How to Plant, Grow, and Care for Hyssop

Hyssop is an old-fashioned herb you may have heard of, but you might not know what it looks like or what to do with it. Hopefully, the tips and advice in this article will answer some of these questions and encourage you to grow it.

There are many reasons to grow hyssop. Firstly, it looks great! You can grow hyssop in the herb garden, as a border, or as a specimen, and it will catch your eye. It looks especially striking when planted en masse, producing a sea of blue blooms.  

Secondly, pollinating and predatory insects such as bees, wasps, and butterflies are drawn to hyssop flowers. Honey bees feeding on hyssop nectar also make excellent honey. If you are lucky enough to have hummingbirds visit your garden, then grow hyssop as they will thank you for it. So will other garden birds that feed on the seeds.   

Used as culinary herbs, hyssop has a strong bittersweet warm mint flavor with floral undertones and has been used for centuries for cooking meat and vegetables, and in soups and stews.  

Finally, like most herbs with ‘officinalis’ in their name, hyssop (Hyssopus officinalis) has a long history of medicinal use. Its anti-inflammatory, antioxidant, and anti-viral properties are used as a natural tool in the fight against infections and viruses, but as with all medicines, it’s best to seek medical advice before trying anything.

What is Hyssop?

Hyssop is a herbaceous/semi-evergreen subshrub with an upright compact growth habit. It is known botanically as Hyssopus officinalis, but had a name change in 2022 to Dracocephalum officinale. You will still see it in the nurseries as a hyssop though.

Native Area

It has its origins in Southern Europe and the Middle East. Today, it is naturalized in Northern Europe and North America where it can be found growing on road verges and in wildflower meadows.

Characteristics

As a member of the extensive mint family (Lamiaceae), hyssop shares many attributes with its mint cousins, such as flower shape, square stems, and strongly scented leaves. Fortunately, it does not share the invasive growth habit of many mint species.

Hyssop plants grow to 20-24 inches in height and 20 inches across. The woody stems are green, erect, and square like mint. Its leaves are dark green, one inch long, lance-shaped, and grow in opposite pairs. Clusters of small two-lipped tubular blue, pinkish-purple flowers appear on tall spikes whorled around stems from July to September. Seed capsules ripen on these spikes a few weeks after flowering, eventually turning brown and dry. Hyssop seeds are small, one to two mm in size, and light brown.

Young fresh leaves are harvested to add to soups, stews, and salads. The bitter-sweet warm mint flavor can pack a punch that is not to everyone’s taste, so it’s best to experiment with quantities until you get it right. The pretty blue flowers are also edible with a spicy thyme-like flavor and look great sprinkled over a salad or as a garnish to meat and vegetable dishes.

In ancient times, the Persians distilled hyssop oil as a body lotion to improve skin health and highlight skin color and tone. Europeans burned the oils in homes as an air freshener, and cultures worldwide have made a tea remedy from the leaves to treat nose, throat, and lung problems. Poultices made with hyssop leaves were used as dressings for wounds and infections. It is believed the mold that grows on the leaves of hyssop produces penicillin which helps in the healing process. 

Planting

Grow hyssop outside in spring after the last frost date. Choose a location in full sun or partial shade with rich, well-drained soil. Hyssop grows well in the ground as part of a border planting scheme, in a raised herb bed, and even a rockery. Space hyssop 12 inches apart to allow adequate ventilation between them and space to grow.

Hyssop is well suited to grow in containers and make a lovely addition on a sunny patio. Its drought-tolerant nature lends itself to growing in containers that are prone to drying out quickly. Choose a container large enough to accommodate the mature size and its extensive root system and use a rich growing medium, supplemented with a slow-release balanced fertilizer.  

Sow hyssop seed in early spring, eight to ten weeks before the last frost date, and set hyssop transplants out when all risk of frost has passed. Seeds can also be sown directly into a bed prepared with lots of organic matter.

If you have access to established herbs, take softwood cuttings in spring and grow them in pots somewhere warm and sheltered. Set hyssop out from mid-summer to early fall. 

Dividing mature hyssop herbs in spring is another excellent way to get free stock. It also helps to rejuvenate current stock. Divisions should be relocated in your garden or potted up to be shared with fellow gardeners or planted later. Replace old spindly hyssops after five years.

How to Grow

Once established, hyssop is easy to care for and will give you lots of enjoyment. Here are a few tips to help you get the best from your herbs.

Light

Hyssop needs at least six hours of sunlight per day, so it should be grown in full sun or partial shade. USDA zones 4-9 are perfect. If grown in full sun, it will flower more than those grown in the shade.

