Central MN Phenology

Plugs and Pollinators

With more and more land being developed for one purpose or another, and more farm land being put into production, pollinator habitat has been in decline. We've been restoring our 80 acre farm to native plants for some time now, and there have always been monarchs. Like many, however, we've noticed a decline in monarch presence over the last ten years. But this year we saw an increase in monarch activity. 

I took this photo a couple weeks ago when the Stiff Goldenrod was in full swing. Had I taken a close-up photo, you would see that these plants were not only full of monarchs, but bees as well. you can see the bees on the flower toward the bottom of the screen. 

I took this photo a couple weeks ago when the Stiff Goldenrod was in full swing. Had I taken a close-up photo, you would see that these plants were not only full of monarchs, but bees as well. you can see the bees on the flower toward the bottom of the screen. 

For the first time in a long time our grove, made up of Norway Pine and Spruce trees, was full of monarchs. By full I mean thousands of them, all flitting about as one walked through the grove. They gathered and rested about two weeks before flying south on the grand migration to Mexico.

Though at a distance, you can see the branches of this spruce tree full of monarchs, hanging like bats in the shade of the grove. 

Though at a distance, you can see the branches of this spruce tree full of monarchs, hanging like bats in the shade of the grove. 

We have been growing wildflower and grass plugs in the greenhouse now for two years, and have been plugging them into existing prairies and into newer prairie plots. The advantage of beginning a prairie from plugs instead of seed is that we can design it , creating swaths of particular colors and transitioning into other colors. 

This is part of a larger project in which the homeowners are restoring their property to woodland natives, all which will be done by seed. But this plot, which is highly visible, we decided to do with plugs. We put down several inches of sand to suppress weed growth and to put the plugs into. 

This is part of a larger project in which the homeowners are restoring their property to woodland natives, all which will be done by seed. But this plot, which is highly visible, we decided to do with plugs. We put down several inches of sand to suppress weed growth and to put the plugs into. 

The homeowners know that these will need to be watered for four weeks or so. But after that the plugs will have rooted into the soil below and will do well on their own.

The homeowners know that these will need to be watered for four weeks or so. But after that the plugs will have rooted into the soil below and will do well on their own.

Here is another project where we removed all the old landscaping and replanted the area with plugs Conventional landscaping, with its landscape fabric and mulch, is doomed to eventual renovation for two reasons: plants don't do well when their roots are covered with fabric, and cultivars (or hybridized plants) generally cannot reproduce themselves. As a result, over time, the vegetation of conventional landscapes get thinner and thinner. 

Here is another project where we removed all the old landscaping and replanted the area with plugs Conventional landscaping, with its landscape fabric and mulch, is doomed to eventual renovation for two reasons: plants don't do well when their roots are covered with fabric, and cultivars (or hybridized plants) generally cannot reproduce themselves. As a result, over time, the vegetation of conventional landscapes get thinner and thinner. 

By inserting approximately 1.25 plugs every square foot, we saturate the area with natives, which should out-compete the weeds and will eventually reproduce themselves, filling up the area with native vegetation. 

By inserting approximately 1.25 plugs every square foot, we saturate the area with natives, which should out-compete the weeds and will eventually reproduce themselves, filling up the area with native vegetation. 

One side note: Another activity of August is checking on prairies that we seeded in the last couple years to see how they're doing. It is always very satisfying to see a plot that has come in well. The photo below is of a woodland restoration that we seeded in the spring of 2016. Here we are, in its second summer of growth, showing a flush of Brown Eyed Susans and Blue Bells, two flowers that complement each other nicely. 

Jacobson Woodland edited.jpg

The Window is Small and Closing Quickly

The time after the ground thaws to before things green up is the time to burn prairies. Also, the time after the ground thaws and before the trees bud is the time we dig up, transplant, pot, or ball and burlap trees. The window for much of what we do this spring of 2018 is a very small one.

As of yesterday, Saturday May 5, the ground is still frozen in spots. But it's thawed enough for us to do what we need to do.

We burn the prairie plots around the farm, and the prairies we have installed for customers. The burns enhance the soil, set back the weeds, and promote growth of the native plants.

We burn the prairie plots around the farm, and the prairies we have installed for customers. The burns enhance the soil, set back the weeds, and promote growth of the native plants.

