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Timeline Through Landscape Design

A blog to guide home gardeners with seasonal landscape improvements.
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Herbs Make a Wonderful Landscape Addition


Herbs are a favorite in most gardens, and transplants can be expensive. Why not try starting seeds indoors this winter as you anticipate warmer weather? March is a good time to begin.

Some herbs that are fairly easy to start as seeds indoors and will beautify your landscape include rosemary, thyme, sage and chives. Most of these seeds are very fine and take a fair amount of time to germinate. You can start these herbs early in March and be ready for transplanting into the garden in mid to late May, depending on your region of Illinois. Refer to Illinois State Water Survey for average frost free dates in your region at: www.isws.illinois.edu.

All of the above herbs are perennials and certain varieties will add visual character to your yard while providing aromatic and culinary delights. Rosemary is considered a tender perennial. One of the more cold hardy varieties (perhaps zone 6) is 'Arp' and has grey-green foliage. Rosemary 'Huntington Carpet' has deep blue foliage with a trailing habit (less hardy in Illinois). Thyme comes in many varieties. One of my favorite varieties is wooly thyme which is low growing with pale pink flowers and performs well in rock gardens and in between stepping stones. Sage also comes in a number of varieties and has great texture. Although it is borderline hardy in zone 5, on the top of my list is Golden Sage, a small compact plant with chartreuse-yellow margins and dark green veins. Chives add great upright habit, fine texture and a pop of purple during mid-summer. Use caution with chives because of their tendency to self-sow. You can help to prevent this by removing the flowers before they fade.

To start herb seeds indoors, use a soil-less seed-starting mix that is peat-based along with a shallow container (roughly 3-4" deep) that provides drainage. Most brand name soil-less mixes work well for seed starting. Moisten the mix with water until it reaches the consistency of a wrung-out sponge. Fill a container or seed-starting flat with the moist mix leaving a little space at the rim.

Now it is time to plant. Plant at least five seeds (or a pinch) of one herb type per container or cell and lightly cover it with mix. As a general rule of thumb, seeds should be planted just two times their thickness under the soil. As plants grow, seedlings can be thinned out to one plant per pot. Don't forget to label your seeds. Labeling appropriately with the herb name and planting date will avoid confusion when it comes time to plant outside.

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. The plastic helps hold in heat and aids in providing consistent moisture. However, be sure to monitor the growing media for mold growth. If mold occurs poke holes in the bag or remove it completely to improve air circulation. Moisture can also be provided by use of a spray bottle. Additionally, the bag should be removed once the seeds germinate in 10 to 14 days. Use of a heat mat will speed the germination rate.

The sown containers or flats need approximately 6 hours of sunlight per day. A window with either west or southern exposure will work well at the beginning, but over time the herb seedlings will require more direct and intense lighting. Using supplemental grow lights or florescent lighting has 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 (adjust light height as seedlings grow taller).

Monitor the seeds on a daily basis until they germinate. Be on the lookout for insects, rot and extremely dry soil. The seeds/seedlings should only need a light sprinkle of water about twice per week (depending on the temperature of your home). A good practice is to allow the planting media to dry out a little before watering again. Over-watering 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 become overgrown, they can be transplanted into a larger cell or a bigger container. If they become leggy, they may not be getting enough light. Be sure fluorescent lights are placed close enough to the plants (at most 4" away) and increase timing up to 16 hours per day. Once seedlings reach 6 to 8 weeks old, pinch back the top leaves to help the plants become bushier.

Most herb seedlings should be ready to transplant outdoors in approximately 10 weeks. Help the tender plants "harden off," or become acclimated to their new climate, by placing them outdoors on mild sunny days and bringing them back indoors at night for 1 to 2 weeks. Once plants are hardened off they can be transplanted safely into the garden for beautification, culinary, and therapeutic purposes.

If you plan to harvest your herb, do so just before they flower for best flavor. You can find details about specific herbs, their growing requirements, and harvesting and storing methods at extension.illinois.edu/herbs/


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