Trees to Avoid in Your Home Landscape

Pyrus calleryana

When you see these trees coming, run the other way…

We’ve all met that person – the one that seems great, but as time goes on, reveals themselves to be a gossip or a liar. Well, the tree universe has those people too. I’ve chosen a list of common trees (and a vine) that seem to cause problems with most of the homeowners I talk to. Major concerns with these trees include damage to houses and property; allergies; messiness; invasive behavior; and flammability.

The list of trees you should avoid planting changes depending on your criteria, the place you want to put the tree, your climate, and several other things. A “problem tree” may be worth the extra work to you, or they may be a fine fit for the place you’re putting them. A liquidambar tree is beautiful and fine as long as its roots can’t reach any pipes or sidewalks, for instance.

We are lucky to live in a mild climate where we have so many choices in trees and plants. Why choose a tree that’s a troublemaker?

A note about allergies: Olive and ash trees are highly allergic to many people, and I recommend not planting any but the sterile varieties in an urban or suburban setting. Pollen from your tree can make allergy sufferers in a couple block radius of you miserable for months out of the year. It’s not worth the bad karma.

They’ve got issues

These two trees have (deservedly) bad reputations. Stay clear!

Bradford Pear (Pyrus calleryana)

Bradford pears are top heavy and prone to splitting. It’s not uncommon for the Bradford pear tree to split in half, especially during wind or rain. Sure, all those white flowers are beautiful in spring, but it’s not worth losing a part of your house over.

Pyrus calleryana

Ash (Fraxinus)

Beautiful street trees that until recently were resistant to severe weather, diseases and pests, ash trees now face devastation from the emerald ash borer (EAB). The insects spread from Asia to Michigan in 2002, and as of last month to the east coast and as far west as Colorado. So far efforts to slow or stop the spread of EABs have not been successful and we expect them to reach the west coast at some point. Stay out of future trouble and don’t make an investment in an ash tree.

Emerald ash borer damage

Damage alert

Be careful of these trees, which can wreak havoc on your property with roots and branches.

Eucalyptus (Eucalyptus)

Imported from Australia and popularized for their speedy growth — some varieties will shoot up 10 feet in a year — the eucalyptus has a bad rap for suddenly and unexpectedly dropping big, heavy, resin-filled branches. In some areas of Australia, campers are warned not to pitch tents under eucalyptus trees. They are also highly flammable.

Eucalyptus alba

Liquidambar, Sweet Gum (Liquidambar styraciflua)

While it can be beautiful, especially in the fall, the sweetgum’s spiny brown balls, which come down by the thousand, are a major drawback. More importantly, this tree has a huge and destructive root system. Unless you have enough land that the roots can’t interfere with houses, fences or plumbing, leave this tree in the park.

Liquidambar seeds

Wisteria (Wisteria)

Not technically a tree, but deserves a place of honor on this list. Wisteria, with its brilliant, cascading purple blooms, is tempting for a gardener who loves flowers—but beware! Its root system can send shoots popping up far away from the main plant, engulfing trees, shrubs, and anything else in its way. It can live hundreds of years and requires serious pruning every year to keep it under control. Large wisterias have brought down trellises, pergolas, and even roofs.

Wisteria sinensis

Such a Slob

From flowers and nuts to seeds and seedlings, these trees keep you busy cleaning up after them on weekends.

Black Walnut (Juglans nigra)

Native to North America, this beautiful shade tree produces prized cabinet- and furniture-making wood. It also produces pollen and plenty of fruit that’ll drive you nuts when you have to clean it all up in the fall. Its true sinister side, however, is that it secretes growth-inhibiting toxins that kill nearby plants, wreaking havoc on anything that tries to grow nearby.

Juglans nigra

Mimosa (Albizia julibrissin)

Plant one, and you’ll be pulling seedlings up constantly—and so will everyone around you. There are some things you just shouldn’t share with your neighbors.

