How to Take Care of Houseplants in Fall: A Complete Season Transition Guide
The short answer: fall houseplant care means less water‚ less fertilizer‚ and a hard look at where your light is actually coming from as the sun's angle drops․ Most people keep watering on their summer schedule straight through October‚ and that single habit kills more indoor plants than cold drafts and low humidity combined․ If you get the water right‚ then everything else is a lot easier․
Here in Tennessee however‚ that comes a little earlier than most people suspect․ The first frost in Middle Tennessee usually occurs in mid-to-late October‚ while in the elevations of East Tennessee‚ it could occur as early as late September․ West Tennessee around Memphis can in some years make it to early November․ But your houseplants don't know from frost; they go by the shortening day and sun angle․ So a few weeks before that first frost arrives‚ take a close look․ By Labor Day you should have an idea of how your plants are responding․
Light: The Problem Nobody Notices Until It's a Problem
As days shorten and fall progresses‚ the sun's angle can become lower enough that a windowsill which received good‚ bright‚ indirect light throughout the summer may be getting weak‚ direct light by October․ Conversely‚ a spot which received poor light in the morning sun in July may be receiving just the right amount of light in October․
Walk through your house on a sunny afternoon in late September and actually look at how the light falls on each room‚ rather than where you'd put your stuff last June․ South-facing windows‚ usually‚ are still strong in autumn‚ and east and west-facing windows fade fastest․
Rotate every pot a quarter turn once a week or so․ Plants lean hard toward available light this time of year‚ since there's less of it to go around‚ and an unrotated pot will start to grow lopsided within a month․
If your natural light is weak (old houses in Tennessee have small‚ few windows or deep porches block the afternoon sun)‚ a cheap basic LED grow light‚ running 15 to 18 watts‚ 12 to 18 inches above plants for six to eight hours per day‚ keeps most tropical houseplants happy during winter and is less expensive than buying old fluorescent grow light panels․
If the plant looks stretched‚ with larger gaps between leaves‚ and the new growth is thin and paler than the rest of the plant‚ this indicates that the plant needs more light‚ not water․
Temperature Swings Are the Real Threat
Fall in Tennessee is very variable‚ such that in the course of one day‚ you can be in the 78-degree range in the afternoon and at 45 degrees during the night (especially in the month of October)․ House plants tend to dislike this if windows are used․
Keep plants back a few feet from single-pane windows or old double-hung windows that leak cold even at night․ If a leaf is pressed against cold glass‚ a day or two later you may see blotches of dark water-soaked tissue․ It's not a disease but cold damage‚ which is often misdiagnosed․
On the other hand‚ once you've turned the heat on‚ keep your plants away from heating vents and radiators․ Hot‚ dry air streaming in can stress a plant's roots when it's already slowing down for the season․ Houseplants like pothos‚ philodendron‚ peace lily‚ snake plant‚ and many others will do well with daytime temperatures 65 to 75 degrees and nighttime temperatures 60 or higher․ If low temperatures are expected and plants are very sensitive to the cold‚ they may need to come indoors․
Humidity Drops Quickly Once the Heat is On
The summers in Tennessee are humid‚ so plants there are accustomed to it․ Starting about October‚ heating systems start kicking on․ When this happens‚ indoor humidity can drop from 50-60% RH down into the 20s‚ which is too dry for tropical plants like ferns‚ calatheas‚ and prayer plants․
A few ways to counter this:
If you group plants closely together‚ they lose moisture through their foliage and increase humidity around them․ You can place them on a shelf or plant stand․ This simple trick may work better than you expect․
A small humidifier running for a few hours each day helps‚ especially if the plants are in a bedroom or office that uses forced-air heating․
Pebble trays (a shallow tray filled with stones and water‚ with the pot perched on top) should also be effective‚ as the water evaporates‚ it can create a moist microclimate for the foliage․
Skip the misting․ It feels nice but humidity only lasts a few minutes and wet leaves in the cool fall months are more susceptible to fungal spotting․
Watering: Cut Back‚ But Check First
This is where most fall plant care goes wrong: the light is lower and temperatures are cooler‚ which means the plant isn't using as much water as it was in July․ Watering the same way will lead to root rot eventually․
Stick your finger in the earth‚ down to the first knuckle․ If it's still damp down there‚ you don't need to water․ This may mean watering once or twice a week during the summer‚ then every 10 days during November‚ depending on the type of plant and size of pot․
Water them in the morning‚ if possible‚ and at room temperature; the shock of cold tap water may not be good for the roots which now have to get used to being in the warmer house․
Fertilizing: Ease Off‚ Don't Stop Cold
Most houseplants go semi-dormant from October to February‚ and do not require heavy feeding at this time․ Half the dosage of fertilizer may be applied about every six weeks instead of the usual every other week application during the summer months․ If the plants go completely dormant (some succulents)‚ stop all feeding until late February when the days lengthen and the plants begin to respond․
Watch for Pests Moving Indoors
Fall is the time when spider mites‚ mealybugs‚ and fungus gnats often come indoors while riding in on houseplants brought in from an outside patio or balcony before frost․ Check the undersides of leaves and the stem joints of your new plants‚ and keep them isolated from your other plants for a week or two․ For most small infestations‚ a shower and body washing with insecticidal soap will kill them before they can spread․
If you plan to expand your houseplant collection this season‚ TN Nursery has a great inventory of low-light houseplants and hardy indoor plants that were bred for this type of seasonal transition‚ so check it out if you're restocking your collection or replacing any indoor plants that didn't survive last winter․
As long as you follow some good practices during October and November‚ your houseplants should sail through the winter in good shape․
