Most poisonous garden plant?

nmcnear(10a/16)May 26, 2011

What is the most toxic plant that can grow in light shade? I have a huge bare spot in my yard outside the fence, because the deer ravage whatever I put there, even though with the late rain we've been having this year there is still plenty of greenery for them to feast upon out in the woods. Why don't they touch the French Broom I have to pull up every year? I've tried various sorts of garden plants that were supposed to be poisonous and deer-proof - Solanum, Nicotiana, and a few different lilies, but the deer eat them anyway. Not just once, but they eat them again once the plants try to grow some new leaves. So much for these plants being poisonous.

Anyway, I need something EXTREMELY toxic to plant there, something that will make the deer a bit sick so hopefully they'll learn to stay away. Preferably something evergreen and with showy flowers, since this particular spot is under a large Myoporum laetum tree and gets only dappled sunlight throughout the day (so it looks pretty dreary as it is). What about Castor Bean? I know that's supposed to be pretty toxic, but is it only the seeds? I can't find much about the foliage being a deterrent. Foxglove would basically be a last resort for me since it's so incredibly common around here and I'm interested in more unusual plants. Has anyone had success with ornamental rhubarb?

I live in a rural area, so there's no chance of children or dogs eating the plants and getting sick. There's only deer here, and I need something that will keep them at bay.

Thanks in advance for any help! I'm at my wit's end with these rats on stilts!

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Look in the Sunset Western Garden Book. They have a section and several pages of deer resistent plants.
Surely you can find something they don't like.
Is there any neighbors around...maybe plant what they have that lives.
You can purchase coyote urine and spray it around but not sure if that would deter deer. But just so you know the coyote urine is obtained in a inhumane way...
I've read they don't like the smell of coast bar soap, hang it inside the bush in a nylon bag.

    Bookmark   May 26, 2011 at 10:33PM
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I think Ricinus communis (castor bean plant) is considered highly toxic, especially the seeds. I started mine from seed last year and it is now a small tree (about 8 ft). They will grow pretty much anywhere...

Btw, I'm growing the variety called 'Red Spire' and many non-gardeners think it's a maple tree.

    Bookmark   May 27, 2011 at 2:05AM
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Thanks for the suggestions! I will try to get ahold of the Sunset book and see what it has to say. One thing I've noticed through online research is that the plants commonly categorized as "deer-resistant" are usually done so because they have small, tough leaves, and most plants with that characteristic grow only in full-sun (lavender is a good example). Finding something that is both deer-resistant and shade tolerant is proving to be quite an undertaking. :0 Most of my neighbors just grow the super common deer-proof fare like foxglove, oleander, and juniper... I'm hoping to find something a little more exotic if possible.

Castor Bean is definitely something I'm interested in, since it has unusual foliage and bright flowers. Are the leaves poisonous too? Also, would I be able to prune it to keep under about four feet in height? The plant will be going under a window, so that's basically my height limit. I've been researching Lantana, which is toxic and seems like it might be able to tolerate the amount of shade this spot gets, but that's also going to require pruning to keep it short.

    Bookmark   May 27, 2011 at 2:48AM
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jenn(SoCal 9/19)

Have you visited the Plants for Difficult Places forum? There's a post there right now, on the front page, called "Deer Resistant AND Shade-Tolerant".

    Bookmark   May 27, 2011 at 2:22PM
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Yep, I've been keeping a close eye on that thread... Seems like mixed results mainly, what works for some people gets completely destroyed in other areas. The main reason I posted here is because I figured people here might be more familiar with the local Black-tailed Deer and their preferences.

    Bookmark   May 27, 2011 at 10:55PM
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Oleander comes to mind, although it is fairly commonly used. It is very poisonous.


    Bookmark   May 28, 2011 at 11:38AM
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Dick_Sonia(Sunset 17)

It's hard for a creature so olfactory-compromised as Homo sapiens to understand how deer know what to eat. A deer will not eat poisonous plants because they can smell the alkaloids or other toxic compounds in the foliage from a few centimeters away. If a deer did pull off some toxic or unpalatable foliage, it would shake its head and spit it out, not ingest it.

