How to Plant, Grow, and Care for Marshmallow Plant

We have great news for your sweet tooth: you can grow marshmallows in your backyard! Well, it won’t exactly be candyland, but you’ll be able to make an old-fashioned type of candy with your very own marshmallow plant. Plus, each flower is as pretty as the confection is sweet!

Marshmallow plants are very old. Ancient Egyptians mixed the mucilaginous sap with honey and nuts to make a sweet confection. The roots were often used as a food source in times of famine (they’re edible but not the most palatable). The delicate flowers and fuzzy leaves can be used as herbs in tea or boiled in soups and stews.

Growing marshmallow plants is a sticky business. The sweet sugar sap is distributed all throughout the stems and can make pruning quite messy. However, marshmallow plants are surprisingly low-maintenance. They’re quite adaptive to different environments, though they prefer very moist soil. After all, as the name implies, these mallows come from marshes!

Marshmallow plants aren’t just for eating. Their tall, leafy stalks and fluttery flower clusters add a whimsical touch to the garden. They’re also perfect for filling in water-logged parts of the yard that most species won’t take to. If you’re adventurous in the garden and creative in the kitchen, grow marshmallow plants!

What is a Marshmallow Plant?

There are lots of species sneaking around with the common name ‘marshmallow’, typically within the Malvaceae (mallow) family. For this article, we’ll focus on Althaea officinalis.

Native Area

This species originates from Europe and Western Asia. There is a small distribution in North Africa, mainly around the Mediterranean. It’s closely related to hollyhocks – a resemblance you can see in the stalks and flower clusters.

Characteristics

Marshmallow plants grow from a tap root, like a carrot. Out of the ground come rigid stalks bearing pointed, lobed leaves. These toothed leaves grow up to four inches long and are coated with soft hairs. The velvety texture makes the leaves a bit unpalatable, so they’re best with the hairs cooked off. The entire perennial contains some amount of mucilage.

The best part of the marshmallow plant, besides the sweets, is the flowers. While smaller and less showy than hollyhocks, they grow in similar clumps and shapes. The pink and white flowers have darkened centers and bloom individually or in clusters. They make a lovely, slightly wild addition to any garden.

This bee-pollinated, flowering herb produces round fruits, often called “cheeses”. Inside are small, black seeds that are self-seeding. Ideally grown in zones 3-7, growing marshmallow plants are very adaptive. They grow three to six feet tall and four feet wide. From July to September, you can expect an abundance of pink and white flowers.

As we mentioned, most of this herb is used culinarily. Ironically, the only part that isn’t eaten is the fruit. Althaea officinalis is also known as a medicinal plant that eases pain and swelling. If you’re planning to grow marshmallow plants for herbal medicine, consult with your doctor first. Reportedly, marshmallow may interfere with medication absorption, cause lowered blood sugar, and potentially put one at risk of hypoglycemia. Althaea officinalis also may not be a good medicinal choice for those with pre-existing conditions such as diabetes.

Planting

Marshmallow seeds need a cold period of several weeks to germinate (called cold stratification). Sow them directly in the ground in late summer or early fall and they’ll pop up in the spring. You can sow the seeds in early spring if you didn’t plan that far ahead. However, you’ll need to stick the seeds in the refrigerator for at least a month. You can leave them in the seed packet for this or place them in a plastic bag with some damp peat moss. Transfer the seeds from the refrigerator to the ground after the last frost.

Unfortunately for indoor growers, marshmallow doesn’t grow well in containers. The only time it will is if you start the seeds indoors and transplant them a few weeks after they’ve sprouted. This is a herb that requires plenty of space above and underground. 

Marshmallow seeds don’t have the most reliable germination, so sow several in each spot. You can always thin out multiple sproutings later. Sow the seeds shallowly, an inch or less deep, and a foot apart, and give them a light covering of soil. With moist soil, the seeds should germinate in a few weeks (about three to four).

Protect your young seedlings from weed bullies by spreading mulch. The mulch will also help with water retention and add nutrients to the moist soil. After several weeks, when the marshmallow plants are established enough to fight off weeds on their own, you can lessen up on the mulch.

How to Grow

Honestly, planting seeds was the hard part. Marshmallow plants grow so easily that it’s usually smooth sailing from there. However, there are a few things to know if you really want your sweet plants to thrive in the garden.

Light

Althaea officinalis absolutely must have full sun. It may be tolerant of many conditions, but shade is not one of them. Because this bushy herb can grow several feet tall, don’t place it near other full sun-loving varieties. The marshmallow will quickly grow up and block the light to them. 

Water

As we know from the name, marshmallow needs marshy, wet conditions. In nature, it grows near bodies of water but not in them. So, we need to keep the soil very wet but not submerged. Place it in a part of your garden that’s always muddy and moist (if you have a small pond, that’s perfect!). 

