Short answer
- Choose the brightest window you have, because most culinary herbs need at least six hours of direct sunlight a day. Use a sturdy box with drainage holes and a tray, fill it with a well-drained commercial potting mix made for containers, and group herbs that share the same water needs in the same box. Plant nursery plants at the same depth they grew in their pots, leave room for their mature spread, and water thoroughly until water runs from the drainage holes. After that, check the soil before every watering and water only when the top layer has started to dry, remembering that basil should never dry out completely while rosemary, thyme, oregano, and sage prefer to dry slightly between waterings. Harvest little and often, cutting just above a leaf or pair of leaves, and wash every harvest thoroughly under running water just before you use it.
Introduction
A window box herb garden puts fresh flavor within arm’s reach of your kitchen. Instead of buying a bunch of herbs, using a few sprigs, and watching the rest wilt in the refrigerator, you snip exactly what you need, when you need it. A box on a sunny sill or mounted outside a window can hold several herbs at once, costs little to set up, and fits even a small apartment. It also teaches you, quickly and forgivingly, how plants respond to light, water, and harvesting.
This guide walks through the whole project: choosing a box and a window, picking herbs that actually grow well together, planting them properly, and keeping them healthy through the seasons. It also covers the mistakes that kill most window box herbs, how to harvest without weakening the plants, and what to do when a plant struggles. You do not need prior gardening experience. You need a sunny spot, a box with drainage, and a habit of checking the soil before you water.
The growing guidance in this article was checked against university extension services, including Iowa State University Extension, Penn State Extension, Montana State University Extension, and the University of Minnesota Extension, and the herb washing and storage guidance was checked against the Food and Drug Administration, on 31 October 2026.
Why a Window Box Works So Well for Herbs
Herbs are well suited to window boxes for practical reasons. Most culinary herbs are compact, so they do not need deep garden beds. Many prefer the well-drained soil and bright light a window box provides, and several are Mediterranean plants that tolerate drier conditions better than constant wetness. Iowa State University Extension notes that container growing is a great way to have fresh herbs close to the kitchen. A herb bed at the far end of a garden is easy to forget; a box beside the kitchen window is hard to ignore.
There are limits to be honest about. A window box will not feed a large household’s herb needs every day, and some herbs, such as a large rosemary plant or spreading mint, will outgrow a small box if left unchecked. A north-facing window in winter may not give sun-loving plants enough light.
Choosing the Right Window
Light is the single most important factor. Penn State Extension states that most herbs need six hours of direct sunlight, and the University of Minnesota Extension gives the same floor, adding that full sun produces the best growth. Montana State University Extension adds that rosemary, thyme, and bay laurel need 12 to 16 hours a day of light indoors, so a grow light may be necessary for them inside. The brightest window you have is the best starting point.
In the northern hemisphere, a window with a southern exposure is the usual first choice: Penn State Extension recommends a sunny location near a window with a southern exposure, and the University of Minnesota Extension notes that south or west facing exposures work best, because strong light increases essential oil production, improving flavor and fragrance. North-facing windows give the least direct light and are hardest for sun-loving herbs. If you are unsure about your window, watch it for a day and note when direct sun arrives and leaves.
Indoor and outdoor boxes behave differently. An indoor box is protected from wind and frost but gets less light, because glass filters some sunlight and the frame limits the angle. An outdoor box gets fuller light and air circulation but faces wind, rain, and temperature swings, and it needs secure mounting: a box full of wet soil is heavy, and it must never be mounted where it could fall onto a walkway below unless the fixings are rated for the loaded weight.
Temperature matters too. Penn State Extension advises keeping indoor herbs at 65 to 70 degrees Fahrenheit during the day and 55 to 60 degrees Fahrenheit at night, and warns that basil cannot survive below 50 degrees Fahrenheit and should not be kept on windowsills in winter. Leave a gap between foliage and the pane so leaves do not touch cold or hot glass, and check soil more often above a radiator, which dries soil quickly.
