Growing Safely

Food forest work is real outdoor work, on real land, in a specific place — and Hawaiʻi's climate and ecology carry a few real, well-documented health risks along with it. None of them should stop anyone from doing this work. All of them are manageable once you know what they are and build a few habits around them. This page exists because knowing the risk is part of doing the work responsibly, not a reason to avoid it.

Rat lungworm disease

What it is: Rat lungworm disease (Angiostrongylus cantonensis, medically called eosinophilic meningitis) is a parasite carried by rats and picked up by slugs and snails that eat rat droppings. People get infected by eating produce that a slug or snail has contaminated — or, more rarely, by accidentally eating a small slug or snail, or a piece of one, hidden in fresh produce.

Why it's relevant here: The University of Hawaiʻi's own on-farm food safety guidance notes that snails in Hawaiʻi are found on land, in trees, and in water — including in taro patches. The main vector on Hawaiʻi Island, an introduced semi-slug, has been found on lettuce, sweet potato, banana, and other fruit, including ripe fruit still on the plant. A 2007 survey in the Puna district found roughly three-quarters of the semi-slugs tested were infected.

What it can do: Most cases resolve on their own — common symptoms are headache, neck stiffness, tingling skin sensations, fever, nausea, and vomiting, usually appearing one to three weeks after exposure. It's a real disease, though, not a mild inconvenience: severe cases have caused paralysis, seizures, and — in a small number of documented Puna cases — comas lasting months. Take the precautions below seriously.

How to reduce the risk:

• Rinse and rub all produce under running water before eating it — friction, not just water, is what removes slime and tiny slugs. Wash leafy greens leaf by leaf.
• Never eat produce with visible slime, a snail, or a snail's feeding damage on it. Don't try to wash off contamination — just don't eat that piece.
• Control rats around growing areas (the parasite's original source) and reduce slug and snail habitat — clear damp hiding places like fallen wood, dense groundcover, and anything stored flat on the soil.
• Wear gloves when clearing vegetation or handling garden debris by hand.
• If you ever eat snails, slugs, or freshwater prawns intentionally, cook them to at least 165°F first.

Source: University of Hawaiʻi CTAHR, Best On-Farm Food Safety Practices: Reducing Risks Associated with Rat Lungworm Infection (FST-39).

Leptospirosis

What it is: A bacterial infection picked up from freshwater, mud, or wet soil contaminated with the urine of infected animals — in Hawaiʻi, mainly rats and feral pigs. It enters through broken skin, or through the eyes, nose, or mouth.

Why it's relevant here: This one is specifically an agricultural risk, not just a general outdoors one. Published Hawaiʻi case data found that nearly 80% of confirmed cases involved freshwater exposure through outdoor recreation or taro farming specifically, with another 11% linked to home gardens. Anyone working wet soil, irrigation water, or a taro patch regularly is in the group this disease actually affects most.

What it can do: Mild cases look like a bad flu — fever, headache, muscle aches. Untreated, it can progress to organ failure, jaundice, and kidney dysfunction. The good news: early antibiotic treatment (within about five days of symptoms starting) works well, which makes recognizing the exposure and telling a doctor about it the most important step.

How to reduce the risk:

• Cover any cuts, scrapes, or open skin before working in wet soil or handling irrigation water.
• Wear gloves, boots, and long sleeves when clearing vegetation or working muddy ground.
• Avoid standing water where you can, especially if it looks stagnant.
• Control rats and feral pigs around growing areas.
• If a fever or flu-like illness follows any wet-soil or freshwater exposure, tell a doctor about that exposure directly — it changes what they test for.

Source: Leptospirosis: The Microscopic Danger in Paradise, and Hawaiʻi Department of Health prevention guidance for farmers and outdoor workers.

Handling Christmas berry safely

What it is: Christmas berry (Schinus terebinthifolius) is one of the four invasive species named specifically on this site's own case study and Plant Selection pages — real, already-cleared work, not a hypothetical. It's in the same plant family as poison ivy and poison sumac (Anacardiaceae), and it carries a real contact hazard that's easy to miss because the plant itself looks unremarkable.

Why it's relevant here: Its sap can cause second-degree burns on skin contact, and the plant is a strong allergen when in bloom — sneezing and allergic reactions are common for people working near it while it's flowering.

How to reduce the risk:

• Wear long sleeves and gloves when cutting or clearing it — don't let cut stems or sap touch bare skin.
• Avoid burning it. Smoke from plants in this family can carry the irritant and cause a reaction in the airway, not just the skin.
• Wash any exposed skin promptly if you've been in contact with cut material.
• If it's in bloom, expect more airborne irritation than usual — this is a reasonable time to mask up or clear it another day if you're sensitive.

Sources: PlantPono.org and the USDA NRCS Pacific Islands Area invasive species fact sheet for Christmas berry.