The burns should be done before the prairie plants green up, as the burn forces them to start over. Unfortunately, during all this, the trees are beginning to bud. Their budding is a function of their activity, and It is not good to disturb tree roots when they become active, as doing so can kill the tree. So disturbing the roots should be done while they are dormant. 

At the tip of this Bur Oak branch you can see the buds beginning to swell. That means this tree is active, and yet we have many of them that we need to ball and burlap, pot, or transplant. So we hustled on Friday, May 4th, to get this done, thinking that by Monday, it may be too late to dig up trees.

At the tip of this Bur Oak branch you can see the buds beginning to swell. That means this tree is active, and yet we have many of them that we need to ball and burlap, pot, or transplant. So we hustled on Friday, May 4th, to get this done, thinking that by Monday, it may be too late to dig up trees.

These crooked sticks in the ground are Bur Oaks. It's hard to grow a straight one, so we plant many of them and then go through them when they get to a certain size, separating the crooked ones from the fairly straight ones. 

These crooked sticks in the ground are Bur Oaks. It's hard to grow a straight one, so we plant many of them and then go through them when they get to a certain size, separating the crooked ones from the fairly straight ones. 

The straighter Bur Oaks get either potted for later use, or balled and burlapped, after which they can be planted at any time. Paul, an employee, is digging holes in the background where the smaller and straighter ones will be transplanted. 

The straighter Bur Oaks get either potted for later use, or balled and burlapped, after which they can be planted at any time. Paul, an employee, is digging holes in the background where the smaller and straighter ones will be transplanted. 

We use a tree spade to cut the roots of tree roots. This allows us to keep the soil on the roots or, in effect, take the soil with the tree. 

We use a tree spade to cut the roots of tree roots. This allows us to keep the soil on the roots or, in effect, take the soil with the tree. 

Here's a photo taken years ago of a balled and burlapped tree that we are about to plant in the yard of the house behind. Our tree spade, which allows us to ball and burlap, allows us to dig up the trees before they become active, and then plant them throughout the rest of the spring, summer, and fall.

Here's a photo taken years ago of a balled and burlapped tree that we are about to plant in the yard of the house behind. Our tree spade, which allows us to ball and burlap, allows us to dig up the trees before they become active, and then plant them throughout the rest of the spring, summer, and fall.

Spring in Full

With our mid-April snows, spring seemed to be put on hold. Funny what a difference a week can make. By the beginning of this week, we heard our first frogs, bird sounds were everywhere, trees and shrubs were budding. Here are a few things we found mucking about in the prairie yesterday.

Here is a Purple Coneflower poking through the duff. Chances are this one germinated last year and was covered with snow in this state. Notice the bits of Bluegrass around it that are greening up. 

Here is a Purple Coneflower poking through the duff. Chances are this one germinated last year and was covered with snow in this state. Notice the bits of Bluegrass around it that are greening up. 

Here is a Monarda plant making its way.

Here is a Monarda plant making its way.

Here's a clump of Little Bluestem we pulled up, only to see that nothing on it is turning green. It's a warm season plant and needs warmer days and nights before it will become active.

Here's a clump of Little Bluestem we pulled up, only to see that nothing on it is turning green. It's a warm season plant and needs warmer days and nights before it will become active.

The Yellow Coneflower (or Grey-Headed Coneflowers) are just beginning to germinate.

The Yellow Coneflower (or Grey-Headed Coneflowers) are just beginning to germinate.

The Red and Silver Maples are budding. This is a Freeman Maple, a cross between a Red and Silver Maple.

The Red and Silver Maples are budding. This is a Freeman Maple, a cross between a Red and Silver Maple.

Elderberry, which is a native shrub, is budding out. Notice the ice on the pond in the background. By yesterday afternoon, that ice was mostly gone. 

Elderberry, which is a native shrub, is budding out. Notice the ice on the pond in the background. By yesterday afternoon, that ice was mostly gone. 

Usually the Bur Oak buds are beginning to swell by this time. But this year, there is not much happening with this Bur Oak. 

Usually the Bur Oak buds are beginning to swell by this time. But this year, there is not much happening with this Bur Oak. 

Shaken, Not Stirred: Pin Oaks in Spring

With the temperatures getting up into the the mid 40s, things are happening. The Willow catkins are puffing out, the Poplars are preparing to pollinate, and the Sliver Maples are beginning to bud.

