Successful Indoor Seed Starting - Ep. 237

[00:00:00] A lot of gardeners fail their first few attempts at getting seeds started indoors properly. Either they don't germinate, they fail to thrive, they fall victim to fungal diseases, or they're just too weak to stand up to the elements once they're moved outdoors. I had my own share of all of these problems when I first started and occasionally I still do. We're dealing with living organisms and in a home environment we can't always control all of the factors involved. It's frustrating.

[00:00:28] And I've seen a lot of gardeners simply just give up or not even make an attempt in the first place. Success with starting seeds indoors comes down to basically a handful of factors. Your materials and technique, soil temperature, air temperature, light and air flow. How we approach each of these is going to determine how successful our outcome is. Just like any new skill, starting seeds indoors and successfully getting them to the transplant state,

[00:00:58] How the age takes practice. Last week we talked about the supplies that we need to get started. This week, we're covering how to use them. Today on Just Grow Something, we're going to run through what I would consider to be best practices in terms of each of these factors. We'll talk about the optimal way to approach seed starting and talk about where we can go wrong. By the end, you'll be able to decide for yourself whether you should tackle indoor seed starting as a beginner or where you can improve if you've been there before.

[00:01:28] Let's dig in.

[00:02:00] Hey, I'm Karen. What do you struggle with most in starting seeds indoors? Let me know in the comments if you're on Spotify or YouTube. Send me a DM on social, put your comment in the Facebook group, or just send me an email. What do you struggle with when it comes to starting seeds for transplant? You have until February 21st to get these answers to me. If you want a written guide for all of your questions. If you want to ask them, you'll be able to answer your questions.

[00:02:23] If you want a written guide for all of these tips and techniques to follow along with on your seed starting journey, grab my free seed starting ebook at justgrowsomethingpodcast.com slash seedbook. You know where to find the link. So last week we talked about seed starting mixes and the containers that you can use. Let's talk about how to actually plant those seeds.

[00:02:44] Part of the success of indoor seed starting depends on how well you follow the planting instructions provided with your seeds. It might seem obvious, but the more you stick to those instructions, especially when you are first learning, the better your germination rate and the better the strength of your seedlings.

[00:03:05] When it comes to seed germination and overall plant health, if we deviate from the recommended planting depths, it can actually have a very significant impact. Seeds require very specific conditions for their optimal growth. And this includes proper soil contact and access to moisture.

[00:03:25] So if we plant those seeds too shallow or too deep, we risk inhibiting the germination or stressing our seedlings out absolutely unnecessarily. So if a tomato seed packet says plant the seed a half inch deep and we shove it down an inch into the soil, then that improperly planted seed is going to struggle to push through the soil.

[00:03:50] This can cause weak seedlings where if you've got a properly planted tomato seed, it might pop up super easily within a week and then they're off to a really strong start. Planting deeper than what's necessary for that soil contact can hinder a seed's ability to be able to emerge from the soil properly. And this is forcing them to use additional energy that would normally be reserved for their first few days of growth until their true leaves start to form.

[00:04:20] The other part of this is that there are certain seeds that need special attention in order to germinate properly. For instance, there are some seeds that benefit from a soak before planting. Other seeds need light to germinate. And then there's other seeds that take an extraordinarily long time to germinate. So pay attention to whatever the seed packet says in terms of how deep to plant, whether to soak or scarify the seeds before planting,

[00:04:47] if they need light to germinate, or if they take an extended period of time to germinate. The next thing we need to concern ourselves with is moisture. Your seed starting medium, whatever it is that you choose to use, should be damp, but not completely saturated or sopping wet. So if you were to squeeze that medium very tightly in your fist, you should be able to just get like a drop or two of water out of it. We don't want like a stream of water.

[00:05:17] And you should be thoroughly moistening the medium prior to planting your seeds. So this is going to allow the seed to be in contact with the moisture. And then we're not going to have to disturb those seeds by additional watering from the top. If the surface of the medium gets dried out, then we can use a spray bottle to re-wet it. But we shouldn't need to water or soak that seed starting medium again.

[00:05:43] If for some reason it's just not wet enough and you realize that it's starting to dry out and you have to water from the top because a spray bottle just isn't doing the job, just make sure that you're doing it very gently. We don't want to move those seeds around in the medium until they actually get a chance to sprout. If drying out is a problem for you, you can retain the moisture during germination by using a cover of some sort. So a lot of the sort of purchased options that are complete sets or kits do come with humidity domes.

