I recently took a plant propagation class at the Berkshires Botanical Garden in Stockbridge, Massachusetts. Although I am a member of a private plant propagation group, have been propagating plants for a few years now, own a company I started that designs, assembles and sells misting systems and misting components for homeowners and startup nurseries, I decided I needed to take a break from everything and attend this small class that was being taught by Adam Wheeler of Broken Arrow Nursery. Adam is the principle plant propagator and development manager at Broken Arrow Nursery and was kind enough to teach this class on how to propagate woody landscape plants using cuttings.
The day started quite early. I had to leave the house by 5AM to be sure I could make the 10 o’clock class. Yes, I said 5 AM; the Berkshires Botanical Garden is a 4 hour drive from my house! I arrived about ½ hour early and strolled around the grounds until the class started.
Adam started the class by introducing himself and explained what he does at Broken Arrow Nursery. He explained that it is his responsibility to take softwood, semi-hardwood and hardwood cuttings at the nursery and make plants out of them. He then explained what propagation is; it is the art and science of making new plants.
He then explained the differences between the three major types of cuttings, softwood, greenwood (or semi-hardwood), and hardwood.
- Will snap if bent
- Is prone to disease and water stress
- Is soft succulent growth
- Is collected during active growth
Greenwood (or semi-hardwood)
- Will bend if bent
- Is firm growth
- Is collected after active growth
- Will break like a stick
- Is the mature stems
- Is collected late in the season or in the winter
After explaining the difference, he then mentioned that most conifers are done as hardwood cuttings.
Adam then went over some tips while collecting cuttings for propagation
- To help retain moisture, collect cuttings in the morning or evening.
- Never take cuttings from a stock plant that is water stressed.
- Label the cuttings immediately. Do not rely on your memory.
- Process the cuttings quickly. Sticking the cuttings soon after collection reduces stress and increases the odds that it will root.
He then went on to tell us a few factors that will influence the cuttings
- Rooting media
- Stock plant
Adam then went into more detail on these factors.
The ideal temperature of the root zone for greenwood (semi-hardwood) cuttings is 65 to 85 degrees F but lower for hardwood cuttings. He also went on to explain that when rooting cuttings with softer wood, “cooler temperatures promote rot”.
Adam then explained that some nurseries use bottom heat to maintain the correct temperatures at the root zone. They do this by burying soil warming cables or using piping that circulates warm water under the soil.
Rooting media can be sand, peat, perlite, vermiculite, or pine bark. He went on to explain that a combination of two or more of these materials is usually best. A mix of 50/50 peat/perlite mix is quite popular as is 50/50 perlite/vermiculite. However, he also stated that some plants prefer different proportions and experimenting is the best way to determine this.
Adam then talked about how to properly mix the media for a 50/50 mix. This is done by filling a container with one of the materials and transferring it to a larger container, then filling the first container with the other material and dumping it into the larger container. Both materials would then be thoroughly mixed together. This is called measuring by volume.
Adam also mentioned that a good rooting media will retain just enough moisture to allow the cuttings to root but also allow enough water to pass through to not keep the media too wet. He then explained that out of the 5 media mentioned, that peat, vermiculite and pine bark are for water holding and the others are used to aid in draining.
He then talked a bit about the rooting media he uses at Broken Arrow Nursery. He revealed that he primarily uses a 50/50 mix of perlite and commercial potting mix. He stressed that propagators should “stay away from retail potting mix for rooting cuttings because most will retain too much moisture”
Adam went on to explain that keeping the cutting humid is essential to getting cuttings to root. He mentioned cold frames, hot frames, and mentioned that larger propagation nurseries use intermittent mist. He then revealed that he uses “5 seconds of mist every minute” while rooting cuttings. What he didn’t say was if these cuttings are in a greenhouse or some other type of structure.
Adam explained that hormones contain various levels of auxin. He also stated that using rooting hormones do not guarantee success. He then went on to talk about willows having natural auxins and that you can cut up willow stems, steep them in water, and use the water as a rooting hormone dip.
He then revealed that he “uses DipNGrow at a 1 to 10 ratio for semi-hardwood cuttings”.
