The Q&A Archives: Attribute Definitions (ie. Partial Shade)

Question: I have a question about planting your Astilbe Fanal.

Our landscape architect chose a location that I'm not sure is correct in terms of light. Can you please send me definitions of Full Sun, Partial Shade, Partial Sun, Full Shade? That would greatly help me evaluate the site plan.


Answer: There are no hard and fast definitions, so in most cases experience with the general growing conditions and plants in the local region and then the microclimate of the site are all important factors in deciding what to plant where or how to evaluate the lighting conditions.

For instance, full sun in a cool summer area might be the equivalent of morning sun-only in a hot summer area. A plant that likes partial shade may be happier with extra moisture or a more moisture retentive soil and a little less sun in a hot summer area. Luckily, most plants will tolerate a range of conditions within some general parameters. For instance, a plant that prefers shade may tolerate partial sun during the morning or dappled light all day if there is ample soil moisture, or a plant that would prefer full sun may be satisfied with afternoon sun for at least six hours including the hour of noon. So there is always a certain amount of judgement call and experimentation when determining a planting plan.

Generally a plant listed as sun to part sun is actually a sun lover, and a plant listed as shade to part shade is actually a shade lover. Take care in that your source for the recommendation is basing it on local conditions as well -- a plant that requires full sun in a cool climate may need partial shade in a warmer one and for this reason many gardening books from England for example can be misleading here.

Having said that, a rough guide would be full sun is sun all day long or for at least six hours including the hour of noon. Partial shade can be dappled light through trees, some direct sun during the morning and shade the rest of the day, or shade most of the day with some direct sun in late afternoon to early evening and/or early morning. Shade would be solid shade as from a building, or from a heavy tree or shrub canopy. Keep in mind too that the sun is higher in the sky in midsummer so the shade patterns shift throughout the year.

One good way to try to consider plant choices is to locate some growing in your area and observe how they are sited and what type of special care they are receiving such as frequency of supplemental watering. Then look for similarities in the growing conditions and microclimate of your own landscape.

I hope this helps you interpret your plan. Since you seem uncomfortable with it, it might be a good idea to discuss the choices with the landscape architect so that you are familiar with the rationale used to select the plants. Perhaps there is also room for alternate choices if you are still worried.

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