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.

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.

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.

Photo: Mark Marathon, Wikipedia

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.

Photo: NYS Parks

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.

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.

Photo: C. Stubler, M. Ritter, W. Mark and J. Reimer, UFEI

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.

Photo: AnRo0002, Wikipedia

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).

Photo: JUSTIN JACKSON/Times-News

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.

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).