Albizia julibrissin

Russian Olive (Eleagnus angustifolia)

This rogue tree is thirsty and aggressive, so often crowds out surrounding plants. They are good at looking messy and thorny, are nearly impossible to kill, and drop olives everywhere (which I guess is a plus if you’re planning to harvest them).

Elaeagnus angustifolia

Gingko biloba, Maidenhair (Gingko biloba)

Female gingko biloba trees produce very stinky and messy fruits in late fall, which stick to shoes and can get tracked indoors. There’s no way to distinguish the male and female trees until they mature. If you really want a gingko biloba, buy a tree marked ‘Autumn Gold’ or ‘Lakeview,’ which are male-only varieties.

Gingko biloba fruits

Great Balls of Fire

I’ll be writing about landscaping for fire safety in the next few months, but for now I’ve included a quick list of the most flammable trees commonly found in home landscapes. I do not recommend any of these for the southern California garden.

Arborvitae (Thuja)
Acacia (Acacia)
Cedar (Cedrus)
Cypress (Cupressus)
Douglas Fir (Pseudotsuga)
Eucalyptus (Eucalyptus)
Juniper (Juniperus)
Some palms
Pine (Pinus).

Planting for Pollinators

Bee on lavender plant

The decline of pollinators such as honeybees and monarch butterflies has been prominent in the news recently, and as a result I am frequently asked if I can design pollinator gardens. The good news is that different types of pollinators exist everywhere, and it does not take much space to provide a place for food, shelter and rest. If you have enough nectar-rich plants in your gardens, hummingbirds, butterflies and bees will find it. Pollinators are not only beautiful to have in the garden, they also increase flowering and the amount of fruit and vegetables your garden produces. A good pollinator garden design can make your yard a neighborhood hotspot and add to the mosaic of habitat available to these important creatures.

Why are pollinators so important?

Birds, butterflies, bees, flies, moths, bats, beetles and other animals pollinate at least 75% of flowering plants. This includes important crops such as almonds, coffee, tomatoes, squash, apples and berries. Our diets would be a lot less interesting without pollinators! Pollination by honeybees and other insects accounted for $29 billion in US crops in 2010. Without the assistance of pollinators, most plants cannot produce fruits and seeds. The fruits and seeds of flowering plants are an important food source for people and wildlife. Some of the seeds that are not eaten will eventually produce new plants, helping to maintain the plant population.

Threats to Pollinators

Populations of honeybees made news in the US in 2006 as 30-90% of colonies died off in what is called Colony Collapse Disorder (CCD). CCD is still being studied but is thought to be caused by several factors that put bees over the tipping point. These include loss of habitat to urbanization, disease, insecticides and climate change.

Bird and butterfly populations face major stresses due to loss of habitat for nesting, food and migration. In California, monarch butterfly numbers dropped by 86% in 2018.

A Note About Neonicotinoids:
Neonicotinoids (neonics) are a class of insecticides from the 1990s that were initially believed to be less harmful to birds and insects than other insecticides. However, since their introduction, the widespread death of bee colonies, known as Colony Collapse Disorder, has been linked to neonics in several studies. Neonics also shed off of plants and pollute water. In fact, recent studies found contamination in more than half of all streams sampled in the US, which can affect all wildlife. The EPA is currently reevaluating neonics to see if their use should be restricted or banned. To ensure that your pollinator garden does not harm the wildlife you’re attracting, do not use neonics. Look for and avoid the following ingredients in pesticides and insecticides: acetamiprid, clothianidin, imidacloprid, nitenpyram, nithiazine, thiacloprid and thiamethoxam.

Planting for Pollinators

Every person with access to a small bit of yard or even a balcony can help build a patchwork of habitat for pollinators. Below are some guidelines on what to plant to attract and support bees, butterflies and birds.

