Making Medicine, Part 2 of 5: Preparing Blue Vervain to Make a Tincture

This is the second in a series of five posts in which I am using the process of wild harvesting and making a fresh herb tincture of blue vervain (Verbena hastata) as an example to explain in detail the process of making medicine. Part 1 in this series was posted on July 9th.

In my practice I primarily use tinctures made from fresh herbs, so the next step is to use the blue vervain that we harvested to make a tincture. When you make as much tinctures as I do, you appreciate good equipment. I have experimented with a variety of tools over the years and will discuss some of them here. I am also going to use the process of preparing blue vervain tincture as an example to explain some of the important details regarding making tinctures.

The basic idea is that we want to separate the more potent from the less potent parts of the portion of the plant that we harvested, chop it up and put it in a bottle with the appropriate menstruum (pronounced MEN-strew-um: the liquid that we use to absorb and preserve the constituents of the herb). As an herbalist, it is important to me that the way I prepare a tincture is consistent so that I know that the tincture of any particular herb that I make from year to year is very similar in potency. There are factors that affect the potency of the herb, like weather conditions, that I can't control. However, if the weather conditions are particularly incompatible with the requirements of a particular herb in a particular year, I won't harvest that herb. What I can control is how I prepare the tincture. In order to accomplish this, the portion of the plant that I use needs to be consistent as must the amount of herb that I use for any given volume of menstruum.

When using fresh herbs, I recommend a 1:5 potency. This means that 1 g of herb is used for every 5 ml of menstruum. There are herbalists who recommend a higher potency for various reasons. However, I disagree with using a higher potency than 1:5 for fresh herb tinctures. I will do a detailed post explaining why I prepare tinctures the way I do at some point in the future, but the bottom line is that 1:5 fresh herb tinctures work and a higher potency isn't necessary. Also, the greater the potency that we use above 1:5, the greater the amount of herb we end up using in order to get the same results. For reasons related to the chemical characteristics of the constituents of an herb, using twice as much herb doesn't make a tincture that is twice as strong therapeutically. For example, a 1:2.5 potency tincture should be twice as strong as a 1:5 tincture because we are adding the same amount of herb to half as much menstruum (2.5 ml instead of 5 ml). If this were true, then when we use a 1:2.5 tincture we should get the same results using a dosage that is half as much as the dosage we use for a 1:5 tincture. However, it doesn't work out that way. We need to use more than half as much of a 1:2.5 tincture to get the same results. This is because as we add more herb to the same volume of menstruum, at some point the percentage of constituents that actually dissolves in the menstruum starts to drop off. In addition, for most herbs it is physically impossible to get enough herb into a given volume of menstruum above a 1:5 or 1:4 potency. This necessitates methodologies such as grinding the herbs, percolation or macerating tinctures more than once, which are more time and energy intensive, often require the use of expensive equipment, and lead to a greater level of degradation of the constituents of the herb. Therefore higher potencies are unnecessary and wasteful. For home use, you don't need to be as accurate with your measurements as I am recommending here, but the more accurate the better.

The equipment I use for preparing fresh blue vervain tincture.

In preparing a tincture we need to be able to measure the amount of herb that we put into each bottle. For this I use a triple beam balance, but digital scales will do as long as they are calibrated to 1 g increments or smaller. We also need to know how much herb to use per bottle. Traditionally the way we calculate this is to first measure how much fluid the bottles we are using contain when they are filled to 0.5 cm (1/4 inch) from the top. It is necessary to measure this because the volume indicated for the bottle is usually not based on filling it this close to the top. Beakers and measuring cups are not accurate enough for this. It is necessary to use something that is calibrated in 1 ml increments. This usually necessitates the use of a graduated cylinder.

