Agastache is an ornamental plant with many appealing qualities. Aesthetically pleasing with its spiked flowers in various colours, this sun-loving perennial delights our sense of smell when its leaves are crushed, releasing a minty fragrance. The culinary use of Agastache rugosa (Korean Mint) as an aromatic herb is very common in North America and Asia. This plant is also known for its medicinal properties, including anti-inflammatory and expectorant effects! Note that depending on the cultivar, the foliage of Agastache can range from green to yellow. Being a nectar-rich plant, it also attracts numerous pollinating insects.

Follow our tutorial to learn how to successfully sow Agastache under cover and transplant the seedlings!

agastache seeds

When to Sow Agastache?

Agastache seeds should be sown indoors from February to April. We do not recommend direct sowing outdoors, as heavy rains or late spring frosts could hinder successful germination.

How to Sow Agastache?

1) Required Materials

To proceed with sowing, gather the following materials:

agastache sowing materials

Seedling tray with lid, seed sower, and biodegradable pot

2) Sowing in a Tray

Agastache seeds should be sown under cover from February onwards, meaning indoors at a temperature between 15-20°C. At this time of year, it is still too cold, and frost is too frequent for outdoor sowing.

Sowing in a tray is the first step:

  • Start by placing a 1 cm layer of clay pebbles at the bottom of the tray or mini greenhouse for drainage (not necessary for seedling trays)
  • Cover with seed compost or a 50/50 mix of sand and compost or peat moss
  • Level and firm the compost with a small board
  • Sow the Agastache seeds evenly using the seed sower
  • Lightly cover the seeds with a thin layer of compost
  • Gently and thoroughly moisten with the spray bottle to ensure the compost is damp
  • Close the mini greenhouse or tray with the lid or a plastic bag to retain warmth and humidity for germination
  • Place your sowing in a bright spot, but out of direct sunlight, such as near a window
  • Ventilate and water regularly to keep the compost moist
  • Allow to germinate and monitor for signs of damping off (fungal disease)

how to sow agastache

3) Transplanting into Pots

Once the seedlings have developed well and reached about 5 cm in height, you can transplant them into individual pots. Keep them under a warm frame until the risk of frost has passed. Using biodegradable pots makes transplanting outdoors easier—simply plant the pots directly into the ground. This avoids disturbing the young plants and keeps the roots intact. Additionally, their natural fibre walls ensure good aeration and water retention.

transplanting agastache, potting on agastache

4) Transplanting Outdoors

In late April, after the last frost, when the seedlings are about 10 cm tall and robust, you can transplant Agastache outdoors in the garden. Choose a warm, sunny spot. Prepare the soil: loosen it, remove roots and large stones, weed, and level. For well-drained soil, enrich it with well-rotted compost. Space plants 40-50 cm apart. Agastache has a short lifespan of about 4-5 years, but self-seeding ensures this perennial continues to thrive.

Further Reading