How to Use Herbs and Dried Flowers for Soap Making

Botanical soap can be beautiful, but it’s easy to make mistakes when using herbs and dried flowers in soap making. As an experienced botanical soapmaker, I’d like to share the best ones to use and tips for avoiding discoloration, mold, and disappointing results. When used well, plants and extracts create stunning color, beautiful interest, and can even enhance the cleansing experience. Let’s dive in.

As a natural soapmaker, I actively seek out and use ingredients from nature rather than synthetic alternatives. I use essential oils to scent my soap, and clays, herbs, and flowers to add color and decoration. Nature offers incredible options, and I’m always discovering something new! There are plenty of wonderful botanicals we can use, but also some that disappoint.

Botanicals can look beautiful, and some professional soapmakers even say that a sprinkling of dried rose petals on their bars is what pays the bills. Customers like to buy pretty things. That’s a perfectly legitimate reason to use them, but the plants we use in soap making should be skin-safe, have longevity, and not spoil the soap bars at any point. Let me share some tips I’ve learned over 15 years of making natural cold-process soap.

Benefits of Herbs and Dried Flowers in Soap

There are many reasons to use botanicals in soap recipes. The most exciting thing for me is that some plants can naturally color soap—you can get a soft pink from ordinary garden rhubarb, sunny yellow from calendula flower petals, and a long-lasting green from alfalfa leaves. That’s just scratching the surface, really!

When naturally coloring soap, we can stir some herbs directly into the soap batter. To get truly vibrant hues, we tend to use other methods that extract the compound(s) responsible for color into oil or water. There are also plant extracts that don’t color soap but add experiential properties. Soap additives like marshmallow can add creaminess and glide. Aloe vera gel can add gentleness to soap and enhance the lather, and lemon juice can help reduce soap scum.

The Best Botanicals for Soap Recipes

Before we jump into the various botanical soapmaking methods, let’s get down to some of the best herbs for soap making. There are many to choose from, but the chart below gives my top twenty picks and how to use them. Feel free to use it as a starting point for your own recipes. I also recommend looking at this extensive list of natural soap colorants for further inspiration.

Exfoliation and Emotive Marketing

You’ll find that many dried herbs and plant parts can provide texture that’s useful for exfoliation. Poppy seeds, oatmeal, and luffa can all be used to create scrubby hand soaps. Finely ground or chopped dried herbs, like rosemary, can add exfoliation, too. The smaller the pieces, the gentler the exfoliation can be.

Dried flowers and herbs can be gorgeous soap decorations, like the speckles of poppy seeds or calendula petals, throughout bars. You can also use them as dried botanicals sprinkled on as soap toppers. A beautifully made bar of soap decorated with dried calendula or lavender can be irresistible.

Lastly, we add botanicals to soap recipes to create a connection to your garden or farm or to reference other ingredients in the recipe. If you grow your own peppermint and use it to make peppermint essential oil soap, it creates a provenance that you and customers can connect with.

Botanicals Don’t Add Scent

One thing that botanicals don’t tend to add to soap is much scent. If there’s any fragrance at all, it will be quite subtle and usually from dried herbs or flower petals as soap toppers. Over time, any scent will diminish, but it won’t have been very strong to begin with. You could potentially get unwanted scents from botanicals, too. For example, fruit purees might scorch if added to the lye solution.

If you’d like to scent your soap with botanicals like rose, lavender, and mint, use essential oils. They are highly concentrated aromas extracted from flowers, leaves, bark, and other plant parts. I have a guide to how much essential oil to use in soap recipes if you’re looking for guidance. May chang (Litsea cubeba), Lavender (Lavandula angustifolia), and Rose geranium (Pelargonium graveolens) are three excellent scent choices for natural soap.

As for making essential oils, it’s not feasible for most people to make them at home. That’s because you need a distilling apparatus and a lot of herbal material. For example, my local lavender farm yields, on average, 70 ml (2.4 oz) of lavandin essential oil from 12 kg (26.45 lbs) of Lavandula x intermedia ‘Grosso’. Most other herbs and flowers aren’t as generous with yield!