But with the frost still four feet deep and lakes still frozen, some plants are finishing their winter work, such as the Pin Oak.

Pin Oaks keep their leaves through the winter and then drop them in spring. If you find a Pin Oak that is exposed to the sun and shake it this weekend, it will drop it's leaves. 

This photo of a Pin Oak was taken yesterday, April 19th, just behind our greenhouse. Pictured under it is Jeff Evander, an employee.

This photo of a Pin Oak was taken yesterday, April 19th, just behind our greenhouse. Pictured under it is Jeff Evander, an employee.

As you can see, after shaking the tree, 90% of its leaves are now on the ground.

As you can see, after shaking the tree, 90% of its leaves are now on the ground.

Leaves give off a lot of moisture as they photosynthesize, and the ducts that channel the moisture are there even after the tree goes dormant in the fall. So shedding leaves is a way to conserve moisture through the winter. We see this in almost all deciduous trees, except for some species of Oaks and Beech trees. 

All of this begs the question: what possible strategy might the Oak have for keeping its leaves until spring?

Some have argued that Oaks evolved and have adapted to dryer soils, and that retaining leaves in the fall and dropping them in the spring provide the trees with organic matter (which provides fertilizer and retains moisture). Others suggest that the lower leaves on the tree act like a snow fence, trapping snow and thus providing more moisture into spring. Still others have argued that the leaves provide frost protection to the buds behind the leaves. A more popular theory is that the Oaks and Beeches are evolutionarily delayed, and are on their way to shedding leaves in the fall, but need a couple thousand more years of evolution to get there. 

So remember, you only have one or two more thousand years to shake (don't stir, as with a James Bond martini) a Pin Oak in spring and see the leaves drop. 

 

 

 

Greenhouse Geekout

After a mid-April snow storm, things in the prairie may be on hold, but the greenhouse is abuzz with activity.

One of the nice things about growing native plants in the greenhouse is that the temperatures can get below freezing in there, as they are at night even in April this year, but that doesn't bother the native grasses and wildflower plugs. For most vegetables--but not all--below freezing temps means death. 

This means that I don't have to turn on the heat and worry about keeping things above freezing, which this winter and spring would be quite expensive. The greenhouse warms up nicely during the day but gets below freezing at night.

One of the challenges of growing plants in a greenhouse in Central Minnesota is how to deal with snow. If this were a hoop house, meaning a greenhouse with just a plastic sheet cover, we would have to be running the heater so that the snow would melt and run off. Without the heat on, the snow might accumulate and collapse the roof of a hoop house.  Because this is a polycarbonate greenhouse, it can withstand a lot of snow before it would collapse, which means we don't have to run the heater. Polycarbonate is a thick plastic material, much like plexiglass, but has channels that run through it like corrugated cardboard. These channels give it strength and add insulation value.  I took this photo on Sunday, April 15, during a break in the 3-day snow storm. The temperature outside was around 32 degrees. But even though there was dense cloud cover, the temperature in the greenhouse was about 50 degrees, even without running a heater. Those temps inside the greenhouse had the effect of melting the snow that accumulated on the roof. 

One of the challenges of growing plants in a greenhouse in Central Minnesota is how to deal with snow. If this were a hoop house, meaning a greenhouse with just a plastic sheet cover, we would have to be running the heater so that the snow would melt and run off. Without the heat on, the snow might accumulate and collapse the roof of a hoop house.

Because this is a polycarbonate greenhouse, it can withstand a lot of snow before it would collapse, which means we don't have to run the heater. Polycarbonate is a thick plastic material, much like plexiglass, but has channels that run through it like corrugated cardboard. These channels give it strength and add insulation value.

I took this photo on Sunday, April 15, during a break in the 3-day snow storm. The temperature outside was around 32 degrees. But even though there was dense cloud cover, the temperature in the greenhouse was about 50 degrees, even without running a heater. Those temps inside the greenhouse had the effect of melting the snow that accumulated on the roof. 

The temperatures may get below freezing in the greenhouse at night, but they stay above freezing in the little galvanized structure you see in front of the greenhouse. That structure is where the water pump is. Pumps must not be allowed to freeze; if they do, the ice in the pump will expand and break the pump (something that's happened to more than a few of my pumps). I have a small heater in that house, which allows me to keep it from freezing, so that I can water the plugs during the day when the temps in the greenhouse can be quite high, but then close it off in the pump house so it won't freeze when the temps drop at night. 

