Marshmallow (Althaea officinalis) is a perennial, herbaceous plant in the Malvaceae family related to hollyhock, cotton and hibiscus. It grows well in most locations down to zone 3, which means almost anyone can grow it!
It does have preferences, however, and will grow better if certain conditions are observed.
It likes to be watered well but doesn’t like to sit in water, so make sure you put it in a place that has fairly well drained soil. It can tolerate just about any soil type. As a matter of fact, I transplanted a few of my errant marshmallow plants early in the summer because they were growing out of one of my garden paths. I had a large hole that was left from where my apprentices had dug up burdock root the previous fall. I grabbed some mulch material (leaves, bark, and some composted straw that was covering the soil around the hole) and used that to plant my marshmallow. I honestly wasn’t sure there was enough substance there to get it to grow, but boy was i wrong! It shot up and put out the most beautiful leaves and flowers then gifted me with easy to harvest roots.
The one thing marshmallow is really particular about is having enough sun. It will not grow well in the shade, so don’t choose even a partially shady spot. You’ll end up with a very sad looking plant that doesn’t produce much. Give it what it needs, and it will grow to be tall, healthy and bountiful.
Marshmallow plants can grow up to 4-feet tall (as mine did this year). You’ll begin to see flowers emerge between July and September, and it will start going to seed as the weather begins to cool down.
Marshmallow is self-fertile (so you don’t need multiple marshmallow plants) and is pollinated by bees, which are naturally attracted to the open, inviting blossoms. Marshmallow is very easy to cultivate both from seed and from the crown. I harvested roots in the early summer (one of my plants was dug up by the dogs) and just replace the crowns in loose soil. They grew back like nothing happened! It did a lot of self-seeding this last year, so I spent a little time moving plants around, as well as pulling the ones I didn’t want growing.
There’s no fear of them taking over like lemon balm or mint, but you may get growth in inconvenient places if you leave it to go to seed. It’s totally up to you how you decide to reign this beauty in. I have a pretty wild looking garden so I usually leave things to do what they want, unless I’m trying to grow another plant that doesn’t do well with competition.