Attracting Pollinators to Your Garden

  1. Don’t use pesticides. Particularly, do not use neonicotinoids. Most pesticides are not selective. You are killing off the beneficial bugs along with the pests. If you must use a pesticide, start with the least toxic one and follow the label instructions to the letter.
  2. Use local native plants and heirloom varieties when possible. Research suggests native plants are four times more attractive to native bees than exotic flowers. They are also usually well adapted to your growing conditions and can thrive with minimum attention.
  3. Make sure not to plant sterile varieties of plants (you can usually find this on the plant tag), since pollinators can’t feed on those. Most “double flowered” plant varieties are sterile.
  4. Plant flowers in clumps. Flowers clustered into clumps of one species will attract more pollinators than individual plants scattered through the habitat patch. Where space allows, make the clumps three feet or more in diameter.
  5. Include flowers of different shapes. There are many different species of pollinators with various tastes that will enjoy the buffet of flowers you’ve planted.
  6. Have a diversity of plants flowering all season so that you can feed pollinators from spring through fall.
  7. Have water and shelter available. A dish of water and some rocks or logs are sufficient. Consider building a bee box to encourage solitary, non-aggressive bees to nest there. Leave some soil uncovered for native bees, many of whom nest in the ground.

Hummingbirds like lots of color, especially red, and gravitate toward tubular-shaped flowers. They appreciate large clusters of their favorite plants so that they can flit from one to another.

Some hummingbird favorites include:

  • Coral Bells (Heuchera)
  • Hummingbird Mint (Agastache)
  • Beardtongue (Penstemon)
  • Sage (Salvia)

Butterflies prefer bright colors including red, yellow, orange, pink and purple blooms with umbel (umbrella) shapes. One thing to keep in mind is that in order to attract and keep butterflies in your garden, you have to be willing to feed their offspring. That means putting up with some destruction from feeding caterpillars in the spring. If you can deal with the temporary destruction, the reward, of course, is a garden alive with the color and beauty of hundreds of butterflies.

Some butterfly favorites include:

  • Milkweed (Asclepias): an essential food source for local Monarch butterfly caterpillars.
  • California lilac (Ceanothus)
  • Dill, parsley, fennel
  • Lantana
  • Yarrow (Achillea)


Bees prefer blue, purple, white and yellow flowers.

Some bee favorites include:

  • Catmint (Nepeta)
  • Lavender (Lavandula)
  • Rosemary (Rosmarinus)
  • Stonecrop (Sedum)

 

Resources for further reading:
U.S. Fish & Wildlife Service: https://www.fws.gov/pollinators/pollinatorpages/yourhelp.html
USDA Forest Service: https://www.fs.fed.us/wildflowers/pollinators/gardening.shtml
Xerces Society: https://xerces.org
Pollinator Partnership: http://pollinator.org

Inspiration Station: Visit a Garden

Meyerburg Waterfall at the Los Angeles Arboretum

In late summer, it may feel too hot to be working in the garden any time but the early morning hours, but that doesn’t mean that you can’t work on improving your landscape in some manner. There are dozens of gardens and arboretums open to the public in the Los Angeles County and surrounding areas. Take a day or two to tour and get new ideas for your own garden. Public gardens are a great way to see what kind of plants and hardscape does well in your climate and what different plants look like in different seasons. And research shows getting outside around nature is good for you. It lowers blood pressure and stress and helps symptoms of ADD, so get out there!

I’ve picked out some of my favorite gardens below, in a rough large-to-small order. The first three have enough to see and do for a full day.

Oak Forest at Descanso Gardens
The Oak Forest at Descanso Gardens. Photo courtesy of Descanso Gardens.

Descanso Gardens – La Cañada Flintridge

This 150-acre botanic garden emphasizes naturalistic landscapes. The plants and trees are less groomed than in many public gardens, which gives it a wild feel. There are acres of huge oak trees, oak woodland and California native plants. When they are blooming the camellia garden, rose garden and cherry blossom trees are fabulous. There’s also an interesting edible garden that experiments with mixing food plants in with ornamental plants, and a Japanese garden. The website has a page telling you what is currently blooming on site.

