By Jim McCausland, Sunset Magazine

Today's blog is for anybody who gardens in Sunset climate zone 10, which is mostly in Arizona and New Mexico (bits of the zone also extend into Nevada, Utah, and Colorado). Albuquerque landscape architect David Cristiani (Quercus) is extraordinarily well attuned to this zone, since he lives and does most of his work there. He thinks it should be subdivided into two parts: Zone 10a and 10b. I'm inclined to agree.

Looking at overall Zone 10, here are the climate averages that come up. (The climate maps above and below show an undivided zone 10.)

Extreme January minimums: -10° to 10°
Average January minimums: 22° to 33°
July maximums: 92° to 102°
Growing season: 190 to 225 days
Precipitation: 9 inches in western Arizona to 18 inches in eastern New Mexico.
Major factors: This zone lies mostly in 3,300- to 4,500-foot elevations. Occasional winter snow; warmer all year than Zone 2, which hems it in on the north; and has more rain, less wind, and colder winters than adjacent parts of zone 11, which it touches only in southern Nevada. About a third of precipitation comes in summer in Phoenix; about half comes in summer from Tucson to Las Cruces; and from the Pecos drainage east, most precipitation falls from late April through the end of summer.

Breaking it down, Cristiani sees zone 10a is the colder zone, including towns such as Page and Lake Powell, AZ; Bernalillo, Albuquerque, Socorro, Clovis, Tucumcari, and Roswell, NM; and Moab, UT. Indicator plants—ones that grow here, but not in colder zones—include the following, assuming correct exposure, soil, and moisture.

Acacia species as shrubs.
Desert willow (Chilopsis linearis) is a common native in the wild, and it grows as a tree in cultivation.
Screwbean mesquite or tornillo (Prosopis pubescens) and honey mesquite (Prosopis glandulosa) are native.
Escarpment live oak (Quercus fusiformis) is a hardy tree that reaches mature sizes.
Mescal bean (Sophora secundiflora) as a shrub.
Creosote bush (Larrea tridentata) is native shrub.
Texas ranger (Leucophyllum frutescens, L. langmaniae, L. zygophyllum) grow well, but often need protection.
Oleander (Nerium oleander) grows here with protection, but at smaller sizes. These sustained damage last February but recovered well.
Agave americana, A. salmiana, grow with protection.
Agave chrysantha, A. palmeri, A. ovatifolia, A. scabra grow well in most areas.
Desert spoon (Dasylirion wheeleri) and giant hesperaloe (Hesperaloe funifera) get little to no freeze damage.
Fishhook barrel cactus (Ferocactus wislizenii) grows with protection. In February, 2011, some were damaged and others died.
Ocotillo (Fouquieria splendens) is rare in the wild here, but thrives in much of the area.
Desert marigold (Baileya multiradiata) is a common native flowering biennial.
Bush muhley (Muhlenbergia porteri) is a common native bunch grass.

Zone 10b is milder, and includes such towns as Benson, Douglas, Sedona, Kingman, and Globe, AZ; Lordsburg, Deming, Truth or Consequences, Las Cruces, Alamogordo, and Carlsbad, NM; and Saint George, Zion National Park, UT.

Indicator plants for milder zone 10b include

Acacia farnesiana is usually fine, but suffered in February, 2011.
Acacia species grow as trees.
Chamaerops humilis reaches mature size.
Ocotillo (Fouquieria splendens) is common in the wild.
Blue palo verde (Parkinsonia florida) usually grows well as a shrubby tree, but most died, including roots, in February, 2011.
Parkinsonia x 'Desert Museum' is usually fine, but sustained major damage in February, 2011.
Canary Island date palm (Phoenix canierensis) grows as a shrubby tree. Sustained damage, but with nice recovery in February, 2011.
Date palm (Phoenix dactylifera) does well in warmer areas. These sustained damage, but with nice recovery in February, 2011.
Mesquite (Prosopis alba and P. chilensis) grow in warmer areas. Sustained major damage or death in February, 2011.
Mescal bean (Sophora secundiflora) reaches mature size.
California fan palm (Washingtonia filifera) reaches mature size.
Mexican fan palm (Washingtonia robusta) grows here, but sustains winter damage in colder areas or colder winters. Some died in February, 2011.
Texas ranger (Leucophyllum species) all grow well here, even in the open.
Oleander (Nerium oleander) needs no protection and reaches mature size. In February, 2011, they sustained damage, but with nice recovery.
Agave americana and A. salmiana need no protection.
Agave murpheyi
Agave parrasana
Agave weberi
Fishhook barrel cactus (Ferocactus wislizenii) is native and needs no protection, though in February, 2011, they sustained damage and some death.

