Podcast

Starting Plants Right

Triangle Gardener podcast logoGrowing plants from seeds or cuttings is easy if you follow a few simple rules. Dr. Elizabeth Riley is back on the show to tell us how to create the optimal environment for growing young plants. Propagating plants at home allows gardeners to try out unusual plants, often for a much lower cost.

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JENKINS

Around here our last frost date is April 15th, give or take a couple of weeks.  I like to get a jump on things by starting seedlings inside, then easing them out to a protected space, and then their final destination outside. I’ve had some successes and I’ve endured a lot of failures too.  So I visited Dr. Elizabeth Riley in one of the greenhouses on the NC State campus.  Dr. Riley is an expert in plant propagation and was on the show last fall talking about strategies for collecting seeds. I’ve been mesmerized lately by all the seed catalogs on my desk and have been dreaming about my ideal garden.  But after talking with Liz I realized I need to focus on the basics —creating the right environment and growing healthy roots. Liz showed me how to get those steps right for the plants I start at my home.

RILEY
The first step is to make sure you have the right environment.  You may already have the seeds or the stem cuttings but the environment is key.  Today we are here in one of our propagation greenhouses on campus and it’s set it with a mist system and solenoid values and time clocks and it’s really complex.  But the main thing is its covered in plastic.  Because that plastic keeps it warm, keeps the humidity up when the water goes off so the plants can work on developing root systems. So definitely starting with your environment is key.

We have here today with us some different examples of environments you can use in your home. This is a tray that you can purchase from the store. The first thing you may notice about it is it has a clear plastic dome on top of it and so that is there in order to keep the humidity up around your seedlings or your cuttings.

JENKINS
How long do I need to keep my plants under plastic, or covered?

RILEY
The length of time your plants or cuttings or seedlings need to stay under plastic and covered in that humid environment is until they establish a nice root system.  Once they’ve established a nice root system you can start to ween them off that environment.  You can start to open it up and let them start growing on their own without the humidity.  Plus in some of these situations you may be limited on space in your home.  So once the seedling gets to a certain height it may start hitting the plastic that you’ve covered it with.  At that point you can go ahead to pull that plastic off or find a way to elevate the plastic more over the plants. But usually once they get big enough that they start hitting the plastic go ahead and uncover them so it doesn’t inhibit their growth.

JENKINS
What’s my next step?

RILEY
You need to select a good potting soil mixture.  Some of the bagged potting soil that you can buy at your local garden center are great.  They need to have peat and perlite in them which usually has a really good airspace and water holding so the seeds or cuttings do not desiccate. The environment and the potting soil need to be able to keep the seeds and the cuttings from drying out and desiccating.  So make sure it has good water holding but also good air space.  Because if it holds too much water than your seeds or cuttings may rot.

JENKINS
It’s warm in here, how warm do I need to keep my house if I want to start seeds?

RILEY
If you want to start seeds in your house it can be just what you keep it at to live in.  You’ll want to sit your container or whatever your propagating in, you want to sit in on a window sill or near a window sill is preferable.  Because the seedlings or cuttings are going to need as much light as possible so they don’t stretch or get too leggy.  So putting them on the window sill with something covering them helps to build up temperature —the greenhouse effect.  Similar to the greenhouse that we are in today.  It helps to build up the temperature, keep it moist and warm.  So as long as your house is set to what you’re comfortable with —anywhere from 65 to 72 is a good temperature.  Keep in mind that when you do take the plastic off, or pull the cover off of your propagation environment, that if you have them sitting under and air vent and its blowing air —wether it’s hot or cold, on those cuttings or seedlings it will dry out the potting soil a little bit more so you want to keep them adequately watered so they don’t dry out.

JENKINS
Keeping them moist is almost more important than keeping them warm?

RILEY
Yes.  Again if they are in your house they are most likely going to be warm enough.  So keeping them moist to a certain extent is important.  Obviously if you keep them super saturated they’re going to rot or get some diseases like damping off.  So keeping them adequately moist so they don’t dry out is really important, more so than keeping them warm.   The temperatures fluctuate a lot.  So once we are past the first frost-free date, which I think for our area is usually April 15th.  Then I’d go ahead and move my seedlings outside.  The more natural sunlight they can get the better they will develop for their leaves, the height, their fruit development, flower development —depends on what you’re propagating for. But moving them outside as soon as possible is really important to get that natural light.

