Archive for Tree Selection

Controlling Erosion on Hillsides – A Portland Landscape Designer’s Perspective

Preventing erosion

My vacation home is above a steep slope. It’s smart to learn about preventing erosion

Controlling Erosion on Hillsides

As a Portland landscape designer I often work with hillside properties.

I also own a vacation home on Harstine Island in Mason County, Washington. We built our house about 10 years ago. The house is 30 feet from a steep hill overlooking the beach. The things I’ve learned about controlling erosion are useful to anyone who has a sloped property.

When we built the house we made some smart choices, we went with a natural landscape instead of lawn, ran our water from downspouts down the hill in pipes rather than spilling it out at the top of the hill.  Nor did we disconnect our downspouts to let water pool and perc down into the soil near the house.  That can be a fine practice for flat properties but not hilly ones.

I have a majestic fir tree on my slope and neighbors have suggested I cut it down for fear that it will remove a lot of my bank someday when it fails.  I want to support this tree for as long as possible so I was inspired to make an appointment with Karin Strelioff with Mason County Conservation District.  Karin is a technician with their Marine Waterfront Assistance Program.  She knows about the slopes and cliffs that make the shoreline of the South Puget Sound and many methods of erosion control.  She gave me some important signs to watch for regarding my tree and the name of a local arborist who is astute in the science of trees on slopes.

Well planted slope controls erosion

My slope is well planted with salal, sword fern and other erosion controlling native plants.

My Tree    

Karin gave me these basic things to watch for with regards to my beautiful huge fir tree.

Pay attention to the surface soil and the plantings around the trees trunk. Know what the ground and general area looks like typically and watch for any changes in that area.  On the uphill side of my tree trunk I’ll look for an area of disturbance, an area of soil higher than it was when I saw it last.  This could mean my trees roots are pushing toward the surface.  On the downhill side of my trunk I will be looking for soil that may have fallen away making a new steeper area.  Either one of these disturbances will have me on the phone to an experienced certified arborist that I trust.  I love knowing what to look for.  It will help me with my anxiety when the wind blows and my tree’s branches whistle like a Hitchcock movie sound track.

I recognize that my tree is supposed to fail at some point, falling down the hill along with a portion of my slope to bring more sand to the beach and add to the natural beachhead.  Given that I would like to keep every square inch of my backyard, when the tree is starting to fail, the arborist will probably recommend it be removed.  Hopefully by that time I will have enough plant material well established to offset its loss to my erosion control plantings.

Erosion Prevention

Blackberry Fruit

How can anything so sweet, be so evil?

I learned important things about my property.  For one thing my various slopes and banks have either a lot of trees or ground covering plants or both so I can take the information from Karin and apply it as a preventative rather than having to rush into a mitigation process. We also have very few invasive plants on the property. I have one Himalayan blackberry plant that we will work on getting rid of.  Lucky me.

Karin says the most important thing that I can do is to learn about the water load on my property and how best to control where it goes.  The biggest water load source is water from the roof of the house.  The county had good rules in place when we built the house so we are also ahead here.  We took our water down the hill in pipes.  The old practice of disconnecting our downspouts and letting the water perc down a slope has caused erosion problems for many properties.  That’s a fine practice for people with flat lots in Portland, in fact Portland encourages disconnecting downspouts and building rain gardens. Karin says be sure to inspect your pipe.  If we had a crack or damage to a pipe that allowed water out in the wrong place, it could create a heavy water load and cause big problems.  We can start inspecting pretty easily because our pipes are not buried.

Other sources of water are as simple as rain water. The way to control rain water is with plants.  Think of it this way………..Gravy and bread.  We use bread to sop up the gravy, well we did until they said it was bad for us and now they are saying animal fats are good for us…….  I love gravy which is a diversion from this article, must be dinner time.  We will use the right plants in the right places to sop up the rain water.

Evergreen trees are most effective on slopes and yet a lot of people cut down evergreen trees because they spoil the view.  It turns out evergreen needled trees (coniferous) perform brilliantly to protect slopes from erosion.  I had no idea. Here’s why:

Coastal feeder slope

This cliff is feeding sand to the beach.