Adding Herbs and Dried Flowers to Soap

There are several methods for using herbs, flowers, and even some fruit and vegetables in soap recipes. Some are easier than others, and how you use them depends on your aim. You could even use several methods to add botanicals to a single soap recipe. I do that regularly when making calendula, peppermint, or chamomile soap.

The aim with each is to use the plant in a way that adds some benefit to the soap. Some herbs will suit some methods and not others. The main methods I use include adding plants or plant exacts as herbal infused oil, herbal tea, dried whole plant parts, fresh plant parts, juice, puree, or powder.

Safely Use Flowers and Herbs for Soap Making

Before you use any of the methods, please be very aware of a few things. The first is to make sure that the plants you use in any skincare are non-toxic. I’ve had people bring beautiful but poisonous pressed flowers to my in-person soapmaking workshops. Many flowers and herbs can also be skin irritants.

Please also avoid using too much of any botanical. The point of “too much” can be subjective, but my stance is to use enough to achieve an effect without making the experience of using the soap unpleasant. Botanicals will almost never make up more than 2% of my soap’s recipe by weight. There are some cases when it may be higher, such as when using puree. Much of that is water, though, anyway.

Too many dried seeds or herbs stirred in can feel scratchy or stop the soap from lathering properly. An overabundance of flower petals embedded on the soap top can get soggy and off-putting once you start using it. That’s especially a problem if you can’t easily pull them off.

Lastly, use botanicals intentionally. Randomly adding whatever’s in the spice cupboard lacks intent, and it can show. Think about your recipe and use plants to accentuate it and make it more exciting in a thoughtful way.

Decorating Soap Tops with Dried Botanicals

If there’s any method to transform a plain bar of soap into something stunning, it’s decorating it with dried botanicals. Dried rose petals, lavender buds, lemon zest, cranberry seeds, and orange slices are among the most popular options, but there are many more to choose from.

For this to work, the plant material must be crispy-dry, and the soap must be stored afterward in a place with 50% or less humidity. To add them, sprinkle the dried herbs or flowers on top of wet soap batter that’s firm enough to hold peaks. If it’s too runny, the botanicals can sink.

If you live in a place with a humid climate, having a dehumidifier running in the room where you store your soap is a big help! Mine is always running in my soapmaking room, since botanicals on soap can mold and rot if the air is too moist.

When I decorate this way, I do so in a sparing way, usually with a very fine line down the middle or one side of a loaf of wet soap. The botanicals should make contact with but not get too stuck inside the soap. After a day or two, I’ll gently turn the soap loaves upside down to cut them into bars. That way, the blade or wire doesn’t drag the plant pieces through the soap and create grooves.

Sticking Botanicals to Cured Soap

Sometimes, you decide you want dried herbs on your bars long after making the soap. In this case, you can often get them to stick by first spraying the soap with isopropyl alcohol or witch hazel. Sprinkle smallish petals and herbs over the area, and make sure they are pressed onto the soap well. Leave the soap to dry, undisturbed, and the botanicals can stick.

This is a less robust way of decorating soap tops, but it does work, especially with small and thin plant material. Pressed flowers are perfect, as are tiny rose petals and calendula petals.

Creating Exfoliation and Herbal Speckles

The easiest way to add botanicals to soap is to stir them into the soap batter. This effect gives you speckles of flower petals, seeds, or other herbal material. Using fine herbal material, like thin or powdered flower petals, gives a visual effect and minimal texture. Larger and harder pieces, such as chopped luffa or seeds, can provide an exfoliating effect.

If you make soap this way, I urge you to be sparing with the amounts. Using too much might give you the look that you’re going for, but the soap can feel too scratchy or impede lather when you use it. I have a simple herbal soap recipe (plus two other recipes) that you can use if you’d like to try this method out.

How Much Herbal Material to Use

When I add herbs, seeds, and flowers to soap batter, I tend to use 1-3 tsp of plant material per pound (454 g) of soap. One teaspoon for dense material, like poppy seeds, and three teaspoons for fluffier herbs, like calendula petals. You can use more or less, but be mindful of how the soap will feel when using it. If it feels or looks gross when wet or causes skin irritation, then you’ll need to rethink the recipe. It never hurts to make a small test batch before committing to a larger one.

