Episode 98: the science of plant propagation

Ever wondered why Echeveria leaves are so easy to propagate? Find out in this episode. Photograph: Leslie Halleck.

Ever wondered why Echeveria leaves are so easy to propagate? Find out in this episode. Photograph: Leslie Halleck.


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If you’ve ever puzzled about why your heart-shaped hoya leaf never grows beyond a single leaf, or why an Echeveria leaf that fell on the floor has grown a baby plant, this episode is for you!

I explore the botany between houseplant propagation with horticulturist Leslie Halleck, finding out the pros and cons of growing from seed and cuttings, and why you need to take care when thinking about propagating plants labelled “PBR”. And I answer a question about a floppy calla lily.

Leslie Halleck’s new book Plant Parenting is out now: there’s more info on it on her website. Find Leslie on Twitter as @LeslieHalleck and on Instagram. (You may remember Leslie from episode 61 where we talked about growlights and her book Gardening Under Lights.)

If you’re a Patreon subscriber of $5 a month or more, you can listen to An Extra Leaf 28, in which Leslie explains the process of air layering, and I give it a go with a spindly Dracaena plant.

Scroll through the links below as you listen to find out more about the terms we talk about…

Vegetative propagation allows you to increase you stock of a particular plant by making genetic clones of the parent plant. Photograph: Leslie Halleck.

Vegetative propagation allows you to increase you stock of a particular plant by making genetic clones of the parent plant. Photograph: Leslie Halleck.

  • Totipotency - a plant cell’s potential to differentiate into all the different structures in an organism. This is what plants need in order to root a cutting.

  • Adventitious roots are roots that emerge from parts of the plant other than the root (think roots emerging from ivy stems). Likewise adventitious shoots.

  • Want to know more about propagating Begonias from split leaf cuttings? Here’s a guide.

  • Here’s a guide to taking tip cuttings from tomatoes from friend of the show James Wong.

  • Plants labelled “PBR” or “patent pending” are someone’s intellectual property - this means you can’t propagate and sell these plants - although you can propagate for your own use. PBR stands for Plant Breeders’ Rights. Here’s information from the UK government on how to get PBR for a plant you have bred.

  • Rooting hormones are useful for propagating some houseplants, particularly those with woody stems, helping them to “root before you rot”.

  • IBA - Indole-3-butyric acid - is rooting hormone, or there’s GA - gibberellic acid. They come in gel and powder form.

Question of the week

Julie has spent too much money on a calla lily that’s already started to droop! What can she do? Calla lilies tender members of the genus Zantedeschia, usually hybrids of a couple of different species as there has been a lot of breeding in this particular genus. They can be grown outside in temperate climates in summer but need to be kept frost free in winter. Calla lilies like a lot of moisture, so need to be regularly watered in the home: in warm weather that may mean once a day! I suspect Julie’s plant may just need a drink. There’s a great RHS guide to growing the Zantedeschias here.

Want to ask me a question about your plant? Either way, tweet @janeperrone, leave a message on my Facebook page or email ontheledgepodcast@gmail.com.

Dates for your diary

Join me at Lullingstone Castle in Kent in the UK on September 21 and 22 for Cactusworld Live where I’ll be doing a live recording of On The Ledge and holding a listener meetup.

The following weekend I’ll be at the Garden Museum on Sunday September 29 for their Houseplant Festival: I’ll be helping out with the houseplant clinic, and there’s also the chance to take part in workshops and browse an awesome range of stalls from some of my favourite houseplant shops!

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This week's show featured the track Overthrown by Josh Woodward. Ad music is by the Heftone Banjo Orchestra:  Dill Pickles and Whistling Rufus. All tracks licensed under Creative Commons.

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