Large evergreen coniferous trees like our Western Red Cedar or our Douglas Fir have needled foliage.  The needles break the impact of hard pelting winter rain into tiny droplets. The surface soil is protected from the impact of the hard rain. That’s helpful, but even better the trees roots take up a tremendous amount of water and utilize a process called transpiration which releases the water from the needles as a fine mist. So water under the soil surface is absorbed by the roots instead of spilling out of the side of the cliff.  Deciduous large trees such as Oregon Bigleaf Maple, or alders have no leaves in the winter, and they are dormant and so their roots do not take up as much water as the needled trees do in winter or any other time of the year.  The conifir reigns as the top water catcher on the slope.  There is also what seems to me to be a rather magical thing fir trees do.  It’s called thigmomorphogenesis.  This word refers to the way trees and plants respond to mechanical stimuli that influences how they can  grow in really unusual ways. Basically, they are responding to the situation on the slope and growing their roots in ways to protect that slope. They may grow a larger branch to balance their mass.  Somehow they know to do this.  It’s seriously cool science stuff here.

Here’s what I’m going to do to help protect my slope.

New plantings that include evergreen coniferous trees.

First I am going to enhance the soil above my big tree to help the native plants spread and grow.  I’ll add compost near my top of slope plantings to try to cajole them into growing toward the house.  The top of this hill was graded flat by the developer to build the house so there isn’t a drop of top soil in my flat yard.  The native plants stop growing and you can see the straight line across the edge of my yard at the top of the steep downhill slope.

Pacific Madrone

Pacific Madrone – Arbutus menziesii
has recently been approved for City of Portland street trees. It’s a NW native plant.

I am going to plant 3 more (tiny sized) Pacific Madrone below my big fir tree and also 5 dwarf Western Red Cedar. I’ll use willow stakes in areas with more sun.  They are easy to plant.  I’m using a modified native tree to try to protect my view.  The Excelsor Western Red Cedar matures at about 20′ tall, not 70’.  Will I be here to see them at 20’ tall?  Hard to say, I better keep eating lots of grass fed butter and Kale.

I got so much from my appointment with Karin that I have another blog that will explain what plants I am planting where.  Stay tuned for part two.

 

Landscape Design for tiny steep backyard

Sango Kaku Japanese Maple set into boulder wall

Sango Kaku Japanese Maple

Big ideas for tiny steep back yard

My new clients were from southern California and now lived in Ridgefield, Washington.  They were  new to the Northwest.   They loved their new home and neighborhood and believed all their difficult small back yard needed was the right designer.

Their lot was challenging.

Their lot was challenging.

The Bodes wanted to make Ridgefield feel like home.   Their list was extensive and precise – their lot was tiny and challenging.  It was one of those small and steep up hill lots.  The builder gave them a slice of level land by building a high utilitarian block wall.  This divided the yard into half and neither half was big enough to do much with.  It’s great that people understand that a good designer can work miracles.  I was flattered they chose me to bring their new outdoor home to life.  It was not going to be easy.

Side yard transformed to easy access edibles garden

Side yard transformed to easy access edibles garden

Lauren and Kathryn’s wish list went like this:

•Large covered outdoor area for year round entertaining

•Covered hot tub room

•Dwarf fruit trees and raised beds for edibles – this was a serious hobby for them

•Convenient access to smoker and BBQ

•Water feature to see from inside the great room for year round enjoyment

•A Sangu Kaku Japanese maple-because they loved it so

They hired me after looking at several designers and we met early one fall morning.  As soon as I saw their lot I knew I’d recommend D & J Landscape Contractors for the installation.  We had teamed up for a similarly difficult site.   Although I am a Portland landscape designer I have several Ridgefield Washington landscape design clients.  See Mastersons swamp to paradise blog.

The Bodes and I  worked together to create their plan using my landscape design in a day process.

Before back porch addition

The basic grading was completed so the back porch addition could be built.

The big items were first.  For seamless outdoor living the thing to do was extend the roof of the house for the cover.  Not inexpensive but an important priority.  We made the ceiling high in this addition so it would add light to the great room and make it feel bigger.  Adding onto the existing small back porch rather than adding a new covered area elsewhere in the landscape kept it simple.  With all the items we needed to add, it would be easy to turn this tiny yard into a hodgepodge.

