
on a smaller scale. These compact units typically
00:18:31
combine LED or fluorescent bulbs with a reflective hood and
00:18:37
that's going to maximize the light efficiency.
00:18:39
There are also much larger modular systems that are fully
00:18:43
customizable. Even Aerogarden has a seed
00:18:47
starting version of their system that is completely hydroponic
00:18:51
and self-contained and designed to help you start seedlings for
00:18:54
the outdoor garden. If you want to get fancy, there
00:18:57
are always options to get fancy, but do not get sucked into
00:19:02
thinking that any of this is absolutely necessary when it
00:19:09
comes to indoor seed. Starting, deciding whether to
00:19:13
use a heat mat and choosing the right grow lights can be crucial
00:19:18
for ensuring healthy and vigorous seedlings, but it
00:19:20
doesn't need to be difficult or expensive.
00:19:23
Consider your budget, your space constraints, and your specific
00:19:27
gardening needs, and you will be well on your way to some
00:19:31
successful seed starting Until next time, my gardening friends,
00:19:34
Keep on cultivating that dream garden and we'll talk again
00:19:37
soon. Thanks for listening to another
00:19:39
episode of the Just Grow Something Podcast For more
00:19:42
information about today's topic and to find all the ways you can
00:19:45
get. In.
00:19:45
Touch with me or support the show.
00:19:47
Go to justgrowsomethingpodcast.com
00:19:50
until next time, my gardening friends.
00:19:51
Keep learning and keep growing.