Adam then explained that too much or a dilution that is too strong is not good because the stems will burn. He stated that there is a threshold for each plant that only experience will reveal.
- Proper timing is essential to successful rooting
- Extensive notes help track the best time to take cuttings of different varieties of plants
- Take note of what other plants are doing at the time you take your cuttings. This may aid you in determining the best time of year to take cuttings of certain plants
- Wounding eliminates physical barriers that affect root development.
- Creates a greater surface area for hormone uptake
- Induces internal hormone changes
Adam explained that “roots form from the cambium layer and in some instances, wounding will increase rooting percentages”. He also revealed that he wounds only about 10% of all his cuttings.
- Juvenility refers to the growth stage of the plant
- Plants can have multiple stages of growth on a single plant
Adam explained that “juvenile cuttings root easier and quicker”. He also stated that “juvenile growth will be toward the base and interior of the plant”. Another way of determining the juvenility of the growth is “the leaves will hang on longer in the fall on juvenile growth”.
Adam stressed the importance of the health of the stock plant. He said to never take a cutting from a water stressed plant or one that has a disease. Taking a cutting will only stress the stock plant even more and in the case of disease, is very likely to spread it.
Preparation of cuttings
Adam then went on to explain how to properly prepare a cutting. He again mentioned that a cutting should be taken during the morning or evening so the cutting has the largest amount of water retained in it. He also had these tips to share:
- The proper length of the cutting is between 4 and 6 inches. Depending on the plant, this may sometimes be 8 inches.
- Always cut just below a node because roots will form from the node itself because there is a natural occurrence of auxins at the node.
- Always remove the tips of the cuttings. The tips are prone to wilting and stress.
- Reduce the foliage on the cutting to help reduce water loss.
At this point in the class Adam took us on a little jaunt and pointed out some plants that would be likely to root. He explained that it was actually the wrong time of the day to be collecting cuttings but we would have to soldier on anyway.
The class followed Adam among the various shrubs where he talked a bit about each plant and we were allowed to take a cutting if we desired. Because I already have stock plants to get cuttings from, I took only a few from two plants; a Diablo Ninebark and an unnamed Deutzia that has bluish flowers and is known only to the Berkshire Botanical Garden. He went on to say that he has been trying to talk the Botanical Garden to propagate and release this particular plant but has had no luck thus far. Of course I had to grab a few cuttings from that plant!
After the collection of the cuttings was done we all headed back to the conference room where we prepared them for sticking, but first we had to mix up a small batch of 50/50 peat/perlite. We mixed it 50/50 by volume. We did this by filling a small container with peat, dumping it on a mixing table, then filling the container with perlite. This container was also dumped onto the mixing table and then both were thoroughly mixed together. We then filled a few smaller container that we would be placing our cuttings into.
Next, we prepared our cuttings by cutting the stem just below a leaf node. Adam explained that the nodes are where the roots will be forming from and that cutting just below the node is a key step in the cuttings ability to root. Next, we cut the tip off the cutting just above a pair of leaves. We then stripped off all the leaves but the very top two. On the cuttings that have large leaves, like Hydrangea, Adam suggests cutting the remaining leaves in half to reduce the loss of water through them, a process called transpiration.
We then applied some rooting hormone to the ends and stuck the cuttings into our containers with the rooting media. Next, we moistened the media, stuck a small piece of bamboo into the pot to hold up the plastic bag, and placed the clear bag over the container, holding it with a rubber band.
Adam explained that when we noticed the droplets of water that will collect on the inside of the bag begin to disappear, that was an indication that we needed to add some water to our container to keep the humidity up.
The class ended with Adam giving the class his email address in case we had any questions.
Even though I use a misting system to root my cuttings instead of the little plastic tents, this class was a nice break from the daily grind and I did learn a thing or two. Namely, Adam’s secret for determining the best time to take cuttings of Purple Smokebush. Although I live many miles north of Connecticut and his secret may not actually work in my zone, I gained valuable knowledge about paying attention to what surrounding plants are doing when you take your cuttings.
Be sure to look for a post that will show the steps needed to root your own cuttings using the method Adam described.