JENKINS
Seeds aren’t the only way to start new plants.  You’ve got some other things here. Tell me about them

RILEY
Yes, there are lots of ways to start new plants.  You can also do stem cuttings which is a method of asexual propagation which means that you are essentially cloning the plant that you are taking the cutting from.  This is great.  I do this a lot in the summer.  It’s great with things like begonias —especially the dragon wing begonias.  They are great for just snapping off a steam.  I sometimes just stick them right in a mason jar with clear water and they root right there for me. Steam cuttings are an option for plants that don’t start well from seeds.  Or from a plant that you want to maintain a certain characteristic.  Cloning it is the only way of doing that.  Starting cuttings in your home is a little more difficult than starting seeds and it changes from species to species.  Like I mentioned the Dragon Wing Begonias are very easy to start from cuttings.  Even just putting them in a mason jar with water.  Coleus is the same way. But once you start getting into things like woody species, like hollies and things like that, it can become really difficult to make sure you are getting a good cutting.  Once you start talking about woody types of plants then taking steam cuttings can become a little bit challenging.  Not to say that you can’t do it in your house, you certainly can, but you need to one – do your research on your plants that you’re wanting to take steam cuttings of because that’s going tell you when to propagate them and how to do it.  Two, you’re going to need to be patient because some woody plants can take a very long time to root.  And that is one of the challenges within a home environment because it’s really hard to maintain that proper humidity and temperature to maintain that moisture level for a long extended period of time for a woody cutting.  It can take several weeks to root.  So for me, I don’t usually take woody cuttings at home.  I usually just do herbaceous plants that I know and have practiced with that I know will root. So many of your annuals and herbaceous plants as well.

JENKINS
Once I’ve taken my cuttings what’s next?

RILEY
If you’re taking a stem cutting you want to make sure you’re picking a plant that’s healthy, disease free. Try to avoid any flower buds because those just take away energy from the roots getting started.  Then you’re going to take your cutting and make it 4-6” long or about the length of a normal size plant label.  Once you’ve got that cutting and you’re ready to stick it you’re going to want to make a fresh cut on the bottom and remove the leaves from the lower third of the stem cutting.  Make sure you are placing it in the proper direction.  Meaning that the bottom goes into the soil and the top goes above the soil.  Sometimes with weeping plants and things like that you can get a little confused as to which way you should stick the cuttings, so make sure you always keep up with that direction so you can have success in rooting it.

Also, some species that may be more difficult to root you can purchase hormodin powders or Dip and Grow type of liquids from your local garden centers.  That just has plant hormones in there that can help get the roots started and give an even distribution of roots through all of your cuttings.

JENKINS
Can you describe your technique as you’re stripping?

RILEY
So some species need to be, the term is wounded, that just helps to encourage rooting.  So you just gently slide your pruners down the side to scrape off that outer layer of the stem that helps it take up more hormones and it helps to start the rooting process.

JENKINS
Liz, you keep emphasizing the importance of a healthy root system before moving plants outdoors. But how do know if the roots are developing properly?

RILEY
To see if the root system is developing properly you can pull the plant, very carefully, out of whatever container you’re growing them in. The easiest thing to do first off is to pick up the container and look at the bottom in the drainage holes.  Then you may see some white roots there and that gives you a first indicator that the roots are growing well.  Then you can very gently tap it and take it out of the container to see how well established the root system is.

JENKINS
So if the roots are coming out of the bottom of the container that’s a good first sign that my plants are getting ready to be transplanted?

RILEY
Yes, it is.  White healthy roots are a great indication.  Roots are very important.  Root health is very important.  If you start to have problems with roots or if you buy plants that have root issues already with them then you’re not going to have success with it in your landscape.  Always look for healthy white roots first and then go from there.

JENKINS
I’ve got a few cuttings I want to try, but right now I’m going to start some seeds.  Talking with Liz has me refocused on creating the best environment —providing plenty of light and making sure to keep the potting mixture moist. I’ve been trading seeds with some of my gardening friends and I have some unusual plants to try this season.  What are you going to try this year?

I’m Lise Jenkins and this is the Triangle Gardener show.  We’re your guide to enjoyable gardening in North Carolina.  You can find this and other episodes on our website, TriangleGardener.com  Thanks for listening.