[00:06:13] You can buy humidity domes separately, but you can also, you know, repurpose lids or you can use cling wrap or a beeswax coated cloth or something to keep the moisture locked in. This is going to reduce that chance that the medium is drying out prior to germination. They are not necessary unless you are sprouting seeds in a dry environment or you see that your seed starting mix is drying out very quickly between waterings and you just need a little bit of extra help.

[00:06:40] But if your mix is staying excessively wet or you see mold or fungus starting to form, then make sure you remove that cover right away and then just leave it off. The next thing to concern ourselves with is soil temperatures. Seeds are absolutely remarkable. I had a professor tell me once that seeds are nothing but little containers that hold a baby plant and a boxed lunch, and I have always loved that analogy.

[00:07:04] What that means is each seed contains enough food energy to allow that seedling to push out into the world when the time is right. But our seeds need specific conditions to unlock them out of that little container. One of those conditions is the temperature of the soil in which they are planted, or in our instance, the seed starting mix, right?

[00:07:27] Different plant species have different temperature requirements for germination, and we need to provide them with the right environment so they don't expend more energy than is necessary to break out of their little shells. A lot of your seed packets are going to come with planting instructions, so they might outline the ideal temperature range for germination specific to each plant species.

[00:07:52] And this usually ranges between 60 and 85 degrees Fahrenheit, or 15.5 to 29.4 Celsius. And this is even for your cool weather plants. So if it's not on your seed packet, you can usually look up the proper temperature online. If you get my Seed Starting Essentials eBook, I have provided a chart with the germination temperature ranges for most of your garden vegetables that are commonly started early indoors for transplanting.

[00:08:20] Now, in order to achieve these ideal temperatures, we likely are going to need some heat. So this can be done in one of two ways. Either we can water our seed starting medium with very warm water at around 100 degrees Fahrenheit, and then cover the tray immediately and move it to a warm space in the house, you know, like on a fridge or something. Or we can use a seedling heat mat. This is my preferred method.

[00:08:46] These mats are placed underneath the trays or the pots or whatever it is that you're starting your seeds in. And they're going to provide a gentle warmth from below that encourages that germination and the root development and just is going to help with the overall plant vigor as they sprout. They generally raise the temperature of the soil about 10 to 20 degrees Fahrenheit above the ambient room temperature.

[00:09:11] So this is ideally sitting our soil temperatures at between 70 and 85. So this is kind of the perfect range for the majority of what we start inside. Heat mats are going to allow a consistent soil temperature. And so this helps us get more uniform germination across all of our seedlings, which leads to more consistent seedling growth. This consistent warmth also helps prevent damping off.

[00:09:41] Damping off is a fungal disease that affects seedlings. And it is usually triggered by cool and damp conditions. So you'll see the stem of the plant, like right where it meets the soil, it just like collapses in and pinches off. And of course, this kills the seedling. If you use a heat mat, you can actually help prevent damping off because this is creating an environment that is less conducive to that fungal growth.

[00:10:06] I will say, though, damping off can still happen even with a heat mat if we're keeping the soil too wet. I just had this happen with some lavender seedlings. Lavender is notoriously slow to germinate. It takes as long as three weeks. And I had the soil way too wet and I lost half of the seedlings as they sprouted because I wasn't paying attention to that tray closely enough to remedy the situation fast enough.

[00:10:35] So even though heat mats can prevent damping off, nothing is foolproof when we're dealing with living organisms. And that includes the gardener. Some seeds will absolutely readily germinate at room temperature with no additional heat. Lettuces specifically, they will germinate in soils as cool as like 40 degrees Fahrenheit. So save the space on the heat mats for like your heat loving annuals.

[00:11:02] So peppers, tomatoes, but also your cool weather crops, you know, broccoli, they prefer warmer soil temperatures for germination too. So the seed starting medium stays at the proper moisture level, right? The trays stay at the proper temperature. Our little seedlings successfully pop out of the soil. Yay! Great. Now what? Now we need to uncover those seed trays, take them off the heat map, and now we're going to concern ourselves with light and air temperatures and air flow.

[00:11:32] So first we'll talk about lighting. If our seedlings don't get enough light while they are growing indoors waiting to head out into the garden, they are going to become weak and leggy as they stretch towards whatever limited light source is available. Your overhead lights in whatever room that you're growing your seedlings in is not enough. Insufficient light exposure is going to lead to unhealthy plants that have poor root development.

[00:12:01] They're going to have weak stems and they're just going to, if they survive, once you move them outside, are going to have lower overall productivity. So it might seem best to have your newly sprouted little seedlings in a sunny window for natural light. Just like when we're seed starting, it may not be enough. It's usually not enough to get them to their best start. You're going to have to rotate them to give them equal access to that sort of filtered light that's coming in through the window.

