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how to plant herb seeds in a pot

How to plant herb seeds in a pot

URBANA, Ill. – Herbs are popular in many gardens, but it can be expensive to buy and transplant mature plants. That’s why University of Illinois Extension horticulture educator Nancy Kreith recommends starting herbs from seed indoors as spring approaches. March is a good time to begin.

Thyme, rosemary, basil, sage, chives, and tarragon are good candidates for starting indoors. Many of these plants have very fine seeds and require a long germination period. If started early in March, they can be ready to transplant into the garden in mid to late May, depending on the region. Refer to Illinois State Water Survey for average frost free dates in your region at: www.isws.illinois.edu.

To start herb seeds indoors, use a peat-based soil-less seed-starting mix in a 3- to 4-inch-deep container or seed-starting flat with drainage holes. Pre-moisten the mix with water until it feels like a wrung-out sponge. Fill labeled containers with the moist mix, leaving about one-quarter inch of space at the top.

“Labeling containers with the herb name and planting date will avoid confusion when it comes time to plant outside,” Kreith says.

Plant at least five seeds (or a pinch) of one herb variety per container or cell and lightly cover with moist mix.

“As a general rule of thumb, plant seed just two times its thickness under the soil,” Kreith notes. “As plants become overgrown, seedlings can be thinned to one plant per pot.”

After planting the seeds, keep them moist during the germination period.

“One technique is to cover the flat or container with a clear plastic bag,” Kreith says. “The plastic helps hold in heat and aids in providing consistent moisture. However, be sure to monitor the growing media for mold growth. If you see mold, poke holes in the bag or remove it completely to improve air circulation.”

Plastic should be removed once the seeds germinate, usually in 10 to 14 days. A heat mat, available at many gardening stores, will speed the germination rate if placed under the container.

The sown containers or flats need approximately six hours of sunlight per day. A window with either western or southern exposure will work well initially, but over time, the herb seedlings will require more direct and intense lighting. Using supplemental grow lights or florescent lighting has been proven to work better than natural sunlight.

“If using fluorescent lights, keep them on for a minimum of 10 hours per day and place them as close to the seedlings as possible,” Kreith says. “Adjust the height as seedlings grow taller.”

Seeds and seedlings should be monitored on a daily basis as the transplants mature; look for insects, rot, and extremely dry soil. The seeds and seedlings should only need a light sprinkle of water about twice per week, depending on the temperature of the home. Allow the planting media to dry out a little before watering again. Overwatering can lead to diseases such as damping-off, a common soilborne fungal disease that ultimately kills young seedlings. Constant moisture can also attract fruit flies.

As seedlings mature, some maintenance will be needed. If seedlings grow too large for their original containers, they can be transplanted into larger ones. If they become leggy, they may not be getting enough light.

“Be sure fluorescent lights are placed close enough to the plants, no more than four inches away,” Kreith says. “You can also increase the amount of time lights are on, up to 16 hours per day.”

Once seedlings reach six to eight weeks old, pinch off the top leaves to encourage lateral spread and a bushier appearance. After 10 weeks, most herb seedlings should be ready to transplant outdoors.

“Help the tender plants ‘harden off,’ or become acclimated to their new climate, by placing them outdoors on mild sunny days and bring them back indoors at night for one to two weeks,” Kreith recommends. “Once plants are hardened off, they can be transplanted safely into the garden for beautification, culinary, and therapeutic purposes.”

Some seeds can be sown directly in the ground around the time that transplants are ready to be planted outdoors. Herbs that do well by direct sowing include cilantro, arugula, and basil. In early spring, direct-seeding cilantro and arugula, both cool-weather herbs, provide a bountiful leafy harvest from mid-spring to mid-summer. Warm season herbs like basil can also be directly sown after the danger of frost has passed.

