How do I measure full sun, part sun, and full shade?
Full sun is usually defined as more than six hours of sun a day. It doesn’t have to be all at once. Some of the sun could be in the morning and some in the afternoon, for example.
Part shade or part sun is four to six hours a day (often morning or afternoon sun).
Full shade is less than four hours of sun a day. Full shade is sometimes divided into dappled shade, or the conditions that occur under a high tree canopy, and heavy shade, the kind you get on the north side of a house or under dense tree cover where the plant never receives direct light. Heavy shade is challenging for plants.
What time of year do we measure sunlight?
Most sources don’t answer the obvious follow-up question: what time of year are we looking at when we measure these hours of sun? Here in Maryland we’re pretty close to the middle of the contiguous US states latitudinally (in a north-south direction). We get nearly 15 hours of light at the summer solstice, around 12 at the spring and fall equinoxes, and 9.5 at the winter solstice. It makes a huge difference what time of year we’re measuring that sunlight. Our sunlight is a lot more scarce and precious in the winter.
I could find no sources that actually discussed this! Every site simply recited that full sun was more than six hours of sunlight. I can only conclude this must be the minimum, which would be measured at the equinox. This means that in late March and late September, your site must get sunlight for at least half of the 12-hour day to be counted as full sun. This seems somewhat logical.
It makes sense until you think about it…
Except in our area, most trees still don’t have leaves at the spring equinox, so the amount of sunlight might be greater in late March than in late April or late September when there are leaves on the trees. This is a fact the spring ephemeral plants use to great advantage, but it does make our calculations difficult.
In the middle of the summer, the sun is much higher in the sky and stronger than at the equinoxes. The sun is also stronger in the middle of the day than at dawn or dusk, meaning one hour of sun isn’t necessarily equivalent to another hour at a different time of day or year.
And also, full sun is a six-hour block of time. Full shade is 0-4 hours of sun, which is a 4-hour block. Part shade is 4-6 hours of sun, which is only a two hour block. Why the discrepancy? Why divide up the day so unevenly? I don’t know. It’s just what we do. It makes no sense.
Full sun isn’t full sun everywhere…
Not to mention that “full sun” isn’t the same across the country. A plant in the open in the Southwest will get more sun in kilojoules than a plant in the open in Cleveland or Seattle simply because of the the Southwest has relatively little cloud cover. I love this interactive map by the Washington Post that shows where America’s sunniest and least sunny places are. (It’s also a useful resource on places to avoid living if you have seasonal depression. I’m looking at you, Island County Washington.) https://www.washingtonpost.com/news/wonk/wp/2015/07/13/map-where-americas-sunniest-and-least-sunny-places-are/ But while ‘solar insolation’ is used to measure sunlight in other contexts, nobody has calculated the tolerance ranges of thousands of perennial plant species in kilojoules.
Honestly, as a professional, I never measure sunlight with any kind of device. I just use my finely-tuned spidey senses. My professional recommendation is to not think about it too much. The honest truth is that these are ‘rule-of-thumb’ categories. Many plants grow in a wide range of conditions. In 2015, I planted sun-loving plants on a site that gets around 5-6 hours of sun at the spring equinox and around 6 hours at the summer solstice. Most of the plants are happy, but the little bluestem would really prefer more sun to flower well and the big bluestem in the back where it’s shadier is struggling. Part shade plants would have worked too, but might have needed more water in the summer. It’s an inexact science.
But I really want some hard guidance!
You can look at solar path calculators like https://www.suncalc.org. Type in your address, turn on the aerial imagery, and take a look at the sun paths on the solstice and equinoxes. Hovering over the light orange line will show you the wedge in which the sun rises during the year. Hovering over the dark orange line will show you the wedge in which the sun sets. Adjusting the slider at the top of the screen will show the position of the sun at various times of day, so you can calculate how many hours from, say, sunrise until the sun is blocked by trees or houses. But again, this is just an estimate.
How do I determine my site's moisture level?
Moisture level is also a bit subjective. It depends on soil type, but also groundwater and topography. I use four different moisture categories: dry, average, moist, and wet. Different parts of your yard can have different moisture levels. For example a ditch or low area is likely to be wetter than the top of a slope.
Soil Moisture Levels
Dry
Dry areas are usually located on hillsides or hilltops, or on sandy or rocky soils. These sites usually have low organic matter and hold very little moisture. Water runs right through or off these soils and even after a heavy rain, there will not be any ponding or squishiness. Many garden plants wilt, struggle to stay green, and die under these conditions. In the driest sites, even grass and weeds may struggle and there may be bare patches of soil. Luckily, some perennials thrive under these conditions- you just need the right ones!
