Plant guides

50 short guides and 101 plant problems, written from university extension services, the RHS and Missouri Botanical Garden.

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Plant basics

• Humidity for houseplantsSigns of dry air, and what really raises humidity
• How to clean plant leavesDust-free leaves catch more light and hide fewer pests
• How to pick a healthy plantWhat to check at the store, and why new plants need a quarantine
• How to read a plant labelLight, hardiness zones and the plant's real name
• Plant care while you're awaySimple ways to keep plants watered for a weekend or a few weeks

Watering

• How often to water houseplantsCheck the soil, not the calendar
• Overwatering vs underwateringHow to tell them apart, and how to fix each one
• Bottom watering: how and whenLet the pot drink from below and keep the leaves dry
• Watering houseplants in winterLess light means less water, but don't forget them
• Tap, rain or filtered water?What's in your water, and which plants mind
• Self-watering pots: pros and consHow reservoir pots work, and which plants like them

Light

• How much light do houseplants need?Low, medium and bright light, and how to tell what you have
• Which window is best for plants?North, south, east and west windows, explained
• Grow lights explainedWhich kind to buy, how close to hang it and how long to run it
• Best houseplants for low lightTough plants for dim rooms and north windows

Soil and pots

• Choosing a pot: size and drainageWhy holes matter, which size to pick and how materials differ
• Potting mix basicsWhat's in the bag, and what perlite, bark and coir actually do
• When and how to repot a plantSigns it's time, and a step-by-step guide
• How to make a terrariumA tiny garden under glass, from layers to care
• Composting at homeTurn kitchen scraps and leaves into rich, crumbly compost
• Mulch basicsWhat mulch does, which kind to use and how deep to spread it

Feeding

• N-P-K: fertilizer numbers explainedWhat the three numbers on the label mean, and how to choose
• How to fertilize houseplantsWhen to feed, how much, and when to stop
• Fertilizer types comparedLiquid vs slow-release, organic vs synthetic, and when to use each
• White crust on soil? How to flush saltsWhat the crust is, why it hurts roots and how to wash it out

Pests and problems

• A 5-minute pest checkCatch bugs early, while they're still easy to stop
• How to save a dying plantA calm, step-by-step rescue plan

Propagation

• 5 ways to propagate houseplantsStem and leaf cuttings, division, offsets and air layering
• Rooting cuttings: water or soil?The pros and cons of each, and how to make the switch
• Starting seeds indoorsTiming, light and care for strong, stocky seedlings

Pruning

• How to prune houseplantsSnip for health, shape and fuller growth
• Pinching for bushier plantsOne small snip, and two stems grow where one was
• How to fix a leggy plantWhy stems stretch, and how to get a full plant back

Seasons

• Moving houseplants outside and back inGive indoor plants a summer outdoors without the shock
• Winter care for houseplantsLight, warmth and humidity through the dark months
• How to protect plants in a heat waveWater, shade and what not to do when it's very hot
• Dormant or dead? Plant dormancyHow plants rest, and how to tell they're still alive
• Frost dates: when to plantHow to use your last and first frost dates to plan the garden

Pets and safety

• Houseplants and pets: what's safePlants that are toxic to cats and dogs, and safer picks
• Plants and kids: staying safeWhich plants to keep out of reach, and what to do if a child eats one

Growing food

• Hardening off seedlingsA simple plan to toughen up seedlings before they go outside
• Companion planting: what worksPairings with real evidence, and popular myths to skip
• Growing vegetables in containersPots, soil, sun and the best crops for small spaces
• Watering a vegetable gardenHow much, how often, and the best way to do it
• Hydroponics at home: the basicsGrow herbs and greens with their roots in water, not soil
• Plants that bring in pollinatorsFlowers for bees and butterflies, and bigger harvests

Lawns

• How high to mow your lawnMowing heights by grass type, and the one-third rule
• How to water a lawnHow much, how often and the best time of day
• How to overseed a lawnThicken thin grass with new seed, step by step
• Weeds 101: know them, beat themAnnuals, perennials and how to keep weeds in check

