First, decide what is trendy. Look at several different houses or apartment buildings of varying ages. You will start to notice similarities. Did you find a house with very large and mature rhodies, azaleas, pieris? Most likely they were planted before the sixties. The recession of the 70's launched a landscaping trend rife with "drought tolerant" conifers and sprawling evergreen ground covers that trap odors like cat urine and provide a stunning platform for spiderwebs and litter come August. Remember the color salmon and sea foam green and the obsession with beach culture in the eighties? Big-haired plants like yucca, palm, and pampas grass took hold in the west as if to pay homage to Miami Vice. Now they stand out like overgrown mullets at a golf tournament.
Next, decide whether or not you care to date yourself. Maybe you're proud of your dated hairstyle. Maybe you like waddling to the store in your discount Clarks. If that's you, than stand proud.
If you don't want to be a fashion victim, consider ways to avoid trends:
*Don't pair trendy plants together. Tuck them into the design where they won't stand out but they will blend in.
*Avoid pruning trends. Ever wonder why those street trees are pruned to look like lollypops in front of Grandpa's house? For the same reason Grandpa still has his buzz cut-it's easy, it doesn't create a mess, and it gives him something to do on the weekends.
*Choose solid colors. Avoid new hybrids with double blooms and multiple colors. Unless, of course, you like it. Select larger perennials, shrubs and patio trees that have a more natural, classical look-green leaves, brown bark. Mix your "crazy" stuff in amongst these larger foundation plantings so that you can remove them if need be. It's much easier to dig up an orange moppy-headed dahlia than it is a mature miscanthus giganteus.
*Select a theme and make sure it goes with your architecture and that it makes sense. This doesn't mean that you can't have fun and experiment-if you like different styles, create different nooks within your yard that are consistent within themselves. An Asian garden in the back, an English garden in the front and a woodland path to bridge the gap.
*If you really like wierd plants show them off in a specimen garden that's set apart from the rest of the garden. That way you can plant your thorny cleome next to your staghorn fern and your red-hot pokers and not get any funny looks from your neighbors.