Also, realize that toxicity is species specific. Chocolate is toxic to dogs. Avocado is toxic to birds. Yet birds can eat berries that are somewhat toxic to mammals. Deer can eat many plants with chemical substances because ruminant ungulates have evolved a different kind of digestive system that can deal with such substances. So you would have to know what kinds of plants are toxic to deer specifically, not use some table of plants known to be dangerous to humans.

There are many kinds of plants that deer avoid; they don't necessarily have to be toxic. But as for any kind of aversion conditioning that will keep them away from your yard because they got sick eating your landscaping, dream on...Mother Nature isn't that easily fooled.

    Bookmark   May 28, 2011 at 2:20PM
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The deer don't touch oleander, but when planted in shade it tends to get leggy and ugly. I wish it came in more colors besides shades of pink and white. :( Mexican Oleander comes in yellow and orange, and is poisonous as well, but it requires full sun.

    Bookmark   May 28, 2011 at 2:52PM
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dick_sonia: Yes, that's what I'm learning quickly, is that it seems like a large number of plants poisonous to humans and other animals have no effect on the deer. I need to find something that they don't like that can grow in shade and stays under 3-4 feet, which is the root of the problem. They are definitely eating the poisonous plants they destroy, not spitting the leaves out because there is no trace of leaves on the ground, the plant is just gone. Here's one of my tobacco plants they ate, it was one of two and they were both over a foot tall with flowers developing:

I might try to see if I can get Datura to grow there, I don't think I've heard any reports of deer eating that stuff.

    Bookmark   May 28, 2011 at 3:00PM
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bahia(SF Bay Area)

Some plants that have worked well for me here in the San Francisco Bay Area would include Asparagus densiflorus 'Sprengeri' and A. d. 'Meyers', Astelia chathamica and A. nivicola 'Red Gem', Rubus calycinoides 'Emerald Carpet', Choisya ternata and C. t. 'Sundance', Euphorbia characias 'Wulfenii', Acanthus mollis and A. spinossimus, Dianella tasmanica and D. intermedia, Helichrysimum petiolare 'Limelight', Helleborus argutifolius, Melianthus major, Neomarica caerulea, Carex species such as C. oshimeinsis 'Evergold', Carex 'Sparkler'. Grasses are generally good too, such as Leymus condensatus 'Canyon Prince' or Deschampsia caespitosa or D. flexuosa. As a ground cover, you might try Trachelospermum jasminoides or Gelsemium sempervirens.

If the shade below the Myoporum is really deep, you might want to do some thinning first to get better growth on some of the plants below. Realize also that Myoporum has pretty greedy roots and you may have to till the soil, add compost or additional soil amendments as well as supplemental irrigation to get these things established. I also find that draping new plantings with bird netting helps keep the baby does from "experimenting" with plants that the adults will not touch.

These are all plants that have worked well for me in unfenced gardens here in the Oakland/Berkeley Hills that see deer regularly, and grow in quite a bit of shade.

I'd stay away from the Castor Bean, it is too tall growing for what you have in mind, and really prefers more sun to look good.

    Bookmark   May 28, 2011 at 8:18PM
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peachymomo(Ca 8)

What about Rhododendrons? My first gardening experience in deer country involved everything I planted getting eaten while the Rhodies that came with the house went untouched.

    Bookmark   May 29, 2011 at 11:47AM
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bahia(SF Bay Area)

None of the plants in this photo are poisonous to deer, but none of them are browsed by them either. There are plenty of plants that can work, here's a few more as seen in this photo, and all good for dappled shade...

Here is a link that might be useful: Deer proof plantings

    Bookmark   May 31, 2011 at 1:15AM
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bluebirdie(Z8 SF E Bay)

I grow Oleander and Castor for their looks, and as border to fend off wild animals from the open field. I only plant dwarf Orleander because I fear the full size one will take over the yard. Dwarf Orleanders are slow growers and only grew to 6ft in 25 years.

Castor leaves are not as poisonous as the seeds. However, deer and gophers stay away because they emit saps unpleasant to the palate.

The plants grow big, over 6'x6'. They require pruning to keep small so I removed most of them. But they're beautiful, especially the red kind.

Both castor and orleander only requires watering when young. After established, they've been off irrigation for years and are still flourishing.

    Bookmark   June 3, 2011 at 5:45PM
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