Find out what a microclimate is and how your house and other buildings create many microclimates around your yard. Also learn what other landscape elements, such as fences and paved surfaces, can affect the temperature in certain parts of your yard.
LESLIE: Well, when you’re planning your landscaping or your garden, it’s always a good idea to choose plants, shrubs and even flowers that are native to your geographic area.
TOM: Absolutely. But beyond your geographic area, you can also get very specific about the climate right around your plants. These are actually called microclimates and planning for these very local conditions – here to tell us more about microclimates and help make sure that they assure the success of your garden or landscape is Roger Cook , the landscaping expert for TV’s This Old House .
ROGER: How are you?
TOM: We are excellent. And how micro exactly are we talking here, Roger? Are there different climates kind of theoretically going on in different places in your yard?
ROGER: Well, let’s start off with a broad point of view.
ROGER: There are hardiness zones that break up the United States into different areas of high and low temperature.
ROGER: This tells you what plant will survive in that area. Like if you buy a plant, you live in zone five? You go to the nursery, you find a plant that’ll grow in zone five so you know you’re safe.
TOM: Got it.
ROGER: Now, if the zone goes colder, like zone four, a zone-four plant will grow in a zone five. If you have a plant that likes warmer temperatures, like a zone seven or eight, and you put that in a zone five, it’s going to die.
TOM: So palm trees in New Jersey don’t do so well.
ROGER: Only if you can take them inside for the winter. But as a general rule, no.
TOM: Alright. So, we know that we have to match our planting to our specific hardiness zone but beyond that, when you get into your own yard, there are conditions that can actually change that and almost move a section of the yard into a different hardiness zone, theoretically, correct?
ROGER: That’s right. And it happens both on the warm side and the cold side. We’ve had several places where the sun will hit off a concrete wall and that gathers and retains the heat.
ROGER: So that area there, we could actually grow a plant that would be out of its zone, because of those warm temperatures. The other thing that happens in that warm zone is those plants will grow faster or flower earlier than other plants in the yard.
LESLIE: But will that zone – that new sort of microclimate that you’ve created just because of this perchance that you’re reflecting the sun off of this building – will that continue throughout the year? Or once you get into a winter season, is that going to be really detrimental to that plant?
ROGER: It’ll revert back to whatever zone you’re in, so you’ve got to be careful. Most people find that with a warm microclimate, the plants bloom earlier and they’re always wondering why. And that’s why.
Then there’s the other side of the house: the north side. Now, it doesn’t get any sun and that stays colder, so you’re almost in a colder area. So what you should do is balance that: make sure you put the right plants that will take that coldness, like a zone-four plant, in that area.
LESLIE: Now, Roger, this is all really fascinating. I mean so many things can affect how your garden succeeds so is there an example where you’ve seen this in effect?
ROGER: We actually did a project on Ask This Old House where we had a homeowner who had a set of stairs with matching plantings on either side of the stairs; they had a dwarf Alberta spruce on either side. The one side, the plant was all shriveling up and diseased because of the heat that was caused in that one corner. The other side, the plant was beautiful.
So we took out the dwarf Alberta spruce, which wasn’t dealing well with that heat in the sun, and we put in a yew, which had the same shape as the other dwarf Alberta spruce but would tolerate those conditions there.
LESLIE: And it all worked out?
ROGER: It all worked out beautiful.
TOM: So it sounds like what you’re saying, Roger, is that, typically, we see a plant that doesn’t do well or seems to do extraordinarily well and we always blame it on the plant or on the soil. But we really need to expand our view to kind of think about what’s happening right around that area of the building – of the yard, the sunlight, the reflecting surfaces – to really get an understanding of what’s going on there.
ROGER: Right. That particular microclimate could be affecting that plant’s performance and you described it perfectly, Tom.
TOM: So the choice might be to move up or down in hardiness zones based on what you’re seeing in that particular area, if the plant is not doing well.
ROGER: That’s right. So we’ve just about confused everyone and they don’t know what to do.
TOM: Well, I think the point is that there’s a lot more than just choosing the plant in the zone; you really need to look at what’s around it. And this kind of advice is very, very insightful. We’re going to have a lot of gardeners out there going, “Aha. Now I know why it’s not doing so well.”
Roger Cook, who always helps us do well with our landscaping  chores, thanks so much for stopping by The Money Pit.
ROGER: You’re welcome.
LESLIE: And remember, guys, you can watch Roger and the entire This Old House team on This Old House and Ask This Old House, which are on your local PBS station.
TOM: And This Old House is brought to you by State Farm. Like a good neighbor, State Farm is there.