Also, if you have a kitchen scale accurate enough to read such small amounts, take a record of the exact weight of ingredients that you used for future reference. This is especially important when creating professional recipes. You can also use it to keep the percentage of the botanicals used to 2% or less of the non-water soap ingredients. If you’re a professional soapmaker in a region, such as the UK or EU, with stricter regulations, you will need to follow your safety assessment’s guidance on how much you can use.

Mixing Botanicals into Soap

You can add botanicals at different points in the soap-making process to have them interspersed throughout your soap. That includes into the lye solution or the oils as they melt. You can also stir them in when the soap mixture reaches trace.

For seeds and botanicals that you don’t want chopped up, stir them in at light to medium trace. If you add them at emulsion, the soap is often so thin that botanicals can sink to the bottom. For others, I usually add them before stick blending. That way, they’ll get chopped into little pieces or blended up at the same time.

In general, it’s best to always work with dried botanicals in soap making. If the material is very thin, like calendula flower petals, or finely chopped, like wet coffee grounds, it can even go in fresh. The finished soap will preserve it long-term, as long as the humidity is below 50%.

Larger pieces, even if originally thoroughly dried, might not fare so well, though. In some cases, it can get soft or rot. Starting with dried plant material and chopping it finely is the best practice.

Powdered Botanicals

There are some herbs and extracts that you can add to soap as a powder. They include madder root powder, indigo, clays, aloe vera, goat milk, and turmeric. Sometimes they add color, and sometimes not.

Powdered ingredients can be tricky to add since they can clump. To avoid this, I tend to add these to the lye solution, as seen in indigo soap. Another method is to mix the powder with a bit of vegetable glycerine or oil before, then add it to the soap batter at emulsion or light trace. Make sure to stir or pulse it in well before pouring. This method is helpful if you want to split a batch to color one or more parts separately.

Botanicals That Won’t Turn Brown

The downside to using whole plant parts or powder in or on soap is that many turn brown. The fragility of some plants and the naturally high pH of soap are to blame, and there’s no real way around it with most herbs. The browning can happen within hours, days, or several weeks, and it can be disappointing if you’re not expecting it.

Herb browning is actually a common issue with all the methods I introduce. Beet puree and hibiscus tea turn soap tan to brown, rose petals will turn rusty brown wherever they touch soap, and almost every herb turns dark brown when mixed in. The only whole dried herbs that I know of that keep their original color in or on soap are calendula and safflower petals. Cornflowers are sometimes said to keep their color, but they, too, can fade and discolor over time.

You can also use herbal browning to your advantage. Very fine pieces of herbs can bleed a little into your soap as it cures, leaving a warm halo effect around each speckle. I use the effect in my Natural Peppermint Soap.

Avoiding Herbal Browning

To prevent herbs from turning brown or making soap brown, consider only using calendula or safflower petals when adding whole herbs. They’re the only ones that you can truly count on. With other herbs and flowers, keep the soap stored in a low-humidity and low-light place, and the color will last longer. Even then, the plant material will turn brown wherever it touches the soap. It can be subtle, though, and the botanicals can stay in good condition for many months.

You could also avoid using whole herbs as decorations altogether. Some plants work beautifully when added as puree, herbal tea, and infused oil, but not as dried herbs added directly. You could also use different soap texture toppings or alternative decorations.

One idea is to make botanical decorations using actual soap. There are small soap molds available that look like flowers, fruit, leaves, and berries. Create small soap decorations and embed them into the tops of future batches of soap.

You can also package soap with botanicals. For example, sprinkle lavender buds or dried flower petals in the soap box or inside the wrapper with the soap. Because they’re not actually attached to the soap, the botanicals will retain their color for longer. You could also tie a ribbon or lace around your soap or soap box with dried botanicals attached.

Infused Oils for Soap Making

If you aim to tint the entire soap a specific color, infused oils are perfect. All they are is one of the carrier oils called for in a soap recipe, such as olive oil, infused with plant material that has oil-soluble properties. Not all do, which is why not much happens when you try to infuse rose petals in oil.

Some of the most common plants we use to make infused oils for soap are calendula, alkanet, annatto, and madder root, but there are many others. For example, St. John’s Wort flower can create a coral color, and dock root infusion a dark magenta.

