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Category Archives: Plants
In part 3 of our “Gardening through the Decades” series, we look at the Roaring Twenties. A time period known for its glittering excess and the start of the gangster era, this was a period of transition for Alcatraz. Alcatraz the Military Prison was ending, but there were still families on Alcatraz, and they were determined to make their gardens beautiful.
From the blues and purples of the Victorian Era, to the pinks of the 1900s and 1910s, these gardens were all about colorful flowers. This changed in the 1920s as the reigning trend became all about the green. There were still flowers, but the lawns became a fixture for many homeowners.
Likewise, they also had a desire to celebrate and welcome nature. Unlike the Victorians, however, their gardens weren’t allowed to grow wild. Instead, they started attracting wildlife. Bird houses, bird baths, fish ponds, and rock gardens were all the rage for the 1920s gardener. They also planted trees and bushes with bird attracting berries, such as holly and crabapples, in hopes of being a paradise for bird watchers.
The 1920s also marked a shift in landscaping focus. Before, backyard gardens were all the rage. It was a private space for entertaining and for showing off your beautiful collections of flowers. However, with more and more people owning homes in the suburbs, the front yard as a public space became the focal point. You couldn’t have your neighbors walk by and see your front lawn in a deplorable state. So, this space received the most attention with gardening and landscaping. Walkways and driveways were lined with perennials, such as irises, foxgloves, hollyhocks, California poppies, and bachelor’s buttons. Shrubs such as boxwood and holly provided the natural, bird attracting green that was so popular. And the lack of fences reinforced the idea that the front yard was public, and not private.
Alcatraz follows many of these trends. While most families lived in the apartment building, meaning no front yards, houses on the parade ground did have front yards. We also have many of the hallmarks associated with the 1920a.boxwood in Officers’s Row and along the Sally port provide some subtle barriers between walkways and garden space. Likewise, one can see California poppies dotting every garden on Alcatraz.
What is perhaps the most striking feature that relates to the 1920s garden aesthetic is the birdbath in the birdbath garden on the west side. The birdbath was originally designed by inmate Elliot Michener. It was sadly destroyed when the gardens were no longer cared for. Thanks to our handy and multi-talented volunteers, we were able to reconstruct the birdbath that is a pleasant surprise in the Bird Bath Garden. Thanks to our work in the gardens, we have many birds for the bird watchers among us. From the snowy egrets to the variety of songbirds, Alcatraz does attract wildlife.
The Roaring Twenties peaks through in many areas of the Alcatraz gardens. Look around the next time you’re out there and see if you can spot any of the historical elements.
The second in this “Historic Gardening Trends” series, we are now moving out of the 1800s and into the 1900s. The 1900s through the 1910s had their own gardening trends; building from what was popular during the Victorian era but rejecting and changing what new gardeners did not like about the style. Alcatraz itself was going through a change. The Civil War had brought a rapid amount of development and change in the structures, trickling down to the gardens. The construction of the main concrete cell block began in 1909 and, once again, the wives of the soldiers sought a way to bring life and civilization to the Rock via gardens.
By the end of the 19th century and the beginning of the 20th century, there was a trend to return to formal gardening. There was no longer a desire to have a “garden growing wild” aesthetic. The plants were often carefully pruned and nurtured to be contained. Furthermore, there was more of an effort to use architecture in gardening. With building projects being wider-spread, people sought to show off their house and its features, using the garden to direct the eye. Similarly, using concrete terraces, paths, and steps provided a bit more structure and more of an architectural feel. The Victorian tradition of using gardens as an outside room continued and would continue to be a hallmark of modern gardening practices. Gardens were places to gather with family and friends, not just a place to grow food. Water was another major feature in the early 1900s gardens. Fountains, pods, and waterfalls were popular.
The plants themselves were almost an afterthought to the garden. Gardeners used geometric lines and an enclosed feeling to make the outside feel more like the inside. Furthermore, the Victorian fascination with wild, sprawling exotics was replaced with neat, boxed hedged beds. The actual flowers and shrubs were kept off verdant laws and bowling greens. It was no use having people over to your garden if they could not walk around without stepping on flowers.
Inside these neat and tidy beds were a variety of peonies, irises, lavender, erigeron, and foxgloves. The colors were muted but more diverse than the Victorian era’s use of mainly greens, pinks, and purples. Roses were common as well. However, instead of ramblers and creepers allowed to sprawl and climb, they were contained into neat, round bushes.
