As a propagator, I often try different approaches to germinating seeds of certain species. Sometimes I get such a definitely positive response to one pre-treatment method, that it becomes the one I’ll always use—like soaking toyon seeds for just one hour before sowing. This treatment results in vigorous germination. I won’t bother with a hot coffee soak of these seeds again. We pot native shrub seedlings into tube-style pots that are designed with internal ridges running the length of the tube. This encourages roots to grow long and fairly straight, and helps to prevent roots from circling and eventually strangling themselves. The seedlings stay under shade for several months, and as they get potted up to larger style tubes, and eventually to tree-pots, they also get more and more exposure to direct sunlight.

Summer is a time for starting perennials and some shrubs from seed. Most often, I’m working with seeds that were collected last year, and at the same time I’m doing a lot of seed collecting. I actually start collecting some seed in late spring. Early-blooming wildflowers like phacelias go to seed by late April when the days get warmer, as does miner’s lettuce. I’ve got stands of different clarkia species to collect from, and I’ll be checking the seed development of the native salvias.

I’m always amazed at the abundance of seeds that most plants produce. It makes me think about all the different functions that seeds serve. First they are food for all sorts of insects and other invertebrates, for birds and rodents and other mammals. Seeds also ensure the survival and genetic diversity of a plant species, and some portion of seeds produced each year may lie dormant, hidden or camouflaged for many years as insurance against bad years for a particular species. I make sure to leave plenty of seeds for all the creatures, and collect in such a way that anyone following behind me would never notice a difference. When I’m collecting seed, I keep this little mantra in mind: If you see more than ten fruits on a plant, take only one in ten. If you see nine, take none.

The only seed I still collect once the rainy season has begun is from toyon (Heteromeles arbutifolia). I’m picking handfuls of bright red, mature berries and contained within each berry will be one or more seeds. The berries will be soaked in water and after a few days gently macerated, which makes it easier to separate the seed from the flesh of each berry.

By the time the rains start, I’ve finished with most of the seed collecting for the year; in many species seeds mature as the seed pods dry, and so collection is done only during dry weather. I collect only from plants with prolific seed set, and then take only small amounts of seed from a number of different plants of the same species. Collecting seeds over a number of days or weeks also increases the genetic variability.

Collected seeds are temporarily stored in open containers all over my house, until they are thoroughly dry. Then I clean and package the seed in the evenings or on rainy days, when it’s not possible to work in the garden. Using simple tools and a set of graduated sieves, the seeds are separated from their pods, capsules, follicles, siliques, or schizocarps.

In botanical terms, these are all different types of fruits, as is a berry, and fruit is the correct botanical term for any mature ovary containing seeds. Plants are grouped together into families based on similarities of flower and fruit structures. Botany for Gardeners by Brian Capon (Timber Press, 2005) is a very useful and interesting book for those of us who are learning about botany as we garden.

Plants in the evening primrose family (Onagraceae) set seeds in capsules, which are usually four-chambered. When I collect seed from clarkias, annual plants in this same family, I cut the tops of stems with capsules attached. These plants produce a prolific amount of seed, much of which is eaten by insects and birds.

Finches usually eat seeds while they’re still on the plant. I’ve watched little goldfinches moving up and down the stems of clarkias and yellow evening primrose (Oenothera elata ssp. hookeri), a biennial plant in the same family, taking seed from the open, upright capsules. Birds are messy eaters, so much seed is scattered on the ground where birds like towhees, juncos and golden-crowned sparrows forage. While they’re foraging with the typical sparrow “double-scratch” method, the seed that is not eaten is scratched into the ground, ready to germinate as soon as the rainy season starts.

Within a week after the first rain in October, dense patches of tiny seedlings are evident all over my garden. There’s some predation, since voles and sparrows like to eat greens, so the patches get thinned out a bit but still, hundreds of seedlings survive. Two months later these seedlings are well developed, about 2 to 3 inches tall, with “true” leaves fully formed, and easy to transplant.

So, although we start a lot of annual wildflowers from seed under controlled conditions in the greenhouse, we also simply transplant a lot of seedlings that I dig out of my garden. Using a hori-hori knife, I can gently tease the seedlings out of my beds and gravel pathways with root systems intact. Then I immediately place them in soil in a trug, making sure the roots are covered. That same day we transplant the seedlings into 4” pots, let them recover for a few days in the shade after transplanting, and then grow them on in a sunny, protected location.

The most important things to be aware of when working with these delicate seedlings: cover roots quickly with soil, and always handle them by their leaves, not the stems. Delicate hair roots can die within minutes when exposed to air, and if the stem is crushed or damaged the lifeline is destroyed, and the seedling will not survive.