Infused oils are strained after their infusion time, and the finished oil will be clear (rather than cloudy) but often tinted. It may even be a different color than the one your soap will be once finished. Though alkanet-infused oil is red, the soap it creates is purple. Himalayan rhubarb-infused oil is yellow, but it creates vibrant magenta-colored soap.

You then use this oil to replace some or all of the oil called for in a soap recipe. You match like for like, so if your recipe calls for rice bran oil, you can replace it with infused rice bran oil.

How to Make Infused Oils

You can make infused oils in at least seven different ways using various plants and plant parts. However, it all comes down to steeping the oil with dried plant material in a closed container in a dark but warm place. This allows the pigment or other active constituents from the plant to disperse into the oil.

I typically use about one part plant material to one part oil for light and fluffy herbs like calendula. For denser herbs, like alkanet, I usually use one part plant to three parts oil. The amount of plant material you use doesn’t have to be specific, but there’s no point in using more botanical than is necessary. It often absorbs some of the carrier oil, making it challenging to extract without a press.

You can also create a double infusion. This involves infusing the oil a second time with new herbs to make it stronger. The stronger the infused oil and the more you use in a recipe, the deeper the color of the soap will be. When making a double infusion, you can use the same herb or another one to get some interesting colors.

Using Herbal Infusions in Soap Recipes

For soapmaking purposes, some plants will only extract into oil, and some will only extract into water. For botanicals that don’t extract well into oil, we can sometimes use a water infusion. We make these “herbal teas” by soaking or cooking plant material in distilled water or deionized water. Both are free from the minerals found in tap or spring water that react with lye and cause oxidation (the dreaded orange spot).

The most common way is to brew an ordinary pot of herbal tea. You could use peppermint, lemon balm, chamomile, green tea, or any other herbs of your choice. Strain the tea, and you can use it to replace the water needed to make a lye solution. Be aware that these will often tint your soap light yellow to beige.

Other herbs need different treatment. For example, marshmallow root should be soaked in cold water overnight. It needs time and cold water for the mucilage to be extracted. While you could use the strained liquid in the lye solution, it’s better to stir it in right before pouring the soap batter into molds.

Adding Puree and Juice to Soap Recipes

Another way to add plant material to your soap is by using juice or puree. Some, like carrots, pumpkin, and sweet potatoes, can add color. Coconut milk, banana, and avocado add creaminess, while ingredients like apple juice, which contain sugars, can help boost lather.

Juices and liquids can replace up to 100% of the water called for when making lye solution. It can scorch and discolor from the heat in that process, though. The way to get around it is to freeze the liquid and add the frozen cubes a little at a time to the lye.

This can be tricky for beginners, so the easiest way to add them is to first make a 1:1 lye solution (with water equalling the amount of lye by weight) and then add another part (by weight) as juice to the melted oils. That method replaces just 50% of the water but stops the juice/liquid from discoloring or smelling bad.

With puree, I use around 3 tsp, and it’s best to add it to the oils before adding the lye or to stir it in at emulsion/light trace. I sometimes add it to the lye solution, too. A word of caution: most fruit and vegetable juices or purees will turn your soap brown or fade to an unexciting tan or yellow. For example, beetroot and blackberry juice will sadly turn brown in soap.

Recommended Suppliers of Herbs for Soapmaking

You can grow many of the flowers, plants, and herbs mentioned in this piece for soap making. I grow, or have grown, most of them, and if you would like to as well, I give tips in my book, A Woman’s Garden. When you grow your own, you can ensure that the herbs you use are fresh (not years old), properly dried, and that you have more control over varieties and species.

If you’re not a gardener or want to get started quickly, I have a list of soap ingredient suppliers by country if you’d like to get shopping. However, the best places to buy herbs for soapmaking are local growers and trusted herbalist supply shops. Some of the best include:

• Starwest Botanicals or Mountain Rose Herbs (USA)
• Baldwins and Woodland Herbs (UK)
• Richters Herbs or Alpine Herb Company (Canada)
• Austral Herbs (AUS)

I hope that this entire piece has given you some ideas and inspiration for your own natural soap creations! If you have any questions or comments, please leave them below. I’d also love to hear which botanicals you prefer to use to make soap.