Propagating Wild Flowers (1998)

by James Hodgins

Jim Hodgins is Editor of WILDFLOWER magazine and a past President of the North American Native Plant Society. He is co-author of Flowers of the Wild: Ontario and the Great Lakes Region.

My wildflower garden was only two years old when I noticed that the golden-seals were crowding out the wild gingers. The normally delicate and diminutive merrybells had grown to the size of bushelbaskets and were squeezing out my Virginia bluebells. The evergreen Christmas ferns had doubled in number and were obscuring the wood anemones.

I had rounded up these locally native wildflowers and ferns from nurseries, construction sites and friends' gardens, and I had planted them with ample space between each specimen. So much space, in fact, that the result was embarrassingly unlike the naturalistic look I was trying to achieve. Yet here I was, a mere two springs later, with too many plants as well as some that had grown too large for their intended purpose. The shapes, textures and colours of the less aggressive species were already almost hidden by the fastergrowing and taller species, and some sections of the garden had taken on a jungle-like appearance. Evolution was in high gear. I decided to play God and steer it in what I perceived to be a more aesthetic direction. This meant digging out those plants that had spread beyond their intended areas. I simply divided robust clumps of plants in half with my spade, making certain to retain as much soil and roots with the removed half as possible.

After my cosmetic improvement project was finished I had, spread out in plastic shopping bags, two to three times as many wildflowers and ferns as I had started with. Thus I had been a somewhat reluctant agent in the process of propagation - from the Latin propagare, to cause multiplication. In horticulture, this basic method of multiplying or increasing plant numbers is called simple division. It is traditionally used for those wildflowers (or any garden plants) that have fibrous and tightly matted roots - for example, asters, goldenrods, daisies, monarda, culver's root, ironweed, boneset, joy-pye weed, rudbeckias, Veronicas, helianthus, obedient plant, some violets and many ferns. In general, spring-blooming species, such as twinleaf, violets and pasqueflower, are best divided in the fall. Autumn bloomers, such as asters, goldenrods, and black cohosh, are best divided in the spring. If the original clump is large enough, it can be divided into three or more sections, provided each new section has sufficient roots.

Division time in the garden is a prime opportunity to promote neighbourliness and wildflower conservation at the same time. Most gardeners are eager to accept free plants. They are often even more receptive if you explain the history and biology of the species you are offering them. Is there a gardener who would not be intrigued to know, for instance, that many of the wildflowers native to the Great Lakes region have been growing as species in the area for 10,000 years? Or one who would not be delighted to receive woodland species once informed that most of them are perennial, are adapted to shade and semi-shade, and require minimal attention? Nurturing wildflowers in a garden of domestic flowers may be your recipient's only tangible contact with nature. This can eventually be built upon to foster a broader appreciation of the natural world.

VEGETATIVE PROPAGATION

When I divided the mature clumps of plants in my garden, I was using one method of vegetative, or asexual, propagation - so-called because only the vegetative parts of the plants, such as roots, stems or leaves, are involved; the sex organs (flowers) play no part in this method. Since simple division is essentially removing juvenile plants from the parent plant, the new plants will be genetically identical to the parent. This is an advantage if you want uniformity in appearance to the parent, but a disadvantage if you are looking for variations in flower colour, height, growth rates, and blooming and fruiting times.

There are several other methods of increasing your plant numbers vegetatively. Which method is best for which species can be gleaned from reference books and gardening experience. Some of the more common methods are as follows:

STEM AND LEAF CUTTINGS

Above-ground stems, especially when they are young and tender in early summer, can be cut from the parent and planted on the spot. Species amenable to this technique include prickly-pear cactus, partridgeberry, Ohio spiderwort, butterflyweed, lobelias, blue phlox, blazing star, Virginia fire pink and alumroot. (The cut section of prickly-pear cactus should be left exposed o the air for several hours to allow the severed cells to dry up or "scar off." This will minimize disease from fungi and bacteria when the cutting is planted in the soil.)

