Glossary of Indoor Plant Terms

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This glossary explains common houseplant and decor terms in clear, practical language. It’s written for real U.S. homes, apartments, and work-from-home setups. For fundamentals, see Indoor Plant Care 101 and Soil & Containers.

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A

Aeration

Air spaces in potting mix that keep roots oxygenated and prevent rot. Improve with perlite, pumice, or bark. See soil guide.

Aerial Root

Roots that grow above soil to anchor or absorb moisture (e.g., Monstera). Harmless indoors; you can gently direct them to a pole.

Air Layering

Propagation method that roots a stem while still attached to the plant using moist sphagnum and wrapping.

Air Pruning

Roots naturally stop circling when exposed to air (fabric pots), encouraging branching roots.

Alkalinity (pH)

How acidic/basic water or mix is. Most houseplants prefer ~pH 5.5–6.5. Extreme pH can lock out nutrients.

Aroid

Members of the Araceae family (Monstera, Philodendron, Anthurium). Often prefer airy mixes with bark/perlite.

Auxin

Plant hormone driving growth and rooting; relevant in pruning and propagation responses.

B

Bottom Watering

Soaking a pot from the saucer so soil wicks water upward; reduces fungus gnats and surface compaction. Drain well after. See watering 101.

Bright, Indirect Light

Very bright room light without direct sun on leaves; typically a few feet back from a south/west window or near an east window with sheer curtains.

Bud

The early stage of a flower or new growth. Handle gently—buds are sensitive to dry air and drafts.

Beneficial Insects

Predators (e.g., lady beetles, predatory mites) used in IPM to suppress pests indoors; most effective in enclosed setups.

C

Callus (Propagation)

Dried, sealed tissue at a cutting end that reduces rot risk before planting.

Chlorosis

Yellowing leaves due to nutrient issues, overwatering, or roots under stress. Diagnose via mix, watering, and fertilizer history.

Coco Coir

Peat alternative from coconut fiber; retains moisture but needs aeration (perlite/pumice) to avoid compaction.

Cultivar

Selected cultivated variety (often variegated or dwarf). Care can differ slightly from the species.

D

Direct Sun

Unfiltered sunbeams hitting leaves (south/west windows). Suits succulents and cacti; many tropicals prefer filtered light.

Dormancy

Slower growth phase (often winter) when watering and feeding needs decrease.

Drainage Hole

An opening at the pot’s base that lets excess water escape—critical to prevent root rot. Avoid “no-hole” planters or use inner nursery pots + cachepot.

“Drainage Layer” (Myth)

Rocks at the bottom don’t improve drainage; they raise the perched water table. Use a well-aerated mix instead.

E

Edema

Water blisters or corky spots from roots taking up more water than leaves can transpire, common after overwatering or sudden light changes.

Epiphyte

Plants that grow on other plants (not parasitic), e.g., many aroids. Prefer airy support like moss poles and chunky mixes.

Etiolation

Leggy, stretched growth from insufficient light. Fix by moving closer to brighter indirect light or adding a grow light.

F

Fertilizer (N-P-K)

Nitrogen–Phosphorus–Potassium ratio. Use diluted, label-led doses during active growth; flush salts periodically. See fertilizer guide.

Foot-Candle (fc)

Light unit used indoors. Low light ~50–250 fc; bright-indirect ~500–1,000 fc; direct sun can exceed 2,000 fc.

Fungus Gnats

Tiny flies breeding in consistently wet soil. Allow top layer to dry, bottom water, use sticky traps, and improve aeration.

Flush (Leach)

Running water through soil to rinse built-up fertilizer salts. Drain thoroughly afterward.

G

Grow Light

LED lighting supplement. For many tropicals, target ~200–600 PPFD at leaf level. Use timers (12–14 h/day) and safe distances.

Gravitropism

Growth response to gravity—roots grow down, shoots grow up; explains bending after rotating a plant.

Guttation

Water droplets exuded from leaf edges, usually at night. Not the same as dew; often harmless.

H

Hard Water

Water high in minerals (TDS). May cause leaf spotting or salt crust; consider filtered or distilled blends.

Hardening Off

Gradual acclimation when moving plants between very different light or humidity environments.

Humidity (RH)

Moisture in air. Many tropicals prefer 40–50% RH. Group plants or use a humidifier + hygrometer.

Hydrogen Peroxide (H₂O₂)

Used diluted to sanitize tools or soil surfaces; handle carefully and follow label guidance.

I

Indirect Light

Ambient brightness without direct sunbeams. Most foliage houseplants thrive here.

Internode

Stem segment between nodes. Short internodes = compact growth, often from higher light.

IPM (Integrated Pest Management)

Stepwise pest control: cultural → mechanical → biological → least-toxic chemicals. See pest control.

Insecticidal Soap

Fatty acid salts that disrupt soft-bodied pests (mites, aphids). Use label rates; test on a leaf first.

J

Juvenile vs. Mature Form

Some plants change leaf shape with age (e.g., Monstera fenestrations). Requires time, light, and support.

K

Kelvin (K)

Color temperature of light. 4,000–6,500K works well for foliage realism under LEDs.

Knuckle Test

Moisture check by inserting a finger ~1–2″ into soil; water when dry at depth for most tropicals.

L

LECA

Lightweight expanded clay aggregate used as a soilless medium; needs nutrient solution and consistent wicking.