Choosing and Preparing the Box
A good window box has three features: adequate depth, drainage holes, and a tray to protect your sill. A box at least six inches deep suits most herbs, and deeper is better for larger plants such as rosemary and for taproot herbs: Penn State Extension notes that dill and other taproot herbs should be grown in deep pots. A very shallow box dries out quickly and restricts root growth.
Drainage is non-negotiable. The University of Minnesota Extension states the rule plainly: all containers, indoors or outdoors, must have drainage holes. Roots that stay wet can rot. If your box has no drainage holes, drill several in the bottom before planting. Place a tray under an indoor box to catch runoff and protect the sill. A plastic liner in a wooden box must also have drainage holes so water can escape rather than pooling inside.
Material is a matter of practicality. Iowa State University Extension notes that terra cotta and clay provide a stable anchor and allow air to move through the root zone, while plastic is lighter and easier to move. Montana State University Extension adds that clay and terracotta are porous, so soil dries more easily between waterings. Wood eventually weathers, and metal can get very hot and very cold, which stresses roots. Make sure the box is sturdy enough to hold wet soil without bowing.
Size the box to your window: a box too long for the sill will overhang and may be unstable, and a box too small will crowd plants. Measure your sill before you buy. If you are starting out, one medium box with three or four herbs is a better first project than three boxes that all need attention at once.
Soil, Planting, and Spacing
Use a light, well-draining potting mix made for containers, not heavy garden soil, which compacts in a container and drains poorly. Iowa State University Extension advises selecting a well-drained commercial potting mix, and the University of Minnesota Extension adds that heavy clay and soggy soils should be avoided.
You can start from nursery plants or from seed. Nursery plants give you a head start and are the easier choice for beginners, because you can see the plant’s health and size before you buy. Seeds are cheaper and offer more varieties, but they take longer and need consistent moisture and warmth to germinate. Start with nursery plants for your first box and try seeds once you are confident.
When planting, fill the box with moistened mix, leaving about an inch below the rim so water does not overflow. Set each plant at the same depth it grew in its nursery pot, firm the mix gently around the roots, and water thoroughly until water runs from the drainage holes, which settles the mix and removes air pockets.
Spacing matters more than it looks. The University of Minnesota Extension advises spacing plants according to their mature size, because crowding causes weak growth, poor air circulation, and increased risk of disease. Leave enough room that each plant can grow outward without completely shading its neighbor, and harvest regularly, which keeps plants compact. Place taller herbs toward the back and trailing herbs near the front edge, where they can spill over without smothering their neighbors.
Choosing Herbs That Grow Well Together
The best groupings combine herbs with similar needs for light and water. Iowa State University Extension makes the same point: when grouping multiple herbs in one container, be sure their water requirements are comparable. A thirsty herb grouped with a drought-tolerant one forces a compromise that suits neither.
A sunny, drier box suits Mediterranean herbs: rosemary, thyme, oregano, and sage. Penn State Extension lists bay, marjoram, oregano, sage, thyme, and rosemary as herbs that should dry out slightly between waterings, and lists rosemary and thyme among the herbs that do best in direct sunlight. These herbs are perennial in mild climates if protected from hard frost. Rosemary can grow large, so choose a compact variety or plan to move it to a larger pot.
A sunny, moister box suits basil, parsley, and chives, which like regular moisture, bright light, and frequent harvesting. Penn State Extension warns that basil’s potting mix should never dry out completely. Basil is a tender annual that cannot survive below 50 degrees Fahrenheit. Parsley is slower to establish, and it is a biennial usually grown as an annual, because it flowers and finishes in its second year. Chives are hardy perennials, and Penn State Extension lists them among the herbs that tolerate lower light, needing only 2 to 6 hours of direct sunlight.
Mint deserves a warning of its own. The University of Minnesota Extension notes that hardy perennial mints can spread aggressively and should be managed carefully. Mint spreads by underground runners, so planted directly in a shared box it will crowd out its neighbors. Give it its own pot inside the box, or its own separate container.
Cilantro, also called coriander leaf, is useful but short-lived. The University of Minnesota Extension classifies it as a cool-season herb; it bolts to seed in hot weather and then finishes, so sow small batches every few weeks in the cooler parts of the season. Penn State Extension lists cilantro among the herbs that tolerate lower light. Dill grows tall and has a taproot, so it suits a deeper box or a pot of its own.
