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[gentle instrumental music] ♪ JOE LAMP'L [voice-over]: I'm Joe Lamp'l.

For 10 years, Growing a Greener World has told the stories of the people and the places who are making a difference in the health of our environment and the sustainability of our global community.

But as we embarked on our 11th season, life changed overnight.

So many things we took for granted would never be the same again.

Now it's up to each of us to take a more active role in not just saving our planet, but making it better, feeding our families with organically grown food, conserving vital resources, protecting natural habitats, starting in our own backyards.

Growing a Greener World-- it's still our mission, and it's more important than ever.

♪ Many of the most popular plants we enjoy today from the top arboretums down to the most memorable backyard gardens originated from plants that came from faraway places, oftentimes from cuttings like this.

And although these twigs don't look like much, they contain all the genetic information needed to make an exact copy of the parent.

And although the process of propagation isn't all that complicated, the mystique behind the practice prevents many of us from trying this ourselves at home.

So today we're going to demystify the process and show you how to make a lot more plants for free from one of the nation's most up and coming experts.

[gentle instrumental music] Over the years I've met a lot of people that share my passion for plants and making more of them.

Some have made it their full time career.

Brie Arthur is one of those people.

In fact, she's part of a small group of nationally recognized rock stars of young horticulturalist making their mark on the world by making more plants.

She studied horticulture and landscape design at Purdue University.

After graduating, she immediately started putting her passion and talents to work as a full time propagate.

15 years later, Brie estimates she's added literally millions of plants to botanical gardens and backyards across the country.

[gentle instrumental music] BRIE ARTHUR: So plant propagation was the first class I ever got an A in when I was in college.

It felt like a huge accomplishment.

And I realized in that class that I had some sort of intuitive understanding about how to propagate plants, different types of wood, how to graft, how to stick cuttings, when to sow seeds.

And I decided I had to follow that for my career.

It was really exciting and inspiring to be good at something like that.

It's really nice to know that in nature plants, their only mission is to propagate.

And with a home gardener with a little bit of help, you can really excel at producing plants.

[gentle instrumental music] I think more home gardeners don't propagate for themselves because they're intimidated by the process.

My goal as a propagator is to take that away, make people understand that it isn't hard, it isn't complicated.

You don't have to have a fancy sophisticated greenhouse to be able to propagate plants.

There are two ways to propagate plants-- sexually, which just from seed which will have a lot of genetic variability, meaning you aren't guaranteed what you will have next season, or asexually, which is essentially cloning.

And cuttings are really the most relevant way to do asexual production.

It's very easy.

It doesn't take a lot of time.

And you're guaranteed to get what you're looking for.

[gentle instrumental music] JOE LAMP'L: So Brie has an exciting day planned for us.

We're off to one of her favorite collection sites to take cuttings.

Now as any good plant professional would have, you need a cooler, right?

BRIE ARTHUR: You do.

JOE LAMP'L: I like how you think, Brie.

BRIE ARTHUR: It may not be as exciting as you're hoping for.

JOE LAMP'L: Yeah, that's what I was afraid of.

But you do have all your important tools in here, right?

BRIE ARTHUR: Yes, we do.

JOE LAMP'L: OK, so let's see what you have because you never want to get out there and find that you're missing some important things.

BRIE ARTHUR: No, you definitely don't.

Well first off, I like to have a good resealable bag.

JOE LAMP'L: Yep.

BRIE ARTHUR: This will help keep the cuttings moist so they don't dry out.

JOE LAMP'L: Very important, because if you took a cutting and got it home and it was dry, it's worthless, right?

BRIE ARTHUR: Exactly.

JOE LAMP'L: Pretty much.

OK, so you have your bags.

BRIE ARTHUR: To go along with that, you need to have a spray bottle of water.

This way you can mist the cuttings right when you take them.

JOE LAMP'L: Yeah, just a little extra added insurance.

BRIE ARTHUR: Exactly.

JOE LAMP'L: OK, good.

BRIE ARTHUR: Another bottle here is repurposed for using rubbing alcohol.

This is a 2-step process for keeping your equipment clean.

JOE LAMP'L: Yeah.

BRIE ARTHUR: A quick spray with rubbing alcohol and then you burn the blade.

JOE LAMP'L: Yeah.

And so it's nothing to fear, very simple process.

But, you know, when you take cuttings from one plant and then go to the next, you really do run a risk of spreading diseases from one to the other.

