Peonies are among the most beautiful flowers that symbolize many good things like love, nobility, honor, and romance. Their beautiful blooms and impressive symbolisms make them attractive plants to gardeners. However, it can be challenging to grow them from seeds due to inhibitors to their germination, making some gardeners wonder whether stratification is necessary.
Peony seeds do not need stratification as they can grow naturally under suitable conditions. However, they can benefit from stratification, especially when you are planning to start them in the fall. The process will make the seeds ready for planting by spring.
Further, we will discuss why some peony seeds require stratification and the benefits of such a method. I will also discuss how to go about the process. Read on!
Is Stratification Necessary to Break Seed Dormancy in Peonies?
It is not necessary to stratify peony seeds since nature can help them grow. When left alone in the ground by the end of summer, the cold conditions in the fall and winter will prepare the seeds for germination as the temperatures drop in spring.
Out in the open, the soil typically contains chemicals and microorganisms that can facilitate the weakening of the outer shell or seed coat of the peony seeds. As a result, the inner components will receive oxygen and moisture and undergo temperature-sensitive reactions that would help them sprout.
The process takes time and patience. With the right conditions, the seeds will naturally be ready for germination by spring.
However, not all peony seeds sown by the end of the summer may germinate by spring. Incorrect timing of seed harvest can negatively affect the seeds’ ability to germinate. To make it even more complex, various types of peonies have different harvest timing preferences.
Phytohormonal Mechanisms in Seed Dormancy
Peony seeds generally have phytohormonal mechanisms that help them regulate their dormancy. These mechanisms help ensure the protection and proliferation of the species.
Seeds usually have various chemicals involved in the said mechanisms. The most common ones are abscisic acid (ABA), which typically promotes dormancy, and gibberellic acid (GA), which helps the seed break out of it.
Environmental factors like temperature and light regulate the balance between the phytohormones ABA and GA. The reactions occur on a genetic or molecular level, affecting individual seeds differently.
That said, some seeds that mature in the summer and are sown late may germinate by spring, while others don’t even when exposed to the same conditions.
Luckily, many peony collectors and breeders have learned from experience the most suitable conditions that would help specific types of peony seeds germinate. If you get your seeds from experienced breeders in your area, you can ask them for tips on how to grow peonies.
Manual Intervention To Break Seed Dormancy
Alternatively, you can let the peony seeds undergo stratification to ensure they will germinate. The process involves exposing the mature seeds to a controlled environment of low temperature to unlock their dormancy.
Peony seeds are unique in their double-dormancy, making it extra challenging to make them sprout. Double-dormancy refers to external and internal dormancy. Thus you need to scarify and physically weaken the seed before stratification.
To stratify the seeds, gardeners often put the peony seeds in the refrigerator and adjust other factors like the humidity and the degree and length of exposure to light. It may be troublesome, but it provides some benefits.
Stratification Benefits: Predictable Germination and Vibrant Blooms
Peonies are perennials that don’t require much care once established. However, before enjoying their beauty, you must ensure that the seeds will germinate.
Below are some benefits of stratifying peony seeds:
The Seeds Can Germinate When You Need Them
Natural environmental conditions can encourage or prohibit the seeds from germinating. Peony seeds need a period of warmth followed by a long period of cold to break their dormancy. However, the early onset of warmth late in the winter can prevent the seeds from germinating.
Since temperatures can be unpredictable and the length of seasons can change annually, human intervention may be necessary to encourage peony seeds to germinate. When done right, you can get the seeds to germinate when you need them.
Failure to have them germinate naturally by spring will require you to wait another whole year to try again. Meanwhile, stratification can expose the seeds to controlled and suitable conditions that can help them break dormancy.
Not all seeds may germinate because of individual molecular or genetic factors. Still, you can improve your chances of getting peony seedlings rather than waiting for natural conditions to be comfortable enough for them.
The Peonies Produce Beautiful Blooms
Another benefit to stratifying peony seeds is the beautiful blooms they produce. They typically take 2-3 years to create aesthetically pleasing flowers. But once they start to, they will continue to do so for several years.