Most cuttings should be planted at a depth of 2 to 4 centimetres. The cutting is now under stress. It has no roots to take up water, yet it continues to lose water from transpiration and respiration. You can increase its chances of survival by covering it with a clean, transparent plastic bag or large jar. The mini-greenhouse formed by the bag or jar increases the humidity and prevents wilting from water loss. Keep the cover on until new growth appears. Such cuttings under glass or plastic should not be located in direct sunlight as the elevated temperature may kill them. Cuttings from plants with thick or waxy stems or leaves, such as cacti, sedums, or rubberweed, do not need increased humidity as it may readily induce rot.

Leaf cuttings from some species, such as wild ginger, Cardamine, Dentaria and Mitella, will root in a similar fashion as stem cuttings.

Some species of wildflowers, most notably foamflower. strawberry, some violets, green and gold, and silverweed, send out specialized above- or below-ground horizontal stems or stolons, sometimes called runners. From the tips or nodes of these stolons, plantlets will develop. Once several leaves have appeared on the stolon, it can be removed and rooted elsewhere, it is best to use the jar-on-top technique for several weeks until additional growth is observed.

UNDERGROUND STEMS

Many species of plants use the underground portion of their stem for the storage of food. One such type of storage organ is the rhizome. A thickened section that usually lies horizontal to the ground, the rhizome sends out roots downward and new stem shoots at its tip and nodes. Species easily propagated with rhizomes are iris, bloodroot, trillium, some violets, goldenseal, Solomon's seal, maidenhair fern, some grasses and sedges, wild geranium, may-apple, wild ginger, Virginia bluebells, yellow lady's slipper, yellow mandarin. acorus and yucca.

The right time to create new plants from a rhizome is the late summer or fall when the plant is relatively inactive. Using a sharp knife, cut a robust rhizome in cross-section so that each piece retains at least one bud or shoot. Leave the sections overnight to "scab off," and plant them the next day at the same depth as the original rhizome. Leave ample space between each planting and mark the site with a stick. You can produce two to seven new plants from the original in this way.

Another type of underground stem that can he used for propagation is the subterranean bulb. Species with this specialized organ include the Canada lily, wild leek, camas-lily, camassia, and violet oxalis. Squirrel corn and Dutchman's breeches also have small bulb-like organs.

The bulb is a food storage organ consisting of layers of leaves tightly wrapped around a central, basal stem. Every two to three years these bulbs should be dug up and examined in the fall. At the base of the original parent bulb will be seen several to many smaller bulbs, known as bulblets. Carefully break off these bulblets with your fingers and replant them at the same depth from which they came. Plant them at least 30 centimetres apart, making certain the pointed end is up. If rodents, (squirrels being the worst offenders) are liable to devour your stock, cover the bulbs with 1/4- to 1/2-inch-mesh chicken wire, depending on the size of the bulbs. Cover the wire with earth and organic litter and mark the site.

Wildflowers such as spring beauty, trout lily, blazing star and yellow star grass produce underground bulb-like structures called corms. The tight leaves surrounding the large central stem of a corm are thin and membranous, rather than thick and fleshy as in a bulb. Cormous plants can be propagated in the same manner as bulbous ones.

BULBILS

Some wildflowers produce above-ground or aerial bulbs known as bulbils. Depending upon the species, they will appear in the leaf/stem axils or in the flower cluster. Look for these curious propagules on wild garlic, swamp candles, water hemlock, alpine bistort. nodding saxifrage, bulbous pea, red fescue, seaside plantain and lesser celandine. Some ferns and clubmosses, including bulblet fern, mountain clubmoss and shining clubmoss. also produce bulbils. Harvest bulbils in the fall and plant them like seeds, marking the site plainly.

LAYERING

If you wish to see things happen quickly, you might try a technique called layering. Species with pliable stems, such as Virginia creeper, cardinal flower, blue lobelia, blue phlox and partridgeberry, can be layered. Carefully bend a young stem over to ground level taking care not to break it. Bury about 8 centimetres of the stem in a shallow trench, leaving the growing tip exposed to the air. Weigh down the buried portion with a rock or peg. Within a growing season new shoots will arise from the buried section, at which time you can sever it from its parent. Once you have mastered the basic propagation techniques, you may wish to explore other challenging methods. Some of the recommended titles in the reference list will introduce you to esoteric but effective methods known as descaling, scoring, scooping and tissue culture.