BRIE ARTHUR: And this ensures that you won't.

JOE LAMP'L: Good plan.

OK, now I took the liberty of getting your trusty holster out.

BRIE ARTHUR: Excellent.

So I like to keep two sets of pruners, one for woody material, one for more softwood herbaceous plants.

JOE LAMP'L: Now why wouldn't you use one for both?

BRIE ARTHUR: Well, you don't want to mash the cuttings.

And if it's a really soft cutting, a smaller blade will do a better job.

JOE LAMP'L: OK, good.

And I also see you have your sharpener with you.

BRIE ARTHUR: Yes, I like to have that in the field, so that my pruners are always sharp.

JOE LAMP'L: So even if you went and sharpened these before you ever left, you run the risk that out there in the field, you get into some wood you might do a little damage or dull your blade.

BRIE ARTHUR: Exactly.

That's a quick two second fix.

JOE LAMP'L: It doesn't take up any space.

It's smart to have this.

BRIE ARTHUR: Exactly.

JOE LAMP'L: Good.

OK, you have pen and markers.

BRIE ARTHUR: Yes, I like to keep track of everything that I'm collecting in the field.

It's really important, you know, to write the name.

I'd like to keep track of the date and the source that I have that to reference back.

JOE LAMP'L: And it's so important to do that in the field, because if you waited to get home, you can't tell one cutting from the next.

BRIE ARTHUR: No, you can't.

JOE LAMP'L: Yeah, and you got to have good information.

BRIE ARTHUR: Got to have good information.

And keep your labels dry, that way you can write on.

JOE LAMP'L: Yeah.

OK, I think that's everything.

BRIE ARTHUR: That's everything.

I think we're ready.

JOE LAMP'L: All right, let's go do it.

[gentle instrumental music] So here we are in the middle of the summer and the classic time to take a lot of cuttings from many types of plants.

But it's not the best season to take cuttings from all plants, right?

BRIE ARTHUR: That's right.

I'd like to stick deciduous trees and shrubs in early spring.

They tend to root best on softwood.

And then you have the whole summer for them to capture energy through photosynthesis before they drop their leaves in the fall.

JOE LAMP'L: OK, when you say stick, you're referring to taking the actual cutting and putting it in the pot immediately, right?

BRIE ARTHUR: Yes.

JOE LAMP'L: OK, so now in the summer that classic season for a lot of plants that we have in our backyard gardens, talk to me about why that's best for some plants.

BRIE ARTHUR: Well, this is the season for broad leaf evergreen production.

They root best on semi-hardwood, meaning the spring flush is slightly hardened.

This applies for camellias, azaleas, rhododendrons, sort of all the classic southern heritage plants.

JOE LAMP'L: Yeah.

And what about conifers?

I've always sort of had a difficult time with conifers.

They're slower to root out, a little bit tricky.

BRIE ARTHUR: I do my conifers in late summer into fall.

They tend to root best on hardwood.

And then you leave them in your potting media for a longer period of time.

They can take anywhere from 9 months to 14 months to root out.

JOE LAMP'L: So once again, for everything, there's a season.

And it explains also why you're a full time propagator too.

BRIE ARTHUR: Yes.

JOE LAMP'L: You stay pretty busy all year.

BRIE ARTHUR: Plant propagation is year round business.

JOE LAMP'L: Wow.

[gentle instrumental music] I love walking under the canopy of trees like this.

It never gets old.

But here we are at the j.s.

Raulston Arboretum where you do your work and probably your playground, right?

BRIE ARTHUR: Absolutely.

JOE LAMP'L: I love this place, but to think that you're coming here and you're taking these cuttings as a pro, and yet you were telling me that you still seek permission and kind of have somebody oversee your work.

BRIE ARTHUR: It's really important to be courteous and get permission.

I like to have a staff member with me, so that I know that I'm taking cuttings from plants that they would like for me to propagate off of.

And I'm making the plants look better as a means of propagating.

JOE LAMP'L: Well, it's interesting to hear you say that because that says a lot for somebody like John Q Public walking through.

You just don't do that with your pruners and start snipping away.

BRIE ARTHUR: No.

There's definitely permission needed.

JOE LAMP'L: Yeah.

And even in a backyard, you just don't do that.

BRIE ARTHUR: No.

JOE LAMP'L: But why we're here, I think we got to make hay while the sun is shining and take as many cuttings as we can get away with.

BRIE ARTHUR: That's right.