After back porch addition

After back porch addition

 

Next the harsh straight wall dividing the landscape in half had to go.    The design broke the steep slope into three levels.   Using naturalistic boulders artfully placed changed this landscape completely.  This is where I have to stop bragging about my spatial skills and brag about the landscape contractor.  It isn’t financially practical or practical in any manner to draw a design that precisely places every boulder.  Sometimes I am on site during construction and I work closely with the excavator to place the boulders but even then it is a very collaborative effort.  Donna Burdick and Brian Woodruff of D & J landscape Contractors  took the design and brought it to life.  It was such a tough site that we were planning to have me on site to help with the artistic efforts but the fall weather was threatening and if they had waited for me, they would have lost an opportunity to install until the next year.  We met on site once and they ran with it……beautifully.

The perfect spot for the smoker.

The perfect spot for the smoker.

A place was made for the smoker just on the edge of the covered back porch.  Nestled among the boulders it sits at a height that makes it an easy reach.

Now that we had created usable space it was easy to nestle the gazebo and tot tub into a curve of the boulder walls.  The hot tub feels private and there is good access.  It is planted beautifully.

 

The gazebo nestled into the boulder walls to create it's own private hot tub room.

The gazebo nestled into the boulder walls to create it’s own private hot tub room.

 

Lauren and Kathryn are get it done people.  Lauren built the hot tub gazebo using a kit, designed and built a potting table and storage cabinet for the back porch.  It was such a pleasure to visit them and hear how much they love their new outdoor heaven.

Their easy access raised beds are a delight to use and to behold.

The water feature, a drilled rock with the hidden echo chamber under it is beloved by their young nieces, they love to play in it.  The sound calls them outdoors.

They are home.

Sometimes I feel a little like Santa Claus –  All the boys and girls deserve a wonderful outdoor heaven to play in.

Birch Trees Going Going Gone

Birch trees going going gone

Another birch tree marked for removal by the City of Portland due to bronze birch borer.

Birch trees marked for removal by the City of Portland due to bronze birch borer.

In 2010 Kym Pokorny, my favorite garden writer, warned that our graceful white bark birch trees might become a tree of the past in Portland.    Fast forward to today.  Boy was she right!!  It seems to me as I look back over these past years that the birches in the subdivisions died first.  Many developers, builders and home owners picked the Himalayan White Birch also called Jacquemontii, for its crisp white bark and over planted them.   In 2009 I was working with landscape design clients in a Vancouver neighborhood.  They had already had 2 birch trees removed and we made a replacement plan for the third as part of the Landscape Design in a Day.  Their neighborhood had already removed over 200 birches.  Their developer had used them extensively.  Back in the 1980’s the Himalayan White Birch was touted as the new success story because it had been hybridized to repel the Bronze Birch Borer.  Over time however the bronze borer changed its preferences and became attracted to the available and over planted Himalayan or White Birch.  It makes sense from an evolution perspective; why not change to fit the food that is available?  Smart bug!!!

Fixed up close view

Himalayan White Birch used to repel birch borer.

Recently I have noticed the dreaded yellow tape of death tied around birch trees in the city.  I create my Landscape Design in a Day drawings on site with my clients so I am in every conceivable neighborhood.  The Bronze Birch Borer is now in North Portland to SE Portland, not just the suburbs.

These days when I have a client who has a healthy looking birch I give them the current research and bad news.  From what I have read there isn’t a whole lot of good news.   I often include in their design a potential replacement tree for when, not if, their tree is devastated by the Birch Bronze Borer.  It’s shocking and pretty sad for them to hear that they will probably witness the demise of their tree especially when it looks just fine.

th2_betula_heritage_3

Heritage River Birch in winter.