<p> URBANA, Ill. &ndash; Herbs are popular in many gardens, but it can be expensive to buy and transplant mature plants. That&rsquo;s why University of Illinois Extension horticulture educator Nancy Kreith recommends starting herbs from seed indoors as spring approaches. March is a good time to begin. </p>

Easy Tips for Growing Herbs in Containers

The Spruce / Kara Riley

Herb container gardens are popular for many reasons. Even if you have miles of property and gardens galore, it’s convenient to be able to step just out your door and pick a handful of fresh herbs from a beautiful container garden. Plant maintenance is also more convenient with containers, and there are fewer problems with weeds and critters getting into your crops.

You can grow almost any herb in a container. However, if you’re mixing herbs in the same pot, you have to be sure you’re using plants with similar growing requirements. For example, some herb plants need more water than others, and some are finicky about how much light they get. But as long as you get the conditions right, you should have thriving plants and fresh herbs at your fingertips.

Planning Your Herb Container

You can grow as many types of herbs in one container as you want if they share the same sun, water, and soil preferences. For example, rosemary likes hot and dry conditions while parsley needs steady moisture. Therefore, they would not work well together in the same pot.

Also, don’t forget that herbs can serve as decorative elements in a container garden, adding texture and scent when mixed with annuals or perennials. Again, just be sure to pair them with plants that have similar needs, and make sure they won’t choke out any other plants in the same container, as some herbs have vigorous growth habits.

woman standing over herb selections

Choosing a Container for Herbs

You can use almost anything for an herb container, as long as it has good drainage. Most herbs don’t have large root systems, so you can get away with relatively small containers.   This is especially true of the herbs that don’t mind drying out between waterings. However, the smaller the container, the less soil there is. This means you have a smaller margin of error with too much or too little water.

Some herbs thrive in self-watering containers because they like a constant level of moisture. Plants, such as chives, parsley, marjoram, and mint, are particularly good candidates for growing in self-watering pots. Other herbs, including oregano, thyme, rosemary, and basil, prefer to dry out between watering, so they wouldn’t be good candidates for self-watering containers.  

herbs in pots next to a large container

Planting and Caring for Herbs

Help your container herbs thrive with the right soil, sun exposure, and fertilizer. Use a high-quality potting mix that allows for good drainage. This soil, paired with the drainage holes in your container, will help prevent accidentally drowning your herbs.

Moreover, most herbs need full sun for at least six to eight hours a day.   That said, containers can really bake on a hot day. So if you live in a climate where temperatures soar, your container herbs might need to be shaded during the hottest part of the day.

Be careful not to overfertilize your herbs. Most herbs don’t need much fertilizer, and some plants will simply die if they are overfed. Plus, certain herbs, such as thyme and oregano, thrive on neglect and often aren’t as tasty if they are given too much food or water.

herbs in full sun

Harvesting Your Herbs

The rule of thumb for harvesting herbs is to snip and pinch back often. Consistent harvesting will encourage the plants to branch and fill out which, in turn, will increase your overall harvest. Always tailor your harvesting to the plant’s growth pattern and avoid cutting more than one third of the plant during the growing season. For example, basil leaves should be harvested regularly, and the flower buds should be removed, but basil plants should not be cut back all the way.

The flowers and seeds of some herbs, such as chives and dill, are edible. The leaves of others including oregano and basil will lose flavor and become bitter if allowed to flower. Remember that once a plant flowers and goes to seed, the seasonal growth cycle for that plant will be complete and the plant will no longer put out new growth.

At the end of the growing season, you can bring many of your herb containers inside if you get lots of indoor sunlight. Some herb plants are easier than others to keep alive indoors during the winter, though it’s worth a shot for all your container herbs.

Finally, if you’ve grown more herbs than you can harvest for yourself, consider giving them as gifts. You can do themed herb container gardens, such as a “pizza” garden or an herbes de Provence container garden. Combine herbs and other edible plants in a pretty basket, or just pick a handful of herbs to put in a nice vase for an herbal bouquet. Many herbs like oregano, sage, rosemary and dill also dry well and can be kept in tightly lidded containers out of direct sunlight for use in cooking all year long.

Try these methods for planting a container herb garden, including choosing the right pot and planting herbs that grow well together.