By Susanne von Rosenberg, UC Master Gardener of Napa County
If you're like most gardeners, you always enjoy learning something new. I recently started learning about mast seeding. I already knew that oak trees tend to have light crops some years and heavy crops other years, but I didn't realize that many other trees do the same thing.
According to the Encyclopedia Britannica, mast seeding is defined as “the production of many seeds by a plant every two or more years in regional synchrony with other plants of the same species.” Even in mast years, the plant produces seed, but there is an obvious difference in seed production between a mast year and a regular year. Mast seeding occurs on every continent except Antarctica, and the regional synchronization can extend thousands of kilometers.
What fascinates me about mast seeding is that trees (or other plants) of one species are all on the same schedule regionally and that botanists still don't know why mast seeding evolved. We know a lot about how mast seeding affects the forest ecology but only have theories about why trees and other plants behave this way.
One theory is predator satiation. If a group of plants produces a huge number of seeds, perhaps predators (hungry squirrels, birds or humans, for example) will miss some because there is so much to eat. That means that every few years, some seeds will survive and reproduce. If trees were to produce an even, but smaller, number of seeds every year, predators might eat them all.
Another theory is that mast seeding is climate driven. Certain weather conditions are favorable to ripening seeds, and the trees detect those patterns and behave accordingly.
A third theory is that trees need to store up sufficient carbohydrates in their roots to support seed production. This theory was previously considered unlikely because mast seeding is a regional phenomenon. If carbohydrate storage is the trigger, then trees that are in prime growing locations with plenty of light and water should be able to store more carbohydrates and produce seed more often than trees in shadier or drier locations.
More recently, however, science has shown that trees are linked by mycorrhizal fungi networks that allow them to exchange carbohydrates. Mycorrhizal fungi form a symbiotic relationship with trees. They colonize the tree roots and receive carbohydrates while providing nutrients and water from the soil. Mycorrhizal fungi extend much farther than a tree's roots. So the third theory is potentially valid again.
A fourth theory is that mast seeding makes for more efficient pollination. Most mast-seeding plants are wind pollinated; when more pollen is released, the odds of fertilization increase. It's nice to know that we still have a lot to learn about plants.
Fortunately, we don't have to know why plants mast seed to understand the effects on ecology. Many animals, including large creatures such as bears and hooved mammals, rely on mast seeding, as do many small rodents and birds.
Because mast seeding is irregular and relatively unpredictable, studying the response of wildlife is challenging. Until recently, researchers assumed that a bumper crop of seeds would increase the breeding success of small mammals (mainly rodents) and attract more birds. Consequently, larger animals would also be drawn to the area due to the greater availability of prey.
A meta-analysis covering nearly 200 other studies found the expected response for small mammals and birds but found that larger predators were not necessarily drawn into a mast area, most likely because they have access to a large habitat.
Mast seeding isn't limited to acorns and nuts. Bamboo is also subject to mast seeding. One generation of bamboo can live up to 100 years before all the bamboo in the same vicinity flowers and dies in the same year.
Other plants that are considered mast plants include American persimmon, coffee berry, the dogwood family, the buckeye family, Mariposa manzanita, the mulberry family, blueberries and the elderberry family.
To create more effective habitat in your garden, you can plant mast-seeding plants in a hedgerow or small wooded area. If you keep chickens or pigs, you can improve their diets by planting mast-seeding plants. And if you like to birdwatch, a mast-seeding year may increase your chances of seeing interesting birds.
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- Author: Esther E Blanco
My friends recently moved to a beautiful new country home, which sits on an acre of land with a creek. While walking in their yard, they pointed to a large tree about 25-30 feet tall and full of what looked like blackberries hanging from the tree. I’d never seen a tree full of blackberries. I looked expecting to see thorns and vines twisting among the branches but they were actually growing from the tree. My friend explained that the wild turkeys come and jump up to eat the berries, so they didn’t think the berries were poisonous. I took a few pictures and started my search…
It turns out that my friends have several mulberry trees in their yard. I’d often heard of fruitless mulberry trees, but I had never seen one with fruit. I discovered there are 150 different varieties of mulberry trees (Morus spp.) and many, many hybrids. The Red mulberry or American mulberry (M. rubra) is native in the eastern United States. The White mulberry (Morus alba) trees were originally imported from Asia during early colonial times because they are used to raise silk worms.
The mulberry tree is deciduous and often grown near the edge of open woodlands and near fresh water, which described the location on their property perfectly. The fruit is edible and is used for pies and jams because of its sweet and slightly tart flavor. The color of the actual fruit, does not determine the variety. The fruit can be white, pink, red and black but the fruit is really not a berry. It’s an aggregate fruit, which means it’s composed of lots of little berries stuck together, each with its own seed. The fruit is long and shaped similar to a blackberry, but hangs from a short, slender fruit stalk. The fruit is supposed to be delicious however; the color from the fruit is used as dyes so can easily stains things that the juices seeps into. That also including the droppings from birds when eat the berry, so the tree has a bad reputation among suburban homeowners.
After looking at the shape of the leaves, I believe that my friends have the Black mulberry (Morus nigra ) species that is native to southwestern Asia. It’s a beautiful full size tree in their large backyard. It’s in a great location. I think they will be gathering lots of delicious black mulberries for many years to come.
Here we go round the mulberry bush, the mulberry bush, the mulberry bush…here we go around the mulberry bush so early in the morning…
Sources:
http://www.crfg.org/pubs/ff/mulberry.html
http://en.wikipedia.org/wiki/Morus_nigra
http://www.pfaf.org/user/plant.aspx?latinname=Morus+nigra
http://www.ehow.com/how_5637978_make-mulberry-trees-produce-fruit.html