PROPAGATION FROM SEED

In the wildflower gardening community one is never considered to be a "real gardener" or conservationist until one has grown at least several species of native wildflowers from seed. The wildflower gardener is also expected to keep records on plants grown, to package and label seed, and to pass the surplus along to others.

Seed production and dispersal is the main means by which most flowering plants propagate themselves. Whereas vegetative propagation produces new plants identical to the parent plant, plants from seed may vary from the parents because the seed is often composed of genetic material from different plants of the same species. In the simplest terms, pollen (male genetic material) is often carried by an insect or the wind from one flower to the ovary (female part) of a flower on a different plant. The resulting seed will contain genetic material slightly different from that of either parent. Plants grown from seed therefore exhibit diversity, while those grown by vegetative methods do not. Why propagate wildflowers from seed when you can buy mature wildflowers from many nurseries? There are several good reasons. For one, aside from gasoline costs and time, the seeds are free; nursery plants are not. For another, nurseries grow and sell approximately 60 species of wild plants native to Ontario, including ferns, grasses, herbs, shrubs, and trees. Of the species sold regularly, only about a dozen are herbaceous wildflowers and most of these are open space. sun-loving species. By harvesting and growing your own seed you have access to 2.000 wild species in Ontario alone. Probably the main reason native plant gardeners prefer to grow from seed, however, is the immense intellectual and spiritual satisfaction derived from working so intimately with a complete cycle of nature - from harvesting seed to planting to germination to flowering, fruiting and harvesting seed again. You soon become an intimate friend of the species you are working with.

In the wildflower gardening community one is never considered to be a "real gardener" or conservationist until one has grown at least several species of native wildflowers from seed. The wildflower gardener is also expected to keep records on plants grown, to package and label seed, and to pass the surplus along to others.

COLLECTING THE SEEDS

When gathering seed from the wild, it is imperative that you harvest no more than 10% of the whole seed crop from any one plant or population. The remainder should he left to ensure the survival of the site population and to accommodate the many organisms that depend upon seed for food. These include wintering birds, mammals and some hibernating insects. The 10% rule applies no matter what kind of seeds you are harvesting. It may be that perennial wildflowers can better afford to part with some of their seeds than annuals, since perennials rely heavily upon vegetative reproduction as well as seed. On the other hand, annuals generally produce much larger seed yields than perennials, as seed is their only means of survival.

Seeds harvested in your immediate locale will almost certainly do better in your garden than those from afar. Local natives have adapted over time to cope with local diseases, predators, soils and climate. Seeds from afar will have adapted to different conditions. (Another reason to harvest wildflower seeds for yourself: large seed houses usually grow their own seed and can assure its quality, but it may not be the optimal seed for your local conditions.)

Make certain the seeds you collect are ripe. Your indicators will be a combination of colour, size, softness and dryness of the fruit containing the seed. Knowledge of how to interpret these signs comes from observation and experience. Keeping notes on seed sites and maturation dates is helpful as such dates may shift from year to year.

Pod-bearing wildflowers, such as milkweeds and members of the pea family, should not be harvested until their fruits have ripened. If it has been a wet summer, they can be dried indoors in a well-ventilated room. Seeds borne in capsules, such as iris, bloodroot, and cardinal flower, should be harvested just prior to the capsule's splitting. Fleshy fruits should be gathered as soon as they feel soft to the touch when gently squeezed. Such fruits include Solomon's seal, trillium, goldenseal and rose twisted-stalk.

Gather seed from the most robust and showy specimens as these are probably best suited for long-term survival. You may wish to collect seed from those plants that bloom or fruit earlier or later than the rest of the population, if these individual plant traits suit the aesthetic needs of your garden. Within a population, harvest seeds from different plants to maintain genetic diversity in your garden. Remember to maintain the 10% rule. In the field, seeds can easily be placed in small paper or plastic bags, tied or folded shut, and kept in a backpack. six-quart basket or shopping bag.