JOE LAMP'L: So I'd like to kind of get some home with me too.

[gentle instrumental music] So we have the camellia here, one of my favorite broad leaf evergreens and the perfect one to be cutting this time of year, right, because it's semi-hardwood at this point.

BRIE ARTHUR: Yes.

JOE LAMP'L: So define, though, exactly what we're talking about when we're looking for semi-hardwood, how do we know that?

BRIE ARTHUR: Well, what we're looking for is this new growth that's slightly hardened.

So in the spring this would have flushed a very soft green, and it would be really flexible and it would break.

JOE LAMP'L: Right.

BRIE ARTHUR: By mid summer, you can see it's actually turned a nice and brown, distinguishing it from the hardwood of last year's new growth.

JOE LAMP'L: Right.

BRIE ARTHUR: So this is really the ideal cutting that you'd want to take.

JOE LAMP'L: Yeah.

So as far as semi-hardwood, it's pliable to the point that you can bend it over like this, but it's not going to break like if it were new wood.

BRIE ARTHUR: Exactly.

JOE LAMP'L: If it were greenwood, it would just kind of crush.

This is not so pliable here.

BRIE ARTHUR: This is not too pliable.

And this is definitely not what you want to be sticking.

This will take a lot longer to root.

JOE LAMP'L: And the other thing that I think it's important to note is that we're lucky here with a camellia, because it gives us a real clear indication with a different color from the hardwood.

But not all evergreens are like that.

Sometimes they're just much harder to tell the difference in the color.

BRIE ARTHUR: What you want to do is go from the tip down and see where the nodes have changed.

So that's really the easiest way.

You can look at any shrub, from the tip down you should be able to see where the new growth came from.

JOE LAMP'L: So here you can see that right here, plus you get the color, so you get two clues as to where to start that new growth.

OK, so now when you're coming to here to make the cut, when you take the sample home, you're not cutting it right here because you want to get multiple samples and be efficient with your cut.

BRIE ARTHUR: Exactly.

And what I want when I'm sticking is a fresh cut.

So what I would come in and do is actually take this branch down to here.

JOE LAMP'L: Yeah.

BRIE ARTHUR: And now when I go home to dissect this, I'll actually have one, two, three, four, five, six pieces from one cut.

JOE LAMP'L: Nice.

So we're off to a good start.

BRIE ARTHUR: Yes.

JOE LAMP'L: All right, so this goes in the bag and labeled and more cuts.

BRIE ARTHUR: Exactly.

JOE LAMP'L: All right.

[gentle instrumental music] You want the date on here?

BRIE ARTHUR: Yes, please, and the location.

JOE LAMP'L: Got it.

And a bag.

BRIE ARTHUR: And a bag.

JOE LAMP'L: OK. BRIE ARTHUR: And these are going to be a little large to fit, so we'll just cut these down, slide them right in.

JOE LAMP'L: And you need the mister.

BRIE ARTHUR: That's right give it a few goodness.

Excellent.

JOE LAMP'L: All right, and the tag.

BRIE ARTHUR: Now you can drop that label right in.

JOE LAMP'L: OK. BRIE ARTHUR: Then we can seal it, and we're ready to move on to the next plant.

JOE LAMP'L: OK. [gentle instrumental music] Good.

BRIE ARTHUR: Excellent.

JOE LAMP'L: Great.

BRIE ARTHUR: We're ready to prune.

JOE LAMP'L: OK, so we're checking out a new gardenia.

I love this form.

Is that one of the best properties of it?

BRIE ARTHUR: Absolutely.

It's a great dwarf that fits into every landscape.

JOE LAMP'L: Yeah, that's good.

We need more of those.

How hardy is it?

BRIE ARTHUR: It's very hardy.

It survives without any trouble to single digits.

JOE LAMP'L: Wow, That's saying a lot for a gardenia.

[gentle instrumental music] So Brie, we're back from the arboretum, our awesome adventure collecting plant cuttings.

But now we're ready to process those cuttings.

The first point I want to make is that you do not need a fancy greenhouse to be successful with propagation, right?

BRIE ARTHUR: That's correct.

JOE LAMP'L: So what are the objectives?

BRIE ARTHUR: Well, what you have to do is balance the plant's rate of respiration with the relative humidity in the environment.

JOE LAMP'L: OK. All right, so in layman's terms what we're talking about here, we want to create a moist environment.

And we also want to keep it cool.