The modern gardens of Alcatraz have these early 1900s touches hidden throughout. The water features are easy to spot since this is an island and the ocean serves that purpose nicely. The foxgloves can be found most commonly in the Rose Garden. While there are creepers and ramblers all over, other rose bushes, such as those in Foundation 8 of Officers’ Row, are kept rounded and contained. Lavender can be spotted peaking through in Foundation 9. The Toolshed Terraces gardens bring forth a more architectural element to these gardens, a subtle call back to the terraces commonly used during this time period.
What is perhaps most in line with the gardening style of the early 1900s is the fact that the gardens serve as a backdrop to the architecture, the prison. Instead of the garden being a separate entity, it is tied to, and often overshadowed by, the main cellhouse. The beds along the pathway are contained and wind around following the road; they are not allowed to grow wild and eclipse the cell house. As gardeners, we sometimes forget people come to Alcatraz not for the gardens, but for the prison. In the 1900s, the gardens were also there as a second thought; meant to enhance life and beauty on the island. It moves away from the “natural” and into the backdrop. These gardens have their own beauty and serve another purpose. But the combination of styles from such a long period of time is what allows the Gardens of Alcatraz to be diverse and beautiful, to represent a time and provide a look back as to what life would have been like for the families living on the island, and not just the prisoners and guards.
One of the most beautiful groups of flowers we have on Alcatraz is the iris. They have been a common staple in gardens for centuries. It is worth taking a moment to look at the long history of these flowers and when they became common garden staples in America.
Irises first grew to prominence as a garden flower in 1469 BCE. The Egyptian pharaoh King Thutmose III conquered Syria, where irises grew. An avid gardener, he brought them back to Egypt to be cultivated. This was the first-time irises had been documented as a gardening flower. From there, irises rose to prominence for their religious significance. They were carved into sculptures at temples and doctors used the rhizomes for medicine and perfume offerings.
As irises began to spread in the popularity, due to their showy flowers and lovely scents, the Greeks were the first to name them “iris”. Iris means rainbow and is the Greek messenger of the gods. Indeed, irises come in an array of colors, from deep purples to brilliant oranges. They continued to spread around Europe, becoming a staple in gardens from Spain to parts of Asia. Indians began to use their rhizomes for religious offerings. In Florence, Italy, the scent became a popular perfume. The iris inspired the design for the Fleur-de-lis. It is a common motif in France, past French Colonies, and with the Catholic Church, usually relating the Virgin Mary.
The first documented iris in America was in 1600s Virginia. From there, irises would continue to hybridize, speciate, and transform into unique American varieties. It wasn’t until Michael Foster (1836-1907) studied and planted these beautiful flowers, that irises were made popular. One of his students, William R. Dykes (1877-1925) took an interest in irises and published a book called “The Genus Iris”. It was this study of irises that brought the flower to the popular conscious. In the early 1900s, there was a rise of irises in American gardens. It became so popular, Tennessee adopted it as the state flower. The most popular iris today is the German or Bearded Iris, an iris we have on Alcatraz. However, most irises have hybridized so much that there are 300 species, and these species are difficult to separate into a clean taxonomy.
The hybridization provides another unique focal point for Alcatraz’s irises. If you smell a modern iris, it doesn’t smell like much. On Alcatraz, the irises have a stronger scent. Different Alcatraz irises smell like root beer, vanilla, and grandma’s perfume (according to
some visitors). We have pastel purple, deep purple, white, orange and yellow Irises scattered about the Rose Garden and Officers’ Row. We use heirloom plants, which means our irises still have the genetic markers to make scent. Our use of heirloom plants provides an extra touch of historical intrigue to visitors who know their flowers.
As a flower, irises inspire the creative and bring delight to the floral enthusiast. They provide intriguing patterns and interesting shapes. They are unique and vibrant against the backdrop of stone and concrete. They are a flower with a long history, and it’s not hard to see why they’ve been a garden staple for thousands of years.
Alcatraz’s gardens were restored with the intention of being a reflection on gardening trends found from the 1830s to the 1960s. But what trends came in and out of fashion during this period? After all, much like clothing, gardening has styles, trend-setters, and certain characteristics that allows gardening historians to identify what was popular at the time.
The Victorian Era, named after Queen Victoria, was a period that ran from 1837 to 1901. This was one of the first times authorities made an effort to provide public gardens in England. The reasoning being the gardens would improve the manners of the lower class. The wives of soldiers on Alcatraz had a similar desire. They wanted to bring a sense of civilization and order to “The Rock”. There was also a need to ease boredom. With little to do while on Alcatraz and with the new soil and sand, they could begin to garden.
