There are two kinds of seed-producing plants, flowering and non-flowering. Flowering plants are called angiosperms; their seeds grow inside tissue that is part of the plants’ ovaries, more commonly called fruit. Non-flowering plants that produce seeds are called gymnosperms. Conifers are gymnosperms; their seeds are “naked,” or unprotected by an ovary/fruit and are often located on the scales of a cone.
Some cones are male and some are female. The male cones produce pollen and the female cones produce ovules which, if fertilized, develop into seeds. The pictured tiny, magenta cones are this year’s seed (female) cones of White Spruce, (Picea glauca) which, when the time is right, open their scales to allow wind-blown pollen to reach and fertilize their ovules. The scales then close and will not open again until the seeds are fully mature. At this point the scales open a second time in order to release the fully developed seeds which are dispersed primarily by the wind.
Large-flowered Trillium (Trillium grandiflorum), also known as White Wake-Robin, is our largest and showiest species of trillium. It can be found throughout New England’s rich woods, sometimes carpeting large expanses of the forest floor in May and June. All species of trillium, as their name implies, have parts arranged in threes, or in multiples of three (petals, bracts, leaves, stamens, carpels).
Nectar, not fragrance, attracts long-tongued bumblebees to Large-flowered Trillium’s funnel-shaped blossoms. Self-pollination occasionally occurs, aided by the fact that as the flowers age, their stigmas reflex downward and come in contact with the anthers. The flowers are exceptionally long-lived, remaining open and fertile for two to three weeks.
When they first open, Large-flowered Trillium’s petals are white. As the flowers age, they become pale to deep pink (see insert). (There is also a pink form of Large-flowered Trillium which is pink from the time of opening.) The seeds that form are dispersed primarily by ants, but yellow jackets, harvestmen and white-tailed deer also contribute to their dispersal. It takes two years for the seeds to germinate and once established, Large-flowered Trillium plants typically require seven to ten years in optimal conditions to reach flowering size.
Congratulations to those of you who guessed correctly, and thank you to everyone who participated in this week’s Mystery Photo. I find patterns in nature both intriguing and beautiful — they will be the subject of more Mystery Photos! When photographing these Common Milkweed (Asclepias syriaca) seeds, I discovered that there were other creatures attracted to them besides myself – hence, today’s blog post:
LARGE MILKWEED BUGS SIPHONING MILKWEED SEEDS
Only two to four percent of Common Milkweed flowers eventually produce mature pods. Each pod contains an average of 226 seeds (all from one flower). Resembling overlapping fish scales, the seeds are arranged in a way that allows the wind to successively, from the top to the bottom of the pod, catch their silk parachutes and disperse them.
Just as milkweed pods are opening and seeds are maturing, Large Milkweed Bugs (Oncopeltus fasciatus) in all stages of metamorphosis (there are five nymphal stages, or instars) congregate on milkweed pods to feed on the seeds. (Their eggs are laid on milkweed plants.) Like all true bugs, their mouthparts (rostrum) are not adapted for biting and chewing food, but are designed for piercing and sucking. The rostrum consists of two side-by-side tubes. The milkweed bugs use one tube to pump digestive enzymes into the tough milkweed seeds and the other to siphon up the softened plant material. Like other milkweed feeders, milkweed bugs obtain poisonous compounds from the milkweed plant that are used for defense, and their orange and black coloration warns predators of their toxicity.
Even without much of anything to go on, all answers were correct! Although Cedar Waxwings were the predominant avian visitor to this crab apple tree when I visited it, there were also robins, starlings and crows feasting away (and presumably several other species, including turkeys, as some of you guessed, at other times).
Cedar Waxwings are among the most frugivorous (fruit-eating) birds in North America. In the winter, sugary fruits dominate their diet to such a degree that occasionally, when the fruit has become overripe and has started to ferment and produce alcohol, the waxwings can become intoxicated and, rarely, die. One individual saw that her front lawn was littered with the bodies of dead Cedar Waxwings on top of the snow, but by the time she went out to dispose of them, the drunken birds had all revived and flown away.
During the winter, Cedar Waxwings travel in flocks of up to several hundred birds. They are nomadic, roaming the countryside in search of crab apples, hawthorns and mountain ashes, as well as serviceberry, juniper, winterberry, dogwood and cedar, among others. Waxwings will descend upon a tree en masse and while perched will bend down and pluck crab apple after crab apple, swallowing them whole, one at a time. Occasionally you will see them hovering briefly in the air while plucking fruit. They are well known for “gifting” fruit to fellow waxwings.
Many birds that eat a lot of fruit separate out the seeds and then regurgitate them. Cedar Waxwings let the seeds pass through them, scarifying the seeds in their digestive tract (breaking down their outer seed coat), which, once the seeds are deposited, allows them to eventually germinate. Because of this, waxwings are considered important seed dispersers for many fruiting plants in North America (including the invasive, non-native honeysuckle which, when eaten during the time feathers are developing, causes Cedar Waxwings to develop orange, not yellow, tail bands).
As a dispersal mechanism, some plants have fatty structures called elaiosomes attached to their seeds’ coats which are very appealing to ants. After collecting a seed and carrying it back to its underground nest, the ant eats the elaiosome (or feeds it to ant larvae) and discards the intact seed in an area where waste and dead ant bodies are stored. Germination is highly likely in such an ideal environment, making myrmecochory a win-win situation. Trillium, bloodroot and violets are some of the thousands of plants that have elaiosomes attached to their seeds.
