Growing Clematis From Seed: A Comprehensive Guide

Online information about growing clematis from seed is limited. Hence, I conducted my own investigation into clematis seed germination. Through 120 test cases involving various types of clematis, I gathered both existing and new information on the subject. In this article, I will summarize the known information and present the novel insights discovered during my research.

Current Information on Growing Clematis From Seed

When it comes to germination information for all types of seeds, my go-to sources are Dr. Deno’s Seed Starting Books (Deno) and the Ontario Rock Garden And Hardy Plant Society website’s Germination Guide (ORGS). These two sources offer some general guidelines for clematis, but the details are limited and sometimes contradictory.

Different clematis species require different germination methods. Some may need cold stratification, while others may not. There are cases where warm, cold, and warm cycles are necessary. The available sources provide per species or cultivar information, but they do not discuss newer germination methods suitable for homeowners, except for Deno’s books.

Another resource, “Clematis From Seed” by Brian R. Collingwood, offers information on potting up the seed and placing it in a greenhouse. However, the details are scarce. The International Clematis Society (ICS) suggests that clematis seeds can take up to three years to germinate, but some germination should occur within six months to a year.

Although there is conflicting information regarding the need for stratification, I have successfully germinated clematis without it in the past. The British Clematis Society (BCS) recommends a similar method to the ICS but does not specify whether stratification is required.

Clematis Germination Procedures

To conduct my study, I obtained seed from the Ontario Rock Garden And Hardy Plant Society. However, it is important to note that the seed may not be viable, and the names may not be accurate. I reviewed the literature for each type of seed to determine the most effective germination procedure and defined specific conditions accordingly.

The standard reference method is the baggy method at room temperature, which I compared to other germination methods. Each method was given a shorthand code to easily identify it. I monitored the seeds weekly, removing any germinated ones and maintaining proper moisture levels. The seed coat was sometimes removed after soaking.

Germination Methods

One of the main goals of this study was to compare common germination methods. The “potted” method, commonly used and described in most references, involves placing seeds in a pot of soil, covering them with grit, and waiting for germination. While effective, this method requires multiple pots and can be impractical for those germinating various types of seeds.

My preferred method, the baggy method, involves placing seeds inside a Ziplock plastic bag with a moistened paper towel. This method allows for efficient storage and germination of multiple seed types in a small space, such as a refrigerator.

Another method, known as the “water” method, involves fully submerging seeds in water until germination. Preliminary testing indicates that this method can be successful, even with old clematis seeds.

The “nude” method involves removing the outer coat of the seed before germination. This method has shown positive results in some cases, potentially speeding up the germination process.

Baggy Method vs Water Method

In most cases, the baggy method worked as well as or better than the water method. One exception was C. virginiana, which had better germination using the water method, possibly due to the longer exposure to GA3 hormone.

Results – Does Removing the Seed Coat Work?

Removing the seed coat did not improve germination in the water method. Seeds tended to get coated with slime and decompose when exposed to water and left naked. Limited testing of the nude method in baggies yielded inconclusive results.

Clematis Germination – Cold Stratification

The need for stratification is not clear-cut. While Deno and ORGS recommend it for certain species, the ICS, BCS, and CFS have differing opinions. Based on my experience, stratification is not required for all species, but it may speed up the germination process.

Results – Cold Stratification

In general, cold stratification does not seem to be a requirement for clematis seed germination. However, there are cases where it is either required or beneficial. For instance, C. orientalis showed poor germination without a cold treatment, contradicting Deno and ORGS reports that it germinates well in warm conditions.

Clematis Germination – Tails

Most references do not mention the need to remove the tails on clematis seeds. However, ORGS suggests removing them to prevent potential interference with germination. Limited testing suggests that leaving tails intact does not significantly affect germination rates.

Clematis Germination – GA3

GA3, a plant hormone, has been used to speed up germination in various plant species. However, there is limited testing on its effects on clematis. Some species, such as C. pitcheri and C. virginiana, have shown a positive response to GA3 treatment. Further testing is warranted to determine the broader impact of GA3 on clematis seed germination.

Clematis Germination – Darkness

There is no consensus on whether darkness is a requirement for clematis seed germination. While Deno and ORGS suggest darkness for certain species, other references do not mention it. Limited testing in the dark with C. viorna and C. viticella showed some improvement in germination rates, but further investigation is needed.

Clematis Germination Results – General

Generally, clematis seed germination is slow, taking several months or even years. The baggy method yields similar or better results than the water method, making it the preferred choice. The baggy method may also result in quicker germination in northern regions, as it eliminates the need for seeds to endure outdoor cold conditions.

Based on my research and existing references, I recommend using the baggy method in the dark, with tails removed, and GA3 treatment if available. However, more experimentation is needed to refine these recommendations and explore species-specific germination procedures.

Conclusions – Species Specific

Based on my study, I have specific recommendations for certain clematis species. For instance, fusca and ispahanica are easy to germinate in warm conditions. On the other hand, C. virginiana requires GA3 treatment and warmth. These recommendations may deviate from Deno and ORGS in some cases.

In conclusion, there is a lack of comprehensive information on growing clematis from seed. My research provides valuable insights and recommendations based on extensive testing. By following the suggested procedures and taking into account species-specific considerations, gardeners can improve their success rates in germinating clematis from seed.