Once we have an accurate read on how much fluid our bottles contain, to approximate how much herb we will need for a 1:5 tincture we divide the total by 6, that is for 1 part herb plus 5 parts menstruum. This is not 100% accurate because herbs are usually less dense than water and not all herbs are of equal density. However, although this is an approximation, it is surprisingly accurate. It is sufficient for most situations. The key is to get as accurate a measurement as possible of the volume of the bottles we are using. I have done extremely detailed calculations for all of the tinctures that I make and, with only a couple of exceptions, this approximation is accurate to within 1-2%, which is good enough.

The harvested portion of one plant.

Once we know how much herb we need per bottle, it is necessary to separate the usable from non-usable parts of the portion of the herb that we harvested. When harvesting the aerial parts of plants (the parts that grow above the ground), this usually means that a portion of the stalk isn't used. This is because the primary purpose of the stalk is to hold up the leaves and flowers. As a result, the stalk tends to contain mostly dense fibrous tissue and a much lower proportion of the therapeutically active constituents. The amount of stalk that has to be removed can be anywhere from 0-100%, depending on the plant and the portion of the plant that is harvested. For most plants from which we harvest the aerial parts we harvest the terminal 25-40%  of the plant and remove 80-90% of the primary stalk and 60-75% of any well-developed secondary stalks. The specifics depend on the species of plant and at what stage we are harvesting it. The portion of the stalk that is usable tends to be the new growth that is less stiff and more succulent. To determine the usable portion for a particular species, we start at the lowest part of the stalk, cut off a small section and taste it. Then cut a similar sized section about 20% further up the stalk, then at 40%, 60%, 80%, and finally the top portion. Finally, we taste a piece of a leaf. The point on the stalk where the flavour of the stalk is about 2/3 to 3/4 as strong as the flavour of the leaf is the point at which the potency of the stalk is strong enough to use. We remove all of the stalk below that point and use all of the stalk above that point. The reason that the taste of the stalk can be used to determine its potency is because its flavour corresponds to the concentration of many of its active chemical constituents. For plants that are relatively bland in flavour because they have little to no aromatic, bitter or pungent constituents, there isn't much difference in the flavour of the different aerial parts of the plant. Therefore we just use the portion of stalk that is less stiff and more succulent.

Blue vervain is unusual in that the flavour of the entire stalk is pretty strong. This is because its flavour is primarily due to chemical constituents called iridoids and the iridoids are in a fairly high concentration in all of the aerial parts of the plant. Nevertheless, for the most part I still only use the less stiff and more succulent parts of the stalk. Overall I remove a little bit less stalk than is typical for most herbs. However, with this herb, if the amount that I harvested is a bit short, I can just use a bit more stalk rather than having to harvest more plants.

The part that is used (above) and the amount of stalk that is not used (below).
This is the same plant that was shown in the previous picture

The next step is removing the unused stalk from all of the plants that we harvested. This can be done with a knife or scissors, but since we tend to cut the stalk at the point where it becomes softer and less fibrous, for most herbs the stalks can be easily torn with our fingers, which takes less time. Once we've separated all of the usable portions of the plants that we harvested, we need to weigh them to make sure that we put the right amount in each bottle. I use four standard sizes of bottles. The blue vervain that I harvested was intended to prepare the largest size, which is a 950 ml bottle. However, the volume of bottles that are narrower at the top than the full width of the bottle are usually calculated to about the top of the shoulder. When the bottles I use are filled to 0.5 cm from the top, they actually hold 990 ml. To determine how much of the usable portion of the herb that we need to use for a bottle this size, we divide 990 by 6 (for a 1:5 tincture), which is 165 g. Although our proportions are made up of 1 part herb, which is measured in grams, and 5 parts menstruum, which is measured in millilitres, this conversion works because the density of menstruum is almost the same as for water. The density of water is 1 g/ml, so 5 ml of water is the same as 5 g of water.

The amount of herb material that is used to prepare one bottle
(990 ml) of tincture with the removed stalks below.