Each one of these pots has been filled with a potting mix, and then seeded with wildflower or native grass seeds. Even though they've been watered, some for a month now, only the cool season plants are germinating.  This time of year, with the sun getting higher, the temperature in a greenhouse will get over 100 degrees. So, we must have a thermostatically controlled ventilation system that kicks in to prevent overheating. Oddly, a big challenge to managing a greenhouse is keeping it from overheating. 

Each one of these pots has been filled with a potting mix, and then seeded with wildflower or native grass seeds. Even though they've been watered, some for a month now, only the cool season plants are germinating.

This time of year, with the sun getting higher, the temperature in a greenhouse will get over 100 degrees. So, we must have a thermostatically controlled ventilation system that kicks in to prevent overheating. Oddly, a big challenge to managing a greenhouse is keeping it from overheating. 

It is worth noting that many plants (including forage crops and vegetables) fall into two categories: cool season plants or warm season plants. It is something many of us are unaware of, but it is a big deal in the plant world. Think, for example, how green the turf grasses of the average residential lawn are in October, and how beautifully the grass contrasts with the brown corn stalks we see on farm land. This is because Kentucky bluegrass is a cool season plant, and therefore thrives in the cool weather of October, but corn is a warm season plant that thrives in the heat of summer and dies after a frost. 

This flat was planted with Lupine seeds in March. Lupine is a cool season plant, which means it geminates and thrives in cooler temperatures. 

This flat was planted with Lupine seeds in March. Lupine is a cool season plant, which means it geminates and thrives in cooler temperatures. 

When it comes to weeds, it is important to know whether they are warm season or cool season plants. For example, Reed Canary grass is a big challenge to prairie restoration work. It's an aggressive non-naive grass that is hard to get rid of. But knowing that it is a cool season plant allows us to, for example, spray it in the fall (even in October) to get a good kill. Herbicides are most effective when plants are active, and are much less effective when plants are inactive. So  spraying Reed Canary grass in September and October allows the herbicide to be more effective.

 

What's not Happening

A phenology is supposed to be about what's happening and when in the natural world. In this year, when not much is happening, I thought we might dedicate this post to what's not happening. 

April 12 is, on average, the time of year when the frost comes out of the ground in Central Minnesota. That means the snow has melted and the ground is no longer frozen. Right now, depending on the type of soil you're digging in, the ground is frozen just a few inches below the surface. It could still be several weeks before the ground thaws. 

By April 12, the Pin Oaks have dropped their brown leaves that they have hung onto all winter, making way for spring's buds.

I took this photo yesterday, April 11, 2018 of a Pin Oak in our grove. By now, it would have dropped all its leaves.

I took this photo yesterday, April 11, 2018 of a Pin Oak in our grove. By now, it would have dropped all its leaves.

This is typically the time of year when tulips and dandelions are beginning to bloom. 

I took this photo in the greenhouse yesterday, April 11, 2018, which serves as a reminder of what it would look like outside. On an average year, dandelions would be beginning to bloom about now, reaching full bloom in the third week of April. 

I took this photo in the greenhouse yesterday, April 11, 2018, which serves as a reminder of what it would look like outside. On an average year, dandelions would be beginning to bloom about now, reaching full bloom in the third week of April. 

Our farm has wetlands on two sides, making for very good frog habitat. Perhaps my favorite marker of spring is the croaking of the Western Chorus frogs, which begin croaking, on average, about now. No sounds from the frogs yet. 

 

Taken from https://www.pca.state.mn.us/living-green/frogs-minnesota  Minnesota's DNR has recordings of the various frog sounds at the above link on their website. It is well worth a listen. 

Taken from https://www.pca.state.mn.us/living-green/frogs-minnesota

Minnesota's DNR has recordings of the various frog sounds at the above link on their website. It is well worth a listen. 

Silver Linings and Silver Maples

One sometimes hears the quote from T.S. Eliot, "April is the cruelest month...." By this a Minnesotan would think he is describing how April disappoints our expectation of spring. But the rest of the quote goes "...breeding lilacs out of the dead land, mixing memory and desire, stirring dull roots with spring rain."

I have to say, if "stirring dull roots with spring rain" qualifies for cruelty, then T.S. Eliot has not experienced April snow storms like the ones we are having this year.  

