OK, so we started our seeds last month (or two weeks ago, or now, if you're me) and we're ready to transplant them into the garden or pots. How do you know when the little plants are ready to transplant?
The leaves tell us when the plants are ready. For all seed-bearing plants, the first three leaves aren't their true leaves; rather, they're called cotyledons (from Latin meaning "seed leaf"). The true leaves are usually darker and larger. Of course, you've hardened off all of your little seedlings by now, right? If not, you need to do that first — get them adapted to being outside their protective starting place, whether greenhouse, windowsill, or just some small pots on your deck or balcony.
We've had some pretty frosty nights here on the coast, cooler than our usual temperatures, so it may be a little early to put those transplants out just yet.
It's best to wait until the soil temperature is about 50 degrees or so, especially for warm weather crops (tomatoes and peppers, which are a challenge to grow outdoors on the coast unless you have the variety that does well in cooler weather). You can purchase a soil thermometer at your local garden center, or you can just stick your hand in the dirt and see if it feels like an ice cube. If it does, it's too cold to plant.
So let's say we've checked all these things and it's time to transplant. You can transplant directly into the ground or you can put your seedlings in pots, depending on the space.
But first, the soil. You want to give your plants the best possible chance to get big and strong, so you need the soil to be prepped — definitely weed it first. If the soil is crappy, add some compost or well-rotted manure, and mix well. Doing this a week or so before transplanting can be helpful, but it's not necessary as long as you amend the soil prior to planting.
Now it's time to plant. The best way to not damage the sweet little seedlings is to pinch the bottom of the cell the plant is in (if you used plastic pots), then gently lift it, root ball and all, out of the cell. Handle gently by the leaves if you can because you can easily damage the stem if you grab it there instead. Try to retain as much of the soil and the roots as possible when you put it in the ground. Make sure the hole is big enough and deep enough for the plant start, then gently replace the soil around the plant. Water in with some diluted fish emulsion or some compost tea to give it some extra nutrients. Since we haven't had a lot of rain in April, it's going to be important to keep the plants watered, but don't overdo it. You can kill a plant with too much water just as easily as you can by depriving it of water. Now is also a good time to spread that Sluggo around, especially for tender plants like lettuce, greens and, well, anything that slugs like to eat (basically everything in my garden). Keep up with the Sluggo, especially if we do end up getting more rain this month and next. It's easier to battle the slugs when they are small, rather than when they get big and fat, and come out at night to mow down all of your carefully nurtured seedlings. Ask me how I know.
There are a few plants that benefit from planting deeper than you think you may need to. Tomatoes are a good example. Again, make sure you're growing a variety that does well in our cool climate if you're here on the coast. Inland growers have more choices in tomatoes since it gets so much warmer there.
I take the very tiny bottom leaves off but you don't need to do this. Plant the tomato all the way up to the first set of leaves. Tomatoes can create roots all along the stem when you plant them this way and it makes for a stronger plant that can draw up nutrients better.
Some seedlings come several to a pot — many summer squashes come this way at the nursery. It's not a bad idea to just plop the whole thing in the hole because odds are one or two of the plants won't make it. Do not plant a gazillion seedlings in one spot, however. This can happen if you've started your own seeds and didn't have the heart to thin out the extra when they started growing. Crowding will not benefit the plants — rather, it will hinder growth.
Finally, spacing. Speaking from personal experience, here's where we all go a little bananas when transplanting: It's tempting to put those little tiny plants right next to each other but it's crucial to give them the space they need to grow. The seed packet (or tag on the six pack, if you purchased the plants rather than seeds) should give you some clues about spacing. Make sure you've planted your starts in a spot that gets at least six hours of sun, more for plants that require a lot of light. Lettuces, kales and other greens can do fine in six hours of light, tomatoes not so much.
Make sure you've watered the transplants well and watch them grow!
Julia Graham-Whitt (she/her) is owner and operator of the landscaping business Two Green Thumbs.