Pod-bearing wildflowers, such as milkweeds and members of the pea family, should not be harvested until their fruits have ripened. If it has been a wet summer, they can be dried indoors in a well-ventilated room. Seeds borne in capsules, such as iris, bloodroot, and cardinal flower, should be harvested just prior to the capsule's splitting. Fleshy fruits should be gathered as soon as they feel soft to the touch when gently squeezed. Such fruits include Solomon's seal, trillium, goldenseal and rose twisted-stalk.

DRYING. CLEANING & STORING

Back at the home front, you must now prepare your seeds for storage. Keep them sorted by species and spread them out in individual dishes, trays or anything else that is flat and shallow. Let them dry for two weeks, stirring them daily. Keep each seed group labelled or you will soon forget what is what.

You can use this extended drying period to clean seed types that require some preparation before storage. There are several reasons for cleaning seeds at this stage: (1) the seeds are easier to store when you know how much and what you have; (2) the seeds are easier to count for germination records and will be easier to plant next spring; and (3) cleaning minimizes the presence of bacteria, fungal spores and insect eggs, all of which can be injurious to your seedlings. Seeds with attached fluff to assist in wind dispersal (e.g., prairie smoke, prairie crocus. clematis) should be separated from such appendages. Similarly the membranous wings of ash, maple, bladdernut and hoptree seeds should be detached and discarded. Seeds embedded in pulpy fruit, such as Jack-in-the-pulpit and rose twisted-stalk, should be extracted from the pulp and placed on paper to dry.

While seed cleaning is a tedious job, it is a prime opportunity to observe seed and fruit structure in detail - and to listen to your favourite radio station.

After the initial cleaning, minute debris can be removed by winnowing. Place seeds in a large, shallow dish with a rounded bottom. Take outdoors or hold near a fan. Holding the sides of the dish, toss the seeds lightly into the air and catch them in the tray. The lighter debris will be blown away.

As an alternative to open-air drying, you can place equal weights of seeds (clean them first) and dry silica gel in a closed jar. The gel wrapped in cloth will absorb moisture from the air and in turn force the seed to release much of its moisture. Small seeds require 8 to 12 days of dessication by this method; large seeds require 12 to 16 days.

Low moisture in and around most seed types is essential to maximize longevity. Studies have shown that when the moisture content of a seed is between 5% and 14%, a 1% reduction in water content doubles the seed's life span. Storage temperature is also critical; the lower the temperature, the slower the seed's respiration and the longer its energy reserves will last.

So once you have finished drying your seeds, it's important to store them correctly. Transfer them immediately to paper envelopes, seal, and label with date, species location and collector. Put the envelopes in a tightly sealed jar and store in a refrigerator at 6°-I0C. If no refrigerator space is available, store in a cool, dry root cellar. (Seeds that have been dried by the silica method may also be stored in the freezer: seeds that have been dried in the open air will not have lost enough moisture to survive freezing.) If properly prepared and stored, most seeds will last two to five years.

The seeds of most cool temperate plants require a minimum cold period of three to ten weeks; otherwise they will not germinate. This cold treatment and its effect on seeds is called stratification. It is a dormancy period which prepares the seed for germination. The cold period in your refrigerator imitates nature's treatment of the seed in winter.

A few seeds, however, have special needs. Certain woodland herbs, for instance, seem to require the presence of high moisture in company with stratification to induce germination. Seeds of trilliums, merrybells, Jack-in-the-pulpit and wood poppy may be in this category and should be planted in the garden shortly after they ripen. Mark the site well, as some of these species may take two years to germinate. As well, native columbine seed has a very short storage life and should he left to self-sow. North American orchids grow very poorly from seed under garden conditions. The seed appears to require the presence of specific mycorrhizal fungi to initiate germination, fungi which may be absent in many garden soils.

PLANTING

After appropriate stratification, your seed is ready for planting. Walt Whitman captured some of the mystery of these unique packets of life when he wrote,

In this broad earth of ours,
Amid the measureless grossness and the slag,
Enclosed and safe within its central heart,
Nestles the seed of perfection.

Many gardeners simply plant their stratified seed outdoors after danger of frost has passed, but there is much to be said for planting indoors in late February or early March. Certainly winter seems a lot shorter when you can watch.

RECOMMENDED REFERENCES

Hodgins, James. "Propagating Wildflowers". Previously Published in WILDFLOWER. 4:3 1988. 28-32.