Every houseplant death follows one of two scripts: the slow desiccation of the forgotten, or — twice as common — the loving drowning of the over-attended. Root rot from overwatering kills more houseplants than drought, which means plant survival is not about caring more. It is about matching care patterns to species tolerance.
This calculator models that match. Species hardiness sets the tolerance envelope (a pothos forgives what a calathea prosecutes), light conditions set the metabolic rate (a plant in dim light drinks slowly and drowns easily), and your actual behavior — watering rhythm, attention style, travel patterns — determines where in the envelope you operate.
Enter the plant and the honest version of yourself. You get a survival probability, the projected failure mode (drought vs. drowning — the fix differs completely), days until the next crisis, and a minimal-effort protocol tuned to your negligence style rather than a fantasy schedule you will not keep.
The formula
H_species- Species hardiness — the width of the tolerance envelope
M_match- Care-pattern match — your rhythm vs. the species’ preferred rhythm
L_light- Light adequacy for the species’ placement
|W_you − W_need|- Watering mismatch in either direction — drought and drowning both count
T_travel- Absence pattern — trips longer than the species’ tolerance window
How it works, step by step
- Pick the species (or its nearest relative) — hardiness varies by an order of magnitude.
- Describe the light honestly: “bright indirect” through a north window in winter is “dim.”
- Describe your actual watering behavior — rhythm and quantity, not intention.
- The model computes the mismatch and, crucially, its direction: drought or drowning.
- Adopt the minimal protocol: usually fewer, better-timed interventions, not more of them.
Worked examples
The loved-to-death calathea
Calathea (hardiness 2), few feet from window, watered most days on vibes, no drainage holes, attention 9/10. Survival: 0% — Hospice, failure mode DROWNING. Maximum attention, minimum system: the model’s point in one plant. First fix: drainage, then halve watering.
The neglected snake plant
Snake plant (hardiness 9), across the room, watered when it visibly begs, travels often. Survival: 81% — the species tolerates what would execute a fern. Failure mode: mild drought; a monthly reminder makes it immortal.
How to read your score
Frequently asked questions
Why do most houseplants actually die?
Overwatering, by a wide margin — root rot from soggy, oxygen-starved soil kills more houseplants than drought. This inverts intuition: attention without a soil-check habit is more dangerous than benign neglect, which is why the calculator can score high attention negatively.
How often should I really water?
No schedule survives contact with reality — light, season, pot and species all move the target. The robust rule: finger-test 5cm of soil; water thoroughly when dry, not before. Frequency emerges from the plant instead of the calendar.
Does the pot really matter that much?
Drainage is close to binary: a no-hole decorative pot turns every generous watering into a root bath. Keeping the nursery pot inside the pretty one (and emptying the saucer) fixes it for free.
Which plants survive genuine neglect?
The high-hardiness tier: snake plants, ZZ plants, pothos — all tolerate weeks of drought and dim light. If your honest attention score is under 4, choosing from this tier is not defeat; it is engineering.
Why does my plant die in winter when nothing changed?
Because everything changed: less light means slower metabolism means the same watering schedule becomes overwatering. Winter root rot from unadjusted summer schedules is a classic — halve frequency when days shorten.
Is my plant-care shame stored anywhere?
No — all computation is local to your browser. The calathea’s fate remains between you and the calathea.
Reference: hardiness & watering by species
| Plant | Hardiness | Water (growing season) | Light minimum | Kills it fastest |
|---|---|---|---|---|
| Snake plant | 9/10 | Every 2–4 weeks | Low | Overwatering in winter |
| ZZ plant | 9/10 | Every 2–3 weeks | Low | Constant moisture |
| Pothos | 8/10 | Weekly-ish | Low–medium | Prolonged darkness |
| Spider plant | 8/10 | Weekly | Medium | Rarely dies; tips brown from fluoride |
| Monstera | 6/10 | Weekly, check soil | Medium–bright indirect | Soggy soil, no drainage |
| Peace lily | 5/10 | When it droops | Medium | It forgives — dramatic but hardy |
| Fern (Boston) | 4/10 | Keep evenly moist | Medium, humid | Dry air + missed watering |
| Fiddle-leaf fig | 3/10 | Weekly, exactly | Bright indirect | Any change whatsoever |
| Calathea | 2/10 | Distilled, evenly moist | Medium, humid | Tap water, dry air, drafts |
Watering frequencies assume a draining pot and moderate light; halve in winter.