Plants that require full sun don't make the best houseplants since daylight hours are often not enough during the winter. Annuals that tolerate part to full shade often make excellent plants for overwintering. Tropicals that are adapted for the dense or dappled shade of the forest understory also make good choices for an indoor garden. Generally, plants that need more sunlight will do best in a southern facing window, while low light plants can survive in bright indirect light or a north facing window.
Most herbs require full sunlight, meaning eight or more hours each day. We've selected a few herbs that seem able to adapt to lower light conditions, and while they may not thrive the way they would outdoors in the summer they can grow and survive, gven the correct care. Your windowsill herb garden should be placed in south facing window. Light can be optimized by painting nearby walls a bright color, and you might consider setting up a small flourescent or grow light.
Houseplants should be watered so soil is completely saturated and excess water runs out the bottom of the pot. Failure to flush the soil completely will allow mineral salts to build up in the soil, which will not make the plant happy. Allow the top couple inches of potting soil to dry out between waterings, checking frequently since indoor heating and low relative winter humidity can cause plants to dry out quickly. Keep in mind that dormant plants and succulents like geraniums and begonias will require less water.
Like people, plants are mostly made of water, but they also need oxygen to be healthy so it's essential to water them properly. When plants dry out, they become stressed and suffer damage at the molecular level, and evident when roots wither and leaves wilt. With too much water, roots are deprived of oxygen and diseases like root rot will take over. Unhealthy plants are easily killed off by pests that wouldn't give a healthy plant much trouble. The species of plant, age, lighting, soil and container size all impact how often plants need to be watered. When you water, don't use shockingly cold water. Even better, keep a spare, clean milk jug for storing water at room temperature. Tap water that sits for a few days will have fewer harsh chemicals.
Watering from the bottom up works well for plants that have sensitive foliage, as this method avoids splashing water on leaves. You can place a pot in a tub, sink or shallow pan filled with tepid water and let it sit and wick for half an hour or so. Pull the plug and let the plant sit to allow sufficient drainage. Never leave plants sitting in a saucer filled with water for longer than 30 minutes.
Temperature & Humidity
Air next to windows is significantly colder than the rest of the room. Try rolling up a towel for a draft dodger to keep plants from catching a chill. Conversely, the space directly over a heat vent is usually extremely dry and warm. Air ducts should be directed away from plant foliage to pevent excessive drying.
Plants that require high humidity will appreciate a periodic steaming in a warm shower.
Potting Indoor Plants
IIndoor plants periodically require transplanting into a larger container to prevent them from becoming pot bound, unless they are a type of plant that prefers this growing condition. Water the plant well before starting to repot so the soil will hold the root ball together while it's being moved from pot to pot, which will prevent unnecessary stress. Sometimes it's necessary to run a knife around the inside of the pot, or gently squeeze a plastic pot to release it. Always use fresh organic potting mix when transplanting, filling around the plant gently and being careful not to pack it too tightly. Resist the urge to fertilize right away, allowing the plant some time to regrow it's roots before you force it to produce new foliage and flowers.
Pest and Disease Problems
Indoor plants have a difficult challenge. They are trying to grow in confined conditions where access to resources like food and water is limited and unnatural. They also lack natural predation of pests and the benefit of having chosen their own place to grow where lighting and temperature is ideal. With all of that said, the healthier you can keep your plants, the fewer pests you will have to deal with. If pests do become a problem, the first step is to identify it. Then you can find a solution.
Pest : Spider Mites
Identification: Spider mites are small, spider-like creatures which love the hot, dry conditions heated homes provide. Spider mites feed with piercing mouth parts, which cause plants to appear yellow and stippled. Leaf drop and plant death can occur with heavy infestations. Spider mites can multiply quickly, with females laying up to 200 eggs in a short life span of only 30 days. Look for the web that they produce covering infested leaves and flowers.
Prevention and Control: If your plant is small enough to submerge in the sink or tub, with water covering all leaves and the pot itself, you can drown the mites. Simply leave plants submerged for 20-30 minutes. Pull the plug and sit the plant up to drain. Spraying with an organic miticide or insecticidal soap is the next safest and most effective treatment.
Pest : Mealybugs
Identification: These small, dull-white and fluffy-looking soft-bodied insects produce a yellow, waxy or powdery covering. They have piercing/sucking mouth parts that suck the sap out of plant tissue. Mealybugs often look like small pieces of cotton and they tend to congregate where leaves and stems branch, and on the undersides of foliage. They attack a wide range of plants. Mealybugs can weaken a plant leading to yellow foliage and leaf drop. They also produce a sweet substance called honeydew which can lead to an unattractive black surface fungal growth called sooty mold.
Prevention and Control: Isolate infested plants from those that are not. Prune plants back hard and dispose of the infested foliage outside. Dormant oil is a safe and effective treatment during cold weather months, and should be applied to the plant after pruning. Reapply bi-weekly until the bugs are banished! Encourage natural enemies such as lady bugs in the garden to help reduce population levels of mealybugs that might hitch a ride indoors on plants in late fall.
Pest : Scale Insects
Identification: Scales related to mealybugs. Young scales crawl until finding a good feeding site, then adult females lose their legs and remain on a spot protected by a hard shell layer. They appear as lumps on the lower sides of leaves, and have piercing mouth parts that suck the sap out of plant tissue. Scales can weaken a plant leading to yellow foliage and leaf drop. They produce an unattractive black surface fungal growth called sooty mold.
Prevention and Control: Control like mealbugs and treat with dormant oil
Pest : Whiteflies
Identification: Whiteflies are small, winged insects that look like tiny moths. Flying adults prefer the underside of leaves to feed and reproduce, and can multiply quickly laying up to 500 eggs in a life span of a mere 2 months. Infested plants will seem to have a cloud of fleeing insects when disturbed. Whiteflies can weaken a plant, eventually leading to plant death if they are not irradicated. They can also transmit harmful viruses. They produce honeydew which can lead to a black surface fungal growth called sooty mold.
Possible controls: Yellow sticky cards work quite well attracting and trapping whiteflies. Insecticidal soup knocks whitefly populations down quickly and safely, and sometimes a good steady shower of water in the tub will simply wash them off.
Fungi : Rusts
Identification: Most rusts are host specific, overwintering on leaves, stems and flower debris. Rust often appears as small, bright orange, yellow, or brown pustules on the underside of leaves. If touched, it will leave a colored spot of spores on your finger. Caused by fungi and spread by splashing water or rain, rust is worse when humidity is high, so it's not generally a problem on houseplants in the winter.
Prevention and Control: Keep plants that don't have a propensity for rust problems, and provide good air circulation for your indoor garden. We run fans in the hothouse, and a similar system can be set up with a small, tabletop fan. Remove all debris from the soil surface, especially around plants that have had a problem. Do not water from overhead and water only during the day so plants have time to dry before night. Apply an organic fungicide.
Fungi : Powdery Mildew
Identification: Powdery mildew is most often found on plants that don't have enough air circulation and adequate light. Problems are worse where nights are cool and days are warm and humid, and is thusly not a common probelm for indoor houseplants during winter. The powdery white or gray fungus is usually found on the upper surface of leaves or fruit, turning them yellow or brown, and causing them to shrivel up and drop off. New foliage emerges crinkled and distorted, and fruit is dwarfed and often drops early.
Prevention and Control: Grow resistant plants and space them properly so they receive adequate light and air circulation. Always water from below, keeping water off the foliage. Apply organic fungicides and clean up and remove all affected leaves and flowers.