The bottom line here is that if you're going to try to push the limits on zone 10, you'll be most likely to get away with that (at least in the short run) in zone 10b cities, but probably not zone 10a cities.

By Sharon Cohoon, Sunset senior garden writer

In one sense, agaves are almost indestructible.  Scorching heat, searing winds, weeks without rain -- it doesn't faze them.  So, in that sense, they're great landscaping plants.  But agaves do have one drawback.  Damage to those big, bold, fleshy leaves is highly visible.  And, because agaves live so long, you have to look at those scars for a long time.  And that is sort of heart-breaking because the geometric perfection of their forms is what we fell in love with in the first place.  ("Fearful symmetry", William Blake might have said about them if he hadn't seen that famous tiger first.) 

Pummeling hail can beat up even agaves.  But not all of them.  Some have such tough skin even hail bounces off without leaving scars, says Jessa Findley, Finished Plant Manager and Succulent Specialist at Euro-American Propagators Proven Winners growing grounds in Bonsall, California.  Normally hail isn't a problem at this Southern California location, but Bonsall did experience a freak hail storm last year, says Findley.  Some of their agaves looked the worse for it but some made it through without a dent.

Agave `Shark Skin', for instance, being the prime example.  "Well-named," says Findley.  "Incredibly thick, strong skin."  

`Titan' is another toughie, she says.  Looks like a plant that could scare away even hail to me.

`Reggae Time' (Agave bovicornuta) is another contender.  You might know this plant by its common name cow horn agave.

Two smaller agaves that Findley found took a beating without a scar -- `Little Shark' on the left; `Pequino' on the right.

Maybe it's the paler skin, but `Retro Choke', shown below, doesn't look as tough as the rest of this group. But Findley vouches for it.  "All these guys are sure bets," she says.

Southern California is not the ultimate test of hail, of course, so we'd love to hear from gardeners who have to endure it more often.  Have these agaves passed the hail test in your garden?  And are there others we should add to the list?

By Jim McCausland, Sunset Magazine

In a recent interview with Dr. Kelly Redmond, who is regional climatologist for the western United States, I asked whether climate change has yet affected gardening in the Western U.S.

Dr. Redmond answered that “We’re seeing more [warming] in the spring months than in the fall months. So … latest spring frosts might be backing up. Fall frosts, to my knowledge, haven’t changed.”  The net effect is that the growing season in most parts of the Western U. S. is apparently lengthening.

That means you can plant warm-season crops outside a few days earlier, and you might want to try growing a variety of corn, melon, pepper, or tomato that needs a little more time to mature. (Vegetables with longer maturity times often taste better.) You might get burned (by frost or a cool summer), but maybe not. The odds are just a little more in your favor than they were 30 years ago.

By Johanna Silver, Sunset test garden coordinator

Everything changes in winter. I remember posting on last year about my troubles in the test garden. My veggies were either stunted or bolting, and I was having to find beauty in subtler places.

I'm in my hometown of Denver this month, realizing once again that winter is a whole different ballgame in a climate with hard freezes and snow.

Though to be honest -- they're having a freakishly warm winter here. It's nothing like the last time I posted from Denver.

Still, it's markedly different from winter in NorCal. But there's beauty all around -- you just have to know where to look.

Crabapples dangle from a bare branch

Miscanthus sinensis catches the morning light

A super grey juniper with blue/grey berries is just stunning

I'm enjoying downtime with my family this month, hoping you all get to do the same. Very happy holidays and I'll catch you in the garden in 2011!

