Yowza! This is not a simple question :-)

With the beginning caveat that photoshopping is not a substitute for design, there's a couple of other reasons this may not work well. If you search by botanical name, you can usually find full-size images - but there is really no way to judge the scale of the images/photos you find. So you could be placing two plants side by side that are indeed full-size images yet one may only grow 2'x2' while the other 5'x5' yet they look exactly the same size in the photo. See what I mean? Plus, photoshopping is only two dimensional so you can't easily judge mature spread and therefore correct spacing or placement. The second is that many Google images are copyrighted and you can't pull them out of their context. And flowering plants are most often shown in flower so you could have a grouping of great looking flowering plants only to discover that in real life they bloom at very different times of the year.

If you think this is the route you want to follow, I'd suggest you find some landscape design software that already has a plant data base associated with it. You can do a very similar process to photoshopping but at least the input will be in scale. A lot of the DIY stuff can be had pretty inexpensively -- you might even find some free downloads.

The other alternative is to draw up your design on paper with the plants you think you'd like to include. You can research growing habits, mature sizes, spacing, flowering times, etc. online. Then check out images either online or in any of a couple hundred books available at your library to see how you like them in combo.

Or we could ask ideashare to whip up one of her photoshopped masterpieces for you :-) (that is a joke!!)

Thanks for the comments. I know the average mature heights of all the plants I'm considering and could use the height of the wall to scale them, but I get your gist ... it probably will be more work than I'm expecting, given that I'd have to mess around with converting not only image height/DPI settings but also then have to erase the background of those images. I can do it, I'm sure, but do I want to put the time into it?

I think what I'm probably going to do is use photoshop filters to transform the photo into a watercolor or sketch image and then -- using online photos to match foliage and flower colors -- brush in the approximate shape, size and color of the plants I'm considering. It'll give me a general sense as far as color and scale, which is primarily what I'm looking for.

Yes, my comment was going to be that it's a fairly simple question if you just eliminate the photoshopping part. You're just trying to imagine, sketch, or paint the plants as they will eventually look.

We're all pretty quick to think the computer can do this because that's where so much of the information is, but pen and paper are actually much more flexible and user-friendly tools!

I can't remember now which of my plant books it is, but there are some - and plant tags have this too - that show you a black "shape" drawing of the plant at maturity. Even if you can't find that, you can translate words to images - you've got your upright arching, spreading ground cover, columnar, round, and so on.

Then there's always working with the real thing. Whether working at home with plants you already have, or at the nursery with plants you're considering buying, you can arrange the pots in some facsimile of your plan and rearrange until the result pleases you. Of course, you still have to project to mature size, but you can observe growth habit.

KarinL

I'd recommend spending time walking/driving the neighborhood if you have older, mature landscapes around, or visit your local botanic garden to get a better idea of the actual plants. In my view, focusing on flowering colors for combinations of plants is too ephemeral, and I would rather focus on size, texture, foliage color, contrasts, etc to design a planting group. If you still want to focus on the flowers, make sure you actually know the seasonality of what you want to use, and again, being able to see actual combinations in the neighborhood or at a botanic garden lets you know that you can achieve similar results.

Best planting designs come from actually knowing what the individual plants will do in your micro climate, and seeing actual combinations that work in your neighborhood/vicinity can eliminate a lot of the guess work. Knowing the plants often means paying attention to what is around you, and repeat visits to see how they look at different times of the year. There really aren't any computer assisted shortcuts to actual attention to detail and experience in the garden.

It is also a bit too easy to state that you know the mature sizes of plants, as this isn't a static commodity, and varies by age of the garden and care given. Taking the time to actually visit gardens that have the same plants you intend to use at different ages will give you a much better idea, and then you can actually do spacings for plants based on what time line you are designing for.