The Victorian Garden has three major characteristics: furniture, statues, and plants. The furniture used in Victorian gardens included benches, canopies, and pavilions. The purpose was to make the gardens feel more like a salon. It was a place to entertain and enjoy nature as well as show off to your neighbors how well you were doing. Statues were also used in Victorian gardens. They were mostly Greek Gods and semi-nude females. It was an attempt to invoke the classicism and culture of Ancient Greece.
The plants were where Victorian gardens started to become unique. Shades of pink, purple, and green were the most common colors. There were also many different types of plants in each garden. Thanks to globalization and imperialism, gardeners had access to more rare and exotic plants than ever. Orchids, tulips, roses, and daisies were all regulars in Victorian gardens. The rarer the plant, the more wealth you had. Another interesting style choice was the various ways these gardens were planted. There were showy, geometrically placed flowers (squares being the most popular shape, followed by triangles). Yet, there was also a call to have “wild” gardens. Creepers, ramblers, hardy shrubs and herbaceous plants emphasized the natural look. Pebbles marked the pathways and they used rocks invoked the image of wild and far off mountains.
On Alcatraz, the Rose Garden is where these Victorian trends are the strongest. The various roses are allowed to creep and ramble over concrete railings and walls. Come at the right time and you’ll see rows of various types of blue bells in both Officers’ Row and the Rose Garden. In Officers’ Row, there is a hidden cache of lavender, showing off muted greens and purples. Luckily, we don’t have to import rocks to get a “rocky” feel throughout the gardens. Alcatraz’s natural terrain already provides us with outcrops of rocks. We even kept the tradition of having rare and exotic plants in our gardens. One of the more famous examples is the Bardou Job Rose, a rose that is so rare it was thought to be extinct until it was found growing on Alcatraz in 1989.
The Victorian Garden is one of contradictions. It is a call back to the wild, but it is characterized by geometric designs and exotic plants. It is an attempt to bring civilization and good manners to the lower classes, but it is also a sign of wealth. On Alcatraz, we try to capture the complexity and beauty in our gardens. And as the climbing roses make their way up the rocky outcrops and bloom, we capture a moment in gardening history.
It seems every day there are stories about pollinators. There are news stories detailing their decline. There are new “Bee Hotels” designed to attract solitary bees. There are websites dedicated to creating a list of plants to attract pollinators. As gardeners, we know pollinators well. Almost any plant that has a showy flower is likely to attract pollinators. Yet, pollinators are not limited to bees and butterflies. They also include ants, male mosquitos, beetles, flies, wasps, birds, and even some mammals and reptiles. Each pollinator has a job within an ecosystem and each plant has a pollinator it is designed to attract.
Preparations for planting at Black Point Historic Gardens are underway. There is a unique opportunity for us to use Alcatraz Gardens and what we learned to make Black Point more successful. Volunteers cleared away the overgrowth and replanted flowering plants. This gave rise to a noticeable increase in bees, flies, butterflies, and birds.
We know now there are at least ten species of bees in the gardens of Alcatraz, some of them native. However, no study was completed to create a baseline estimate for species diversity before restoration work began. We know the number of pollinator species before the military’s use of the island in the 1800s was likely zero since Alcatraz was a rock with no native vegetation. The wives of soldiers established gardens. These beautiful blooms provide food and habitat for the pollinators. A baseline would have helped us know if our efforts were beneficial and guide us to future planting plans.
As historical gardeners, we have a duty to present Alcatraz and Black Point as they would have been. Heirloom plants are used to represent a specific time frame. Even where we plant certain plants is dictated by historic photographs. As a result, the ideal gardens of the late 1800s through the 1960s guide us; and in those time periods, native pollinator gardens were not in fashion. As we design the plantings at Black Point, we wish to include plants that will help native pollinators but still have the look and feel of a Victorian strolling garden.
Studies have shown planting native plants and increasing the diversity of blooms will help native pollinators. So, we have begun to start observing pollinator species diversity and population numbers. Does the garden, previously overrun with ivy, blackberries, and oxalis, function as a pollinator garden? Does the presence of native California flowering plants help increase the amount of diversity? Do the pollinator population levels increase as more flowering plants and space are made available?
These are questions we want to answer. We can only learn from the past and use Alcatraz as a guiding force for Black Point.