But there is a silver lining to all this, and that is the Silver Maple tree, the first deciduous tree in our parts to bud. Ours here on the farm have been budding since before Easter, but I only got to photographing them yesterday, April 4.

I wish I could have photographed this Silver Maple with all the snow around it, but I had to look pretty much straight up to capture the buds on this tree on the edge of St. Joseph.

I wish I could have photographed this Silver Maple with all the snow around it, but I had to look pretty much straight up to capture the buds on this tree on the edge of St. Joseph.

Sorry to say, for those who know trees, the Silver Maple is not desirable for landscape use. It generates large, shallow roots, making it difficult to mow around, and it puts out many seeds. Due to poor pruning or lack of pruning, one sees many Silver Maples that are deformed in such a way that their limbs will come off in a high wind. They have been overused in residential developments due to their fast growth. And they get very large, making it all the more important that they be pruned to have structural strength, or removed before they get too big to easily remove. Their hybridized half-sister or brother, the Autumn Blaze Maple, is a cross between a Silver Maple and a Red Maple, and continues to be a very popular choice of tree for residential landscapes. 

Silver Maples are at their best in their natural habitat--along the banks of creeks and rivers where their shallow roots allow them to survive in wet conditions. In a way, they are our version of the Mangrove tree, doing well in the wettest of conditions.

Courtesy of  Illinois WildFlowers       

Courtesy of Illinois WildFlowers

 

 

Pasque Flower: First Native Wildflowers to Bud

The first wildflowers to bud around here every spring is the Pasque Flower. "Pasque" is French for Easter. "Pasque" in English translates more as "paschal", as in "paschal mystery," meaning the suffering, death, and resurrection" of Christ. It seems to me a very apt name for a very liturgically-minded plant.  

Pasque flowers make good companions with Tulips, which you see in this photo, taken March 20 in St. Joseph. The Tulips are the maroon-colored plants, and the Pasque Flower is the white, fuzzy plant to the back right. Pasque flower is one of the first flowers to bloom in the spring, often coming up while there is still snow on the ground. Look for it on south facing slopes in dry to average sandy soil, typically in scattered clumps. 

Pasque flowers make good companions with Tulips, which you see in this photo, taken March 20 in St. Joseph. The Tulips are the maroon-colored plants, and the Pasque Flower is the white, fuzzy plant to the back right. Pasque flower is one of the first flowers to bloom in the spring, often coming up while there is still snow on the ground. Look for it on south facing slopes in dry to average sandy soil, typically in scattered clumps. 

Pasque flowers are an invaluable source of early season nectar for honey and native bees.

Pasque flower is a very delicate, leaning when the wind blows. 

Pasque flower is a very delicate, leaning when the wind blows. 

pulsatilla-nuttalliana late spring.jpg

Although a native, it struggles to self seed. It is more common to see them in cultivated landscapes as garden plants. They make a for a wonderful plant as nothing flowers sooner than the Pasque flower. They are in Minnesota and throughout much of North America. We start them as plugs in our green house, and then transplant them into landscapes later in the season. As plugs, they seem to do well. 

Willows and Aspen are Budding

Winter this year has been colder and longer than average. We still have a fair bit of snow here in St. Joseph, though there is less to the east and west of us. Nevertheless, a quick walk through the wetlands Friday (March 17) and this Monday (March 19) show that things are happening. 

One of the first signs of spring among plant life around here is that of the American Pussy Willow (Salix discolor). It is native to North America and is found in the wetlands of Minnesota and throughout the eastern half of the continent. There is also the Western Pussy Willow which, as the name suggests, dwells to the west of us. The ones on our property are just beginning to bud. 

 

I took this photo of a Pussy Willow on March 19th, 2018, on our property in Central Minnesota   

I took this photo of a Pussy Willow on March 19th, 2018, on our property in Central Minnesota

 

This grayish fur resembles a cat or kitten, and so the bud is called a "catkin."  This flower bud will eventually flower and pollinate the females. 

 

Male catkin of Pussy Willow getting ready to pollinate. Photo from Chestnut School of Herbal Medicine

Male catkin of Pussy Willow getting ready to pollinate. Photo from Chestnut School of Herbal Medicine

Though not a "stand out" plant in the landscape, Pussy Willows are very important in terms of their medicinal value. Their active ingredient is salicin, named after the Latin for willow, Salix. The making of the powder, Salix, eventually led to the manufacture of acetyl salicylic acid, better known as aspirin. It stands to reason that the common, and often overlooked, Pussy Willow was the source of this most common, and perhaps overlooked, of medicines--aspirin! 

