Lemon thyme: planting, care & uses

Lemon thyme not only makes a lovely groundcover, but it also transforms the garden or balcony into a Mediterranean-scented oasis.

Lemon thyme (Thymus x citriodorus) has a few location requirements. If you choose the right location, you can enjoy its fine fragrance all year round. Read on to find out how to plant and care for lemon thyme.

Lemon thyme: flower, origin and properties

The Thymus x citriodorus herb is the result of a natural cross between broadleaved thyme (Thymus pulegioides) and common thyme (Thymus vulgaris) and was named after its fine lemon fragrance. Lemon thyme is also known as citrus thyme. The Thymus genus belongs to the Labiatae family (Lamiaceae), which is known for its aromatic herbs such as rosemary (Rosmarinus), sage (Salvia) and lavender (Lavandula). Lemon thyme is native to the Mediterranean but can also be grown in the UK. Typical of Lamiaceae plants, lemon thyme has lipped, tubular flowers in pale purple or pink. The leaves are elliptical and broader than common thyme with a sweet lemon scent. Overall, it reaches a height of 8 to 15 cm and is 25 to 30 cm wide. It has a mat-forming growth habit. This aromatic herb is both evergreen and perennial, forming lovely green accents in rock gardens.

Tip: lemon thyme is a favourite of bees and bumblebees. Insects can easily reach the nectar because the lipped flowers act as a runway for the critters.

When does lemon thyme flower? The original lemon thyme blooms from July to August with delicate purple flowers. Some varieties have a slightly shorter flowering time

The best lemon thyme varieties

Although the original form of lemon thyme already has a lot to offer, there are also many beautiful lemon thyme cultivars.

• ‘Aureus’ has yellow-green leaves and lovely light pink flowers which bloom from June to July.

• ‘Golden Dwarf’ has purple flowers and yellow leaves. This variety is less frost-hardy and is best grown beside a house wall in winter. Grows well in pots.

• ‘Lemon Variegated’ grows up to 12cm tall and produces yellow-green to white leaves.
• ‘Rasta’ grows up to 40cm wide with light purple to pink flowers, blooming between June and August. ‘Rasta’ lemon thyme also boasts a rich green foliage.
• ‘Silver Queen’ has green leaves with white edges. This variety generally has a silvery tone.

Planting lemon thyme: location and procedure

Lemon thyme thrives in both pots and beds. If planted in a bed, choose the location carefully because lemon thyme reacts quickly to unfavourable soil conditions. Thymus x citriodorus grows best in poor, well-drained soil and does not tolerate waterlogging. Likewise, due to its Mediterranean origins, it needs a warm, sunny location with at least five hours of sunlight per day.

Once you have chosen a suitable location, it is time to plant the thyme. Although lemon thyme can be planted all year round, do so in spring for the best results. Dig a planting hole that is twice as wide as the root ball. Loosen the soil if possible.

Tip: to avoid unwanted waterlogging, add a drainage layer of expanded clay, grit or gravel to the bottom of the hole. For lemon thyme in pots, expanded clay is also suitable as the bottom layer.

If you wish to grow several plants next to each other, space them 20 to 25 cm apart. Place the lemon thyme plant deeply in the hole so that the lowest branches are barely above the soil surface, then fill in with soil.

If you do not want to buy a potted plant, you can sow lemon thyme seeds. That said, growing lemon thyme from seed is a less common practice. It is best to start the lemon thyme seeds indoors from March onwards.

Sowing lemon thyme:

• Fill the seed pots with sowing soil and moisten thoroughly
• Press the lemon thyme seeds lightly onto the soil, as the seeds need light to germinate
• Place the seed pots on a bright windowsill with a temperature of 15 to 20 °C
• After 10 to 15 days, the first sprouts should appear
• Once you spot the first real leaves, gently pot on the seedlings into individual pots
• From mid-May after the last frosts, plant your lemon thyme seedlings outdoors in a bed or pot

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Caring for lemon thyme

If its location requirements are met, lemon thyme is a low-maintenance herb. Lemon thyme tolerates a little more water immediately after planting, but keep the soil dry in general. Later on, lemon thyme tolerates dry periods well, but water it regularly with just a little water. Let the soil dry out between waterings.

