master the garden: microclimate management

I have lived in 7 different planting zones and not one has been a perfect match for growing what I wanted. I had to get creative. What I learned was some plants will struggle to survive or fail to thrive without a little intervention on my part and just a few subtle manipulations in adjusting the microclimates in the garden.

Shady glen at Bloedel Reserve, Bainbridge Island, WA photo – l. fowler

First…what is a microclimate? It’s a small area within your zone where the climate is slightly different from the USDA Hardiness Zone predictions and has different growing conditions. An example would be urban heat islands – where asphalt, concrete and brick absorb the sun’s energy, heating up and radiating that heat to the ambient air. Urban growers may be able to successfully grow plants recommended for warmer zones because of this heat. Other microclimates include patios and courtyards – or how cool air flows off a body of water. In a microclimate the air may be cooler or slightly warmer than our zone map indicates. Around your garden, home, fences, and structures, patios and even the amount of moisture and shade, all give rise to the character of your microclimates.

The term microclimate can refer to an area as small as a few square meters and is usually altered by features of the landscape – so you really have to observe your garden and landscape for a while and during different planting seasons to find solutions to alter the climate. These “mini-climates” are usually what the home gardener experiences along a fence, against a wall, or an area on the southside…The other way to work with mini-climates is to alter your plantings to accommodate the conditions – for example – if you are on a slope, drainage creates a ‘pond’, than plants with ‘wet feet’ (canna, cattail, dogwood, iris…) would be an appropriate choice.

You can also create mini or microclimates in your garden. below are some simple suggestions to ‘tweak’ the climate in your garden.

1. warming the soil

These vegetable boxes were placed by a southeastern wall (sun-facing) because the ‘thermal mass’, the ability to absorb heat, used to create warmth during the day and aid with a few essential degrees at night. Any wall, fence, or paving can work as a thermal mass and be a huge benefit for ripening vegetables and prolonging tender perennials through the season.

2. warming your greenhouse

I love the permaculture practice of using water bottles to warm your hoop, greenhouse, tunnel, or cloche. Just about any container will work – these are painted black for more solar absorption. Water bottles can also be placed around your tender starts after transplant for a few extra degrees at night.

a word on warming…

Just a little ‘cheat’ of a few degrees for an earlier seasonal planting can be achieved by warming your soil with sheets of plastic cover – this not only warms the soil but help to dry for gardens in wet regions. Optimal soil temperature for planting and growing is 65° to 75°F – check the information on the back of your seed packs for minimum temperatures to germinate and grow and use row cover fabric after planting to ensure an easy transition for seedlings.

Another way to create a warm microclimate for the early spring or late fall is to plant shade trees on the north side of your garden. By the trees absorbing the sun’s heat during the day and emitting it at night you will increase the amount of heat disbursement from the sun over a 24 hour period while enjoying the cooler temps provided by the shade during the day.

3. raised bed support

Back support was added to these raised beds in the form of a short fence and served to shade and protect transplants until they were establishing from both wind and sun damage. It added some aesthetic interest also!

4. multi-purpose fence

The fence in the photo serves multiple purpose for these garden plants. Located in the front NE corner of the home, plantings were at the mercy of strong summer hot and drying winds as well as freezing winter wind. The structure buffers the wind effect and the black color absorbs the winter sun as a thermal mass. It also serves as a privacy screen from the neighbors driveway.

Wind can be tamed in most areas through carefully placed windbreaks and they do not have to be manufactured structures. Living windbreaks, trees and shrubs, to slow prevailing winds can add to the landscape as well as serve a function in altering your microclimate. Even temporary ‘screens’ of mesh or netting can be effective for protecting tender plants and blooms.

photo – l. fowler

5. shade for the cool season plants

Summer heat can take its toll on even the hardiest of plants, and your cool season crops and shade loving perennials need a little extra help to escape the relentless heat of summer. Using companion plants can offer many benefits – from attracting pollinators and adding nutrients to the soil to as seen above, the use of taller plants to protect shade loving understory plantings. This is not only attractive but offers a cool shaded microclimate.

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