The flowers of a plant are designed for the purpose of making seeds. If a flower is pollinated, then fertilization can take place, and a seed develops in the ovary of the plant. This is sexual reproduction, and ensures genetic diversity. As the fertilized seed develops, so does the fruit (pome, pod, or capsule, etc.) which surrounds the seed.

 

But, first let’s get back to real basics; flowers need to be pollinated to start the whole process of seed formation. There are many different agents of pollination employed by different genera of plants; wind, water, insects, birds, and mammals.  Insects are by far the most common agent of pollination amongst the flowering plants, or Angiosperms. Flowers developed to attract insects and facilitate cross-pollination, and thereby create ample genetic diversity. Flowering plants often co-evolved with particular insect species so that their life cycles coincided.

Many insects are important pollinators, and flowers developed as sometimes really clever lures offering rewards, such as nectar and pollen, for the service provided. A garden would be a sterile, lifeless place without insects. So, when humans use insecticides around the home and especially in the garden, there is far-reaching damage done. By destroying these important players in symbiotic relationships that have evolved over millennia, we also have a damaging effect on the viability and diversity of the plant kingdom; and (as the concern over the crisis with honeybee colonies demonstrates) our own food supplies could also be jeopardized.

Flowers are the sexual organs of a plant. Stamens are the male reproductive parts and consist of a stalk, or filament, with an anther on top, from which the pollen grains are distributed. Female reproductive parts are collectively called the pistil, and consist of three parts; the stigma, the style, and the ovary.  It is the ovary that enlarges to become the ‘fruit’, which in botanical terms is the receptacle that contains the ripe seed; whether it’s an apple, a pea pod, or the seed capsule of a Columbine. When both male and female parts are contained within one flower it is termed a ‘perfect’ flower. Sometimes male and female parts are found on separate flowers on the same plant, sometimes on separate (dioecious) male and female plants.

During the course of pollination a grain of pollen is moved, often by an insect, from the anther of one flower onto the stigma of another flower. If the pollen is compatible, hormones contained in the female plant parts set the fertilization process in motion. There are two cells in each pollen grain; one cell grows into the pollen tube, and the other cell divides into two sperm cells. The pollen tube grows down through the style to reach the ovary. The two sperm cells are then able to move down through this tube; where one fertilizes an ovule, or immature seed, and the other creates the endosperm, which is the food supply for the developing embryo, and later, in the form of cotyledons, also provides a food store for the newly germinated seedling. Until the embryo is fully developed, it is connected to the parent plant by a placenta. It is fully dependent on the parent plant for water and nutrients, which are received through this placental connection. Once the embryo is fully developed, and food storage reserves are in place, the seed coat starts to harden, and tissues within the ovule loose water.

When fully desiccated the seed contains about 5% moisture, and is considered ‘ripe’ when it readily separates from the parent with no attached plant parts. (Compare that to mature plants which are about 95% moisture!) This is the definition of an ‘Orthodox’ seed, which can often survive for decades, and sometimes even longer, as a viable entity if properly stored. ‘Recalcitrant’ seeds have a higher moisture content, such as acorns and other nuts, and are only viable as long as the fleshy tissues remain moist.

Mature plants are termed ‘auto-trophic’ because they make their own food molecules from non-living sources; such as carbon dioxide, water, minerals, and the energy from sunlight. As seeds, and as seedlings still relying on the cotyledons, however, they are ‘hetero-trophic’  (just like most creatures) because they rely on this stored food supply until the true leaves develop, and they are able to photosynthesize and create their own food energy.

There are many different types of seeds, often encased in distinctive capsules.  Many fruits have evolved clever tactics and ploys to solicit help with distribution of a plants progeny. To summarize, whether the seed is dust-like, and ‘Orthodox’, such as that of Mimulus, or the substantial, ‘Recalcitrant’ nut of the Buckeye; classification of plants is according to flower, and thereby fruit structure.

The best way to learn plant species ID is to really learn and understand the characteristics of specific genera and the larger plant family groupings. Learn to look for similarity in the attributes of flowers and fruits when trying to identify a plant, then compare these structures to those of plants you are familiar with. Once you’re pretty certain that an unidentified plant shares the characteristics of a plant family or genera, it is easier to narrow down the search to a particular species.

Two books I have found to be readable, interesting, and very useful for a home gardener wishing to learn more about botany and plant classification are:

‘Botany for Gardeners’ by Brian Capon( Timber Press, 2005)

‘Botany in a Day; The Patterns Method of Plant Identification, By Thomas J. Elpel (HOPS Press, LLC, 2006)

Did you know that in the world of botany there are ‘floral formulas’? I found this fascinating, and very useful in learning the plant families! For example; in the Mustard family the floral formula is by 2’s and 4’s – In the Lily family the floral formula is by 3’s and 6’s –