Average
Average areas are somewhere in the middle between dry and moist. These sites have a range of soil types and more organic matter than dry sites, but hold less water than moist or wet sites. If you’ve never noticed a lot of water ponding and don’t have an issue with most plants drying out, you’ve been blessed with average soil and can grow a wide range of plants. Unfortunately, many weeds also grow well in these conditions.
Moist
Moist areas, unsurprisingly, hold moisture well. You may notice that parts of your yard are soggy, squishy, or hold water after it rains, usually in low spots or drainage areas. These soils do eventually dry out, unlike wet soils. Often these soils have a high organic matter component such as mulch or leaf litter to hold the moisture in. These sites often tend toward loam or clay soils, which hold water longer than sand. Hydrangeas love moist soil- notice that the first part of their name is from the Greek hydro, for water.
Wet
Truly wet areas are submerged most or all of the time, drying out only on very rare occasions. This is the realm of aquatic plants. In these plans I will more often use the category ‘moist-wet,’ which indicates plants that can tolerate some seasonal standing water or grow on the edges of streams, lakes, or ponds, but are not true aquatic plants.
What if I’m not sure?
Use your best guess. Plants are adaptable. If you’re a little off, it shouldn’t be a big deal, although your plants might need some extra care. Back in 2013 I planted Joe-Pye weed (which likes moist to wet sites) on a hillside at my parents’ house with other perennials that prefer medium to dry conditions. It has survived, and even spread a bit, but it wilts in droughts and needs additional water, which my mother is happy to give it. If you find they are not happy, most perennials can also be moved after planting to a better location.
On the other hand, some perennials spread rapidly through rhizomes (roots) to form a large stand. You can often reduce the rate of spread of these plants by planting them in conditions they will tolerate but do not prefer. For example, if I had planted the same Joe-Pye weed in a moist ditch, it might have spread to become a huge patch in the last ten years, and I might be pulling it out and cursing it by now.
How can I determine my soil type?
Take a look at the USDA’s Web Soil Survey application to determine the soil type(s) on your property. Once you enter the application, select ‘address’ on the left menu and type in your address. In order to return results, you must select an Area of Interest (AOI) using the tool above the map with the rectangular icon that says ‘AOI’. Select a generous area around your property. The soil maps are only valid to a certain scale, and unless you have a really big property, it will give you a warning that the results may not be valid.
Once the AOI is created, look at the tabs at the top. I like to select ‘Soil Map’ first. Select the soil type(s) on your property from the left menu bar. Scroll down to find ‘drainage class’ and ‘depth to water table,’ which will help with moisture. My soils are moderately well drained and well drained, with no frequency of ponding or flooding and a depth to water table of 20-40 and 80 inches. This tracks, as I live on the side of a hill and only see water sitting at the bottom of the street. The site has a lot of information. Take your time and poke around; you’re likely to find something interesting.
Your lived experience holds more weight than the map. If the map says well drained and you have a puddle, maybe the map doesn’t know you have a buried swimming pool in your yard that no one removed properly. You think I’m joking but this happened to one of my clients!
What is a USDA hardiness zone? How can I find mine?
USDA hardiness zones are geographic areas defined by their average annual minimum temperature. This is useful for determining which plants will survive in your area. You can find your USDA hardiness zone by entering your zip code at https://planthardiness.ars.usda.gov/ There are also state-level maps available for download, but I find the zoomable map the most useful.
The USDA hardiness zone is a rather coarse metric. While it’s a good guide for whether a plant will thrive in your area, it’s not a guarantee. Note that it says nothing about the average annual maximum temperature– two places in the same USDA hardiness zone may have very different annual maximums. A truer zone system would take into account additional climactic and rainfall data, like the Sunset Zones out west or the Köppen climate system. For example, plants that grow in Mediterranean climates with warm dry summers and mild rainy winters may be technically hardy where I live in Maryland, but they don’t thrive- they tend to melt out in our hot, humid, and rainy summers.
What's the difference between a freestanding bed, a border, a matrix planting, and a foundation planting?
Freestanding bed
A freestanding bed is like a garden ‘island’ in that it can stand alone in the middle of a lawn or pavement and look good from all sides. Generally shorter plants are placed around the edges and taller plants are placed in the middle. Freestanding beds can be any shape- square, kidney, circular, oblong, or freestyle. Here are some examples of freestanding beds.
Borders
Borders are linear beds that go along an edge (a fenceline, a hedge, a building, a forest edge) and have a defined front and back. You are usually only meant to see a border from one of the long sides. Shorter plants are placed in the front of a border and taller plants are placed at the back.