Cat's claw's thorns

What it is: Cat's claw (Caesalpinia decapetala) is the third of the four invasive species named on this site's Plant Selection page. Unlike Christmas berry, its hazard isn't chemical — it's purely physical. This is an aggressively thorny vine, with sharp curved thorns running the full length of every stem, right down to ground level.

Why it's relevant here: Reports on this species in Hawaiʻi describe thickets dense and sharp enough to make walking through them impossible, and there's at least one documented case of a cow becoming fatally tangled in a cat's claw thicket on Kauaʻi. A vine that can seriously injure a large animal deserves real respect from a person clearing it by hand.

How to reduce the risk:

• Wear thick, puncture-resistant gloves and long sleeves — regular garden gloves won't stop these thorns.
• Work slowly and clear a path before you commit to reaching into a thicket; don't assume you can see every stem before you touch it.
• Treat any puncture wound from it like you would any deep scratch working outdoors — clean it promptly and watch for signs of infection.
• On steep ground, be especially careful: several reports flag this species as hardest and most dangerous to control on slopes.

Sources: Hawaiian Ecosystems at Risk (HEAR) project report and the Hawaiʻi Cattlemen's Council species profile for cat's claw.

Fire risk from guinea grass and maile pilau

What it is: Guinea grass and maile pilau — the other two invasives named on the Plant Selection page — don't carry a direct contact hazard the way Christmas berry or cat's claw do. Their real risk is fire. Guinea grass dries into dense, fast-igniting fuel; maile pilau climbs and smothers trees until they die standing, then persists as a tangle of dead vine draped through the canopy — what fire researchers call a fuel ladder, carrying a ground fire up into the treetops.

Why it's relevant here: Hawaiʻi's invasive grasses and vines are directly implicated in the state's wildfire trend — they burn readily, and the burned ground then favors more of the same invasive growth over native recovery, a self-reinforcing cycle. Any pile of cut guinea grass or dead, vine-choked material left to dry on-site is real fuel, not just yard waste.

How to reduce the risk:

• Don't let cut guinea grass or dead vine material pile up and fully dry near structures, fences, or anything else worth protecting.
• Be especially cautious with any fire (burning cleared brush, even a small one) near stands of guinea grass or dead trees smothered in maile pilau — this is exactly the fuel combination that carries a fire further and faster than expected.
• Clear a defensible buffer around structures if dry invasive grass is present nearby.
• If burning cleared material at all, check local burn restrictions first and never leave a burn pile unattended.

Sources: Hawaiʻi Invasive Species Council and Pacific Fire Exchange on the grass-fire cycle in Hawaiʻi.

Heat-related illness

What it is: Straightforward physical exertion in full tropical sun — clearing, planting, hauling — carries a real risk of heat exhaustion or, in more severe cases, heat stroke. This isn't Hawaiʻi-specific, but it's one of the most common real risks in this kind of work anywhere it happens outdoors.

Why it's relevant here: Heat exhaustion looks like headache, nausea, dizziness, weakness, heavy sweating, and muscle cramps. Heat stroke — the dangerous escalation — can bring confusion, fainting, seizures, and hot, dry (or profusely sweating) skin at a very high body temperature. It's the kind of thing that builds gradually during a long clearing or planting session and gets missed until it's already serious.

How to reduce the risk:

• Water, rest, and shade — the three things federal workplace safety guidance leads with, in that order of importance.
• Build up your workload gradually if you're new to this kind of labor, rather than starting at full pace.
• Take scheduled breaks rather than waiting until you feel you need one.
• Work with someone else when doing sustained physical labor in full sun, and check on each other — heat stroke can impair someone's own judgment about how they're doing.

Source: CDC/NIOSH, Preventing Heat-related Illness or Death of Outdoor Workers.

Cutting tool safety

What it is: Machetes and similar clearing tools are standard equipment for this kind of work, and they're also the most obvious way to get hurt doing it. This one is general good practice rather than Hawaiʻi- or research-specific — worth saying plainly rather than dressing it up as more than it is.

How to reduce the risk:

• Always cut away from your body and away from anyone else nearby — clear a full swing radius before you start.
• Keep blades sharp. A dull blade requires more force and is more likely to glance off unpredictably than a sharp one.
• Wear real gloves and sturdy footwear, not just what happens to be on hand.
• Sheath the tool immediately when you're not actively using it, and never hand off an unsheathed blade.

The point of this page

None of this is meant to make food forest work sound more dangerous than it is — most people who garden, farm, or restore land in Hawaiʻi never run into any of it directly. But real work on real land means real conditions, and the honest version of "how to build a food forest" includes knowing what to watch for, the same way it includes knowing what to plant. See Further Reading for the full sourcing behind this page.