In the last segment of our Guide to Seed Starting, we left off with our little seeds sprouted. At that time, you shut your heat mat off and turned your grow light on. In the coming weeks, you will watch those first green shoots poke through the soil surface. You’ll watch those shoots rapidly stretch for the light, growing the first leaves. Soon, more leaves will develop and in that baby plant, you will recognize its adult self. You’ll nurture these seedlings and each day find they are a bit bigger. With the right conditions, they keep growing and growing until you’re harvesting your meals! All from that tiny seed you placed in the dirt. Year after year, I still marvel at this miracle. So it’s with much gusto that I offer some tips for keeping those seedlings healthy and eventually transitioning them outdoors.
LIGHT and WATER are the two most important things keeping your indoor seedlings charging ahead toward summer sun.
Seedlings require a strong light source to develop into strong plants. You will need to keep your light just two inches from the top of your plants. As the plants grow taller, raise your light along with them. If your plants are looking tall, thin, or floppy, the gardening world would use the very clever term “leggy” to describe your seedlings. This condition is often the case when starting seeds at a window, or under a light that is up too high. This legginess causes weakness in your plants; take it as a cue that your plants need stronger light. A stout, upright and sturdy stalk is your goal for healthy, productive plants.
In addition to strong light, your seedlings need long light; another reason I advocate the use of a fluorescent light fixture. To be exact, your seedlings grow best when given 12 hours of light each day. In my seed-starting past, I could be found guilty of leaving the grow light on 24/7, but your plants will be their healthiest if you shut the lights off regularly. A timer is a sanity-saver and inexpensive.
Do not overwater! When the soil surface is dry, give a little water. Do a daily check to keep a good eye, but you likely won’t need to water every day. Too much water can actually cause the roots to rot, or cause dampening off, leading to the the death of your plants.
As I’ve mentioned in previous parts of this Guide to Seed Starting series, I find it best to spray the soil surface with water until the seeds germinate. This is a gentle way to provide moisture without disrupting the tiny seeds. Once roots are starting to develop, I switch to watering via the bottom drainage tray. The soil and roots soak up the water from the bottom-up. This way, I’m still not disturbing the bitty plants, and the bottom-up method encourages deeper root growth. To water in this way, pour an inch of water into the tray and check back a half day later to ensure it’s all been soaked up. If the soil is plenty moist, and there is standing water in the tray, dump the extra out.
Remember how we planted more than one seed in each cell? If all of your seeds sprout, you’ll have some thinning to do. The easiest way to do this is simply pull all but the biggest sprout in each cell. To maximize your seed usage, you can transplant that little sprout to an empty cell and tend it as you do the others. Fair warning: this method is a maximizer of your seed stock, not your time. You choose.
Transplanting to larger containers
And so it goes! You’re well on your way to starting your garden from seed. Once your plants have a couple “true leaves,” consider moving them to larger containers, especially if they have a while to go before being placed in the garden. This step is really crucial for those warm-weather plants like tomatoes, pepper and eggplant. When I move my tomato seedlings to bigger cups, they really take off. I can easily grow a tomato start a foot, or taller! They love the extra space. You can purchase small, individual pots for this. I like to use the bottom of a half gallon milk jug with drainage holes added, which you can see in the bottom right of this photo.
It’s at this time that I move my seedlings to the greenhouse because it’s usually warm enough by then, and I don’t have space under my lights for the bigger containers. If you have fewer plants, you might still be able to keep them under the light. If you choose to move them to another location, watch again for legginess and consider supplemental light, if necessary. Bottom center of this photo, you can see some super leggy basil plants. They got crowded out under some big tomato plants and were really stretching to find light!
A couple weeks before you are ready to put your seedlings in the ground (yey warm weather!), you will need to “harden off” your seedlings. This is a gentle process of introducing your coddled and literally sheltered plants to the elements outdoors. I begin by bringing my trays outside on a warm day and placing them under a tree for just half of the day. You’ll want to choose a location that is only dappled sunlight and sheltered from the wind. Bring them back in after a few hours and repeat this process for a couple weeks until you’ve gradually worked up to being able to leave your seedlings outdoors all day in sun and breeze. Gradual is key. I remember setting my seedlings out on a windy day and not taking any precautions. They were a tired-looking mess at the end of that stint! The little bit of extra work is worth it to have strong and resilient plants.
A word of caution to you chicken keepers: At no other time in the year is my chicken-loving self at greater odds with my garden-loving self than these tender Spring days. I always want the ladies to roam free throughout the yard and garden before I have all the plants in the ground, but I’ve learned the hard way to fiercely guard those seed flats. I think the lack of green grass that comes with winter makes them go for anything by Spring, even these poor pepper seedlings!
When the sun has sufficiently warmed the soil and the threat of frost is long gone, I grab my hand spade and jump up and down like a kid at a carnival. Well maybe I do a little dance without holding the spade. Either way, make the transition seamless for your plants by choosing to work in the early morning, or the late afternoon. Avoid working on the hottest day yet, the windiest day, the coldest day… Go easy on ’em. Get on your knees, and scoop out a generous hole. Some people add a little compost in the hole for an extra oomph. Gently slide the plant out of its container and place it in your hole.
This is a fun activity for kids, too! I tend to dig the hole so I can determine the spacing, then let them place the plants in and backfill around the stem.
No need to shake off extra soil or spread roots out. Just plunk the root ball in your hole until the soil lines are level. Tomatoes and peppers benefit from sinking the plant deep into the hole, so the stem is down in there, too. There are little nodes on the stem that will grow into roots and provide a stronger base for you plant (see photo). I plunk these plants in the hole until the bottom leaves are at the soil line.
Covering your plants gently with row cover can help deter pests from your new plants, and add a couple degrees of warmth if those nights are still on the chilly side.
In these early days, it’s really important to keep the seedlings hydrated. Don’t put your plants in the ground, then leave town for four days. The babies need a little extra attention until they’re standing on their own two feet and running. At the time of planting, I also like to add a hefty layer of mulch (if I’m not already planting into mulch put down in Fall). Mulch has numerous benefits, but especially for seedlings, it helps to retain moisture in the soil.
It makes me so happy to think of all of you starting your gardens. Happy growing everyone!
That’s a wrap to our Guide to Seed Starting series. Have you learned a thing or two? Like what you’ve read? Give our series a shout out, or share on your social media! Thank you!