Written by Josefina Pacheco
Before volunteering at Alcatraz, I worked at a summer camp in Maine that emphasized teaching ecology and sustainability to elementary and middle school aged students. After ten weeks of running around in the sun and eating lobster every Thursday I found myself asking the question that many college students find themselves asking after graduation, “So, now what?”. I began searching for jobs in the Bay Area and soon discovered that I needed more experience. A friend of mine suggested to look for an internship using volunteer.org; this is where I found the post about volunteering on Alcatraz. I thought to myself I could help with gardening (one of my favorite activities), volunteer (this means experience), and look for jobs at the same time. It seemed like a win-win situation.
I contacted Shelagh about volunteering in September 2016. In early October, I was given the unique opportunity to apply for the intern position at Alcatraz. After a cover letter, resume, and interview I became Alcatraz’s newest intern. As an intern I now get to go on the ferry five days of the week (yay!). Twice a week I work with the volunteers which usually starts off with answering the question “So, what are we doing today?”. I then quickly take attendance and work alongside the volunteers for the day’s project for the remainder of the morning. On the other days of the week, I work one-on-one with Shelagh. The day’s schedule varies day by day but some of the more notable ‘behind the scenes’ projects include: learning to prune roses, learning to transfer seedlings to planting pots, propagating succulents, assist with leading volunteer groups, and taking pictures of the watercolor paintings from the Alcatraz Florilegium next to the actual flowers from Alcatraz. Additionally as an intern, I’m learning in greater depth about gardening and plant maintenance in general, along with gardening specifically on Alcatraz and its history.
What many people don’t know is that as an intern one gets a stipend and housing at (one of the most breathtaking places) the Marin Headlands. At the Headlands, other interns from other parts of the Park live there as well. To help meet even more interns, specifically those in the Presidio, there are monthly intern swaps. At a swap, interns get to go to another park site and volunteer there for a day (so far I’ve only participated in the Milagra Ridge intern swap where I planted native grasses). To further enhance your knowledge there are Park Academy Classes held a couple times a month. The topics range from botany to fire management to leadership training. Being able to meet new people, volunteer at different parks, and learn more about whatever topic you want to learn more about makes this an incredible experience.
At first I was a little nervous about the transition from volunteer to intern but everyone (staff and volunteers) have been really helpful and supportive, so thank you and I’m looking forward to seeing the gardens through the seasons!
Alcatraz these days is a bustling place of projects. The big project of repairing the west side wall of the cellblock is very apparent but visitors can’t see the work being done as the scaffolding is wrapped in white plastic.
The other significant project that was just completed at the end of December was in full sight of visitors and left a dramatic difference to the island. The Eucalyptus grove at the south end of the island (just off the dock), was removed. The project had been two years in the planning and finally had enough urgency and funding to make it possible. The trees, originally planted by the military in the early 1920s, had reached maturity and were a safety risk of falling.
Marin County Arborists were trusted with the tree removal. The company had previously worked on tree removals on the island and was familiar with barging equipment over and working around visitors.
Sixteen blue gum eucalyptus trees and two non-historic Monterey cypress trees were removed and chipped over three weeks.
The chips were hauled to the Parade Ground to be stored until the National Park Service’s archeologist had a chance to examine the bare slope for evidence of military construction. We received the ‘all clear’ within a day of the trees being removed and we set to work!
First, chips from 18 trees is a heck of a lot more than I could envision! The recommendation from consulting arborist was to put the chips back on the slope to a depth of 4”, place jute netting over top and anchor wattles horizontally across the slope to stabilize the slope. The slope had been eroding badly for years, so this would be the perfect opportunity to stop the erosion.
Volunteer groups were enlisted to manually place the chips on the slope. With bucket brigades and teamwork, the slope was covered over a month. The Golden Gate National Parks Conservancy’s Stewardship Team (of which the Alcatraz Gardens is a division within the company’s organization) were set to take a day off from their normal sites and lend a hand. To sweeten the deal, an overnight was planned (and what better way to say thank you than a night in solitary?).
The effort was a huge success with people filling
buckets, people carrying the full buckets to the bottom of the slope, to the chain of people to send the full buckets up the slope, and empty bucket retrievers! Maria Durana captured the well-oiled machine of the bucket brigade:
Once the chips were in place, the jute netting could be placed on top. The rolls were heavy and we soon figured that cutting them first was best.
Aside from the Stewardship Team, four corporate groups and the regular drop-in garden volunteers pitched in to help spread the mulch. In total 900 yards of jute netting was placed and 750′ of wattles were installed.
