Gardening Tip for March: Prune Fruit Trees

Flowering peach tree

This applies to pome fruits like apples and pears, and stone fruits like peaches, apricots and cherries. Once fruit trees start leafing out, it’s a good time to prune because you can see and remove the branches that became damaged or diseased or didn’t survive winter. You can also remove suckers from the base of the tree, thin out the branches and trim the whole tree to increase the fruit and keep it smaller. I encourage you to use the excellent resources of the Master Gardener program in California to get free advice on pruning your fruit trees. Or ask any experienced gardener. Your tree will be around for many years and you want to treat it well!

If you want to start with some online research about fruit tree pruning, here is an excellent article (with drawings) from Modern Farmer.

Be careful with citrus!

Citrus trees (orange, lemon, lime, grapefruit) appreciate having the suckers removed, being trimmed and shaped from the outside and from the bottom to make a nice, vase-shaped tree. This can be done at any time of the year. Unlike pome and stone fruit trees, which benefit from having branches taken out of the inside of the tree to increase light and air circulation, citrus trees will get burned and damaged from internal pruning. So keep to the outside of the tree!

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.

Caring for your garden in extreme heat

Thermometer reading 100 degrees

Plants aren’t that different from the rest of us in many respects. When it is very hot outside, we need shade, sun protection and hydration, and so do our gardens. Plants carry some tools with them to deal with sun, heat and wind. Many develop light or grayish leaves or fuzzy leaves that act as sunscreen. Some rotate their leaves away from the sun all day like little anti-solar panels. Some just go dormant in summer, a plant’s version of hibernation. But when temperatures climb to 100 degrees and above, most plants appreciate some extra assistance. There are several things you can do to help your plants withstand the weather.

Apply mulch

Deep mulch in the garden

Bark chips, grass clippings and old leaves are all great for helping soil retain moisture. Mulch also creates shade, which keeps the soil cooler. If you use old grass clippings or even straw, the light color will even help to reflect sunlight.  Mulch also helps protect soil from wind seeking to dry it out. Use a two to three inch layer for best results.  Use mulch made out of biodegradable materials that will decay over time and feed the soil. If you use rocks as a ground cover, don’t add mulch to this. You are already helping your plants. Even rocks provide shade and help to keep moisture in the soil.

Be careful to keep the mulch away from the immediate area of the plant’s stems or tree trunks. Mulch is so good at retaining moisture that if it’s too close to the plant it may contribute to fungus or root rot. And just pour the mulch on top and rake it – don’t mix it into the soil or it will pull nitrogen (nutrients) out of the soil as it decays.

Set up a shade structure

Build shade structures for stressed plants

Shade cloth or row cloth is often seen in vegetable gardens, but I also use it for ornamental plants, particularly when the planting is less than a year old. I build tiny shade structures out of a sheet of 30% shade cloth, dowels and garden ties or staples, although I’m sure there are many ways to do this. It helps to position the cloth to the south or west side of the plant or directly above it. Make sure you’re giving the plant room to breathe, and don’t forget to remove the shade cloth when the heat wave is over.

Water early and deeply

Water as early in the day as possible, particularly if you have sprinklers since most sprinkler water is lost to wind and evaporation during hot times of the day. Additionally, watering leaves when the sun is directly overhead can cause leaf scald. Watering too late in the day is deadly for many plants. For low-water plants that are adapted to dry summers, sitting in warm soil and being damp at sunset and into the evening is a recipe for fungal infections that can lead to root rot or sudden death.

Hose watering tree

Using drip irrigation or soaker hoses (or just a hose laid on the ground) gives you a lot more flexibility. Leaves don’t get wet and if positioned correctly, the plant itself will not get as wet so watering during the day or early evening is not as harmful.

How much water to give your plants during a heat wave depends on the type of plant and how long the plant has been in the ground. If I have designed your garden, you have low water plants that will not appreciate being deluged during a heat wave any more than they would at any other time. What they will appreciate is an extra long, slow watering or two during the week. Drip irrigation, soaker hoses or just a trickling hose set next to plants are the best ways to deliver extra water.

Plants that have been in the ground less than two years are still developing a strong, deep root structure. The heat drying out the top few inches of the soil has a bigger impact on them. Take extra care to keep that top layer from drying out into an impenetrable brick. Only you know how quickly your soil dries out, but maybe increase to watering three times a week during very hot or dry weather. Young trees should get two to four inches of water per week once temperatures hit 100 degrees. Again, a trickling hose or soaker hose is best for this supplemental water.

Prepare when you can

After two years when plants are well established and their roots are deep, you should be able to water deeply one additional time per week when it’s really hot and/or dry. Many of you only water monthly in the summer, so just do one deep watering a week in extreme heat.

If you’ve done the work to water deeply and infrequently the prior two years you have helped your plants to set up deep, extensive root structures and are set up for success, so pay attention to your soil as you are establishing your garden. It will pay off later.


Plant with wilting leavesWhat about wilting leaves? Garden author and TV/radio personality Nan Sterman offers a great tip to help gauge how stressed your plants are in the heat by when their leaves wilt. She says “if they look droopy at the end of the day, don’t worry. If they look droopy first thing in the morning, worry.” Read the full article.