Tag Archives: climate zones

Gardening 101 – Climate Zones

You can tell right away when you walk out the door how hot or cold it is, how windy, shady, moist or dry. You know if your soil is pure sand or hard clay because you’ve dug a few holes in your time. You don’t need a book to tell you these things. So why are the gardening zones described in Sunset Western Gardening book important when you add a new plant to your garden? And why are they so confusing in our area? The USDA Plant Hardiness zone map may tell you where a plant may survive the winter but climate zone maps let you see where that plant will thrive year round.

Mixed forest Bonny Doon- zone 15

For decades, climatic data has been complied and maps generated to help make sense of local growing conditions. In the 1930’s, Sunset Magazine began mapping the western states, taking into consideration the unique climatic growing conditions along with the traditional data of minimum and maximum temperatures, latitude, elevation, ocean influence, continental air influence, mountains, hills and the local topography.

Today the map has become known by many as the gold standard for western growing advice. Zones are numbered from the harshest (Zone 1) in the north to the mildest (Zone 33) in the south.

To accompany the map a plant encyclopedia was developed that assigned the appropriate zone(s) for each plant. The system helps take some of the guesswork out of plant selection if you take into account your microclimate.

The zone system isn’t perfect. After all, the data collectors don’t live here in our neck of the woods. Still, it’s a good idea to take a look at the Sunset zone you live in to see if a plant might survive in your garden – if you keep these exceptions in mind.

Light dusting of snow in February 2018- Bonny Doon

We really only garden in two zones around here – zone 15 and 16. The Sunset map erroneously shows Felton as being in zone 7. Based on my experience even ridge tops like the highest portions of Bonny Doon and the Summit area which gets an occasional dusting of snow fall mostly in a colder zone 15.

Zone 15 – this zone encompasses most of our area. Winter lows average 20-30 degrees although we are trending toward warmer winters these last few years. The valley floor of both San Lorenzo and Scotts Valley lie in this zone and are what I call “a cold 15”. Cold air sinks and is trapped in these areas. There are warmer parts of this zone, though. These areas rarely get a freeze after March 15th or before Thanksgiving.

Zone 16 – those who live up off the valley floor but below ridge tops live in this “banana belt”. Light frost can occur during the winter but mostly the winter lows in this zone stay above freezing.

Ceanothus near Felton Covered Bridge, a cold area near San Lorenzo River.

Beside the zone you also need to note how much sun or shade you get during the growing season. There may also be microclimates on your property. And soil quality is not taken into consideration in zone mapping. Since the soil houses the water and nutrient uptake system for most plants, it plays an important role. Most plant guides describe soil requirements in terms of well-drained, acid or alkaline, poorly drained or high organic matter.

If you have questions about which zone you are in, email me and I’d be happy to help. I hope this helps in choosing plants that will thrive in your garden.

Zones for the Santa Cruz Mountains

Gardening is a tricky thing up here in the Santa Cruz Mountains. Recently I got an inquiry from a new resident to the area. She moved up here last year from the west side of Santa Cruz. Not that far away on the map. A world of difference in soils and climate. She lamented, "I Can't believe the difference in the soil here. I lived a mile from the beach and now that I'm miles away, I have the sandiest soil ever."  Welcome to our wonderful world.

Our soils were formed from marine deposits and from molten rock emerging from the earth's crust. Areas underlayed with shale creep and slide during wet weather. Serpentine and granite soils crisscross the mountains.
What's a gardener to do?

It helps to know which zone you garden in. So here's a review. Sunset Western Gardening Guide is confusing as our area has many microclimates and their map is not detailed enough to reflect this. They even show Felton as being on a ridge top instead of on the valley floor. Hopefully, the new Sunset book out this month will be more accurate. Here are some tips to help you determine which zone you live in.

Zone 7  has the coldest winters in our area.  Very high ridge tops like the Summit area and the most northern portions of Bonny Doon lie in this zone.  My records show average winter lows ranging from 15-25 degrees based on 20 years of input from gardeners in these areas.  This does not apply to other areas of zone 7, just those around here.   Record lows have occurred during freezes in 1990, 1996 and 2007 but as gardeners we rely on average highs and lows to help guide our planting times.  Spring weather comes later in this zone with the growing season mainly from April – October.

Zone 15 – this zone encompasses most of our area.  Winter lows average 20-30 degrees. The valley floor of both San Lorenzo and Scotts Valley lie in this zone and are what I call "a cold 15".  Cold air sinks and is trapped in these areas. Often there is damage to the tips of oleanders and citrus while gardenias and tropical hibiscus need extra protection.There are warmer parts of this zone, though, where the growing season starts in March and ends in November.  These areas rarely get a freeze after March 15th or before Thanksgiving.

Zone 16 – those who live up off the valley floor but below ridge tops live in this "banana belt". Pasatiempo also falls in this thermal zone.  Light frost can occur during the winter but mostly the winter lows in this zone stay above freezing. Lucky you.

Beside the zone you also need to note how much sun or shade you get during the growing season- April through September. Most plants can survive without sun during the winter as they are either dormant or semi-dormant. It's those areas that get a blast of sun from about 11 am to 4 pm in the summer that you need to plan more carefully for.  

There may also be microclimates on your property. Areas in your garden that are several degrees warmer than other spots. Maybe a brick wall or the top of a slope from where cold air drains generates a few extra degrees.  Planting a citrus at the top of a slope that drains away the cold will make your tree much happier than if planted in a low open area.

If you have questions about which zone you are in, email me and I'd be happy to help.
 

What Zone Are We?

Spring is coming. Like me, you’re  probably anxious to get started in your garden. We’ve gotten some much needed rain and hopefully there is more to come. As you’re thoughts turn to gardening, though, make sure those new plant choices are the right ones for your area.

Notice how much sun or shade an area gets during the growing season- from April through September. Knowing  also which Sunset climate zone you are in is equally as important to make sure your garden thrives. Every year I get asked which zone the areas of Scotts Valley, San Lorenzo Valley, Bonny Doon are in. It’s confusing in Sunset Western Gardening Guide as our area has many microclimates and their map is not detailed enough to reflect this. They even show Felton as being on a ridge top instead of on the valley floor. Here are some tips to help you determine in what zone you garden.

Zone 7  has the coldest winters in our area.  Very high ridge tops like the Summit area and the most northern portions of Bonny Doon lie in this zone.  My records show average winter lows ranging from 15-25 degrees based on 20 years of input from gardeners in these areas.  This does not apply to other areas of zone 7, just those around here.   Record lows have occurred during freezes in 1990, 1996 and 2007 but as gardeners we rely on average highs and lows to help guide our planting times.  Spring weather comes later in this zone with the growing season mainly from April – October.

Zone 15 – this zone encompasses most of our area.  Winter lows average 20-30 degrees. The valley floor of both San Lorenzo and Scotts Valley lie in this zone and are what I call "a cold 15".  Cold air sinks and is trapped in these areas. Often there is damage to the tips of oleanders and citrus while gardenias and tropical hibiscus need extra protection.There are warmer parts of this zone, though, where the growing season starts in March and ends in November.  These areas rarely get a freeze after March 15th or before Thanksgiving.

Zone 16 – those who live up off the valley floor but below ridge tops live in this "banana belt". Pasatiempo also falls in this thermal zone.  Light frost can occur during the winter but mostly the winter lows in this zone stay above freezing. Lucky you.