Autumn is nearly here, and for many of us with oak trees nearby, the ground will soon be scattered with acorns. You may have heard that acorns are poisonous to horses, and while that’s partly true, the real story is far more interesting (and a lot more about balance than danger).
This year seems to be an abundant one for acorns, so let’s unpack what’s really going on, why some horses seek them out and others won’t touch them, and how we can work with nature to keep our horses safe and healthy.
What’s in Acorns That Can Harm — and Heal
One of the active ingredients in acorns are tannins — bitter plant compounds that in high amounts can irritate the gut and damage the kidneys.
But tannins aren’t “bad” by default. In small, self-selected amounts, they can actually offer benefits, including:
- Pain relief
- Anti-inflammatory effects
- Anti-parasitic action
Horses are incredibly intuitive eaters when given the chance. In the wild, they might choose to nibble on acorns when they need these properties, then leave them alone when they don’t.
Why Some Horses Eat Acorns and Others Don’t
You might notice one horse hoovering up acorns while another ignores them completely. This is normal.
It’s all about self-selection – animals instinctively choosing what they need in the moment.
If a horse’s body signals that tannins could help (perhaps they’re dealing with inflammation or parasites), they’ll be drawn to acorns. If not, they’ll walk right past them.
Nature’s Balancing Act: The Role of Chickweed
Here’s where it gets fascinating. In natural, undisturbed pastures, you’ll often find chickweed growing under oak trees. Chickweed contains saponins, which can help neutralise excess tannins from acorns.
So, in a healthy ecosystem:
- A horse eats some acorns for the tannins.
- If they get more tannins than they need, they wander over and nibble chickweed to balance things out.
It’s nature’s built-in safety net. Calendula officinalis is also rich in natural saponins, so this can be offered if chickweed is not available. Many horses (and other animals) love this
When the Balance Breaks
In many modern paddocks, especially those that are sprayed, manicured, or overgrazed, chickweed is nowhere to be found.
This means:
- Horses can still eat acorns if they feel the need.
- But they can’t find the balancing plants to prevent toxicity.
- This is when poisoning risk goes up.
Zoopharmacognosy: Nature’s Medicine Cabinet
What’s really happening here is something called zoopharmacognosy, the ability of animals to self-medicate by selecting plants, clays, algae, or other natural substances their body needs in that moment (this is critical; as their needs will change daily) .
Most of our pharmaceutical medicines were originally derived from plants and natural compounds. Nature already provides a vast pharmacy, but in modern environments, animals often can’t access the full range they would have in the wild.
This is where Applied Zoopharmacognosy comes in.
As caretakers, we can:
- Learn which natural substances support different health needs.
- Offer them in a way that allows animals to choose what they want and need.
- Read their responses so we can understand whether something is helping, or not needed.
And here’s the key – these substances are medicine when needed, but can be toxic when they’re not required. It’s a fine balance. That is why just adding things to your animal feed can often do more harm than good.
When a horse is “out of balance”, whether due to parasites, pain, inflammation, or emotional stress, it may select very different natural substances than when it’s well. Just like us, their needs shift day by day, season by season.
Understanding self-medication is not just essential for physical health, but also for emotional well-being. It empowers both us and our animals to take back control over health choices, and to work with nature’s pharmacy rather than against it.
Practical Plant List: Saponin-Rich or Tannin-Balancing Options
If your horses have access to acorns, you can support them by offering plants that help balance tannins. These should always be offered for self-selection, not mixed into feed, so the horse can decide how much (or whether) to take.
Herbs:
- Chickweed (Stellaria media) – The classic under-oak companion plant.
- Calendula (Calendula officinalis) – High in saponins and soothing to tissues.
- Fenugreek seeds (Trigonella foenum-graecum) – Palatable and gut-friendly.
- Alfalfa (Medicago sativa) – Contains saponins and helps buffer digestion.
- Yarrow (Achillea millefolium) – Tannin-modulating and anti-inflammatory.
- Licorice root (Glycyrrhiza glabra) – Soothes mucous membranes (use with care in metabolic horses).
Essential Oils (offered via applied zoopharmacognosy):
- German Chamomile – Anti-inflammatory, gut-soothing.
- Sweet Marjoram – Gentle liver and digestive support.
- Peppermint – Cooling and helps relieve gut discomfort.
Important: The way you offer these matters as much as what you offer. Without the right approach, you can cause more harm than good. This is why I teach safe, effective methods in my courses so you can confidently read your horse’s responses (and dogs etc) and support them without guesswork.
👉Learn how to offer herbs and oils safely through my zoopharmacognosy courses
How to Support Horses Around Acorns
The ideal solution is to keep horses on natural pastures with a variety of native trees, shrubs, and “weeds” — nature’s own medicine cabinet.
But I know this isn’t always possible.
If you have acorns in your grazing, here’s a practical way to help:
- Offer dried chickweed or calendula daily.
- Allow horses to take as much or as little as they want (true self-selection).
- Offer the above essential oils in separate buckets of water for self-selection (see this course for HOW ) or this BUNDLE
This gives them the natural tools to process acorns safely, just as they would in the wild.
What This Teaches Us
This is a perfect example of how:
- Plants we often label as weeds are actually medicines.
- Everything in nature is connected and balanced.
- Our role as horse guardians is to understand these needs and replace what’s missing from modern environments.
By observing, learning, and supplementing wisely, we can keep our horses healthy while respecting their natural instincts.
💡 Want to learn more about zoopharmacognosy, plant-based self-selection, and keeping your horses in balance with nature?
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