And a good way to do that is to take your tray or your pots and keep them down low, maybe on top of some gravel in a contained area, so maybe some plastic around the sides, and then mist it periodically throughout the day to give you that environment.

So we have that out of the way.

That's good to know.

Now we have our media, the thing that we want to plant our cuttings into.

And there are some good options and some not so good options.

BRIE ARTHUR: That's right.

JOE LAMP'L: Talk about that.

BRIE ARTHUR: Well, I think the bad option that people sometimes fall into is buying seed sowing mix, which is a vermiculite based soil.

JOE LAMP'L: Good for seeds.

BRIE ARTHUR: It holds entirely too much moisture for cuttings.

JOE LAMP'L: Yeah, it's not so good for cuttings.

And that's this right here.

So it's very fine.

But this is what we're after, right?

BRIE ARTHUR: That's right.

JOE LAMP'L: So what I see in here is first of all perlite.

And that's this right here.

And this is designed to actually improve drainage and create air pores, air pockets.

BRIE ARTHUR: That's right.

JOE LAMP'L: OK, I see some coarse bark in here.

That obviously is to create some more space in the soil.

BRIE ARTHUR: And better drainage.

JOE LAMP'L: And better drainage.

And then just some potting mix.

BRIE ARTHUR: That's correct.

JOE LAMP'L: So you can buy all three of these separate and mix them together.

And sometimes you can find it already mixed together, right?

BRIE ARTHUR: That's right.

JOE LAMP'L: OK, so that's what we want.

We have our media out of the way.

Now we need to plant it into something.

And again, we have good options and not so good options.

Talk about those.

BRIE ARTHUR: So the ideal option, and what nurseries tend to grow in, are these cell trays.

JOE LAMP'L: Right.

BRIE ARTHUR: And you know, it's a small space and it has great drainage because it has great depth.

JOE LAMP'L: OK. BRIE ARTHUR: For homeowners who don't have access to cell trays, we have a bad option and a good option.

JOE LAMP'L: OK. BRIE ARTHUR: The bad option, you can see it's got the depth, but it's too big.

It's going to hold too much soil.

By the time the plant roots out, it will probably rot.

JOE LAMP'L: Hum, OK. BRIE ARTHUR: A better option is this.

It also has the depth, but it's significantly smaller.

JOE LAMP'L: Right.

Plus you're using less media, less water, and you can get a lot more of these in the same sized space-- BRIE ARTHUR: That's right.

JOE LAMP'L: --hence a lot more cuttings.

I like that option.

OK, so now we have that done, we're ready to process our cuttings.

And I understand there are exceptions to every rule.

But as some general steps for our cuttings, what do we want to do here to process these?

BRIE ARTHUR: Well, what you really want to have is a cutting that has three to four leaves and at least two nodes that will be underground.

JOE LAMP'L: OK. BRIE ARTHUR: So on a cutting like this, we're going to take it off of the central stem, just like that.

I'm going to actually take this leaf off and I'm going to remove the flower bud, because you don't want any energy to go into flowering.

You want all the energy to go to root.

JOE LAMP'L: And you reference the nodes.

The nodes are the area where leaves could come out in the future.

BRIE ARTHUR: That's right.

And it's actually where roots will come out.

JOE LAMP'L: OK, and we want two of those at least underground.

BRIE ARTHUR: Now on a hardwood or semi-hardwood cutting, we want to give a small wound, just like that.

JOE LAMP'L: And you're exposing the tissue.

The reason for that?

BRIE ARTHUR: That is so that it will absorb more rooting hormone.

JOE LAMP'L: OK. And that's this right here.

We have some options.

You're using the liquid form.

BRIE ARTHUR: I use the liquid for broad leaf evergreens.

I think that it works the best for these sorts of plants.

JOE LAMP'L: OK. BRIE ARTHUR: You want to dip it for 8 to 10 seconds, so that it absorbs all the hormone.

JOE LAMP'L: OK. Now we do have several options for this.

They all work.

They're all basically comprised of the same components.

Some are better for others in different applications.

Don't worry about the details right now.

We'll have that information for you later.

OK, so we're going to put that into the container at this point.

BRIE ARTHUR: And all you want to do is center it in the cell, make sure two nodes are underground, and give it a light squeeze.

And that will make it so there's no air pockets surrounding it and it won't dry out.

JOE LAMP'L: Perfect.

OK, so one down, about 200 more to go, right?

BRIE ARTHUR: That's right.

JOE LAMP'L: OK, so we'll get busy.