Watering: The Skill That Matters Most
Overwatering kills more window box herbs than underwatering. Montana State University Extension calls overwatering the most common houseplant issue and links it to disease, most commonly root rot. The fix is simple: check the soil before you water. The University of Minnesota Extension gives a concrete test for indoor herbs: water when the soil is dry one half inch below the surface. If it feels moist at that depth, wait. If it feels dry, water thoroughly until water runs from the drainage holes, then empty the tray after about half an hour.
How often you water depends on box size, material, weather, window, and herbs. Iowa State University Extension notes that clay containers dry out faster and that in the heat of summer watering could be as frequent as once or twice a day; the University of Minnesota Extension likewise notes that outdoor container herbs may need daily watering in hot weather. Build a checking habit instead of following a fixed schedule: look at the soil every day or two. In winter, when growth slows, most herbs need less water.
Water in the morning when you can, at soil level rather than soaking the leaves, which reduces disease risk. Avoid soggy soil: the University of Minnesota Extension warns that constant moisture encourages root rot, especially indoors.
Light, Feeding, and Pruning
If your herbs grow leggy, with long stems and sparse leaves, they are reaching for more light. Montana State University Extension describes the same sign, and Penn State Extension adds that herbs denied their preferred light become thin and spindly, produce smaller leaves, and have a reduced aroma. Move the box to a brighter window if possible, rotate it every few days so all sides get light, and prune leggy stems back to encourage bushier growth. If moving is not possible, consider a grow light for the darkest months: Penn State Extension gives one tested arrangement of herbs placed 6 to 12 inches from two 40-watt, cool white fluorescent bulbs for 14 to 16 hours a day.
Feeding should be light. Iowa State University Extension notes that herbs need less fertilizer than other container plants but benefit from periodic light feeding with a dilute solution. The University of Minnesota Extension gives container rates: a half-strength liquid fertilizer every six weeks indoors and every three to four weeks outdoors. Follow the product label and ease off in winter. Penn State Extension cautions that fertilizing more often may negatively affect an herb’s aroma and taste.
Pruning and harvesting are the same act for most herbs, and regular cutting keeps plants bushy and productive. For basil, pinch the top growth regularly to encourage side branches, and remove flower heads before they set seed. Montana State University Extension advises cutting basil and other mint family herbs on the stem right above a set of leaves, which promotes growth and a bushier plant. For parsley and chives, cut outer stems first, leaving the center to keep growing. For woody herbs such as rosemary and thyme, trim lightly and avoid cutting into old, bare wood, which may not regrow.
Pests, Problems, and Troubleshooting
Most problems announce themselves early if you look at your plants when you water. Aphids are small, soft insects that cluster on new growth and undersides of leaves. Penn State Extension advises cultural and mechanical control first: trim off infested branches and dispose of them in the trash. A strong spray of water can also dislodge light infestations. Fungus gnats, small flies around damp soil, point to soil that stays too wet; Penn State Extension notes they can be controlled with yellow sticky traps and proper watering technique.
Yellowing leaves can mean several things, so check the context before acting. Widespread yellowing with wet soil suggests overwatering; yellowing with dry soil and slow growth may suggest underwatering or a need for feeding. Brown leaf edges often point to dry air, inconsistent watering, or salt buildup from overfeeding. Adjust one factor at a time and watch for a week before changing another.
Mold on the soil surface usually signals soil that stays too wet or air circulation that is too poor. Scrape off the moldy layer, let the soil dry a little more between waterings, and improve air flow. If a plant wilts despite moist soil, its roots may be damaged; check drainage and reduce watering.
If a plant is badly infested or diseased, remove it promptly so the problem does not spread. Penn State Extension notes that soft insecticides can be used in extreme cases, following all label directions, but are not typically recommended for herbs meant to be regularly harvested and eaten fresh. Whatever product you consider, check that it is labeled for edible plants and follow its harvest waiting period exactly.