If you have a birch tree that is thriving consider starting to irrigate it if you haven’t already. You might start by deep watering it every two weeks. Under no circumstances should you water your tree every day – that is not helpful  (see my watering tips blog).   There are chemical protections that you can apply to your tree before it becomes infected that will typically keep it from getting the borer.  General Tree Service is one company who provides this  service.    Sometimes the tree can be saved  if you can catch the infestation at the very beginning but you will need to apply the pesticide every year.  Another important issue to think about it this:  The product is a systemic pesticide.  Many people refuse to use any systemic pesticide because some can kill honey bees.  Birch trees are wind pollinated not bee pollinated and so the systemic should not theoretically affect honeybees.   If you have flowering plants of any kind under or near the birch those plants will uptake the pesticide and that can harm bees.  This protection for your birch is contrary to protecting bees.  I guess you could take out your hostas or other flowering plants and put in sword ferns.  In short, if you love your tree, start taking care of it.  The first trees that died seem to me to have been neglected trees in full sun and in areas where there were too many birch trees so the borers could move from one tree to the next door neighbors tree.

Weeping Katsura is my go to birch replacement now since borers have killed so many birches.

Weeping Katsura is my go to birch replacement now since borers have killed so many birches.

What to look for:  The first signs are yellowing foliage in the top of the tree.  As the insect infestation continues, small branches and tips die.  It moves on into the larger branches.  Declining to the point of death usually takes several years but remember last years horrid, hot and nasty summer?  There were trees who seemed to get the borer early and by the end of the summer, the trees were gone.   There are other signs of borer; ridges in a lightning pattern and a distinctive D shaped hole in the bark.  There can be a kind of stain coming from the hole, a sort of reddish liquid which looks as bad as it sounds………Is my tree bleeding?  So this is not a happy blog but there are some great trees to consider for replacement.

th2_cercidiphyllum_japonicum

Katsura tree with beautiful fall color.

New resistant varieties;   I am hesitant to trust that new resistant white barked birch varieties will stay resistant since the Jacquemontii/Himalayan did not stay resistant.  When I have a client who loves birch trees I offer the River Birch which has a brown peeling  bark and typical birch leaves.   Alternatively my favorite replacement  for birch trees is the Katsura tree also called Cercidiphyllum.  The Katsura has the graceful shape somewhat reminiscent of a birch tree and since it is not related to birch I am not worried about Borers.  I know that the trees I place in a home landscape may be removed for capricious reasons by the next homeowners but selecting trees that have the best chance of becoming mature old specimens in their neighborhood is my chance to contribute not only to my clients well being but for my city and region.  Keeping up to date up on the best trees to use and keeping my selection diverse will make the best urban forest for the future.

Katsura 'Red Fox' is a smaller tree that is getting used in irrigated parking strips.

Katsura ‘Red Fox’ is a smaller tree that is getting used in irrigated parking strips.

White birch trees that have been planted in part shade, in good soil that drains well and that get irrigation may continue to survive.  Another bit of advice from Kym Pokorny’s article is to mulch over the shallow roots of your birch tree.  This provides some protection from heat and also from physically damaging the surface roots.  I’ve been told by an arborist in the past not to put more than 2 inches of mulch over  roots.  The best person to ask about these fine points of tree care is an ISA Certified Arborist.

Katsura 'Red Fox' has unique red foliage.

Katsura ‘Red Fox’ has unique red foliage.

I came across a lovely white birch tree just the other day in the Buckman neighborhood and gave my new client, who had just purchased the home, some information on how to care for the tree. The tree doesn’t seem to be infected.  Some birch trees that are individuals, seed propagated instead of cutting, may have some unique genetic protection and so we can only hope that some of these individual trees will remain to grace our landscapes and homes.

 

 

 

Diversity of Dogwoods Part II

Venus dogwood from Heritage Seedlings

The flowers of  ‘Venus’  dogwood compared to a typical dogwood flower. See Diversity of Dogwoods Part I.  Photo courtesy of Heritage Seedlings

Continued from Diversity of Dogwoods Part I

The diversity of dogwoods is well illustrated by these two trees:  Cornus Kousa ‘Summer Gold’ and Cornus Controversa ‘June Snow’.

Summer Gold dogwood

Bright cream flowers are backed by colorful variegation of  ‘Summer Gold’ dogwood. Photo courtesy of Heritage Seedlings

I love ‘Summer Gold’ partially because it’s so different from other dogwoods.  Typical dogwoods have a wide oval green leaf and a round wide canopy.  ‘Summer Gold’ has narrow bright green and gold leaves and has an upright narrow shape.  This means it fits into urban settings much better than a typical dogwood.  It was created by  local grower Crispin Silva who is a delight.  His curiosity and enthusiasm about plants has certainly inspired me.  People in the industry refer to his plants as “Crispin’s Creations”.