The slope will be replanted with Eucalyptus cinerea ‘Pendula’ in September 2017 in keeping with the historic look of the island.
On another note of discovery, the perimeter wall of the Parade ground was further revealed along with the basement of one of the former cottages. And a new fern was found growing! With more years of planning to come, hopefully this neglected garden are will be the next focus of garden preservation.
The island’s first purpose as a military prison introduced the construction of the Sally port and this is where all visitors first walk by today on their way up to the cell house. Before entering the Sally port, they are greeted with the island’s first garden and home to some survivor plants thought to be planted in the 1920s. Among this bed are two historic Cordyline that are very old and are showing signs of decline. The Cordyline australis planted in the Sally port gardens is an old variety and have been very hard to find in the nursery trade. The Cultural Landscape report suggests that these be replaced, but not until we have the same plant with the same genetic makeup of the replacements.
In efforts to replace these declining historic Cordyline, we have tried several propagation methods to ensure they remain as part of the gardens for years to come. All of the methods were done in mid-March and we recently have had some promising results. Below are detailed descriptions of the propagation techniques trialed.
Methods of Propagation
We first tried just a cutting of one of the canes and potted it up in a pot of our compost. We removed some of the foliage and trimmed some of the fronds back to reduce that amount of energy going into the foliage and instead put it into the formation of roots. At first, it seemed as though this method might work, but after about a month, the fronds were almost all dead. The cane itself had become soft and the inside had become rotten. I think this method would work using a thinner cane or a smaller one with less foliage.
For this method, we took three pieces of cane, about 6 inches long each and laid them horizontally, half way deep, in a tray of sphagnum peat moss mixed with our compost. I had thought this method would work best, and we actually did have roots start to form alongside the canes, but I think they ended up getting over watered and the canes started to rot. Unfortunately, all three were unsuccessful. I think if we were to try this method again, we would use a different media composition and not allow the soil to get too wet.
The air layering method turned out to be the most successful of the three that we tried. This method is actually done on the mother plant itself. We started by soaking sphagnum peat moss for a few hours. This is crucial to keep the stem moisturized to allow roots to form. On one of the canes, we cut an inch wide ring through the cambium layer and removed the bark around the cane. Next, we took the soaked peat moss and wrapped it around the cut tightly and then wrapped it with plastic wrap and tied string around it to hold it in place. We did this twice more on separate canes. We recently cut the three successful air layered canes from the mother plant because roots had formed and they were ready to be potted up. We first soaked them before potting them to allow the peat moss to rehydrate. We put the new plants in five gallon containers and they are happily living in our greenhouse until they reach a more mature state with more developed roots to replace the ones at the Sally port.
The air layering method can be used for other woody shrubs and works well for some trees. This method does take a while to see some roots form, but once they do and it is cut from the mother plant, you already have a bigger plant than you would if you propagated it by seed or a cutting.
To replace the survivors, it is important that they are replanted with the same species of the current Cordyline. By propagating them by the methods we tried, it ensures that the replacements have the same genetic makeup of the current plants. We are very excited to have successful clones to replace the current failing Cordyline.
The gardens were fortunate this summer to have two youth interns through the Parks Conservancy youth program. As they wrap up their 140 hours working in the gardens, there was still another skill they needed to know – how to select plants from a nursery.
We headed down to Pacific Nurseries, a wholesale nursery in Colma to do our shopping. Our mission was to find plants that would fill in areas on the windy west side of the island in the Prisoner Gardens. Sections of this garden are always struggling to cope with the extremes of heat and fog, wind and the curiosity of gulls, even after the gardens were restored in 2009, they still aren’t quite right.
Upon pulling into the parking area, my eyes always light up with seeing the plants laid out in groupings of perennials, shrubs, roses, succulents, annuals and shade lovers. Sometimes, I place an order and can go and have everything ready, but often, I just see what is available and chose from the vast selection.
For the Prisoner gardens we were on the hunt for perennials, mostly Salvias as the ones we already have are thriving.
We started with 1 gallon pots of Salvia clevelandii. The first thing to notice was the health of the leaves and checking that the stems are not broken. Salvia clevelandii tends to be brittle anyway so extra care needs to be taken while handling them.
Turning the pots around, it’s is essential that we are not taking any hitchhikers to Alcatraz – namely snails and slugs and weeds.
Explaining what a ‘root bound’ plant
looks like is a lot easier when standing in a nursery. While Pacific Nurseries have excellent plants to choose from, sometimes roots get circling the inside of their container and can even root into the ground through the drainage holes. Plants like this tend not to adapt well once wrestled out of their stricken home and in bad cases, there may be hardly any soil left in the pot, leaving the plant suffering from drought as well.