[00:12:28] And that's still likely not going to prevent them from stretching to get more. You can help with this a little bit by putting up some aluminum behind the seedlings so it reflects some of that light back in. And if you're in a more southern area or you have a lot of southern exposure, this might be enough. But for the rest of us, this is where we want to give them a hand with some artificial lighting. What we're concerned with for plant growth is visible light.

[00:12:57] And the color of that light varies. Plants absorb red and blue light primarily for their photosynthesis. So blue light is necessary for vegetative growth. And red light promotes flowering and fruit production. So obviously, when we're looking at vegetative growth, that's what we're concerned about for our baby seedlings. This is the kind that we get from the blue color spectrum.

[00:13:21] We talked last week about how the color temperature of a light source is measured in Kelvin and what that means. The Kelvin scale ranges from 1,000 to 10,000. 1,000 being the warm or red side and 10,000 being the cool or blue side. And light bulbs usually sit on one end of the spectrum or the other. But you also have lights that are full spectrum and they emit light across the entire range.

[00:13:50] So once again, we are concerned about vegetative growth for the seedlings. And that's the kind of light that we get or that's the kind of growth that we get from the blue color spectrum. Okay. So you're going to want to look for lights that are labeled in a range of 5,000 to 6,500 or even 7,500 Kelvin. Sometimes these are labeled as lumens, but generally you're just going to see them in terms of like 6,500 K. This is generally referred to as a daylight bulb.

[00:14:19] A full spectrum light would be fine too, but they're generally more expensive. So that's up to you. Fluorescent lights, super popular because they are affordable and they are suitable for most plant species during their early growth stages. Fluorescents do tend to put off a little bit of heat though. So keep this in mind. It might be good for you because if you're starting seeds in a very cool area that needs a little bit of help in that, then that might be good.

[00:14:46] Or it also could like dry your seedlings out more quickly in the early stage because we're keeping the lights very close to those seedlings. So just be aware that the fluorescents may put off a little bit of heat. If you're looking for more efficient lighting options that also have higher intensity levels, then you might look at LED lights. These are a little bit more expensive initially compared to fluorescent lights, but they are definitely more energy efficient and they definitely have a longer lifespan.

[00:15:15] All of my old fluorescents, as they burn out, they are being replaced with LEDs. LEDs come in a wider range of kind of styles of how you can use them. So you can flip them on or you have tabletop versions that have like multiple arms on them. You've also got just, you know, standard shop lights. They're more accessible and they're easier to use for gardeners than they used to be. And if we only need to light up a small space, you have a bunch of different versions for the LEDs now.

[00:15:44] There are also ready-made systems for starting your seedlings indoors and they have lights that are built in and generally some sort of adjustable shelf to be able to raise and lower the plants or a pulley system to raise and lower the lights or whatever. They're fancy and fancy systems generally come with a fancy price. But hey, no shame if you want to spring for an all-in-one system that's easy to set up and it totally takes the guesswork out of it for you.

[00:16:11] But just know that you can absolutely DIY a system in a wide range of sizes for a lot less money. It's totally up to you, okay? It is not necessary to purchase lights that are labeled specifically as grow lights if you are only starting and growing seedlings for just a few weeks before moving outside, okay? You want to move your seedlings to the light or the lights to the seedlings, whatever works for you, as soon as they spread.

[00:16:37] So if you're waiting for more of the seeds to pop up through your seed starting medium, then you might need to move those lights over your heat mat temporarily or wherever you're keeping your seedlings warm or your seed starting mix warm. Or move the seedlings earlier and just allow the remainder of the seedlings to pop up and germinate off of the mat. Either way, the proximity to the light for seedlings is very important.

[00:17:03] They will begin to stretch for that light within just a few hours after they germinate. I actually have lights on over top of my heat mats as my seeds are germinating. So I know if I miss them sprouting, nobody's going to be going without light while they're waiting for the rest of the tray to germinate. And then once they're about 75% germinated, I move them from the mat to a different set of lights and then I start the process all over again. No matter which way you do it, however you get your seedlings under light,

[00:17:30] you're going to want to aim for those lights to be about two to four inches above your seedlings initially and then just adjust it as they grow taller. If the lights are too far away, once again, those plants are going to stretch and they're going to stretch excessively and that's going to make them become weak. And this is when you start to see seedlings just sort of flop over on their side. So you can either adjust the height of the light up and down

[00:17:57] or use books or boxes or something else to raise your seedlings up to the light and then lower them as they grow. You want a distance of no more than six inches between the lights and your plants throughout their growth stages and this is going to prevent that stretching. I also recommend setting your lights on a timer and aim for about 12 to 16 hours of light per day because this is going to mimic the natural daylight cycle.

