How to grow an indoor herb garden

I’m pretty disappointed Groundhog Day didn’t go as planned. I’m not looking forward to six more weeks of winter. Clearly, Punxsutawney Phil didn’t get the memo.

I’m ready for warmth. I’m ready for the smell of new growth. I’m ready for signs of life and vitality. I’m ready for the colors of spring!

An indoor herb garden offers fragrant foliage, various colors and a constant supply of herb leaves for cooking.

Best herbs for indoor growing

Not all herbs grow well indoors and some require large containers for their extensive root systems. The first step to planting a successful herb garden is picking the right herbs, which generally means varieties that can tolerate limited space and light. Herbs that grow well indoors include:

• Grolau (windowsill) chives
• Horehound
• Winter savory
• Creeping savory
• Fernleaf dill
• English mint
• Spicy Globe basil
• Greek oregano
• Broadleaf thyme
• Vietnamese coriander
• Dwarf garden sage
• Tri-color sage
• Parsley
• Bay laurel
• Cilantro
• Lemongrass
• Marjoram
• Rosemary
• Stevia

When growing herbs indoors it’s better to select herbs that grow less than 12 inches tall. For taller herbs, choose dwarf varieties so that they will fit on a windowsill or under grow lights. You’ll get fewer leaves, but they are easier to maintain indoors.

Lighting

Many herbs are native to Mediterranean regions, so it’s no surprise they need a lot of sunlight to thrive. If you plan on growing your garden in a windowsill to utilize natural sunlight, south-facing windows with at least six hours of sunlight work best. Herbs will not tolerate north-facing windows. It’s also necessary to rotate your window box or pots to promote uniform growth.

A second option is placing your plants under a grow light. You want to set up two 40 watt, cool white fluorescent bulbs six to 12 inches from your herbs for 14 to 16 hours a day.

Herbs that don’t get enough light will become thin, produce smaller leaves and lose their scent. However, a few varieties can tolerate indirect sunlight, including mint, bay, rosemary and thyme.

Ideal conditions

Although lighting is the most important factor to the growth of a healthy herb garden, humidity, temperature, fertilizer, pots, soil and water all play an important role. Optimizing these factors can help you increase production.

Temperature: Herbs prefer rooms that have a temperature of 65 to 70 F during the day and 55 to 60 F through the night. Many herbs can survive temperatures in the mid to low 40s, but not all.

Humidity: Herbs need a humid environment with adequate air circulation, which is sometimes difficult in a dry home during the winter. You can increase the humidity in the air around your plants by setting your pots on a tray filled with gravel and water, using a humidifier in the room, misting your plants regularly or grouping plants with similar needs together. However, the closer together containers are, the tougher it is for air to circulate properly. A fan can be used to increase air circulation.

Pots, soil and water: Herbs need to be grown in a container with a drainage hole, using a potting mix that will help with water drainage. You can add sharp sand or perlite to a compost-based soil mix to improve drainage without sacrificing nutrients. Most herbs grow well in soils of pH six to seven. When the mix starts to dry out, it’s time to water your plants.

Seedlings need to be watered from the bottom up by pouring water in a tray and letting it soak into the soil, then draining the tray. Once your plants are larger, you can water from above. Be sure to add enough water so it drains out of the bottom of the pot. If water doesn’t come out, there’s a drainage problem and you may have to consider repotting with a soil that improves drainage.

Some herbs should dry out between waterings — bay, marjoram, oregano, sage and thyme. Others, like rosemary, should never dry out completely. This is why it is important to only plant herbs with similar preferences together.

Herbs should be repotted when their roots begin to grow through the drainage hole in the bottom of the pot. The best time to do this is early spring, allowing them to adjust during the growing season.

Finally, take note of the different root systems your herbs have. Any herbs with taproot, such as dill, should be grown in deep pots. Herbs with more trailing can thrive in hanging baskets.

Fertilizer: Plants grown indoors need supplemental fertilizer. You should give your herbs a diluted solution of water-soluble fertilizer every two weeks. Fertilizing more often may negatively affect the aroma and taste of your herbs.

Pests and diseases

Like most indoor plants herbs can attract some pests. Aphids, whiteflies and mealybugs are the most common insects you’ll find. You can limit infestations by washing the leaves of your plants with water to remove them. In more severe cases a soapy solution — one to two tablespoons of dishwashing soap to one gallon of water — can be used to get rid of most insects. Apply the solution once a week until your plants are clear, but make sure the soap is not affecting the leaves.

Creative garden ideas

• Indoor Herb Garden Ideas
• The Lazy Lady’s Guide to DIY: Hanging Herb Garden
• DIY Clothespin Herb Planters

Resources

• Penn State Extension
• The National Gardening Association
• Chicago Botanic Garden