‘June Snow’ dogwood is also different from most dogwoods.  She matures at 30′ tall and spreads to 40′ wide.  I use her for light shade for medium to smaller landscapes.  She is too big for your typical row house back yard that is only 20′ wide, but in landscapes with a little more room she can be the single tree.  This is because she has it all.  Her branch structure is incredibly graceful and open.  When she flowers in June these flat topped clusters (which often exceed 6 inches) seem to float above the foliage.

Cornus 'June Snow'

‘June Snow’ dogwood at Portland’s Legacy-Emanuel Hospital in The Children’s Garden.

 

 

The fall color can compete with any dogwood starting with orange yellows and moving into purple red and deep purple as fall deepens.  The fruit that develops from the flower clusters are tiny and not messy.  The local birds will eat them.

 

Diversity of Dogwoods Part I

Cornus Kousa 'Satomi' at Joy Creek Nursery.

Cornus Kousa ‘Satomi‘ at Joy Creek Nursery.

Diversity of Dogwoods – Part I

Dogwoods are a very large family.  There are twiggy shrub dogwoods whose hot colored stems light up the winter landscape.  There is a dogwood who blooms in March with yellow flowers and makes an edible fruit.  There are semi evergreen dogwoods we are experimenting with here in Portland.  This is the kind of knowledge homeowners need their designers to be up to date on.  When a client asks me for a dogwood I know its the visual and emotional impact of the flowers they are thinking of.  Designers think through the details to find the right variety for the clients size of yard and environment so our clients don’t have to.  Landscapes come in all different sizes and environments and now so do Dogwoods.

Plant designers have been busy improving our old-fashioned dogwood tree into a garden designers dream tree. Our old dogwood varieties have problems that plant designers have been working on for 40 years.

Cornus-Kousa 'Satomi' Intense pink flowers. Photo by Randall C. Smith, courtesy of Great Plant Picks

Cornus Kousa ‘Satomi’  Intense pink flowers.  New on the scene, ‘Little Ruby’  is a deeper pink. Photo by Randall C. Smith, courtesy of Great Plant Picks

They are improving drought tolerance, disease resistance (okay not sexy but important!)  and cold hardiness.  They’ve created new shapes that fit better into the urban environment.

What is sexy or desirable are the improvements made to the flowers.  Let’s admit it, where dogwoods are concerned,  we want even pinker flowers.   Everyone wants more color than nature supplies on her own. There are darker shades of more intense pink red.

Cornus Kousa 'Venus' has large dogwood flowers

Cornus Kousa ‘Venus’ has large white flowers which are 6 to 7 inches across.

Varieties such as ‘Little Ruby’  showcase the new strong colors.   ‘Little Ruby’ is wider than tall.  She is  plump and round headed and can be used in the landscape as a shrub or small tree.

Another new variety is called ‘Starlight’.  This cross is from our own native Pacific Northwest Dogwood;  the shape is upright and more narrow.  It works for your small yard or as a street tree. There’s a beautiful ‘Starlight’ in the courtyard of the Edith Green federal building in downtown Portland as an example of a tree perfect for urban life.

Cornus Kousa 'Starlight' dogwood

‘Starlight’ dogwood is a cross from our Pacific Northwest native dogwood. The narrow shape is perfect for urban life. http://landscapeplants.oregonstate.edu/plants/cornus-starlight

 

‘Venus’ features ginormus white flowers which are 6″-7″ across.  Like ‘Starlight’ they produce little to no  fruit unlike the many Korean dogwoods hybridized and sold in the last 15 years.  In fact even Friends of Trees offer messy Korean dogwoods.  I confess I make a TSKK TSKK when I see the huge mess they make on the sidewalks. In the fall they drop a large raspberry colored fruit.  Friends of Trees is a fabulous organization and many clients have been happy to purchase an inexpensive tree and learn how to care for their tree.  I would use the fruitless varieties near walkways and for small yards and save the old fashioned fruiting types for large properties.