By Johanna Silver, Sunset test garden coordinator

This recent article in the San Francisco Chronicle caught the eye of our garden department. It speaks of bug hotels, a European tradition that involves creating perfect mini-environments in which beneficial bugs can overwinter.

Design: Colleen Smith / Photo credit: David Paul Morris & SF Chronicle

Urban Hedgerow, an organization dedicated to creative ways to increase wildlife habitat, is partnering with local artists in hopes to amp up the popularity of bug hotels in the states. 

The design can be as simple as hanging upturned terracotta pots from a branch and filling them with pine needles, but with examples as creative as these, you might find yourself dreaming of your own bug chateau.

Photo: Lisa Lee Benjamin

Here are the instructions from the article in the Chronicle:

How to make a bug hotel

Insects are fairly undiscerning when it comes to lodging, says Urban Hedgerow founder Lisa Lee Benjamin, "Generally, they like dark crevices that are in a south-facing location so they can stay warm. Small sticks, logs, hollow spaces like straws, bamboo and reeds, oat or wheat straw, mulch and bark also make good bedding material. They also require nearby plant matter and nectar sources for food, a little bit of water to drink and, depending on species, anywhere from feet to thousands of miles to roam," she says. "Think of these hotels as small altars to the zillions of bugs that are essential to our planet's survival. It is the least we can do."

Step 1. Frame: Create or find a structure or frame to contain your bug hotel: a large piece of pipe, a box, a picture frame, a bicycle wheel or other found object, all preferably 6 to 12 inches deep, will do. The frame can vary in size and can either hang or be freestanding in the garden.

Step 2. Compartments: Find or build structures to create compartments on the inside of the frame. Pipes can be welded together or compartments created with wood, bottles, pots, etc. Make sure that these are secure and attached to the frame.

Step 3. Site: Position the bug hotel in its new home. Find a south-facing spot in your garden, preferably by some forage plants and nectar sources.

Step 4. Gather: Grab a pair of pruners. Search around your yard or neighborhood for fill material, such as weeds, sticks, bricks, old hose, leaves, burlap, rolled paper, string and anything else you can think of to fill each compartment. Think of creative ways to organize and arrange the materials, cut on angles, woven together or stacked. Remember to have fun and that there is no right way. Think like a bug and you will probably be spot on.

Step 5: Observe: Now see who shows up. You can look up your visitors on www.whatsthatbug.com.

Beneficials that would love a reservation include solitary bees and lacewings, and ladybugs.

My one concern is whether the crevices might also provide winter hideaways for less-than-desirable insects. The article mentions ants as critters like the nooks and crannies of a hotel. Last I checked, ants are not on the beneficial list. But truth be told, these insects -- beneficial and otherwise -- can manage without a bug hotel, so I think this is better viewed as an art project rather than serious habitat creation. 

I am going to play around with creating a few of our own for the test garden. I'll definitely post some pictures. And be sure to send yours to garden@sunset.com.

By Jim McCausland, Sunset Magazine

In 1874, John Muir wrote about how he made the most of a shrieking windstorm along the Yuba River in California's Sierra Nevada.

After cautiously casting about, I made a choice of the tallest of a group of Douglas Spruces [whose] lithe, brushy tops were rocking and swirling in wild ecstasy. Being accustomed to climb trees in making botanical studies, I experienced no difficulty in reaching the top of this one, and never before did I enjoy so noble an exhilaration of motion. The slender tops fairly flapped and swished in the passionate torrent, bending and swirling backward and forward, round and round, tracing indescribable combinations of vertical and horizontal curves, while I clung with muscles firm braced, like a bobolink on a reed.*

He stayed up there for hours, savoring the scents, sounds, and vistas—and, by the way, hearing "trees falling for hours at the rate of one every two or three minutes." This was more than a zephyr.

When such a storm slams your garden, you can't be quite so sanguine, since a falling tree can remodel your house in seconds. Your best defense is to assess your risk and get your trees ready in advance.

First think about wind direction. Where I live, most storm winds come from the south, but we sometimes get big blows from the north. Knowing direction, you can anticipate which way your trees (or their major limbs) are likely to fall. If you're fortunate, the wind will direct them to fall harmlessly across your lawn. But if wind direction and tree placement makes them a real danger, call an arborist.