Harvesting, Washing, and Storing Your Herbs
Timing and technique decide both flavor and how well the plant recovers. Iowa State University Extension advises harvesting leafy annual herbs when the flower buds first appear, because that is when the flavor from the volatile oils is best. Cut just above a leaf or pair of leaves, and leave 4 to 6 inches of plant material on annual herbs. Perennial herbs cannot be harvested as heavily: Iowa State advises removing only the top third of the plant or the leafy tip growth, and Montana State University Extension gives the same one third limit for perennials such as chives, oregano, and thyme. Use clean scissors rather than tearing leaves. Harvest in the morning where you can: the University of Minnesota Extension advises harvesting for air drying after the dew has dried.
Wash every harvest before you eat it, including herbs from your own box. The Food and Drug Administration advises washing all produce thoroughly under running water before preparing or eating it, including produce grown at home. Begin with clean hands, washed for at least 20 seconds with soap and warm water before and after preparation. Do not wash herbs with soap, detergent, or a commercial produce wash: the Food and Drug Administration does not recommend them, because produce is porous and soap and household detergents can be absorbed despite thorough rinsing and can make you sick, and the safety and effectiveness of commercial produce washes have not been established. Washing can reduce bacteria that may be present, but it will not eliminate it, so washing is a risk reduction step, not a guarantee. After washing, dry herbs with a clean cloth towel or paper towel, which the Food and Drug Administration notes can further reduce bacteria on the surface. Wash herbs just before use, not hours ahead. This guidance applies with full force to outdoor boxes exposed to dust, birds, or nearby traffic, and it is not softened for homegrown produce.
For short storage, the Food and Drug Administration advises storing perishable fresh produce, including herbs, in a clean refrigerator at 40 degrees Fahrenheit or below, checked with a refrigerator thermometer. The University of Maine Cooperative Extension found that storing bunches of herbs in a glass of water in the refrigerator, covered with a plastic bag, keeps herbs perky for at least a week.
Fresh herbs are best used fresh, but you can preserve a glut. The University of Maine Cooperative Extension notes that herbs freeze well when protected: finely chop them or blend them with water, broth, or oil, portion the mixture into ice cube trays, freeze, and transfer the cubes to a labeled container, keeping them frozen until use. Do not keep fresh herbs standing in oil at room temperature or as a homemade infused oil: the University of Maine Cooperative Extension warns that putting fresh herbs or garlic in oil can create a risk of botulism, and that practice is not recommended. Woody herbs such as rosemary, thyme, and oregano also dry well. The University of Minnesota Extension describes air drying as the best overall method: bundle 4 or 5 stems, hang them upside down in a dark, dry, well-ventilated area, and allow 7 to 14 days to dry. Store the leaves in airtight containers away from heat and light, and use dried herbs within one year. Soft herbs such as basil and parsley lose more flavor when dried, so freezing suits them better.
Through the Seasons
Spring is the main planting season. The University of Minnesota Extension notes that transplanting outdoors should wait until after the danger of frost has passed and soil temperatures are consistently at or above 50 degrees Fahrenheit. Start with a few plants, and add more as you learn your window’s light and your watering rhythm. Protect tender herbs from late frost by bringing an outdoor box inside overnight if a cold snap is forecast.
Summer is the peak harvesting season, and watering needs rise sharply. Check soil daily in hot weather, harvest often to keep plants compact, and watch for pests, which multiply faster in warm weather. Basil thrives now, while cilantro may bolt in the heat; sow replacements in small batches.
Autumn is a time to tidy and plan. Cut back tired annuals, pot up tender perennials to bring indoors if your winters are cold, and reduce feeding as growth slows. Check that outdoor boxes are securely mounted before autumn winds strengthen.
Winter is the resting season for many herbs. Growth slows, water needs drop, and light is at its weakest. Keep the box in the brightest window available, water sparingly based on soil checks, and avoid placing it above a hot radiator. Iowa State University Extension notes that perennial herbs grown inside over the winter may require supplemental lighting. Some herbs look sparse in winter and recover in spring; do not assume a quiet plant is dead until spring growth fails to appear.
