When is it safe to plant? Your spring gardening questions, answered

CATHY WURZER: Well, it took a while, but blossoms and new leaves are sprouting up everywhere. And maybe your seasonal allergies are even acting up. Our resident full-time gardener, Meg Cowden, is author of the book Plant Grow Harvest Repeat. She is back and ready to share what's new in her garden as the warm weather has arrived, or at least mostly warm weather. Hey, Meg. How are you?

MEG COWDEN: Hi, Cathy. What a difference a month makes.

CATHY WURZER: Well, let's hope so. It's been kind of depressing.

MEG COWDEN: It better. It better.

CATHY WURZER: Oh my gosh. No kidding.

MEG COWDEN: It's not been easy. No,

CATHY WURZER: It has not been. You might have heard the discussion I had with Paul Huttner earlier here on the program about, when is it safe to plant? And I have several listeners wanting to know that same question. With a state with varied temperatures-- in fact, there's probably still some snow up north-- when do you know when it's safe to plant?

MEG COWDEN: Yeah, I go by my soil temperatures, Cathy. So I let my soil temperature tell me when it's good to plant what. So that's why, in the very early spring, when I put up my low tunnels to warm my soil in just a few spots in our garden, and so I put up hoops and cover them with plastic and secure them, I get that soil temperature to about 50 degrees before I put things in. And that was early April this year.

And now I've used that same structure, and I've put it over a tomato bed. And soil temperatures in there are in the 60s, which is great for hotter things. So all I do is I take our digital meat thermometer, and I stick it into the ground. And you want to go as deep as the roots will be.

So if you're planting seeds, say, you could really just let it skim the surface, like an inch. But if you've got a one-gallon tomato that you picked up at a garden center, you're going to want to really consider where the roots are going to be when it goes into your garden bed. So yeah.

Now, I also went out there before I got on air with you. And I did just some probing in different parts of our garden. And my garden's on a hill. And so I've got, like-- the higher areas are naturally warmer right now. But the lower areas down by my barn, I just dug a couple of trenches to plant potatoes today. And down that six inches or so, the soil is only about 48, 45, which is kind of a minimum for that potato.

And then even further down, the soil temperatures are in the 40s at six inches, whereas higher up, the soil temperature is more like in the 50s. This generally does correspond with our last frost too, right? We don't plant things before our last frost, not only because the plants are frost-tender, like our tomatoes and our zinnia and all of the even more tender things, like cucumbers and squash. But it's also because our soils are still warming up.

CATHY WURZER: Hmm. OK. Gosh, that's all interesting. Did you say a meat thermometer? I mean--

MEG COWDEN: Yeah.

CATHY WURZER: --can I get away with that OK?

MEG COWDEN: Why not?

CATHY WURZER: Well, why not? Sure.

MEG COWDEN: I am all about not-- I really try to not promote consumption. Like, that's part of my-- I consider that kind of part of my brand. You don't need to buy a garden thermometer. You probably already have a thermometer in your kitchen. Go use it, you know?

CATHY WURZER: Exactly.

MEG COWDEN: Yeah.

CATHY WURZER: Wind. Wind, wind, wind. I mean, in April, we had 26 days of 30-plus mile an hour winds. You probably know that because you've been outside, right? Are the seedlings that you've been raising indoors responding to being planted in this windy world of ours?

MEG COWDEN: Well, they have to. So there's a whole process of doing that. So when you grow things indoors or if you're a commercial grower, you want to harden the plants off. And some of that is literally hardening the cells of the plants off and exposing them to wind and to full sunlight because our indoor lights are not as strong as the actual beautiful sun that we have in the sky for us here.

And so yes, wind is tricky. A lot of the things that I'm planting right now are low-growing things. My tomatoes soon will be going out. And I will stake those. But you want strong plants. So if people are going and buying plants, you don't want a plant that's got a skinny stem and looks really tall. To me, that's a telltale sign that it didn't have enough light when they were raising it, whoever was growing that plant at whatever garden center.

So you want a stocky stem. And I would even go for the shorter plants, the plant that's not flowering, even, because I know that come June, July, August, we're going to have plenty of flowers, even if the plants that we plant right now aren't in full bloom. I mean, a lot of people would argue it's even better to not buy things that are in full bloom.

CATHY WURZER: Right. And of course, you mentioned thick stalks, as you're going to get whipped around here if you're a little plant. It probably does help to be a little more robust, obviously. I am going to assume, my friend, that from here on out, you are going to be probably incredibly busy. I mean, what does your life look like?

MEG COWDEN: Oh, it's chaos.