Miterwort, also known as Bishop’s–cap, is named for the resemblance of its fruits to the hats (known as miters) worn by bishops of the Roman Catholic Church. If you examine a flower closely, you will see its delicate, 5-pointed, snowflake-like beauty. Each flower is in the shape of a tiny cup, with dissected petals arising from the rim of the cup, resembling fine lacework. There is a glandular ring of nectar-producing tissue inside the cup which attracts small bees, flies and ants. Once pollinated, the flowers produce open seed-containing capsules. Water, not animals, is the dispersal agent for Miterwort’s seeds. The capsules orient themselves so that their opening faces upward. When it rains, the falling rain drops splash the seeds out of the capsules, dispersing them up to three feet away from the parent plant. The distance traveled by the seeds is dependent upon both the size of the raindrop and the distance that it has fallen before landing in a capsule.
Being a gymnosperm (its seeds are not enclosed in an ovary), American Yew, Taxus canadensis, lacks true flowers or fruits and possesses separate male and female (seed) cones. Each male cone produces up to 100 pollen sacs or more. The modified female cones do not resemble the typical woody cones of evergreens. Yews are the only conifers that produce seed cones that consist of a fleshy (and mucilaginous), scarlet, cup-shaped structure called an aril, each of which holds one seed. The seeds (not the aril) are poisonous to humans, but thrushes, waxwings and other birds consume them and aid in their dispersal.
Although it has a beautiful white flower, Thimbleweed, Anemone virginiana, is not as noticeable in the summer as it is when its seeds mature in the fall. Looking like a small ball of cotton, its thimble-shaped seedhead consists of a cone covered with tiny dark hooks that white, fluffy seeds cling to and cover until the wind carries them away from the parent plant. The seedhead of this member of the Buttercup family looks very much like that of its close relative, Long-head Thimbleweed, Anemone cylindrica, except A. cylindrica’s seedhead is slightly longer. As impressive as these eastern species are, there’s a species of Thimbleweed out West whose seedhead is so big the plant is referred to as “Mouse on a Stick.” In the summer, plant-eating animals usually leave Thimbleweed alone because the foliage contains a blistering agent that can irritate the mouth parts and digestive tract.
Although the breeding and winter ranges of White-throated Sparrows overlap, most, if not all, populations are migratory. During their flight southward in the fall, White-throated Sparrows stop during the day to refuel on seeds, fruits and insects, if available. Winged Euonymus (Euonymus alatus), or Burning Bush, is an invasive shrub that, in addition to shading and crowding out native plants, produces vast quantities of capsules, each containing up to four seeds. White-throated Sparrows and many other bird species find these bright red seeds attractive, but unfortunately, they are of little nutritional value to the birds and other wildlife that feed on them. How ironic that these birds, whose health and migratory success may be compromised by the seeds of this invasive plant, are facilitating its establishment by dispersing its seeds.
Red and Gray Squirrels remain active year round, and thus, need to have access to food throughout the year. In order for this to happen, seeds and nuts must be stored in the warmer months for consumption during the winter and early spring, when food is much harder to find. While Gray Squirrels tend to bury nuts and seeds individually for this purpose, Red Squirrels often cache numerous seeds (mostly conifers and maples) in one spot, dispersing these caches throughout the woods. During the winter Red Squirrels use their memory (and sometimes their sense of smell) to locate these buried treasures. Inevitably some are overlooked and in many of these cases, the seeds germinate. Finding little patches of multiple seedlings, such as this miniature stand of young Sugar Maples, is a good indication that at least one Red Squirrel overwintered in the vicinity.
Even though it snowed in Vermont this weekend, there is something else white and fluffy that is also being blown about, and it doesn’t melt when it hits the ground. The tiny white bits of fluff that are floating in the air are the seeds of aspens (also referred to as poplars), primarily Bigtooth Aspen (Populus grandidentata), that are borne in capsules that develop along a 3 to 6-inch dangling stem. These former flower clusters, and the capsules and seeds they developed into, are referred to as catkins. The capsules split apart when the seeds are mature, releasing the cottony-tufted seeds that are well-designed for dispersal by the wind. Looking into the fluff-filled sky, it’s not hard to believe that a single Bigtooth Aspen tree can produce over a million seeds.
If you find clumps of empty burdock fruits lying on top of the snow, there may well be wild turkeys in the area. During the winter, especially when the snow pack is deep, wild turkeys feed on vegetation poking up above the surface of the snow, such as burdock seeds. There are tell-tail signs when turkeys have been eating burdock, even if no tracks are evident, because of the way in which they consume the seeds. Turkeys somehow pluck the burdock fruits off and then turn them inside-out, exposing the seeds which they then eat. Typically several of these empty fruits will be “velcroed” together, leaving small bunches of them scattered over the snow.
Common Juniper (Juniperus communis) is one of the few evergreen shrubs in New England and has one of the largest ranges of any woody plant. You often find it in old pastures and meadows, where its sharp needles protect it from most herbivores. It is a member of the Pine family, and even though its fruits look like berries, structurally they are cones (with fleshy scales). Whereas most of the cone-bearing members of the Pine family disperse their seeds in the wind, Common Juniper uses birds and mammals to do this deed. Cedar waxwings, evening grosbeaks and purple finches consume quantities of juniper fruit, and many other songbirds are frequent visitors. White-footed mice and white-tailed deer occasionally eat the fruit as well. While not aiding the dispersal of seeds, humans do use the fruit to flavor gin.