passion flower (Passiflora edulis)

Q: We just bought a house at the base of a hillside. The back yard is one-third grassy lawn bordered by privacy bushes; beyond that is a hillside covered with shrubs and moderate-size trees. Steps lead up to a gazebo. I love purple and lilac colors and want to make this my dream yard. What’s the name of the plant that blankets the sides of freeways in purple? I’m wondering if that plant would work on our little hillside. And would a lilac tree do well here? What other purple/lilac plants or trees could I add?
– Lorelei Smith, Chatsworth
A: The plant that blankets freeways in purple is trailing lantana (Lantana montevidensis), and it would grow fine for you, assuming your slope is sun-exposed. I would definitely plant a passion vine (Passiflora) with purple flowers to climb up your gazebo. Actually, you are in luck, since many drought-tolerant plants have purple, violet or lilac flowers. One of the most prolific bloomers is a wallflower known as Erysimum “Bowles Mauve.” It is a small shrub that grows only a few feet in height, but when it is in bloom, it has no rival for flowering brilliance.
You should also consider butterfly bushes (Buddleia species) in both lilac and purple. There is also the blue potato bush (Solanum rantonnetii), improperly named since it actually has purple flowers. This incredible shrub is typically grown as a 3-foot-tall lollipop tree. This a great injustice, in my opinion, because when it is confined in size, the blue potato’s flowering is curtailed. Left to grow as a large shrub or legitimate 12- to 15-foot tree, the blue potato bush flowers regally for months on end.
Keep lavender in mind. There are many types of lavender, and lavender flowers cover a color spectrum in the blue to purple range. Finally, though few in number, there are true lilac (Syringa) varieties that bloom in the Valley. Ask your neighborhood nursery to special-order them for you.
TIP OF THE WEEK: When staking a tree in a windy area, place the stakes in the direction of the prevailing wind. In other words, if the wind generally blows from the north, your stakes should be placed on the north and south sides of the trunk. Stakes should be 12 to 18 inches away from the trunk and driven 18 inches deep into the soil. Use plastic or rubber ties. No tree should be staked for more than two years. Trees staked beyond two years are increasingly susceptible to wind damage and to falling over once stakes are removed.