[LAUGHTER]

I mean, it really is chaos. I have more things to do than I have time. I actually have a niece visiting this week. And having an extra person around, I'm realizing, is really great. We got a couple hundred onions planted yesterday. We planted some beans. We planted some popcorn. And then now we're going to plant our potatoes this afternoon. So yes, I'll enlist the kids in the evenings, after they're done with homework and instruments and things like that.

So it's every day, I need to get something in the garden. But I'm not trying to plant my whole garden by Mother's Day. That's not my style of gardening. It's not what I think is necessary. So I've got spaces that are just earmarked for transplants in July. All my spaces where my squash will go, my winter squash, my summer squash, my cucumbers-- that space is also just sitting still for a while.

So I'm slowly waking beds up, like where the onions all have a place. And now the potatoes have a place. And next, the tomatoes will have a place. And so every week, I add a few crops to the garden. So it's enjoyable. It'll take me until the first week of June to really feel like the garden's fully planted.

CATHY WURZER: How in the heck do you keep track of everything? See, this is why I'm a lousy gardener. I throw seeds in there, and I think, now what was that? You know what I mean? I'm just not very--

MEG COWDEN: Yeah.

CATHY WURZER: I'm not very organized.

MEG COWDEN: Well, I think-- did we talk about maybe you don't have enough sun too? I think that might have been a conversation.

CATHY WURZER: Well, that's an issue. Yeah.

MEG COWDEN: Because I mean, you can't just throw seeds in the ground, Cathy. You need sunlight. You need good soil.

How do I keep track of things? I use spreadsheets for a lot of my sowing. So I've got, like-- I know I can look on my spreadsheet right now. I use Google Sheets. And I've got one that keeps track of all of my legends of all the flats that I start inside. And then I have another one that I just-- each cell is, like, the date. OK, today, I'll write, May 3. And I'll write how many row feet of each variety of potato we planted.

And then I can look back on that, which I just did this morning of last year's. I compared the row feet to how many pounds we harvested. So as I'm thinking about what potatoes I want to grow, I can be like, OK, well, that one tasted good, but it didn't produce that much. This one hasn't sprouted yet in storage, and it didn't produce that much, but longer storage is great.

But I'm also complete chaos, as I had already mentioned a couple minutes ago. I mean, I do keep a lot of it in my head. And it makes me a little crazy. But it's how I'm creative. So I'm very tactile. And so just the experience of being in the garden and moving things around, I kind of-- I don't know. It's like my third child, basically. So I pay a lot of attention to it.

CATHY WURZER: OK. So we're in No Mow May, right? Are you one of the no-mowers?

MEG COWDEN: Oh, yeah. Why mow?

CATHY WURZER: I'm not surprised.

MEG COWDEN: Yeah, I mean, first of all, the thatch and the areas of our lawn that is lawn is so thick that our lawn isn't very green yet. You can tell who fertilizes their lawn around here and who doesn't. We're pretty much out at this time of year.

And then we have quite a bit of our front yard that is planted in native seeds, so either shady woodland, like an oak, like an open woodland, or in several different kinds of prairie plants. And so there's a lot of our yard that we don't mow. So I'm seeing lots of bees, both honeybees and native bees out and about. And so I'm a fan of just letting it ride for a few more weeks here before we touch anything.

CATHY WURZER: Good. I'm glad to hear that. OK, final question for you then. What advice do you have for listeners who don't have a lot of time or space for a big garden and might want to grow just a few herbs? Can they just throw a couple plants in a pot and call it good?

MEG COWDEN: It really can be that simple. I would say good soil. So if you buy some potting soil, I would put at least a third of it or even maybe half of it as compost. I'm a big fan of amending because what that'll do is that'll give you a little extra nutrition.

Sunlight, water, and really good soil. And then if things are in pots, you might want to take some time and just invest in a little bit of fish emulsion and a tiny hand sprayer, maybe a one-gallon hand sprayer. And foliar feed them because nutrients are going to move through pots more quickly than they would soil, if you're in the ground. So that's one thing to consider.

But herbs are just such a great way to start. Cilantro. You can keep growing cilantro all summer if you like it. You could get away with growing arugula all summer if you just keep planting it. The idea is to maybe set a few pots aside and plant one now and plant another one in a few weeks, things like that. Just sow seeds, Cathy. That's what we've got to do.

CATHY WURZER: Got to sow seeds. That's kind of a really nice life lesson. All right, Meg Cowden, have a great day. I'll talk to you later.

MEG COWDEN: Thanks, Cathy. Take care. Bye-bye.

CATHY WURZER: You too. Meg Cowden, author of the book Plant Grow Harvest Repeat, founder of the website Seed to Fork and the Modern Garden Guild, a gardening advice group. She's great.

Hope you have a good rest of the day. Thanks for listening to Minnesota Now, right here on MPR News.