With plants we choose, we have to go through quite an effort to haul them to the boat to get them to the island. Checking that the plants are well watered helps the plants with the trip. The interns could feel the weight difference in pots that were dry versus heavier pots that were well watered. Of course, the growing median makes a difference too (but we’ll save this lesson for another day).
We soon had our carts full and packed the van!
While we checked out with our purchases, the interns had 15 minutes to run around and look at all the types of plants. I’m sure their Instagram accounts are full of selfies with the plants. Pulling off the freeway to come back along the Embarcadero, the van was noticeably quieter – a look into the back showed both interns had fallen asleep. Definitely a sign of a great shopping day!
The term ‘invasive’ is often misused to label plants or anything that is intrusive in the natural environment. It is something I have only recently began to question. What actually validates a plant being invasive? (I’m going to stick to just talking about plants… I am a gardener after all!) My experience with talking to the public when removing invasive or unwanted plants has been pretty limited, but this past week as I was weeding the lawn, a guest on the island asked me, “Are you weeding invasive grasses?” Without really thinking about the question, I said, “Yeah.” The grasses we were removing from the lawn were crabgrass, annual bluegrass, and rattail six weeks grass. After he walked away I was left thinking, “Are those really considered ‘invasive’?” This led me to a bit of research in pursuit of an answer…
Plants that are invasive are actually scientifically categorized as so. It seems like scientists also have trouble labeling whether or not a plant is invasive or how plants can eventually become invasive over a long period of time. Plants that aren’t native to an area aren’t considered to be an invasive species until they have a negative impact in disrupting a native area. The displacement of native species and the ability for a non-native to cause economic and human harm are the two attributes for a plant becoming an invasive species. The Environmental Detection Distribution and Mapping System (EDDMS) have a simple list of characteristics showing the differences between an invasive and an ornamental plant:
The three grasses we were removing from the lawn are actually not on the invasive list for California. They are weeds, unwanted in our native sedge lawn, but aren’t labeled as invasive. Plants can however become invasive over a period of time. Because of this, it’s important to monitor non-natives and their growth in native areas.
This graph is a good representation of how plants begin to become a threat to natives and the actions that should take place to keep it under control.
During the lag phase and early recognition is when it is less costly and easier to eradicate. To prevent plants from reaching levels of higher efforts to control, it is crucial to catch them and be aware of the plant’s potential threat to a native area.
So, with all that being said, let’s see if we can clear up some misunderstanding on a few plants that call Alcatraz home. I think my favorite example, is the Echium candicans or commonly known as Pride of Madeira. It is a plant native to the island of Madeira, but has been introduced to the coast of California and thrives very well here. Many think that this plant is invasive because it is found among the hillsides and coastal bluffs mixed with native plants. Although it does spread fairly easily, it has shown no threat to native plants and is listed on the California Invasive Plant Council, (Cal-IPC), as a limited threat. It is a well admired plant on the island and copes well with the high winds and little rainfall. It is an island survivor plant that has naturalized itself and is a great pollinator for bees.
On the other hand, English ivy, (Hedera canariensis), is a plant that is considered to be a high threat on the Cal- IPC list. It is found all over the island and was one of the more prevalent plants contributing to the overgrowth in the gardens and is still a plant that we are consistently working on cutting back to keep it at bay from the garden beds. In other overgrown areas though, the ivy plays a vital role during water bird nesting season. They use the ivy overgrowth as a nesting site to lay their eggs and raise their young. Himalayan blackberry (Rubus armeniacus), is another plant found on the island that is listed as a high threat and we eradicate it from the garden beds, but leave it be in overgrowth areas because the birds also use it for nesting.
Jupiter’s beard (Centranthus ruber), and Mimosa tree (Albizia distachya), are examples of plants on the island that are commonly mistaken as invasive. They both are island survivors and spread fairly easily, but neither is listed on Cal-IPC as invasive. We like to use the term ‘aggressive’ and we monitor them and remove any unwanted seedlings. The mimosa tree is a nesting site for Anna’s hummingbirds and Jupiter’s beard adds a seasonal burst of color throughout the gardens.
I hope this clears up some confusion about what invasive actually signifies. Just because a plant isn’t native doesn’t make it invasive. The invasive plants on the island are kept in check and tell the story of the islands past gardeners. For today’s gardeners, you should check local plant lists for invasive species before purchasing.