Plant problems A–Z

• Aerial rootsRoots growing from stems above the soil are normal on climbers such as monstera and pothos.
• AnthracnoseSunken brown blotches along the veins and leaf tips, spread in wet weather.
• Ants on plantsAnts on a plant are usually farming aphids, scale or mealybugs for honeydew, or nesting in the pot.
• AphidsSmall soft-bodied insects that crowd onto new growth and suck the sap.
• Apple scabOlive-green to black scabby spots on apple and crabapple leaves and fruit, worst after cool, wet springs.
• Bacterial leaf spotWater-soaked spots that turn brown or black, spread by splashing water and hands.
• Bacterial soft rotMushy, foul-smelling rot of stems, bulbs and tubers.
• Bacterial wiltCucumber and melon vines wilt suddenly and die, from bacteria spread by cucumber beetles; tomatoes get a soil-borne kind.
• Blossom end rotA dark, sunken patch on the bottom of tomatoes and peppers, from uneven watering.
• BoltingLettuce, spinach and herbs shoot up a flower stalk and turn bitter.
• Broad and cyclamen mitesMites too small to see that twist, harden and stunt new growth and buds on houseplants and strawberries.
• Brown leaf tipsLeaf edges dry out first when water runs short: dry air, uneven watering or salts.
• Brown patchRoughly circular brown patches in lawns in hot, humid weather, sometimes with a smoky ring at the edge.
• Brown rot of fruitSoft brown rot with gray spore tufts on stone fruit, apples and pears.
• Bud dropFlower buds fall before they open, usually after a move, a chill or a swing in watering.
• CankersSunken, dead patches of bark on trunks and branches that can girdle and kill the shoots above them.
• CaterpillarsMoth and butterfly larvae that chew holes in leaves, often overnight.
• Cedar-apple rustBright orange spots on apple and crabapple leaves, and jelly-like orange galls on nearby junipers in spring.
• Chinch bugsTiny sap-sucking bugs that turn sunny patches of St. Augustine and other lawns yellow, then brown, in summer.
• ClubrootSwollen, club-shaped roots on cabbage-family plants, which wilt on warm days and stay stunted.
• Cold damageDark, water-soaked leaves that turn black after frost or a cold draft.
• Colorado potato beetleStriped beetles and plump red-orange larvae that strip the leaves of potatoes, eggplant and tomatoes.
• Cucumber beetlesYellow beetles with black stripes or spots that chew cucumbers and melons and spread bacterial wilt.
• CutwormsFat gray or brown caterpillars that hide in the soil by day and cut seedlings off at ground level at night.
• Damping-offSeedlings that topple over with a thin, pinched stem at the soil line.
• Dead or dying plantA collapsed plant with no new growth may still have living parts; test the stems and roots before giving up.
• Deer damageDeer tear off leaves and shoots, leaving ragged edges, and can strip plants up to about 6 feet (1.8 m) high.
• Dog urine spotsRound, straw-colored patches in the lawn, often ringed with dark green grass, where a dog urinates.
• Dollar spotSmall, round, bleached spots in the lawn about the size of a silver dollar, often merging into larger patches.
• DormancyMany plants rest for part of the year: growth stops, and bulbs may lose all their leaves. That's normal.
• Downy mildewPale blotches on top of the leaves and fuzzy growth underneath, after cool, damp nights.
• Drooping or wiltingLeaves droop when they lose water faster than the roots can deliver it.
• Drought-dormant lawnGrass turns brown and stops growing in heat and drought to protect its crowns; it usually greens up again.
• Dry airHeated or air-conditioned air dries leaf edges and buds faster than roots can keep up.
• Early and late blightTomato and potato diseases: slow target-ring spots (early) or fast black rot (late).
• EarwigsNight-feeding insects with tail pincers that chew ragged holes in seedlings, flowers and soft fruit.
• EdemaSmall corky bumps under the leaves when roots take up more water than the leaves can use.
• Fairy ringsRings of dark green or dead grass, often with mushrooms, made by fungi growing outward through the soil.
• Fertilizer and salt burnScorched leaf edges and a white crust when fertilizer and minerals build up in the pot.
• Fire blightBlossoms and shoots of pears and apples suddenly blacken, as if scorched.
• Flea beetlesTiny jumping beetles that pepper young leaves with small round holes, worst on seedlings in spring.
• Flowers but no fruitTomatoes, peppers, squash and beans flower but drop blossoms or tiny fruit, usually from heat or poor pollination.
• Flowers fading after bloomingFlowers fade and drop once their bloom is over, while the leaves stay healthy.
• Fruit crackingRipening tomatoes, melons and other fruit split open when heavy rain or watering follows a dry spell.
• Fungal leaf spotBrown or black spots, often with a yellow halo, spread by splashing water.
• Fungus gnatsSmall dark flies that breed in damp potting mix; mostly a nuisance.
• Fusarium and Verticillium wiltSoil fungi that block the plant's water pipes, so it wilts even when watered.
• GallsOdd bumps, balls or pouches on leaves and twigs, made by tiny insects or mites; usually harmless.
• Gray moldFuzzy gray mold on fading flowers, soft fruit and damp leaves.
• GuttationBeads of water at leaf tips or edges in the morning, pushed out by the roots overnight; harmless.