Now I know this was a lot of information, but you do not have to worry about trying to remember all of this because we're going to have it for you on our website under the show notes for this episode.

Brie's got a great article for you.

The website address, it's the same as our show name.

It's GrowingAGreenerWorld.com.

OK, I'm ready to get busy.

I'll do the boxes.

BRIE ARTHUR: All right.

[gentle instrumental music] JOE LAMP'L: Now our goal for these cuttings is to get them into the landscape.

But it doesn't happen overnight.

There's quite a few things that take place between now and then, whenever then is.

And let's talk about what those steps are and when we'll finally be able to plant these.

BRIE ARTHUR: Well, it's going to take about four to six months for these to be rooted.

So the way you tell, you kind of pull on them, if you feel resistance that means they've already set roots.

That's the time to get them out of the mist into a transitional area that's shady, cool, that you can still water.

JOE LAMP'L: OK, so the mist is providing the moisture these plants need until they get those roots.

But once that happens, we don't need the mist any longer.

BRIE ARTHUR: That's right.

JOE LAMP'L: OK, so out it goes into the transitional area.

Then we want these to be potted up into a larger container to get bigger.

But you don't just do that yet.

BRIE ARTHUR: No, my trigger is to see roots coming out of the bottom.

Otherwise, you can pull and if the whole cell comes out whole, doesn't shatter, then it's ready to be potted into a one gallon.

JOE LAMP'L: OK. Now I want my cuttings to look like the plants that I see in the nursery when I go to buy them and spend big money.

But they're much bigger and they're much fuller.

So you're going to bump these up into another container.

But then how do you make them get to that fullness?

BRIE ARTHUR: Make sure they stay fertilized.

Make sure that you keep them evenly moist.

Don't let them dry out.

And then be sure to give them pruning.

JOE LAMP'L: Because every time you make the cut, you're stimulating new growth.

And typically for every one cut, you get two new branches.

BRIE ARTHUR: That's right.

JOE LAMP'L: Great.

So in about what?

A little over a year, we can have this kind of plant that we would pay for in the nursery.

So a cutting like this, what would we pay for that plant?

BRIE ARTHUR: A one gallon of this type of osmanthus runs about $25.

JOE LAMP'L: $25 for one cutting.

We need to make more cuttings.

[gentle instrumental music] When you're looking for the perfect medium to root your cuttings or pots or seedlings, the basic ingredients is almost always the same no matter what you buy.

And it's usually sphagnum peat moss and perlite and maybe some other minor ingredients mixed in.

But these are the two stars of the show.

So while you could spend some money and have it already premade, you don't have to.

You could save a lot of money and buy it in bulk.

And that's what I did right here.

Both of these ingredients are readily available.

And it's just a 50/50 mix.

So all I do is just scoop out some of the peat moss.

Now peat moss is really nice.

It's very lightweight.

And once you get it hydrated, it holds moisture very well.

But the trick is getting it hydrated.

So let's just start with three scoops of peat moss and three scoops perlite.

Perlite is a natural ingredient.

It's expanded through heat to look like little pieces of popcorn.

But the beauty of perlite is it adds a lot of drainage and airspace to your soil mix and it also retains some moisture.

So it's kind of the perfect combination here, a very lightweight medium, plenty of moisture retention, and lots of airspace.

That's what you're looking for.

For any of your seedlings or cuttings, that's all it takes.

Got a cutting, get that nice and wet, initially well hydrated, and this is all you need.

And when you put the cutting in, don't push it all the way down to the bottom, give it some space beneath it, and you're good to go.

[gentle instrumental music] Well chances are you've dug up a plant or two in your day to relocate it to a different part of your landscape.

Or maybe when you dug those plants up, you divided them or separated them, in which case you did a simple technique of plant propagation.

That's a really effective form and it works great on perennials, like these irises.

But if you can do that, you can propagate any number of plants in your garden.

Leaf cuttings are another super simple way to make more plants.

Again, not all plants work well for this type of method.

But perhaps the best known example is African violets.

Other easy options are what we're doing here with begonias, succulents, such as echeveria, and pineapple lily.

With the begonias, the key is to make sure the point where the stem meets the leaf is firmly in contact with the soil.

With the echeveria, the end of the leaf directly attached to the main stem has to have contact with the soil, since that's where the cells are located that will generate the roots.

And with a lily, you just have to make sure you insert the leaf section into the soil in the same direction it was growing, so orientation is key.