Foundation Planting
A foundation planting is a special type of border that is intended to go along a house foundation and ‘ground’ a house in the landscape. It usually (but not always) contains evergreen shrubs to provide winter interest. The height of the windows from the ground will determine the lowest height of the foundation planting.
Matrix Planting
A matrix planting is a planting meant to cover a larger area of space, like a meadow or an open forest understory. There is a base groundcover layer or low grass planting from which taller plants emerge, for example a ‘Sesleria matrix’ contains Sesleria grass around and in between clumps of taller perennials. Sometimes a matrix planting is set up like a grid and can be tiled in all four directions but this is not always the case.
Grid Planting
A grid planting is tileable in one or more directions, meaning that it can be repeated. A border grid is usually just tileable in one direction, while a matrix grid is usually tileable in both directions and can be used to cover large areas of space.
What's the difference between beginner, intermediate, and advanced plans?
Beginner Plans
Beginner plans are very straightforward. I have chosen the plants for their toughness and resiliency east of the Mississippi River in the zones listed on the plan. They should stay green and look good for most of the year (except for winter). There are fewer species, smaller planting layouts, and plants should for the most part be available at local retail nurseries.
Intermediate Plans
Intermediate plans have more complexity, a greater variety of plants, and some species that may come up for part of the year, then die back (for example, bulbs, spring ephemerals, or late-emerging plants). Intermediate plans are also suitable for committed beginners who are excited about a little more complexity.
Advanced Plans
Advanced plans have multiple layers of planting, larger areas, many more plant species, plants that may be more difficult to grow, and plants that may be difficult to find or source from retail nurseries. Advanced plans are for people who have gardening experience, aren’t afraid to hunt less common plants down, and/or who want a garden adventure!
How do you determine deer resistance?
Deer tend to like some plants more than others. They particularly dislike bitter, hairy, or grasslike plants. For the deer-resistant plans I’ve tried my best to use plants that deer don’t enjoy but there’s no guarantee. The level of deer pressure and the tastes of your particular deer will determine whether your plants are browsed. Young deer will try anything- I once found a bite in a thorny agave leaf. I laughed. Never saw that again. You can apply deer-repellent sprays but you need to be consistent and apply again after it rains, which can be a bit tedious. If zoning code and budget allow, you can install a 7′ or taller deer fence. Keep in mind that these fences can also keep beneficial or desired smaller animals out depending on the mesh size (turtles, foxes, etc.).
Unfortunately I often have to limit myself to deer-resistant plants, which is frustrating, as it limits biodiversity and eliminates some great plants from consideration. The best way to solve the problem is community-wide deer control. People often get very upset about managing deer populations, but for some reason they don’t consider that by taking no action, they’re killing thousands of plant lives and eliminating entire species from the landscape which in turn would support pollinators and birds. Some native bees depend entirely on one type of native wildflower for their life cycle. If deer like to eat that wildflower, then the bees disappear. It’s all connected, and we’ve eliminated the natural predators of deer, putting the system off balance. We can’t fix it by doubling down on that imbalance.
With that said, here are some plans with deer resistant plants.
What do you consider native?
This is the million-dollar question. I could write a book on the complexities related to this topic. (I might!). For this website, I’m considering any plant native to eastern or central North America to be ‘native’. In the future I may offer more granular options, but that’s just not possible at this point. I’m currently focusing on beginner and intermediate-level planting plans with a broad appeal. If you have questions about the plants in a particular design or you’d like a planting design native to your state/region, reach out. Of course I don’t include any invasive plants in any of the designs!
Why can't we see what plants are in the plans?
Most other companies are selling planting plans bundled with live plants. These companies make money off of the plants and use the plans only as a sales tool. We’re designers, not nursery growers, and we want you to be able to source plants in an affordable manner from wherever you like. We don’t want to give away our plant species selection because it’s 50% of the secret sauce of our designs. If you have concerns about what’s in a specific plan and you absolutely hate a specific plant or something, reach out and we can clarify as much as possible.
What are the legal terms and conditions?
All plans are copyright Perennial Garden Plans. These plans are for personal, noncommercial use only. You may not pass them off as your own or resell them to others. If you are a landscaper, you are welcome to charge clients to install these designs, but each client must individually purchase a plan from perennialgardenplans.com. Consider that the cost of these plans is a small fraction of the cost of hiring a landscape designer. Your support is essential in allowing me to make a living and continue creating new and exciting planting designs that are accessible to as many people as possible.
Thanks! -Renee