• Heat stressWilting, curling and dropped flowers in long hot spells.
• Holes in leavesHoles, notches or missing chunks of leaf, chewed by caterpillars, beetles, slugs or snails.
• Iron chlorosisNew leaves turn yellow between green veins because alkaline soil locks up iron; acid lovers suffer most.
• Japanese beetlesMetallic green and copper beetles that skeletonize leaves and flowers in summer; their grubs eat lawn roots.
• Leaf dropSudden leaf fall after a move, a draft or a change in light.
• Leaf minersTiny larvae that tunnel inside leaves, leaving pale winding trails.
• Leggy growthLong, thin stems reaching for the light: the plant needs a brighter spot.
• MealybugsCottony white insects that hide in leaf joints and suck the sap.
• Mechanical and storm damageTorn leaves, broken stems or bark wounds from hail, wind, snow, mowers, pets or people.
• Moles and volesMoles leave raised tunnels and soil mounds in lawns; voles make surface runways and gnaw roots and bark.
• Mushrooms in houseplant potsSmall yellow mushrooms that pop up in potting mix; they don't harm the plant but are poisonous to eat.
• New leaf unfurlingBrand-new leaves often look pale, soft, rolled or oddly colored, then firm up and darken within a week or two.
• Not floweringA healthy plant that won't bloom usually needs more light, less nitrogen, better-timed pruning or more time.
• Nutrient deficiencyPale or yellowing leaves and weak growth when the plant runs short of food.
• Old leaves yellowingA few of the oldest leaves yellow and fall as the plant grows. That's normal.
• OverwateringSoil that never dries pushes out the air roots need, so they suffocate and rot.
• Peach leaf curlSpring leaves on peaches and nectarines pucker, thicken and turn red, then drop.
• Plant virusesMottled, ringed or twisted leaves from viruses that have no cure.
• Powdery mildewA white, dusty fungus on leaves and shoots that thrives in still, shady air.
• Pups and offsetsSmall new plants growing from the base of succulents and snake plants; a sign of a healthy, mature plant.
• Purple leavesPurple or reddish leaves and slow growth on young plants, usually from cold soil limiting phosphorus.
• Rabbit damageRabbits nibble low plants and young bark, leaving clean, angled cuts and small round droppings.
• Root rotRoots that rot in soggy soil, so the plant wilts even though the soil is wet.
• Root-boundThe plant has outgrown its pot: more roots than soil.
• Root-knot nematodesMicroscopic soil worms that cause knobby swellings on roots, so plants wilt in the heat and stay small.
• Rose black spotPurple-black spots with feathery edges on rose leaves, then early leaf drop.
• RustOrange, yellow or brown powdery pustules, mostly under the leaves.
• Sap-sucking pestsAphids, mealybugs, scale, mites, whiteflies and thrips all feed on plant sap.
• Sawfly larvaeCaterpillar-like larvae that skeletonize or strip the leaves of roses, pines and fruit; Bt won't kill them.
• Scale insectsInsects that sit still under a shell-like cover on stems and leaves, sucking the sap.
• Slime moldColorful slimy or crusty growths on grass, mulch or stems after wet weather; harmless and short-lived.
• Slugs and snailsNight feeders that leave smooth-edged holes and silvery slime trails.
• Soil mitesTiny round mites crawling in potting mix or compost; they eat decaying matter and don't harm plants.
• Sooty moldA black, wipeable coating that grows on the honeydew of sap-sucking insects.
• Southern blightA hot-weather soil fungus that rots stems at the soil line, with white threads and mustard-seed-like balls.
• Spider mitesTiny mites that speckle leaves and spin fine webs, worst in hot, dry air.
• Spray or weedkiller damageScorched spots or twisted growth after a spray, weedkiller drift or tainted compost.
• SpringtailsTiny jumping specks that feed on mold and decay in damp potting soil; a sign of wet soil, not a pest.
• Squash bugsGray-brown bugs that suck sap from squash and pumpkins, leaving speckled, wilting leaves and bronze egg clusters.
• Squash vine borerA white grub tunnels inside squash and pumpkin stems, so vines suddenly wilt; look for sawdust at the base.
• Sunburn and scorchBleached or brown papery patches where strong sun, a lamp or a heater hit the leaves.
• ThripsTiny slender insects that leave silvery streaks and black specks on leaves and flowers.
• Transplant shockA plant sulks after a move or repotting while it grows new roots.
• UnderwateringA thirsty plant droops and crisps, but most bounce back fast.
• Variegation lossVariegated plants put out plain green shoots that grow faster and can take over unless they are cut out.
• Vine weevilBeetles notch leaf edges at night while their white grubs eat roots, killing potted plants from autumn to spring.
• Water spots and rosette rotPale rings from cold water, mineral marks, or rot where water sits in a rosette.
• White grubs in lawnsC-shaped beetle larvae that eat grass roots, leaving brown patches that peel up like a loose carpet.
• White moldFluffy white mold and hard black seed-like bodies on rotting stems of beans, lettuce and many flowers in cool, wet weather.
• WhitefliesTiny white-winged insects that fly up in a cloud when you touch the plant.
• Yellow leavesA general stress signal; indoors the most common cause is too much water.