Step-by-step tutorial on caring for seedlings after one week of growth with photos and tips for thinning, transplanting, and watering.
You can find more seed starting information in our Seed Starting Guide.
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It's a pretty quick task, but also an important one since it can give your baby seedlings a strong start in the growing season.
Caring for seedlings after their first week of growth basically consists of:
- Transplanting to other pots, if needed
- Watering well (and fertilizing, maybe)
- Providing strong light
I'm going to use the seed tray I started last week to walk through these steps with you so you can easily what your seedlings may look like before thinning, transplanting, and watering, as well as provide you with some tips I've learned after years of starting my own seeds.
Caring For Seedlings at Week 1
1. Evaluate your seed trays
The tray 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 article that I like to plant tomatoes and peppers in larger pots (instead of the 6-cell seedling pots) since they are grown much longer inside and it eliminates one transplanting step.
Note: although not pictured, peppers take much longer - about 1-2 weeks longer - to germinate than tomato seeds, so you will have to provide this care for them a little later. I still plant 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.
There are two things you may notice right away from the above photo:
- There are lots of seedlings clumped together (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 - there are some pots in the photo with only 2-4 seedlings.
However, as I show here, I keep my seeds from year to year and when a packet of seeds is more than 2 years old I plant more because I'm not sure of it's germination rate. These seeds 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
Thin 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. Of course, you can transplant every little seedling and you will be overrun with plants you can't use (like my in-laws who found that they had too many tomatoes). Or you can simply compost them just like we do all our other garden waste. It's just a fact of seed starting:
You must thin now if you want strong, healthy plants that will survive outside.
On quick-to-mature plants like lettuce or basil 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, I like to make sure my bases are covered and keep 2-3 of the strongest seedlings just to make sure that if I do lose a seedling or two after the thinning phase I will have at least 1 to grow to maturity.
- When I do leave more than one, I 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 because by that time their roots will be growing together and I won't want the strong plant disturbed.
- You can use your fingers to gently pull out the little seedling - 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 most of your thinned seedlings, there will also be some you may need to move 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 showing.
- Use the tool to make a shallow hole.
- 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.
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 right with 1-3 seedlings only in each pot.
Note: I did have a pot that I apparently forgot to put seeds in - sigh - since it didn't have a label either. That's why you see an empty pot in the after photo - I planted new seed and I'll have to wait another week for them to sprout.
Here's another before-and-after thinning example - a tray of "cole crops" (ie, cabbage, cauliflower, broccoli) in 6-cell trays.
As you can see in the before photo, some cells 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 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.
For 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, water around (never on top) your seedlings with a light water stream (this watering can with a flower nozzle is gentle). I like to use warm water since I have a seedling heat mat - 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.
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.
Optional: you may add a half-strength organic fertilizer or fish emulsion fertilizer (get "odorless" though - it will still smell some, but not nearly as bad as regular fish emulsion - this is a good option) if you wish at this stage. I usually wait until about week 3, though, because I want to wait until all my seedlings have sprouted before fertilizing.
5. Provide Strong Light For Your Seedlings
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 some off to plant and transplant others to larger pots.
Next in the Vegetable Gardening 101 Series:
Note: AOC's classic vegetable gardening series was published in the first year of the blog – 2009. It’s been republished with updated information and clearer formatting.
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