When I am harvesting any herb, it is important for me to determine in advance how much that I am going to need. That means the number and size of the bottles of tincture that I need to prepare, how much of the usable portion of the herb I need per bottle, and approximately how much extra that I need to harvest to account for the unused portion of the plant. I don't want to be short or I might have to go out again to harvest the same herb. In some cases, due to the number of herbs that I need to harvest, weather conditions, etc., harvesting an herb a second time might not be possible. So I might run short before I am able to prepare it again the following year. The flip side is that I don't want to over-harvest because it is wasteful and disrespectful to the medicine. When I'm out harvesting I bring a small spring scale that is accurate to within 10 g, so I can make sure I harvest the right amount. I will always harvest just a bit more than I need so that I don't accidentally run short. Any small amounts of extra herb I dry and use for teas.

After I processed 165 g of the usable portion of the blue vervain to make my bottle of tincture, the amount of stalk that I had removed was 51 g. That means that I had to harvest an extra 31% of the herb to get the amount that I needed. If I had harvested the blue vervain a bit later, the proportion of unused stalk would have increased because as the plants mature the stalk gets stiffer and the amount of stalk between the nodes (the points where the leaves join the stem) gets longer.

Once we have measured the appropriate amount of the usable parts of an herb, we need to chop it up. For this we need a fairly large hardwood cutting board and some kind of knife. Over the years I have experimented with just about every kind of knife for chopping the many herbs that I use. Some herbs are best chopped using a cleaver, a few require a serrated knife, but for most herbs the best knife by far is the mezzaluna. This is a curved knife with a handle at each end (see the first photograph in this post). When used correctly, it can finely chop herbs much more quickly than other knives. This is important because the process of chopping our herbs requires finding a balance between two opposing requirements. On the one hand, the more finely we chop the herb, the greater the surface area that we create that allows its constituents to dissolve in our menstruum. On the other hand, the more finely chopped our herb and the longer it takes to do it, the more it is exposed to air which results in greater oxidation of its chemical constituents. Most constituents are less potent when oxidized and in some cases it may even change their properties. It is true that a few constituents are more potent when oxidized, but this is not the case for the vast majority of them. In addition, they will have plenty of opportunity to oxidize after we press the herb, the final stage in making a tincture. For the best results, we want to minimize the amount of oxidation that takes place before and while the herbs are macerating. Maceration is the process of soaking the herbs in our menstruum. With the mezzaluna, I can chop an herb a little bit finer than I would with other kinds of knives in about half the time. It doesn't get any better than that! I really love those special tools that significantly increase the efficiency of the work that I do. The mezzaluna is one of those special tools. In choosing a mezzaluna, it is important that it be a larger one, 25-30 cm (10-12 inches) wide. Do not skimp on quality. Purchase one that is professional quality. The best ones are made in Italy or Portugal using high quality molybdenum vanadium steel. The ones made in China are not good. Also, only use the ones that have a single blade. One of my students once bought one with a double blade. She though this would make it easier. All it did was slow things down because the herbs kept getting caught between the blades. I don't believe they even make double bladed models in Europe.

Using a mezzaluna takes a bit of practice. Basically we hold the handles and rotate the blade back and forth over the herbs. Each time we do that we twist the blade to change the angle very slightly, first one way and then the opposite way on the next stroke. This allows it to move forward across the cutting board. What works best is to cut moving forward down the board, then begin at one of the front corners and cut diagonally in one direction, then cut diagonally in the other direction from the other front corner. Keep rotating between cutting in these three directions until the herb is chopped the right amount. It is very important that the cutting board is oriented so that the grain of the wood is running down the board away from us. Never use a mezzaluna to cut parallel to the grain of the board. This is because when we slightly twist the blade at the end of each stroke, if we are cutting with the blade parallel to the grain, it digs between the layers of wood. Over time it will start cutting out thin slivers of wood which will significantly reduce the life of the cutting board.

This is the what the herb should look like when it is sufficiently chopped.

This is the end of Part 2 of this series. In Part 3 I'll discuss making a blue vervain maceration.