Meyerburg Waterfall at the Los Angeles Arboretum
Meyerburg Waterfall at the Los Angeles Arboretum. Photo courtesy gardenvisit.com

Los Angeles County Arboretum and Botanic Garden – Arcadia

Plan at least 3 hours to see The Arboretum, and that’s at a fast pace. The Arboretum is 127 acres of rare and endangered plant collections, Southern California history and peacocks that lurk everywhere. There are water conservation gardens, an aquatic garden and a lake, a greenhouse with several thousand orchids, original houses and a train depot. My favorite area is the Madagascar Spiny Forest, housing some of the most endangered plants on the planet. The Arboretum also hosts concerts and educational events, and just started a forest bathing program.

Huntington Japanese Garden
The Japanese Garden at the Huntington. Photo by gardenvisit.com.

Huntington Library, Art Collections & Botanical Gardens – San Marino

I often wish they sold weekend passes to The Huntington, as I need at least two days to see everything! The original site of Henry Huntington’s ranch in the early 20thcentury, The Huntington today is home to 15,000 plant species, several art galleries and one of the largest research libraries in the United States. The gardens include the well-loved Japanese garden, a newer Chinese garden, an enormous Desert garden with over 2,000 species of cacti and more than I can list. Start early and plan your routes to fit in as much as possible!

South Coast Botanic Garden
South Coast Botanic Garden. Photo by southbaybyjackie.com.

South Coast Botanic Garden – Palos Verdes Peninsula

An incredible example of land reclamation and environmental improvement, the South Coast Botanic Garden was built on top of a sanitary landfill in 1961. The 87-acre garden is home to Mediterranean, Japanese and California gardens. Specialties include a Dahlia garden, blooming from mid-summer to late fall, a Fuchsia garden and a Garden of the Senses filled with plants to touch and smell.

Rancho Santa Ana Botanic Garden
Rancho Santa Ana Botanic Garden. Photo by mynewsla.com.

Rancho Santa Ana Botanic Garden – Claremont

This 86-acre garden is the largest in the world dedicated to California plants. The garden is organized into plant communities like desert, yellow pine forest and chaparral. There are large palm tree and oak groves.

LA Zoo and Botanical Gardens
LA Zoo and Botanical Gardens

Los Angeles Zoo and Botanic Gardens – Los Angeles

Who knew the zoo was also a botanical garden? LA Zoo achieved botanical garden status in 2003 and organizes its 800 species of plants geographically, so you get to see animals in something close to their native physical environment.

Getty Center Central Garden
Getty Center Central Garden. Photo by getty.edu.

Getty Center – Los Angeles

Artist Robert Irwin designed the Central Garden that winds through a shady ravine into an intricately planted central courtyard. Walking the garden takes the visitor on a journey of sight, sound and scent. There are also several smaller gardens and fountains at the Getty.

Japanese Garden in Van Nuys
Japanese Garden in Van Nuys. Wikipedia photo.

The Japanese Garden – Van Nuys

Also known as Suiho-En or “Garden of Water and Fragrance,” this 6.5 acres Japanese garden has a dry Zen garden, a wet strolling garden and a teahouse. The garden was designed to use reclaimed water from the adjacent Tillman Reclamation Plant and is a quiet green nook right at the 101/405 freeway interchange. A four-season garden, there is always something to see at Suiho-En.

Santa Clarita Water Conservation Garden
Santa Clarita Water Conservation Garden

Santa Clarita Water Conservation Garden – Santa Clarita

Located on the hill behind Central Park, the Demonstration Garden is filled with low water plants and grasses. Instructional signage and free gardening classes help people successfully move toward a water-conserving garden.

Arlington Garden
Arlington Garden. Photo by arlingtongardenpasadena.com.

Arlington Garden – Pasadena

Arlington Garden is the only public garden in Pasadena. It’s built on three acres of Caltrans land and is filled with California natives and Mediterranean plants, birds and butterflies. It’s run by volunteers and is a great example of taking a patch of unused dirt and turning into something beautiful for the community.

Meditation Garden at Self Realization Fellowship
Meditation Garden at Self Realization Fellowship. Photo by lake shrine.org.

Self Realization Fellowship Lake Shrine – Pacific Palisades

Enjoy the natural spring-fed lake, waterfalls, fern grottos and peaceful atmosphere at the Self Realization Fellowship just a few miles from the beach.