Safety and Practical Notes
Window boxes, especially outdoor ones, need secure fixing. Check brackets and screws at the start of each season and after storms. Do not overload a box beyond what its fixings can hold, and remember that wet soil is much heavier than dry soil. Follow any building or rental rules about exterior fixtures before mounting anything.
If you have pets or small children, check that your chosen herbs are safe for your household before planting. Penn State Extension gives one specific warning worth naming: tarragon is toxic to dogs and cats and should be avoided in homes with pets, and Montana State University Extension gives the same advice. Keep boxes out of reach if a child or pet is likely to pull at them.
Getting Started This Week
You can start in a single weekend. On day one, measure your sill, watch your window’s light, and choose a box with drainage and a tray. On day two, buy container mix and three or four nursery herbs that share similar light and water needs, plant them at the right spacing, and water thoroughly. Then build the habit that matters most: check the soil before you water, and harvest a little and often.
Frequently Asked Questions
How many herbs can I fit in one window box?
It depends on the box size and the herbs, but a medium box of about two feet long usually holds three to five herbs comfortably. Crowding more plants in may look full at first, but the University of Minnesota Extension warns that crowding causes weak growth, poor air circulation, and increased risk of disease. Start with fewer plants and let them fill the space.
Can I grow herbs on a north-facing window?
It is harder, but not impossible. Penn State Extension lists lemon balm, chives, and cilantro as herbs that can tolerate low light levels and need only 2 to 6 hours of direct sunlight, while most herbs need six hours. Choose from the lower light group, accept slower growth, and consider a grow light in winter. Sun-loving herbs such as basil and rosemary will struggle on a north-facing window and are better placed elsewhere if you have a brighter option.
Why does my basil keep dying?
Basil usually fails from cold, overwatering, or underwatering in hot sun. Penn State Extension states that basil cannot survive temperatures lower than 50 degrees Fahrenheit, should not be kept on windowsills during winter months, and should never be allowed to dry out completely. Keep it away from cold drafts and cold glass, water when the top of the soil starts to dry, and pinch it regularly to keep it bushy.
Should I start from seed or buy plants?
Buy plants for your first box, especially for slow herbs such as parsley and rosemary. Seeds are rewarding and cheaper, but they add weeks before harvest and need steady warmth and moisture. Seeds are typically started indoors under lights in late winter, about 6 to 8 weeks before transplanting outdoors, according to the University of Minnesota Extension. Once your box is established, try seeds for fast herbs such as basil and cilantro as a low-risk experiment.
How long will my window box herbs last?
It varies by herb. Annuals such as basil and cilantro last one growing season. Biennial parsley is usually grown as an annual and finishes after it flowers. Perennials such as thyme, oregano, sage, rosemary, chives, and mint can last several years if protected from hard frost and repotted when they outgrow the box. Penn State Extension advises repotting when roots grow through the drainage hole, with early spring the best time.
Do I need to replace the soil each year?
Not necessarily, but refreshing helps. Each spring, top up the box with fresh container mix, remove any tired plants, and check drainage holes. Every couple of years, or when plants seem stunted despite good care, empty the box, clean it, and refill with fresh mix.
Keep reading: Pet-Friendly Garden That Still Looks Good
Sources & references
- Iowa State University Extension, Growing Herbs in Containers. Used for window boxes being suitable herb containers with sufficient drainage holes in the bottom, terra cotta and clay providing a stable anchor and allowing air to move through the root zone, plastic being lighter and easier to move, selecting a well-drained commercial potting mix, water requirements varying by species, clay containers requiring more frequent watering, summer watering as frequent as once or twice a day, grouping herbs with comparable water requirements in one container, herbs benefiting from periodic light fertilization with a dilute solution, leafy annual herbs being harvested when flower buds first appear and cut just above a leaf or pair of leaves with 4 to 6 inches of plant material left, perennial herbs being harvested by removing only the top third or the leafy tip growth, and some perennial herbs being taken inside for the winter.