Water

Keep the soil around young hyssop moist until their roots have become established. As they mature, they will become quite drought-tolerant. For optimum plant health, water when the top few inches of soil have dried out, and water deeply. This applies to container-grown hyssop as well, although the time between drying out and watering will be shorter. Water in the morning at soil level using a watering can or timed drip hoses, being careful not to wet the leaves. They do not require watering during winter.

Soil

Hyssop adapts well to a wide range of soil conditions. They prefer rich, well-drained chalky loam soil. However, they will thrive in sandy or rocky soils with the addition of organic matter and/or regular feeds during the growing season. Container grown hyssop should be grown in an 80:20 mix of rich potting media and grit for added drainage. The soil pH should be within the range of 7.0 to 8.5.

Temperature

Hyssop is cold-hardy down to around -35°F (-37°C) and tends not to require any frost protection. They may look a bit rough around the edges, especially in cooler climates, but it’s nothing a good spring prune won’t sort out.

Fertilizing

Feed hyssop with a good quality balanced liquid fertilizer in spring when the first shoots appear. Add a slow-release fertilizer to container-grown herbs to replace nutrients leached from watering.

Maintenance

In cooler climates, hyssop can be pruned back hard, removing old or dead wood. This will stimulate lots of new vigorous growth. In warmer climates, they may only need a quick shape and tidy up, cutting out any dead or dry stems. Lightly prune again after flowering to keep them bushy and to encourage a new flush of late-season growth. To prevent hyssop from self-seeding, prune when flowers begin to fade. 

Propagation

Sow hyssop seed indoors in early spring, eight to ten weeks before the last frost date. Sow into seed or cell trays and cover very lightly with vermiculite or sieved compost. Hyssop seeds require light to germinate, so if seeds are peeping out, that’s fine. Keep the growing medium moist but not wet and place it in a bright location at a temperature between 65 -70°F (18-24°C). The seeds should germinate in 14 to 21 days. Harden transplants off outside during the day for at least a week before planting out, bringing them indoors at night.

Softwood cuttings can be taken in late spring/early summer. Cut five to six inches of new growth from established herbs, and strip off the bottom leaves. Place the cuttings into pots prepared with a 70:30 mix of compost and perlite/horticultural grit. Set the cuttings somewhere warm and bright but not in direct sunlight and keep the compost moist until roots have developed.

Mature plants, two years and older, can be divided in spring to produce new stock for the garden. Carefully dig up the entire herb and split the plant in two with either a sharp pruning saw or knife or a pair of garden forks back-to-back. Further divisions can be taken if sufficient material is available. Space hyssop divisions 12 inches apart into their new planting locations or pots as soon as possible and water well.

Harvesting

Hyssop leaves can be harvested to use fresh or stored for longer-term use.  Follow the advice below to help get the best results from your crops.

Once hyssop herbs are well established with lots of healthy bushy growth, it’s time to harvest.  Young leaves provide the best flavor and start to deteriorate when flowers develop. Their flowers are also edible and can be harvested during the flowering season when they have just opened. Use them to add color and flavor to salads and garnishes. Harvest seeds for future sowing when the seed capsules have turned brown and dry. 

Hyssop is increasingly popular as a cut flower and provides long-lasting foliage, flowers, and scent to bouquets. Regular harvesting will encourage new growth throughout the growing season. 

Storage

Store freshly cut leaves somewhere cool, wrapped in damp kitchen paper, for up to a week.  Stems can be placed in a glass of water somewhere cool until needed. For longer-term storage, dry leaves on a flat tray or hang in bunches upside down in a cool, dark, well-ventilated area until completely dry. Dehydrators are good for this too. Crumble the dried hyssop leaves and store them in an airtight container for up to a year.

Common Problems

Hyssop is relatively trouble-free and easy to grow, making it an excellent herb for beginners.  There are a couple of things to look out for while growing hyssop, however.  

Pests

The strong aroma and essential oil contained in hyssop leaves provide a built-in self-defense system to deter most garden pests. It also makes hyssop a great companion, especially as good company for vegetables regularly devoured by cabbage moth larvae and flea beetles!

Diseases

The fungal disease powdery mildew may affect the leaves of hyssop if grown in hot, humid, shaded conditions. It grows as thick white dust on leaves, inhibiting photosynthesis and hindering growth. Maintain good garden hygiene and avoid conditions the disease thrives on.  Spray with neem oil prior to or at the first sight of disease.

If your hyssop looks a little lackluster, and its leaves are yellowing or falling off, but there are no obvious signs of pest or disease, then there might be a problem with the roots. Root rot affects herbs that are overwatered or have poor drainage. To check, carefully dig up your hyssop and look for brownish or black roots, a sure sign of rot. Snip off as much damaged root as possible and replant somewhere with better drainage or ameliorate the planting hole with horticultural grit and fresh compost.

Frequently Asked Questions