Microclimates

Hi guys, I also posted in the "Beginner Landscape" forum, but I do know there are some VERY knowledgeable folks in our California forum, so, posting here too!

I'm trying to understand my garden's microclimates. I've read that cold air drains down slopes and accumulates in pockets at the bottom. But I've ALSO read that protected areas adjacent to brick walls can be much warmer than other areas, sometimes a whole zone warmer. (?)
I would like to find the best spot to plant a heat-loving tree and heat loving/tropical plants. Can you please help me sort this out? This is a picture of my garden, looking NE.
Thanks for any clarification, I would love to learn more about this!
Roberta

Many conditions can create microclimates... including but not limited to, the exposure of where the microclimate is, time of year and physical stuctures like walls, fences, and even other plants.

You are correct about cold air and how it tends to drop down slopes, etc. and "collect" at the base as cold air is heavier than warm air.

Areas of a garden with differences of just a few degrees can be a microclimate.

2 winters ago, when we had a cold snap, I lost common old sword fern to frost in one area of my garden. The ferns in the area that froze were not protected by any other plants, walls, or structures. Three feet away, (across a cement walk) the same ferns were unscathed. They were also protected by a very low branching tree, some tall camellias and an arbor.

Similarly, in another corner, which faces NW, a tall fuchsia, up against a stucco wall survived just fine. The wall trapped the heat of the day enough to keep that area warm enough, along with some shorter camellias which sort of act as insulators when it gets cold.

One half of my garden is in complete shade from November to April because of how the lot faces, where the house sits, and the pattern of the sun. From April on, it is in full sun...and I actually have to put up portable shade covers for some of my hydrangeas and a few other sun-sensitive plants. That particular area is always a good 10 to 15 degrees colder in the winter than the opposite half which is closer to the house.

Discovering where your microclimates exist, and at what times of the year, is challenging at best. Trial and error with different plants in those areas will ultimately prove to be the solution and you will learn what will survive and for how long.

It's all a learning and observation process...but we can't control the weather so I think everyone at some point has difficult areas of a garden that always present some sort of challenge.

Yes, you are so right about trial and error! I had the same problem with some hydrangeas. I planted in the fall and now - ta-da! - they are in the sun. I should have known better!
My situation is tricky because the area that gets warmth from that brick wall is also the area where possibly cold air drops from the slope....it's confusing!

I'll second the trial and error thing! There are just too many variables that impact it, my warmest winter microclimate is actually not where you'd predict it would be based on how cold air flows and where it would collect, but I know that's the warmest area based on 2 winters here seeing which parts of the garden get frost and which don't, etc. With summer temperatures though I've found it's easier to predict where the hottest parts of the garden are going to be--anything on the west side of my house is always hotter than anything on the east side. The south side will frequently be warmer too for many people, but for me I've got a row of Italian cypresses shading the couple feet of south-facing side yard that exists between my house and my neighbor's, and between the houses and the trees that part stays pretty cool because there's so much shade.

Ecrane...as always..thank you! I am also posting on the other thread.

My sunny hilltop is a whole zone different from the closest town. On the sunny South wall I can over winter Cacti and semi-tropicals but on the North side Rhodedendrons and shade loving plants are happy with minimal water. I would say be very observant and actually keep track of tempertures and hours of sun in a garden diary. Just pay attention. carri

I'll never forget coming across a Trachycarpus fortunii in Seattle one drizzly day. I was walking to my bus stop and took an alternate route to go see if some enormous Horse Chestnuts were in bloom near an old school in my Wallingford neighborhood. I literally stopped in my tracks when I saw the 15 ft. high palm tree. Now, this was about 20 years ago, and they were not at all widely planted in the Pacific Northwest at that time (now, many have them near patios, etc.).

To this day, it is one of the tallest of this species I have seen in Seattle (I live in SoCal now, of course, but visit family yearly), all due to MICROCLIMATE! It is on a hilltop (cold air drains!), against a south-facing wall (wall collects heat), with shelter from winds by other big trees (less cooling), but NOT shaded (all day sun exposure), and it is on a street corner, where it gets reflected heat from the asphalt.

A perfect example of how microclimate affects plant growth.

Jungleman, what a cool (or should I say warm?) story! I actually had to google the palm tree you talk about....and it totally looks like one of my palm trees (which I had no clue about id). Do you think that's what I have here?

I don't know why on earth it won't let me post the picture vertically, sorry if I give you neck pain, lol!

robcorreia - yep - no doubt about it. These are very common in Southern California, but have only become a common sight in Seattle in the last 15 or so years. They say that they have a small grove in Butchart Gardens in Victoria, British Columbia, Canada.

Seattle, while being rather rainy, is also mild - some years there is no snow at all, and many subtropicals can be grown as either perennials or as deciduous plants. I grew Chamaerops humilis there as well, without trouble (though excruciatingly slowly!).