Complete step-by-step tutorial on caring for seedlings after one week of growth. Learn how to care for your new seedlings with these photos and tips for thinning, transplanting, and watering.
You can find more seed starting information in the Seed Starting Guide.
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It's a pretty quick task, but also an important one since it will give your baby seedlings the strong start they need for the growing season.
Caring for seedlings after their first week of growth consists of:
- Transplanting to other pots, if needed
- Watering well (and fertilizing, maybe)
- Providing strong light
I'm using the seed tray I started last week to walk you through the steps so you can easily see what your seedlings may look like before (and then after) thinning, transplanting, and watering.
I'll also provide you with some tips I've learned after years of starting my own seeds (spoiler: not all seeds sprout - it's not just you!).
Caring For Seedlings at Week 1
1. Evaluate your seed trays
The tray pictured above is planted with tomatoes in 4-inch pots and most of the tomatoes have come up (they're pretty easy).
You may remember from the seed starting tutorial that I like to plant tomatoes and peppers in larger pots (instead of the 6-cell seedling pots) since they grow much longer inside to have larger plants to put into the garden, and it eliminates one transplanting step.
Note on peppers: the peppers aren't pictured because they take much longer to germinate than tomato seeds, about 1-2 weeks longer, so you will have to provide this care for them a little later. I still start them at the same time, however, since I don't plant peppers until the first week of June most of the time - peppers like it reliably hot. (You can read more about peppers in the Ultimate Sweet Pepper Guide and Ultimate Hot Pepper Guide.)
There are two things you may notice right away from the above photo:
- There are lots of seedlings clumped together (um...aren't you supposed to plant only 2-4 seeds?)
- There are empty pots.
It is important to plant 2-4 seeds - not all seeds are viable, which is why you need to put more than one seed in each cell or pot.
When I have fresh seed packets I've just purchased I do plant 2-4 seeds - you can see that there are some pots in the photo with only 2-4 seedlings.
However, as I show here, you can keep seeds from year to year and when a packet of seeds is more than 2 years old it's a good idea to plant more to account for a potentially spotty germination rate.
The tomato seeds planted here were obviously still going strong, so I just have more thinning to do.
And the empty pot?
This is normal - sometimes seeds just won't germinate for some reason or another. I wasn't surprised by this, as it was another old seed packet - but this time it was 7 years old (hey, it doesn't hurt to try).
It was a different variety of Roma tomato, and I was planting other Romas that I knew I could transplant if none came up.
Also, it's not unusual for some seeds to take two weeks to germinate, like the peppers I mentioned, so sometimes it's not a failure yet!
2. Thin out seedlings
You want to thin the seedlings now in the first couple weeks of life before the roots get too tangled.
Thinning is something I know people struggle with, thinking they are killing or wasting the plants.
It's just a fact of starting your own seeds:
You must thin now if you want strong, healthy plants that will survive outside.
Of course, you can transplant every little seedling and you will be overrun with plants you can't use. Or you can simply compost them like we do all our other garden waste.
On quick-to-mature plants like lettuce or spinach that can be planted out when they're smaller, I sometimes leave two seedlings to a 6-pack cell, but for all others, they should eventually be thinned to 1 plant per cell.
Here are some tips when thinning your seedlings:
- At this week 1 stage, it's a good idea to make sure your bases are still covered by keeping 2-3 of the strongest seedlings in each cell. Then if you do lose a seedling or two after the thinning phase you will have at least one to grow to maturity.
- When you do leave more than one plant, thin to the strongest plant at week 2 or 3 by snipping off the weaker seedlings at the base of the stem with small scissors - by that time their roots will be growing together and you don't want the strong plant disturbed.
- You can use your fingers to gently pull out the little seedling at the week 1 stage - the roots are small enough that they easily pull out. Start at the outside and just pull a few at a time.
- You can also use a narrow tool - I like a chopstick - to help remove the unwanted seedlings from the roots up - just be careful not to dislodge the seedlings you do want to stay.
3. Transplant Seedlings
While you will be composting many of your thinned seedlings, there will also be some to move to other pots, either to fill in for those that didn't germinate or because you've decided you want a few more of that variety.