The arborist will usually start by assessing the health of your tree. If it (and its root system) are generally sound, the arborist will probably start by removing whatever branches are unhealthy. Then they'll open the tree up so the wind will pass through. Left unpruned, evergreen leaves act like the sail on a boat, heeling the tree over so far that it may be uprooted or break.

Though there are rare exceptions, nearly always requiring years of professional follow-up maintenance, it's generally unwise to top trees. It usually gives them an ugly, amputated look, and the top they regrow will be weaker than the original, and more at risk of blowing out. As the people at Plant Amnesty used to say, "better death than mutilation."

If you have your trees pruned correctly, you'll save money in the long run, and nurture that element of your landscape that it takes the most time to replace.

Finally, much as I admire John Muir, I suggest that you stay out of the woods when it's windy. When a conifer's branch breaks off, the foliage has enough wind resistance to make the branch fall pointy end first. It can skewer you; that's why loggers call these widowmakers. Walk through the forest after a storm and you'll see lots of these stuck deep into the ground.

—

*"The Tree Ride" was first published in Scribner's Monthly, then reprinted in The Wild Muir (Yosemite Association, Yosemite National Park, CA).

By Johanna Silver, Sunset test garden coordinator        

Los Angeles had a record high of 113 degrees on Monday. Yowza.

We didn't climb quite that high, but it still feels like we're melting up here in the Bay Area.

Here are some photos I took yesterday of my cool-season babies wilting in the heat.

Wilting Swiss chard

Wilting collard greens

Wilting cabbage

I'm being a typically mom and worrying about them, but they'll be fine. I'm keeping them well watered. Wilting is normal by the end of a hot day. It's really only something to worry about if they're drooped over in the morning when it's still cool out. Then you've likely got a sick or under-watered plant. 

Here's more information on basic watering guidelines. 

By Jim McCausland, Sunset Magazine

Living in the Northwest, I’ve developed a particular fondness for what rain does for gardens. In a broad sense, it makes moss gardens thrive. In a more immediate sense, it bejewels leaves in a most amazing way, affecting some plants more than others.

Here are my favorites: leaves that deserve a place in the garden just for the way they wear their raindrops.

Lady’s mantle (Alchemilla mollis). This is the classic. Its leaves catch and hold raindrops better than any other plant.

Hosta sieboldiana ‘Elegans’. Water beads up on its big leaves like sprinkles on a just-waxed Porsche.

Kale and cabbage leaves. It makes sense. With leaves that are the functional equivalents of Gore-Tex, these plants never get soggy.

Lupines. Who’d have thought that these are as hydrophobic as they are drought tolerant?

Skunk cabbage. The mystery here is how this swamp lover’s giant leaves remain spatter free in the muddiest swamp. The same principle is probably what helps them repel water. Cannas behave in much the same way.

Tulips. Like kale and cabbage, these thrive in blustery spring weather, so it’s no surprise that their leaves have excellent water resistance.

By Sharon Cohoon, Sunset senior garden writer

Now that the holidays are over, it's time to think about bare-root fruit tree planting.  If you live in California, before you shop, check out the U.C. Davis website, The California Backyard Orchard.

The site provides the approximate chill hours needed for all the commonly grown fruit trees, describes some of the best varieties of same for home gardeners, and suggests specific varieties for different counties in the state based on their respective climates.

It also contains one of the best explanations of why fruit trees need winter chill I've read.  I''ve attempted to summarize it below, but I'd encourage you to read the full explanation.

Deciduous fruit trees have evolved to grow rapidly during the spring and early summer and then slow down as the length of day and temperatures decrease.  The trees then produce growth inhibitors (hormones) that keep them in a state of dormancy throughout winter.  They remain in dormancy until they have accumulated a specific number of chill hours (temperatures between 32°F-45°F), which varies with type of fruit and the variety.

Chill requirements prevent trees from growing again when unnaturally warm weather occurs in winter or early spring only to be damaged by normal freezing temperatures later.

By Jim McCausland, Sunset Magazine