Horehound is a lovely herb that is hardy down to USDA Plant Hardiness Zone 4. This plant does have the “square” stem of the mint family. Having said that, keep in mind that this plant can and will become very invasive if not controlled. This can be done by planting in a container or clay chimney flue.
When it comes to propagating horehound, you have two choices. If you have a friend with horehound, they will graciously share a cutting or division but……….what do you do if you do not have that friend. The answer is simple and that is to start your horehound from seed.
To begin this process, one must decide if they are going to directly seed or start indoors. While both techniques are viable, the latter will require one to start three weeks prior to your local frost free date. The first approach will only allow you to plant your seed after your local frost free date.
Once you have decided which approach you want to use, the next step is to prepare the planting surface. If you are directly seeding into the garden, prepare the garden space by removing unwanted plants and loosening up the soil. Next, sprinkle the seed on top of the soil. Top the seed with a very thin layer of soil. This seed does not need to be covered completely. A fine layer is all that is needed to hold the seed down to the ground. Next, mist the soil with water until completely damp.
On the other hand, if you choose to start early the first step is to plan your planting date. Horehound seed needs to be started three weeks prior to your local frost free date. Once you have this date, clean and sterilize your container. Moisten an all purpose potting soil mix and add to the prepared container(s). Sprinkle the seed on top of the potting mix. Mist with water and place on a sunny windowsill.
Horehound seed is notorious for having a poor germination rate. In doing so, do not be too discouraged with your seed.
While horehound will really grow anywhere due to its invasive nature, it does thrive in sunny locations that have a well draining soil. Techniques for dealing with its invasive nature have been offered but there is one that was left out. This technique will help keep your horehound from taking over while keeping it bushy. What is this technique? It is pruning. Clipping back your plant once it has started blooming will reduce the chances of seed production while encouraging a bush shape.