Lemon thyme is a slow grower with low nutrient requirements. If you wish to fertilise lemon thyme, only do so in spring with an organic fertiliser. Overfertilising results in rapid elongated growth and a loss of aroma. Do not fertilise in summer, as the young shoots may not be able to withstand the coming frosts in autumn and winter.

Lemon thyme shrubs are actually sub-shrubs that benefit from being cut back to the woody part in spring. This ensures a compact growing habit, as well as an abundance of aromatic leaves.

Tip: pay attention to the weather forecast as pruning before coming frosts can harm your lemon thyme plant.

There is another care practice that rejuvenates these herbs. Lemon thyme grows runners, which means that these side shoots form roots when they touch the ground. It is best to cut these off the mother plant every two to three years and replant in a new location. This allows the mother plant to invest more energy in fragrant leaves and blooming flowers.

Is lemon thyme hardy?

Yes, lemon thyme is one of the hardiest thyme species, surviving temperatures as low as -18 °C. Nevertheless, successful overwintering outdoors depends on the health of the plant. Cover any young, non-woody plants with brushwood in late autumn. Place potted lemon thyme plants in a rain-protected location, such as beside a house wall. In extremely cold temperatures, wrap the pots with fleece to prevent the root ball from freezing through.

Tip: if you keep your lemon thyme in a frost-free indoor location over winter, it will be less frost-resistant than its fellow plants that have spent the winter outdoors. Acclimatise such plants to outdoor temperatures gradually in the spring, bringing them inside at night until May.

Propagate lemon thyme

Lemon thyme propagation is a simple process and is most successful in summer before the flowers appear. One propagation method is via lemon thyme cuttings.

• Choose a shoot that is about 15cm long and half woody
• Remove the bottom leaves, leaving the top 2-3 leaves on the stem
• Put the cutting halfway into the growing medium
• Place in a bright and warm location with a temperature of approx. 20 °C
• Cover the cuttings with plastic bags or film to keep them humid and air regularly to prevent mould
• Keep the soil moist but not too wet
• If new leaves appear after about 3 weeks, the cutting has formed roots
• Wait another 2 weeks before potting on to a larger pot or plant out in the garden

Another method of propagation is to separate the previously mentioned runners from the mother plant. Use a clean, sharp knife to separate. Then plant the runner plants singly in a new location. Ensure that the young plants are growing in a temperature range of 15 to 20 °C. You can even intentionally induce ground layering propagation by digging the mother plant’s shoots into the soil and binding them in place so that they grow their own roots.

Lemon thyme flavour, aroma and use

Lemon thyme is a good choice for rock gardens or sites that have a rocky, sandy terrain i.e. barren and loose conditions. As a culinary herb, it is also suitable for balcony boxes as well as herb spirals. It makes a good ground cover due to its creeping and relatively flat growth. Moreover, the mat-forming lemon thyme thrives in places where other plants, like grass, do not because of its low soil requirements.

Lemon thyme plants are very tolerant of pruning and can sprout again and again. The harvest time corresponds to the common thyme harvest season. Like its relatives, lemon thyme contains an abundance of essential oils like thymol, which is responsible for the typical thyme flavour. It also produces citral, which gives it a lemony aroma and flavour. Lemon thyme is a very versatile herb in the kitchen, providing freshness in Mediterranean dishes, on fish, and as a unique embellishment in cold drinks.

If you do not intend to use the lemon thyme right away, it can also be dried by hanging the shoots upside down. This method works best in a dark location. Dried lemon thyme tastes even more intense and can be steeped to make tea.