Leaching

Rinsing salts from mixes by flushing with water. Prevents tip burn on sensitive plants.

Lux

Metric light unit (lumens/m²). Roughly: low ~200–1,000 lux; bright-indirect ~5,000–10,000 lux.

M

Micronutrients

Iron, manganese, zinc, etc. Deficiencies show as pattern-specific chlorosis; balanced fertilizers include micros.

Moisture Meter

Tool to estimate soil moisture; verify against feel/weight to learn accuracy. See watering 101.

Mealybug

White, cottony sap-sucker. Treat with swabs of isopropyl alcohol, insecticidal soap, and persistence.

Misting

Spritzing leaves; gives brief humidity spikes and can spread pests. Prefer room-level RH control.

Mycorrhizae

Beneficial fungi that can improve root nutrient uptake in some mixes.

N

Neem Oil

Plant-based treatment for soft-bodied pests; use label directions and avoid hot, direct sun after application.

Nitrogen Deficiency

Older leaves yellow first; growth slows. Address with balanced feeding and check watering.

Node

Point on a stem where leaves/roots emerge; essential for stem cutting propagation.

NPK

Fertilizer ratio of Nitrogen–Phosphorus–Potassium (e.g., 3–1–2). Choose by plant type and season.

O

Organic Matter

Decomposed plant materials in mixes; improves water holding and nutrient capacity.

Overwatering

Too-frequent watering leading to oxygen-poor roots and rot. Fix via aerated mix, drainage, and proper intervals.

P

pH

Acidity/alkalinity scale. Most houseplants like slightly acidic mixes (≈5.5–6.5).

Perlite

Expanded volcanic glass that adds air pockets and speeds drainage in potting mixes.

Pest (Common)

Spider mites, mealybugs, thrips, scale, fungus gnats. Identify early and follow IPM steps. See guide.

Potting Mix vs. Garden Soil

Use sterile, soilless potting mix indoors. Garden soil compacts and harbors pests.

Pumice

Porous volcanic rock improving aeration; heavier than perlite, less likely to float.

Propagation

Creating new plants from cuttings, division, or layering. Sanitize tools and label dates. See pruning/prop.

Q

Quarantine

Isolating new or sick plants for 2–4 weeks to prevent pest spread.

R

Repotting

Refreshing mix and/or moving to a slightly larger pot. Best in active growth; water lightly after. See repot guide.

Root Ball

Mass of roots and mix that fills the pot. Check for circling roots or rot when repotting.

Root Bound (Potbound)

Roots circle and fill the pot; water runs through quickly. Time to up-pot 1–2″ or root prune.

Root Rot

Decay from oxygen-poor, wet conditions. Smells sour; roots turn mushy/brown. Correct watering and mix, trim affected roots.

Rhizome

Thick, horizontal stem (ZZ, Sansevieria) that stores energy; handle gently when dividing.

S

Self-Watering Planter

Pot with a reservoir and wicking action. Reduces frequency but still check salt buildup and algae.

Soil-less Substrate

Non-soil media (LECA, pon, perlite mixes). Requires nutrient solution management.

Sphagnum Moss (Long-Fiber)

Used for propagation and poles; keep evenly moist but not soggy to avoid rot.

Spider Mite

Tiny pest causing stippling/webbing. Increase humidity, rinse leaves, and use labeled treatments.

Sunburn (Leaf Scorch)

Brown, crispy patches from intense sun. Move to bright-indirect and acclimate gradually.

Succulent

Plants storing water in leaves/stems; prefer high light and fast-draining mixes.

T

Terracotta

Porous clay pots that dry faster—great for plants prone to overwatering.

Thrips

Slender pests that scar leaves. Quarantine, sticky traps, and targeted treatments per label.

Top Dressing

Layer of decorative/functional material on soil surface (pebbles, bark) to reduce splash and gnats.

Transpiration

Water movement through plants into the air; drives nutrient flow and cooling.

U

Underwatering

Too-little water causing wilt, crispy tips, and slow growth. Rehydrate slowly; adjust routine.

Up-Potting

Moving to a slightly larger pot (usually +1–2″ diameter) to accommodate growth.

V

Variegation

White/yellow/cream/green patterning on leaves. Often slower growth; avoid low light to prevent revert.

Vermiculite

Expanded mineral that increases water holding; often mixed with perlite for seed starting.

VOC (Volatile Organic Compound)

Airborne chemicals from paints, cleaners, etc. Ventilation and filtration matter most; plants can complement aesthetics and well-being.

W

Watering Schedule

A flexible cadence based on light, pot size, and mix—check the soil, don’t just follow a calendar. See watering 101.

Wicking

Capillary movement of water through media (self-watering systems, capillary mats).

Winterize

Adjust care in cold seasons: more light, less water, draft protection, target 40–50% RH. See winter care.

X

Xylem

Plant tissue transporting water and minerals from roots to leaves.

Y

Yellow Leaves

Symptom, not a diagnosis. Common causes: overwatering, low light, aging leaves, or nutrient issues. Use our diagnostic guide.

Z

Zone (USDA)

Outdoor cold-hardiness rating; less critical indoors but useful when moving plants outside seasonally.

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Pet safety: Always verify species and keep plants out of reach of pets and children. See Pet-Friendly Plants.