[00:18:24] So once we have about 50 to 75% of our seedlings germinated, it is time to move them from the heat map. If you continue having those warmer soil temperatures after germination, it can not only dry out the soil more quickly, but it can also damage the sensitive roots as they grow deeper into the medium. At this stage, now we're going to consider the ambient air temperature in your growing space.

[00:18:51] So plants need a certain range of temperatures to thrive. If the temperature is too cold, the seedlings may grow slowly or they may become stunted. If the temperatures are too high, this can also be detrimental and this can lead to leggy growth and to weak stems. Depending on your ambient air temperature in your seed starting area and the type of plants that you're starting, you may need to use either a space heater or a fan to heat or cool your growing area.

[00:19:19] Your little seedlings are going to want to be in ambient air temperature that is appropriate for their species. So cooler air for your cool weather crops, warmer for your warm weather ones, right? The balance comes when you're starting both types of plants in the same space. I often have some overlap with all of my brassicas, my early, early stuff. Just still kind of hanging out in my seed starting room and waiting to go outside

[00:19:47] while I am starting all of my warm weather stuff like to my tomatoes and my peppers, my eggplant. So an ambient air temperature of between 65 and 70 Fahrenheit is kind of that happy medium for most vegetable plants and herbs. So pay attention to the ambient air temperature, especially if you're starting your seedlings in an out-of-the-way area like a basement or a garage. And then finally, we need to consider the air flow. So soil temperature is essential for germination.

[00:20:18] Air temperature is, or proper air temperature, is needed for optimal growth. But proper air flow around the plants is just as important. Stagnant air can hinder plant growth and it can create an environment that is perfect for fungal diseases. So to avoid this issue, you may need to incorporate something into your setup to promote proper air circulation. Without this air circulation, we are more likely to see stunted growth

[00:20:45] and we're increased susceptibility to diseases in those little baby seedlings. That stagnant air around your seedlings is going to create a micro environment that encourages that fungal growth. The other thing is excessive heat from the lights that we have to place really closely to those plants can also cause the air temperature to heat up around the seedlings. So if we have proper airflow, that's going to help to cool the air immediately around the plants. If you have a window nearby, then you can just pop it open slightly

[00:21:14] and create a gentle cross breeze that's going to aid in that air circulation. But if you are starting seeds, while it's still winter, like most of us, pay attention because we don't want the air, you know, exposing the seedlings to too cold of temperatures or like really wildly, you know, fluctuating conditions. So another way that you can enhance airflow is just by strategically arranging your seed trays or your pots. Just give them some space from each other.

[00:21:42] Avoid overcrowding so that we're not restricting that sort of ventilation between the plants or increasing the humidity levels too much. So if you have enough lights, you can space out your seedlings enough to allow air to circulate freely between the seedlings. And this is going to help reduce that risk of fungal diseases. Of course, my favorite and recommended way, honestly, to provide proper airflow is with a fan. That gentle movement of air

[00:22:10] is not only going to help prevent those fungal problems and overheating, but it also stimulates stronger stem development as those plants respond to the gentle swaying. I said it before, your plants like to dance. Having air blowing directly at your seedlings helps promote the strong stems by forcing the plant to hold itself up against the flow of air. We're just aiming for a gentle breeze here, not gusts of wind that could damage our seedlings.

[00:22:39] So you can place a fan at an angle or use an oscillating fan. That's my favorite approach. And that's going to help distribute the air evenly around the space. So for successful indoor seed starting, we are concerning ourselves with proper planting techniques, soil moisture and soil temperatures, lighting, air temperature and air flow. By bringing all of these together, we're basically creating a framework for successful indoor seed starting.

[00:23:08] So following the planting instructions and using the proper starting mediums and containers, make sure that we are off on the right foot. Using heat provides the optimal soil conditions for germination. If we monitor the air temperatures, that's going to support healthy growth. We're maximizing the light exposure, which is giving our seedlings the energy that they need to grow. And then we're just ensuring that we have adequate airflow to prevent issues like fungal growth and strengthening our seedlings in preparation for them moving outdoors.

[00:23:39] All of these things combined basically create an environment where our seeds have every opportunity to reach our full potential. It is not foolproof. Again, we are dealing with living organisms. So it's going to take some practice, but practice makes perfect plants and you will be giving your plants the best possible chance at success. Until next time, my gardening friends, keep on cultivating that dream garden and we'll talk again soon.