To ensure that you can enjoy these blooms sooner, you will need to have them germinate sooner. As discussed, you will have to wait another whole year to expose your seeds to a second fall, winter, and spring if they don’t germinate the first time.
If the seeds fail to germinate in the second spring, they will likely never germinate. Peony seeds stay viable for up to three years but may die much sooner.
Stratification helps reduce the amount of wait time significantly and increases the chances of the seeds germinating. And you’ll have beautiful flowers in your garden before you know it.
Steps to Stratify Peony Seeds for Successful Germination and Planting
Various types of peony seeds have different stratification needs. Even similar types may require additional steps. Because of this, trial and error is your best bet until you find which works best for your seeds.
However, there are some steps that you can apply to all peony seeds. Whether they germinate depends on various factors that may or may not be within your control. Nonetheless, it helps to know the basics.
You can also prepare various setups using the alternatives presented below for better chances of getting some, if not all, seeds to germinate. Below are the steps to stratify peony seeds:
- Harvest the seeds when the pods turn yellow or brown. Peony seed pods form in the summer and typically turn yellow or brown as they mature. They would then crack open and reveal tan or bluish-black seeds. You can harvest these seeds for propagation.
- Place the seeds in a paper bag and leave them on the counter for one to two weeks. Ideally, the room temperature should be around 75 – 80 °F (24 – 26 °C) to replicate the warm temperature outdoors and provide the period of warmth needed by the seeds. You can put the seeds in separate bags with different durations of exposure to warmth. Label the bags accordingly.
- Soak the black seeds in acid. Black peony seeds are generally harder to germinate since they tend to be overmatured. However, in some cases, they grow just as well as tan seeds. If you want to be sure they will sprout, you can soak them in a glass of diluted sulfuric acid (10%) for 10-12 hours. You can also use vinegar to be safer.
- Alternatively, scratch the seeds with sandpaper. If you feel uncomfortable using acids or don’t have much time, you can break external dormancy using sandpaper. Avoid scratching them so much that it exposes the inner white layer. You can also use a metal file the same way, but it helps to be extra gentle. When using various methods, note them during packing and storage.
- Wash the seeds and place them inside an airtight container. Whether you use an acid solution or manual scarification, you’ll have to wash the seeds with tepid distilled water. Afterward, place the seeds in an airtight container, such as a ziplock bag. Be sure to label the containers accordingly.
- Put moist loamy sand into the container. You can also use a combination of perlite or vermiculite and peat moss. Avoid putting in too much water as it can cause the seeds to rot. You can check for signs of sprouting weekly and spray sufficient moisture to prevent the substrate from drying up.
- Refrigerate the setup at 35 – 40 °F (2 – 4 °C). Leave the setup inside the refrigerator for at least three months while occasionally checking the soil moisture and sprouting progress. If you are using a home refrigerator with your foodstuff, make sure that the setups occupy a separate and preferably enclosed space, like the fruit drawer, so as not to be disturbed by frequent opening and closing.
- Sort your setups to receive an artificial light source. Some peony seeds successfully germinate after staying in darkness, while others may need 12 hours of light per day. You can separate your setups in the refrigerator by covering some with a dark cloth and using artificial light on the others.
- Plant the seeds in pots at 50 – 60 °F (10 – 15 °C). If your seeds have successfully broken dormancy and developed enough roots while outdoor temperatures are still low, you can plant them in indoor pots and keep them within optimal temperatures. Wait for them to germinate with leaves and move them outdoors when temperatures become stable.
Peony seeds do not need stratification, but manual intervention may help guarantee that you’ll have successful seedlings in spring.
Although you may not get your desired results the first time, try stratifying your peony seeds, learn from the experience and make necessary adjustments next time. Also, feel free to ask for advice from experienced breeders in your area.
Peonies are perennials that take a long time to establish and produce beautiful blooms. But once they do, you will find that all the efforts put into forcing the seeds to germinate are well worth it.