Hyssop (Hyssopus officinalis)

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 a hyssop plant in your garden! 

I. Appearance and Characteristics 

Hyssopus officinalis or hyssop is a shrub in the Lamiaceae or mint family native to Southern Europe, the Middle East, and the region surrounding the Caspian Sea. Due to its purported properties as an antiseptic, cough reliever, and expectorant, it has been used in traditional herbal medicine.

Hyssop is a brightly coloured shrub or subshrub that ranges from 30 to 60 cm (12 to 24 in) in height. The stem is woody at the base, from which grows a number of upright branches. Its leaves are lanceolate, dark green, and from 2 to 2.5 cm (3⁄4 to 1 in) long.

During the summer, hyssop produces pink, blue (ssp. aristadus), or, more rarely, white fragrant (ssp. f. albus) flowers. These give rise to small oblong tetra-achenes.

Hyssop is resistant to drought, and tolerant of chalky, sandy soils. It thrives in full sun and warm climates.

II. How to Grow and Care

Sunlight and Temperature

Hyssop plants need a minimum of 6 hrs sunlight per day, so grow in full sun or partial shade.  USDA zones 4 – 9 are perfect.  Hyssop is cold hardy down to around -35°F and tends not to require any frost protection. Plants may look a bit rough around the edges, especially in cooler climates, but it’s nothing a good spring prune won’t sort out.

Watering

Hyssop plant requires consistent watering until it is established, after which it is drought tolerant. Water deeply after the top few inches of soil have dried out for optimum plant health.

The same holds true for plants grown in containers, albeit the interval between drying out and watering will be shorter.

Use a watering can or timed drip hoses to water plants at soil level in the morning, Be careful not to get the leaves wet. Plants don’t need to be watered in the winter.

Soil

Hyssop adapts well to a wide range of soil conditions. They prefer rich, well-drained chalky loam soil. However, plants 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.

Fertilizing

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

Pruning

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

Propagation

Hyssop is easy to propagate, whether by dividing mature plants, taking cuttings, or sowing seed. We’ll cover each of these options.

  • From Cuttings

Take cuttings either in the late spring or early autumn. Snip six-inch stems, and strip the leaves from the bottom two inches. Pinch off the top of each, to encourage branching growth.

Place individual cuttings in small pots filled with a moist soilless medium, or a combination of half builder’s sand and half soilless medium.

Keep the medium moist but not wet by misting regularly. Roots will form within about a month.

Allow spring-started plants to develop branches, and roots that stretch to the bottom of the pot, before planting into your garden.

Or, if you took cuttings in the fall, keep them indoors through the winter before planting out the following spring.

  • By Division

Large, mature plants may be divided in the spring. On a cool day, or early in the morning, use a shovel to dig up the fibrous root ball and divide it in half, or into three pieces.

Replant the parent plant. Dig a hole the size of the root ball of each division, and loosen the soil on the bottom before planting.

Backfill with garden soil, but make sure the plants are not set too deep, and keep the soil away from the stems.

Water well, and irrigate regularly until plants are established.

  • From Seed

You can collect the dry seed heads from existing plants, and store them in a dry, dark place over the winter.

Sow seeds out in your garden in the spring after the last frost, spacing the seeds an inch apart. Thin to six inches apart after seedlings sprout.

You can also sow seeds indoors about eight to ten weeks before the last average frost date.

These seeds need light to germinate, so whether you are sowing in the ground or in pots filled with soilless propagation medium, be sure to only cover them lightly.

If sowing indoors, keep the medium moist, and place your pots in a well-lit 65 to 70°F space.

Seeds will germinate within 14 to 21 days.

You can transplant the seedlings out into the garden once the risk of frost has passed in your area and the plants have two sets of true leaves. Space transplants six inches apart.

Harden the seedlings off first by setting them outdoors every day for a couple hours and slowly increasing the amount of time each day before bringing them back in.

Pests and Diseases

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

  • Common Pests

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

  • Common 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 an organic fungicide such as sulfur, lime sulfur, neem oil, or potassium bicarbonate, prior to or at the first sight of disease.

If your hyssop plant 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 plants that are overwatered or have poor drainage.  To check, carefully dig up your plant 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.

III. Uses and Benefits 

  • Ornamental uses

Through the summer and autumn, hyssop grows exceedingly ornamental blooms that add beauty to both cottage or herb gardens. The spreading nature of this plant makes it a good ground cover, while its blooms and evergreen foliage make it popular in flower beds or path borders. Bees, butterflies, and hummingbirds will visit the gardens where this plant grows.

  • Culinary uses

The fresh herb is commonly used in cooking. Za’atar is a famous Middle Eastern herbal mixture, some versions of which include dried hyssop leaves.

Essence of hyssop can be obtained by steaming, and is used in cooking to a lesser extent.

The plant is commonly used by beekeepers to produce nectar from which western honey bees make a rich and aromatic honey.

Herb hyssop leaves are used as an aromatic condiment. The leaves have a lightly bitter taste due to its tannins, and an intense minty aroma. Due to its intensity, it is used moderately in cooking. The herb is also used to flavor liqueur, and is part of the official formulation of Chartreuse. It is also a key ingredient in many formulations of absinthe, where it is the main source of the green color.

  • Medicinal uses

In herbal medicine hyssop is believed to have soothing, expectorant, and cough suppressant properties. Hyssop has been used for centuries in traditional medicine in order to increase circulation and to treat multiple conditions such as coughing and sore throat. Hyssop can stimulate the gastrointestinal system.

IV. Harvesting and Storage

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.

  • Harvesting

Once hyssop plants 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. 

  • Storing

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.

Hyssop (Hyssopus officinalis) Details

Common name Hyssop
Botanical name Hyssopus officinalis
Plant type Edible
Hardiness zone 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Medium
Height 1 ft. 6 in. - 2 ft. 0 in.
Width 1 ft. 6 in. - 2 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Loam (Silt)
Flower color Blue
Leaf color Green