- Penn State Extension, Growing Herbs Indoors. Used for most herbs needing 6 hours of direct sunlight, a sunny location near a window with a southern exposure, the fluorescent alternative of herbs placed 6 to 12 inches from two 40-watt, cool white fluorescent bulbs for 14 to 16 hours, lemon balm, chives, and cilantro tolerating low light at 2 to 6 hours of direct sunlight, herbs denied preferred light becoming thin and spindly with smaller leaves and reduced aroma, rotating pots on windowsills for uniform growth, daytime temperatures of 65 to 70 degrees Fahrenheit and nighttime temperatures of 55 to 60 degrees Fahrenheit, basil being unable to survive temperatures lower than 50 degrees Fahrenheit and not being kept on windowsills during winter, containers requiring a drainage hole and a potting mix that aids drainage, bay, marjoram, oregano, sage, thyme, and rosemary drying out slightly between waterings, basil never being allowed to dry out completely, the warning that fertilizing more often may negatively affect aroma and taste, aphids being controlled by trimming infested branches and disposing of them in the trash, fungus gnats being controlled with yellow sticky traps and proper watering, soft insecticides not typically being recommended for herbs harvested and eaten fresh, always washing leaves before use, repotting when roots grow through the drainage hole with early spring the best time, dill and other taproot herbs needing deep pots, and tarragon being toxic to dogs and cats.
- Montana State University Extension, Pots of Possibility: Herbs that Thrive Indoors. Used for herbs needing at least six hours of direct sunlight at minimum, rosemary, thyme, and bay laurel needing 12 to 16 hours a day with supplemental light, long and lanky plants signaling insufficient light, containers needing sufficient drainage holes and well-drained potting soil, clay and terracotta being porous and allowing soil to dry more easily between waterings, grouping plants with similar growing requirements, overwatering being the most common houseplant issue and leading most commonly to root rot, basil and other mint family herbs being cut on the stem right above a set of leaves to promote bushier growth, perennial herbs such as chives, oregano, and thyme having only one third of top growth removed, and tarragon being a plant to avoid with indoor cats and dogs.
- University of Minnesota Extension, Growing Herbs in Home Gardens. Used for most herbs needing at least six hours of direct sunlight daily with full sun producing the best growth, south or west facing exposures working best and strong light increasing essential oil production, all containers indoors or outdoors requiring drainage holes, most herbs growing best in well-drained soil with heavy clay and soggy soils avoided, spacing plants according to mature size because crowding causes weak growth, poor air circulation, and increased risk of disease, hardy perennial mints spreading aggressively and needing careful management, cilantro being a cool-season herb, soil temperatures consistently at or above 50 degrees Fahrenheit for transplanting after frost danger has passed, seeds being started indoors 6 to 8 weeks before transplanting, container herbs being fertilized with half-strength liquid fertilizer every six weeks indoors and every three to four weeks outdoors, indoor herbs being watered when the soil is dry one half inch below the surface, outdoor container herbs possibly needing daily watering in hot weather, constant moisture encouraging root rot especially indoors, air drying being the best overall preservation method with harvest after dew dries, bundles of 4 or 5 stems hung upside down in a dark, dry, well-ventilated area for 7 to 14 days, dried herbs being stored in airtight containers away from heat and light and keeping up to one year, and chopped herbs being frozen in ice cube trays with water.
- University of Maine Cooperative Extension, 7 Ways to Best Preserve Spring Herbs. Used for storing herb bunches in a glass of water in the refrigerator, covered with a plastic bag, keeping herbs perky for at least a week, freezing finely chopped herbs blended with water, broth, or oil in ice cube trays and labeled containers, and the warning that putting fresh herbs or garlic in oil can create a risk of botulism and is not recommended.
- Food and Drug Administration, Selecting and Serving Produce Safely. Used for washing hands for at least 20 seconds with soap and warm water before and after preparation, washing all produce thoroughly under running water before preparing or eating it including produce grown at home, not washing produce with soap, detergent, or commercial produce wash because produce is porous and soap and detergents can be absorbed despite rinsing and can make you sick and because the safety of produce wash residues is not known and effectiveness has not been tested, washing reducing bacteria that may be present without eliminating it, drying produce after washing with a clean cloth towel or paper towel to further reduce bacteria on the surface, and storing perishable fresh produce including herbs in a clean refrigerator at 40 degrees Fahrenheit or below checked with a refrigerator thermometer.