To keep it simple, Brie likes to make angled cuts and then plant the pointed end into the soil.

Once you have your leaf cuttings inserted, keep them moist and in a shady location.

But with leave cuttings, misting is not required or even recommended since if the leaf remains to wet, it can rot.

But do make sure the soil media remains moist.

After that, just fertilize periodically and plant them elsewhere once they put on new growth.

[gentle instrumental music] Providing a moist environment for our new cuttings is critical over the next several months.

And there are a couple ways to provide that mist.

One is to use a spray bottle and apply it several times a day.

Now, it works.

But how practical is that really, especially in our busy lives?

The other thing that you can do is put the system on autopilot and it might be a lot easier than you think.

Now you know those patio umbrellas that you've seen and that tubing that is underneath it and it puts out that mist?

Well, that same system can easily be applied to a potting bench like this to do the same thing.

And that's what Brie has done.

Now listen to how easy this is.

You buy this kit in the store for about $20.

Now according to the labeling, it cuts the temperature down by about 20%.

And that was one of the key objectives to their survival.

The other thing it's already pre-assembled, so basically you're just attaching it to a firm surface, so that when the mist goes on, it goes down onto the plants.

You attach that misting system to an automatic timer to come on several times a day and you have it.

The only other thing that you need to do is to provide an enclosed environment, and typically you do that with plastic, drop the plastic down, keep the plants down low because that also helps keep them cool.

And you're ready to go.

And for only $15, that's a very good investment.

[gentle instrumental music] Now in case making more plants from cuttings as we've seen Brie already demonstrate so far is a little more than you want to take on for now, but you still want more plants and you want to try your hand at propagation, well, there's a very simple technique.

And it's a matter of simply taking cuttings and sticking them into water.

Now some plants do well and some plants not so well.

The ones you want to focus on are the ones that are foliage plants, such as basil and coleus and plectranthus and even sweet potato vine.

Now check this out.

Brie took some cuttings about a week ago.

And look at these roots how they've already formed.

Now once they get to be about an inch long, like these are, they're ready to go in the ground.

But the most important thing that you need to do once you put them in the ground is to continue to add water because, remember, these things have been living in water this whole time.

So if you put them in the ground and don't water them after that, well chances are they may not make it.

So the hardest thing you've got to do once you put them in the ground is just to keep them watered.

Now when these are ready, are you going to ship these to me or do I need to come back and get them?

BRIE ARTHUR: You'll have to come back.

JOE LAMP'L: That's OK. That's one trip I don't mind.

Thanks, Brie.

Well, I hope today that you found a new found confidence or at least a curiosity for trying to start more plants yourself, because once you master the basics, I think you'll be very impressed with your newfound skills.

Plus, it's the best way I know to add to a garden with special plants from special friends.

Now, if you like what you saw today, you can watch the episode again and you can also download an article on plant propagation, everything we cover today plus a whole lot more that we didn't have a chance to talk about.

It's on our website under the show notes for this episode.

It's GrowingaGreenerWorld.com.

Thanks for joining us, everybody.

I'm Joe Lamp'l.

And we'll see you back here next time for more Growing a Greener World.

MALE ANNOUNCER: Growing a Greener World is made possible in part by-- FEMALE ANNOUNCER: The Subaru Crosstrek, designed with adventure in mind, built in a zero landfill plant, so you can roam the earth with a lighter footprint.

Subaru-- proud sponsor of Growing a Greener World.

MALE ANNOUNCER: And the following-- the US Composting Council, Milorganite, and Rain Bird.

BRIE ARTHUR: While you're trying to balance the relative humidity-- [laughter] I did it backwards.

Can I do it over?

[laughter] OK, let's start again.

JOE LAMP'L: OK. Oh, that's great.

BRIE ARTHUR: What do I say?

What was my line?

JOE LAMP'L: We're trying to balance relative humidity with dew point of the relative medium of the hyperbole divided by the Celsius centigrade factor.

BRIE ARTHUR: If the plants rate of respiration with the relative humidity-- ♪ MALE ANNOUNCER: Continue the garden learning from the program you just watched, Growing a Greener World.

Program host, Joe Lamp'l's Online Gardening Academy offers classes designed to teach gardeners of all levels, from the fundamentals to master skills.

Classes are on demand any time.

Plus, opportunities to ask Joe questions about your specific garden in real time.

Courses are available online.

For more information or to enroll, go to growingagreenerworld.com/learn.

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