Earl Burns Miller Japanese Garden at Cal State Long Beach
Earl Burns Miller Japanese Garden at Cal State Long Beach. Photo by csulb.edu.

Earl Burns Miller Japanese Garden – Long Beach

A small, beautifully designed Japanese garden on the campus of Cal State Long Beach.

Designing for a Low Maintenance Garden, Part 2

Low water, low maintenance garden in West Los Angeles

Last month I talked about the importance of knowing your yard or landscape site really well and making choices to get the best use out of the space you have. In landscape design, we hear the term Right Plant, Right Place a lot. You can spend an awful lot of time, money and water on a design that will never look the way you envision if the plants you pick are not the right choice for your climate, or even that particular spot in your yard.

The following checklist should help you to focus in on things you can do while planning that will make your landscape easy to care for. And if you’d like to consult with a professional, contact me or someone in your neighborhood. The Association of Professional Landscape Designers (APLD) has a great search function on their website for this. Good luck!

Right Plant, Right Place Action Checklist:

  • Determine how much open lawn area is ideal for children, pets, and recreation. Where possible, use low-maintenance groundcovers, shrubs, mulch, or other porous surfaces that allow water to infiltrate. By letting rain sink into the ground, you’re cutting down on the amount of water your plants need from irrigation. And porous surfaces are substantially cooler than concrete or artificial turf.
  • Be flexible in your plant choices. There is usually a way to have what you want. For instance, if you have shade but love roses, perhaps you can have some in pots on a sunny patio. A successful planting design will suit the environment your home and landscape offer.
  • Design and maintain a yard that thrives predominantly on rainfall once plants are established. Use the stormwater approach to landscaping so that you can keep more rainfall on your property instead of sending it to the storm drains.
  • Reduce the need for water, fertilizer, and pesticides by choosing plants suited to the site conditions in your yard.
  • Group plants according to their water needs, or hydrozones.
  • Reduce later work by choosing plants that will not require frequent pruning when they reach maturity.
  • Decrease soil erosion by planting groundcovers where lawn will not grow well, such as under trees or on steep slopes.
  • Save energy by using trees and shrubs to shade the eastern and western walls of your home. Use deciduous trees or shrubs on southern exposures to allow sun to passively heat your home in winter.

Many of the maintenance needs of a garden are determined by the design. A good design will flourish over many years and require cleanup and pruning only once or twice a year. After the first two years, you will rarely need to water your yard while still having flowers, butterflies and hummingbirds.

Designing For a Low Maintenance Garden, Part 1

Lantana and calandrinia in a low-maintenance yard

Right Plant, Right Place

Good landscape design hinges on one basic concept—the right plant in the right place. It is tempting to run to the garden center the moment the gardening bug hits in the spring, but taking the time for planning and site evaluation will save time, money and frustration later.

Plan for your yard use

Take the time to map out your yard based on who uses it and how you use it. Do you have pets and/or children? Do you entertain in your backyard? Grow vegetables? Play soccer? Make a list of all of the things you use your yard for, or want to use your yard for. Think about how areas could serve more than one purpose.

Get to know your site

Soil types, temperature ranges and rainfall patterns differ dramatically from region to region in California. It’s important to remember that a plant that thrives in a friend’s yard on the coast may freeze in your yard just a few miles inland. Different conditions often exist even in the same yard. The front yard may be high and dry, while the backyard may be poorly drained and soggy.

How much sun does your yard get? Are there shady spots? Where does the sun rise and set? These are just a few of the questions you should ask yourself when doing a site analysis. A landscape professional spends a great deal of time on a site plan before beginning a design to make sure the design is suited to the space it is in.

Many of the maintenance needs of a garden are determined by the design. A good design will flourish over many years and require cleanup and pruning only once or twice a year. After the first two years, you will rarely need to water your yard while still having flowers, butterflies and hummingbirds.

Part 2 will include a checklist to help you attain a beautiful, low-maintenance garden!