How to Grow a Windowsill Herb Garden, From Planting to Harvesting

A windowsill garden allows you to have fresh ingredients in your kitchen without venturing outside to your garden or the market. Just a few quick snips, and you can add homegrown basil to a tomato sauce or cilantro to guacamole. You can start your garden either with seeds or small plants, though the latter gives you herbs to start cooking with immediately. A windowsill in the kitchen is the most convenient for proximity purposes, but any window in your home will work as long as it provides adequate light.

Choose Your Herbs

When selecting plants for your windowsill herb garden, first consider what you like to cook with. From that list, choose herbs that don't get too big, grow well in containers, and that are most tolerant of indoor conditions. A few popular options include:

• Basil
• Oregano
• Parsley
• Rosemary
• Lavender
• Chives
• Thyme
• Cilantro
• Mint

How to Plant Herbs in Containers

Most herbs won’t mind being planted together in a low bowl to create a lush mini indoor garden, says Lisa Hilgenberg, horticulturist for Chicago Botanic Garden. You can also grow them in individual pots, but place the containers in a tight grouping for increased humidity.

1. Fill pots halfway with a light potting soil mixed with a scoop of perlite.
2. Pinch the plants out of the plastic container they came in and place the plant on the soil.
3. Fill in around the plant with additional soil to just the top of the soil block.
4. Tamp down and firm the soil around the plant. Take care not to bury too deeply, covering the crown of the plants. 
5. Water well.

How to Plant Herbs From Seed

Generally, you'll need to start seeds indoors about six to eight weeks before the last frost. "Self sowing annual herbs like dill and cilantro are best started from seed for your indoor herb garden," says Hilgenberg. "It might be hard to wait for herbs to grow into large plants; don’t hesitate to enjoy a few of the seedlings as microgreens."

1. Fill your containers with fresh potting soil up to 1 inch from the rim.
2. Sprinkle a few seeds on top of the soil or, for larger seeds, bury them.
3. Cover with a bit of soil and pat down.
4. Water well.
5. Cover with a plastic wrap or a dome to keep moist and promote germination.
6. When seedlings start to show, remove the plastic.

Choosing Containers for Herbs

Select containers with drainage holes in the bottom. "Terra cotta is a good choice for herbs because clay wicks moisture away from root systems and minimizes the chance of mold or mildew," says Hilgenberg. "Planting in clay allows for air exchange, which helps keep herb plants healthy. This is especially true for sage, lavender, and rosemary that prefer to be grown on the dry side.

Choose a pot that is about 1 or 2 inches bigger than the container the plant came in. "Selecting a container that is too large makes it easy to make the mistake of overwatering," says Hilgenberg. "Low bowls look great, lending themselves proportionally to growing herbs."

How to Care for Windowsill Herbs

Caring for windowsill herbs is relatively easy, but there are a few things to keep in mind to ensure they thrive.

Light

Most herbs need 6 to 8 hours of bright light, says Melinda Myers, gardening expert and host of the Great Courses How to Grow Anything DVD series. A south-facing window is ideal, but east- or west-facing windows are also suitable. If you don't get enough light through any windows, grow lights are your best bet.

Water

How much water you give your windowsill herbs depends on the type you're growing, but generally, you should allow the top inch of soil to dry before watering again. Avoid overwatering your herbs, which can cause root rot.

Soil

When growing herbs, use a quality potting mix that retains moisture while providing adequate drainage. Amending the soil with perlite will help improve drainage and avoid root rot.

Temperature

Most herbs prefer warmer temperatures of around 55 to 70 degrees Fahrenheit but are tolerant of normal room temperature. To increase humidity, cluster your windowsill herbs close together.

Fertilizer

Dilute an organic fertilizer according to the package's instructions when fertilizing windowsill herbs. "Too much fertility can cause the leaves to lose their powerful flavor," says Hilgenberg. "Avoid fertilizing in November, December, or January when growth is slow. Begin fertilizing regularly after repotting or when growth begins again in February."

How to Harvest Herbs

Harvest your herbs when the plant is at least 4 to 6 inches tall. "You want to make sure there will be enough leaves left on the plant to support new growth," says Meyers. "Harvest just what you need, when you need it." Harvest stems from the top or outside of the plants by cutting with sharp pruners. Harvest regularly to encourage new growth.

How to Prune Herbs

Generally, harvesting herbs is all the pruning the plant needs. But if you don't harvest often you'll need to prune the plants to promote growth and reduce legginess. "Consider removing no more than 1/3 of the overall growth," says Meyers. "Cut back to above a leaf or side shoot."

How to Repot Herbs

If herbs look tired, either from a lack of fertility, over-harvesting, or lack of sunlight, it can help to repot them and move them to a sunny spot, says Hilgenberg. "Plants drying out too quickly or roots showing in the bottom drainage hole are signs the plants need repotting."

1. Slide the plant out of the container when the soil is still slightly damp.
2. If the herb is pot bound, loosen the roots and move it into a container one size larger.
3. Plant the herb in the container so it is growing at the same depth as before.
4. Backfill in with soil
5. Water to remove air pockets.

Common Problems With Herbs

Lack of light is a common problem when growing herbs; to fix this, consider using artificial grow lights. Additionally, over-watering can be an issue for herbs. "Adjust watering and select a container that matches your water habits," says Meyers.

Pests aren't typically an issue when growing windowsill herbs, but you may bring them home from the nursery with you. "Soap sprays or a homemade dilution of dish soap and water spray helps rid plants of insects," says Hilgenberg.