If you’re enjoying the mild fall, you are not alone. Some native plants have evolved to take advantage of the remaining warmth and sun during this normally wetter end to the growing season. There are several annual wildflowers that germinate in the fall and establish leaves before hunkering down for the cold winter. When the spring weather ushers in warmth and longer days, they have a head start in the rush to complete their life cycle before summer droughts hit. The plants that adopt this strategy typically grow in very dry places where the summer drought comes early, and the short spring growing season is a limiting factor for success. Below we’ve described a few strategies plants use to time their seed germination and highlighted some local wildflowers that germinate in the late summer or early fall. Understanding the life cycles of local plants helps us protect their habitat and gives us the knowledge we need to grow them in our own gardens.
Timing is Critical
When seeds first germinate, they are particularly susceptible to excessive drought, cold, and heat. Though each plant species has different tolerances and specific conditions they thrive in, they have in common the need for seeds to germinate at the right time. So how do seeds know when to wake up?
Picture your tomato seeds stored during the winter; it would be no good if they germinated inside their envelopes in the middle of winter. The most basic condition any seed needs to initiate germination is water. Seeds from plants adapted to germinate in the fall typically do so as soon as they get wet. For many seeds, they need the proper combination of both water and light. The need for light is an adaptation to prevent seeds from germinating too deeply in the soil. Other seeds need additional conditions met before they will germinate, often to delay germination until the spring.
There are several mechanisms by which seeds delay their germination, one of which is physical dormancy. Seeds that exhibit physical dormancy typically have a water impermeable coating that needs to be scratched or worn down before water can penetrate the seed and initiate germination. You may have heard the term seed scarification, which refers to intentionally scratching the outer coat of seeds to allow water past that impermeable layer and initiate germination. Seeds with this coating can remain dormant in the soil for years. This can result in just some of the seeds germinating in any given year while others lay dormant for longer, and this is a good strategy for avoiding threats that may impact all seedlings in any given year such as inclement weather. Extended dormancy also allows more time for seeds to disperse, making their way into new growing sites further afield.
Other seeds have an internal chemical which inhibits germination. This acts as a biological alarm clock, with the chemical slowly breaking down over the winter. Most of our native seeds have this type of germination and require months of cold, moist conditions. This period is often referred to as the seed stratification period. When the chemical inhibiting germination is gone, the plants will start to grow. If everything has gone to plan, the seeds will germinate when spring conditions are favourable. However, not all our local seeds wake up in spring.
Since it’s fall, let’s look at four examples of local wildflowers whose seeds germinate as soon as they get wet. These species are all adapted to survive in environments that experience severe drought conditions. Note that at the time I write this (September 26th 2022), we are experiencing an unusually hot, dry September and the conditions that are often present for fall germinating seeds have not yet arrived. That means there will be a shorter fall growing season for these plants, especially if the temperatures turn cool in late October as they sometimes do. As you can imagine, when weather patterns depart from normal, it can cause problems for plants and animals adapted to those weather patterns.
Seablush (Plectritis congesta)
This is one of my favorite local plant species, and I’ve been slowly increasing its spread around my property. It’s an annual wildflower that begins its germination as early as mid-August when we typically get our first heavy dews of the season. It grows from September until cold weather slows it down in November or December. It can provide a nice green cover crop during the winter. When warmer weather returns in March and April it continues growing again, producing beautiful pink flowers in April and May, with seeds maturing by late June. The seeds can be collected each year in late June or early July and sown in late August or early September. If you’re familiar with the native plant demonstration garden in front of the Root Seller (478 Village Bay Rd), you will recognize this wildflower. Look for the fresh green leaves later this fall or wait for the display of pink flowers next spring.
Miner’s lettuce (Claytonia perfoliata)
This is another fall germinating native annual wildflower. What is lacks in showy flowers, it makes up for in edibility. This is easily the most delicious edible native leafy green we have on Mayne Island. It germinates a little later than the seablush but can still be seen in the fall. The first leaves that come out are longer and thinner than the ones that will follow in the spring. By mid-April the Miner’s lettuce is perfect for harvesting for salads or digging into garden beds as a green manure. The seeds of this species can be difficult to collect by hand since they mature at different times on the same plant. The best method for seed collection is to take the entire plant and put it into a paper bag once the first seeds begin to disperse, allowing the remaining seeds to mature on the plant and fall to the bottom of the bag. The seeds are mature when they turn black and hard.
Farewell to Spring (Clarkia amoena)
The third fall-germinating native wildflower we will highlight is farewell to spring. This annual species loves sunny dry habitats and has beautiful flowers in June. It sends down a taproot to overcome the drought and extend its growing season. Seeds are produced in long pods that split from the tip, and typically aren’t ready to collect until August. Seed pods will bend open in the drought, but sometimes need to be removed manually by crushing the seed pod. This species is in the primrose family and those familiar with other primrose species such as fireweed will recognize similarities in the seed pod structure, though unlike fireweed, the seeds of farewell to spring do not float majestically on the wind.
Chickweed monkey flower (Erythanthe alsinoides)
The final species we’ll look at has small but brilliant yellow flowers and is one of our very first local wildflowers to bloom in the early spring. It can be found naturally growing on sunny or semi-shaded slopes where water seeps to the surface. These seep sites often stay wetter for a few extra weeks in the late spring when surrounding areas have gone dry, allowing more time for the plants to complete their life cycle. Like the other three species, the monkeyflower is an annual and germinates in the fall. The seeds are very tiny, and float like dust from their parents to new growing sites. We have established this species successfully in pots, and often add it to pots containing camas or other perennial plants to create complementary colour schemes.
Beware the Cold Snap
In recent years we’ve experienced relatively severe cold temperatures of -5 °C to -7 °C in late January or even February. In our native plant nursery, we’ve sometimes watched in dismay as the lush green growth of these overwintering wildflowers turns to mush right before the spring. In the past two years we’ve avoided this by moving the pots temporarily into a greenhouse until the worst of the cold has passed.
We’re happy to help landholders identify and protect wildflower habitats, and to grow these species and others in their home gardens. Plants are important building blocks of ecosystem function, providing food and structural habitat for other organisms. Check out our free Landholder Consultation Program or stop by our new office for a chat.