How to Transplant Seedlings
- Use your narrow tool/chopstick to gently push the roots up from the side - you want to make sure the seedlings have a good amount of roots you can see in the soil.
- Use the tool to make a shallow hole in the new pot.
- Plant the seedlings with some space between them, using your tool to gently push the root down into the hole and covering back up with soil.
- Use your finger to tamp the soil firmly around the newly planted seedlings.
You will always want to transplant a number of seedlings, if they are available, because you don't know how many will survive (yes, you'll have to thin these, too, later if they do...).
Here's what the example tray looks like before and after thinning and transplanting:
So your seedling tray at week one should look like the tray on the bottom with 1-3 seedlings only in each pot.
Note: The empty pot in the after photo has a new seed planted of the variety that didn't come up the first time - I'll have to wait another week for them to sprout.
Here's another before-and-after thinning example - a tray of brassicas (cabbage, cauliflower, broccoli) in 6-cell trays:
As you can see, some cells in the before photo have an abundance of seedlings just like the tomatoes did and some have just a few or even none (the slightly larger cells at the top right contain the slow germinating peppers so these will be cared for in a week or two).
For the cells with lots of seedlings, just take the same steps of thinning and transplanting that we did for the tray of tomatoes.
I do want to point one of the quirks of starting plants from seeds - just to let you know that you didn't necessarily do anything wrong:
Some varieties of seeds are just less viable than others - even when the seeds are fresh.
As an example, in the two 6-cell trays of cauliflower seedlings pictured above, the Cheddar, Purple, and White cauliflower were all brand new seed and the Romanesco seed was actually 3 years old!
I have problems starting Cheddar and purple varieties of cauliflower every year - they are just a touchy seed. We'll see if that tiny purple cauliflower sprout actually grows - sometimes they just stay that size and then disappear.
So, don't despair - just try a new variety next time or stick to the vegetables and flowers that grow well for you and buy nursery starts of the types that are harder to grow.
4. Water Your Seedlings
After thinning and transplanting, it time to water around (never on top) your seedlings with a light water stream.
I like to use warm water since I use a seedling heat mat to help the peppers and tomatoes germinate and grow better - it just seems like it's better than putting cold water in and then making the heat mat work to heat it up.
After watering, no matter how gentle your stream was, some seedlings will be laying on the soil. Just use your finger to gently lift them up and re-firm the soil back around them to help them stand up strong again.
Water From the Bottom
To make sure there is enough water for the next week, remove one of the pots/cells and fill the bottom of the tray with water about half-way full.
This is "watering from the bottom" and it is the best way to water your seedlings from now on to encourage deep rooting.
From now on, this is the best way to water your trays, making sure they have enough water so the plants can take it up from the roots.
What about fertilizing?
While optional at this point, you may add a half-strength organic fish fertilizer (make sure to get "odorless" though - it will still smell some, but not nearly as bad as regular fish emulsion - this is a good option).
I usually wait until about week 3, though, because it's a good idea to wait until all the seedlings have sprouted before fertilizing.
5. Provide Strong Light For Your Seedlings
Place your seedling trays back under your strong light.
I used to use a basic shop light like shown with a warm bulb and a cool bulb for an even spectrum, but they are harder to find, so if you need one, this LED light is similar (I've read that LED lights don't dry out the soil as much).
Make sure that the light stays as close as possible to the tops of the plants (ideally just a few inches) and check them daily, moving the light up when needed as they grow.
6. Let Them Grow
That's it for week one of caring for seedlings - it took only about 10-15 minutes to pull extra seedlings, transplant some, water and then put them back under the lights.
Over the next few weeks keep caring for your seed trays by:
- Watering from the bottom only, keeping the trays half-full of water.
- Adding half-strength organic fertilizer at about week three.
- Thin/transplant any other seedlings that need it.
- Remove all but the strongest seedling from all pots by clipping weaker seedlings at the base of the stem.
Once they are planted, there's not a lot of time involved and it's fun seeing your little "babies" come up!
We'll check in again at the 6-week mark when we'll "harden off" some of the seedlings to plant and transplant others to larger pots.
More in the Vegetable Gardening 101 Series:
Note: This article has been updated - it was originally published in 2009, updated in 2016 and again in 2022.
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