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Plant Answer Line Question

Keywords: Recycling (Waste, etc.), Euphorbia

I have a large Euphorbia trigona (also known as an African milk tree), nearly 7 feet tall that currently lives in my living room. I will be moving soon, and it is too large to take with me. I'm concerned about putting it in the yard waste bin and exposing the people who collect it to the irritating sap. Also, is this type of Euphorbia a noxious weed that I should keep out of the yard waste altogether?


I believe it should be fine to put the Euphorbia in your yard waste, as yard waste handlers wear gloves. You could minimize the amount of sap going into the recycling by cutting it into the largest allowable sections, then setting them on a tarp to ooze their sap for a while before adding them to the container. There are a few varieties of Euphorbia that are classified as noxious weeds and would need appropriate disposal, and your plant is not one of them.

Date 2018-03-15
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Plant Answer Line Question

Keywords: Helianthemum, Helleborus, Heuchera, Propagation, Invasive plants, Invasive plants, Euphorbia

I am wondering if the following plants can be divided or propagated successfully: Heuchera, Donkey Tail Spurge (Euphorbia), Corsican Hellebore, and Helianthemum.


I consulted The American Horticultural Society Plant Propagation book, edited by Alan Toogood (DK Publishing, 1999), and it says the following:

  1. Heuchera: by division or by seed in spring. Since cultivars may not come true from seed, I would recommend dividing your plants. Once spring growth has begun, lift the plant from the ground and remove small sections from around the edge (look for good roots, and 2-3 shoots).
  2. Euphorbia myrsinites: (Just a note: based on the USDA information that this plant is invasive in Oregon and banned in Colorado, I would think twice before propagating it. This species does a fine job of propagating itself, apparently. In general, the genus Euphorbia can be propagated by division in early spring, or from spring to summer, by seeds in fall or spring, and by cuttings in summer or fall, but if you were to propagate by cuttings, you would need to protect your skin from the sap.
  3. Helleborus argutifolius can be propagated by division after flowering, or by seeds in summer. Test seed capsules for readiness by gently squeezing. If the seed capsule splits to reveal dark seeds, it is ready for harvest. Wear gloves! H. argutifolius (Corsican hellebore) often self-seeds. Check around the base of the plant in spring. When each seedling has at least one true leaf, gently lift and transplant to moist, fertile soil in light shade.
  4. Helianthemum can be started from greenwood cuttings rooted in summer and fall, and by seeds sown in spring in a frost-free location.

If you would like further information on the relative ease or difficulty of each of these methods for each of these plants, I recommend coming to the Miller Library and looking at our books and other resources on propagation. Here is a link to a booklist.

Date 2018-03-15
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Plant Answer Line Question

Keywords: Plant cuttings, Euphorbia

I have a Euphorbia trigona houseplant which is about 6 feet tall and quite thin. It has gotten weak and is bending. It looks like it is going to break. I have read it can be propagated by stem cuttings. I don't know if this means cut the end off OR cut several sections of the stem. If I just cut off the end will the original stem survive?


According to Indoor Gardening by Kate Jerome (Pantheon Books, 1995), Euphorbia trigona often becomes top-heavy, which sounds like what is happening to yours. They do tolerate pruning well and may branch out from the place where you prune. Do be very cautious in handling this plant, and be sure to wear gloves: it has a toxic sap that can cause skin irritation. Generally when cuttings are taken, they are from the tips, where the new growth is occuring, but you can also try several cut pieces of stem. Ordinarily not every cutting is able to form roots, but according to The Complete Houseplant Book by Peter McHoy (Smithmark, 1995), you can increase your chances of success by letting the cut ends of the stem dry out in the air before putting them into potting soil.

Date 2018-03-14
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Garden Tip

Keywords: Lavatera, Snails, Slugs, Geranium, Euphorbia

What unites gardeners from all walks of life? A passionate loathing of slugs and snails. Perhaps if we understood these little slimy mollusks better - their lifecycle, their tastes - we'd learn to appreciate them for the successful creatures they are. Or at least we could learn how to drive them out of our gardens with the latest science has to offer.
The BBC's Science and Nature web site has an in-depth article on snails and slugs that makes fascinating reading. http://www.bbc.co.uk/nature/animals/features/291feature1.shtml
  • Slugs have memory and will return another night to finish off tasty seedlings until they are all gone.
  • A few plants slugs find distasteful: foxgloves, many species in the daisy family, Lavateras, hollyhocks, azaleas, Euphorbia, hardy Geraniums.

A long list of "Slug Resistant Plants" is given in a Seattle Times article by local writer Valerie Easton

Date: 2006-08-24
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May 31 2018 13:14:08