Another sign of spring is the bud of the Quaking Aspen, the first of the larger trees to come out of dormancy in our parts.  

 

This photo of the buds of a Quaking Aspen was taken in St. Joseph, Central Minnesota, on March 17, 2018

This photo of the buds of a Quaking Aspen was taken in St. Joseph, Central Minnesota, on March 17, 2018

The Quaking Aspen also produce catkins, which flower before its leaves bud. We see this on other plants in the Populus family (which is a subset of the genus willow), such as poplars, birch, and cottonwood. They are funny things to see in spring. I think of them as garland on a Christmas tree, drooping from the trees for my amusement. 

The catkin of a Cottonwood, though this is what they look like on the Poplars and Quaking Aspens as well. Photo from Austinbotany.wordpress.com

The catkin of a Cottonwood, though this is what they look like on the Poplars and Quaking Aspens as well. Photo from Austinbotany.wordpress.com

The only thing is that it's not Christmas and they don't come from Christmas trees. And, while we're at it, they're also not for my amusement. These catkins form the staminate of the male aspen and, like the Pussy Willow, pollinate the females in spring. 

It's only the middle of March and I'm already overwhelmed by all that's going on in nature around here!

The Problem with Buckthorn

Some of us own homes in woodlands, and do so for the privacy and to enjoyment they give us. When you point out to people that much of what they see is Buckthorn, they might say that Buckthorn is part of nature too. Why not enjoy it as one plant among others? The answer is because it is invasive.

All plants come from particular biomes or ecosystems which make up a network of plants, insects, micro-organism, and animals that keep each other in check. 

Buckthorn's signature is its scaly bark, thorns, and shiny leaves. It was introduced by Europeans who used it for hedges. 

Buckthorn's signature is its scaly bark, thorns, and shiny leaves. It was introduced by Europeans who used it for hedges. 

Invasive plants and animals are species that have been taken out of their network of plants and are in a context in which there are no constraints. Whether its the wild boars of Texas, or the kudzu of Arkansas, or the zebra muscles in the lakes of Minnesota, these animals, plants, and mollusks are invasive because they have no predators to keep them in their place. 

Nature tends toward diversity. Biomes often see an expansion of species as species evolve to maximize niches in an environment. This tendency toward proliferation of species, and how they work together to form an ecosystem is, in great part, what makes nature interesting, as well as what makes it work. Invasive species throw a wrench in this project of plant diversity by dominating and replacing them.

The three Bur Oaks of our wetland

The three Bur Oaks of our wetland

These three oaks in our wetland are remnants of an Oak Savanna biome. A closer look under and behind these oaks shows the results of thirty years of unchecked Buckthorn growth. The Buckthorn thicket under these trees is so dense that neither deer nor humans can traverse it. The Buckthorn has the ability to inhibit the growth of other species, including the Bur Oaks, so much so that little else grows in this area. When the Bur Oaks die, there will remain a Buckthorn canopy that reaches a final height of about 25 feet. 

If nothing is done, there will be a dramatic reduction in diversity. In effect, the Oak Savanna biome will be undone. So, we here on the farm continue to pick away at removing Buckthorn.

This is a photo I took of Jeff, an employee, who cuts Buckthorn with a brush cutter and then sprays the stump with an herbicide right after cutting. If the stump is not sprayed, the plant will eventually come back with a vengeance. 

This is a photo I took of Jeff, an employee, who cuts Buckthorn with a brush cutter and then sprays the stump with an herbicide right after cutting. If the stump is not sprayed, the plant will eventually come back with a vengeance. 

Another challenge is that after it has been removed, Buckthorn often comes back. Mature Buckthorn plants put out a lot of seed in berries, which birds eat and spread through their droppings. This seed can remain viable in the soil for up to five years. 

Buckthorn berries are attractive to certain birds, which eat and spread the plant. The berry producing plants are the ones we go after first. 

Buckthorn berries are attractive to certain birds, which eat and spread the plant. The berry producing plants are the ones we go after first. 

This is why removing Buckthorn should be part of a restoration program--a plan to restore the woodland with native plants and through prescribed burns, a program we will save for another post.