Even though they love moist soil, they can survive small bouts of drought. We don’t recommend you test their abilities, but it won’t just keel over if the soil dries out.

Soil

This is where the marshmallow’s versatility really shines. It will grow in clay soil, sand, loamy soil – whatever’s available. It also tolerates mildly acidic to mildly basic soil. If you want to make the perfect conditions for your marshmallow though, give it clay soil that’s slightly acidic and very fertile (and moist, of course!). 

Although marshmallow is a swampy herb, it still needs good drainage. Unlike lotus root, marshmallow does not grow in standing water.

Temperature

This is a cold-hardy herb. Marshmallow will survive temperatures as low as -13°F (-25°C) and can handle a maximum of 86°F (30°C). To meet these conditions, the marshmallow plant is best grown in zones 3-7.

Fertilizing

If you’ve been adding organic matter as mulch, you don’t really need to fertilize your marsh mallow. However, if you want, you can give it an extra boost when it starts to bloom. Just apply a one-time dose of a balanced fertilizer to the soil.

Maintenance

This herb is self-seeding. If you don’t want it to spread, you’ll need to remove spent flower clusters before they can release their seeds. You don’t have to worry too much about that because, unlike common mallow, marshmallow isn’t invasive.

Anytime you take shears to this herb, be sure to wear gloves. Otherwise, you’re going to get very sticky! Thankfully, the sticky sap is water-soluble, so you can clean your hands and tools with soap and water later. A little rubbing alcohol can deal with any very sticky residue on tools.

Propagation

Marshmallow plant is propagated via seed or division. Since it reseeds itself easily, you can just let it go and end up with a plethora of white flowers. If you want a say in the placement though, collect the mature seed pods and plant the seeds right away. They’ll experience cold stratification over the winter and pop up the following spring. 

Marshmallow grows from a tap root, which you must include when you divide. In late summer or fall, when the herb is dormant, use a spade to slice off a chunk all the way through the roots. Replant the division in its new location and fill in the soil from where you took it.

Harvesting

You’ve been working in the garden since early spring and can now harvest your dessert! You’ll find that marshmallow is as easy to harvest as it was to sow.

Since marshmallow is edible all over, there are several ways to harvest it. Marshmallow is usually grown for the roots, which are used to thicken up the liquified sugar solutions used to make marshmallows. When it starts to die back in early fall, remove parts of the roots with a spade. Unless you harvest the entire marshmallow root, this part will continue growing in the spring. We know you’re eager for marshmallows, but wait until it is a couple of years old before harvesting the roots. After all, those gorgeous flowers deserve an encore next summer!

Marshmallow can also be harvested like an herb, usually for tea. Clip off young leaves and flowers for steeping and cooking. These can be harvested throughout the growing season, though you don’t want to take too much at once.

Storage

After harvesting marshmallow root, wash it off and chop it into small pieces. Immediately dry off each piece. Dry the roots further in a food dehydrator or the oven. Once all moisture is gone, store the pieces in a sealed container or plastic bag someplace cool and dark. Like most herbs, marshmallow root will last for a couple years but loses quality as time goes by. 

Cook your marshmallow pieces like any root vegetable. Alternatively, grind them into powder for making tea or marshmallows. When making traditional marshmallows, the powder is usually used in place of gelatin and mixed with egg whites and sugar. You can also add this powder as a thickening agent to soups or stews.

Common Problems

Althaea officinalis is fairly easy when it comes to pests and diseases. We still need to be prepared though, so here’s a quick overview of the potential dangers to your sweet herb.

Growing Problems

If your marshmallow plant isn’t growing well or seems to have lost its vigor, evaluate its basic needs. Check that it isn’t being over or underwatered. Add organic matter to the soil to increase fertility and water drainage. Ensure that the mallow is in a sunny part of the garden. If none of these seems to be the problem, check your marshmallow for pests and diseases.

Pests

You won’t come across many pests on your marshmallow plant. The one major exception is flea beetles. These pests aren’t actually fleas, but they’re just as pesky! Flea beetles are very tiny and dark in color. Their larvae feed on roots and adults will skeletonize the leaves. 

Flea beetles like to hide under debris, so keep the stems and ground clear. Protect young seedlings by using row covers (remember to remove them for pollination though!).

Diseases

Mallows, like hollyhocks, are vulnerable to rust. This type of rust is a fungus, not what we deal with on our garden tools. It spreads through red-orange spores that eventually turn the leaves black. The first symptoms will show up on the undersides of the leaves, usually as white spots. Over time, the orangish sporing bodies will form.

At the first sign of rust, remove any infected foliage and destroy it away from the garden. Rust thrives with moisture, which is unfortunate for such a water-loving perennial. Try to keep the stems and leaves as dry as possible by watering at the soil level. 

Frequently Asked Questions