You can save big bucks when it comes to planting perennials in your window boxes. After all, why shell out money on annuals every year when you know they are just going to die anyway? If you are going to spend money on flowers, choose perennials, they'll give you the biggest bang for your buck in the end.
The Best Perennials to Plant in Window Boxes
Ivy geranium, asters, dianthus, miniature roses, salvia and various spring bulbs are excellent perennial flower choices to plant in window boxes.
Herbs like lavender, sage, rosemary and even chives can also make great additions to window boxes. If you live in a mild climate, rosemary plants will keep their leaves all year long providing an inexpensive evergreen appearance. Not only do herbs look and smell great in window boxes, but being able to open your window and snip a few for recipes is pretty rad.
If you are unsure if the plants you selected will work best in full sun or shade, check your plant tags or ask an associate at your local nursery for specifics.
Trailing Evergreen Plants
English ivy, vinca minor and ivy-leafed geranium are great choices for low-maintenance trailing plants. All you really need to do is keep them trimmed to the desired length and make sure they are getting enough water during dry periods.
Timing Perennial Blooms
Mini-daffodils, tulips, ranunculus and grape hyacinths can be planted in the fall months for springtime blooms. English daisies, mini carnations and Iceland poppies are gorgeous during the late spring months and herbs are at their peak in summer. Chinese lantern, coreopsis, violas, stock and perennial grasses typically bloom beautifully into the early fall.
Use Plastic Inserts or Potted Perennials for Rotating Plants
Most window boxes are limited on space so timing perennial blooms can get a little tricky if you want a lot of variety. The easiest way to solve that problem is to line your flower box with a removable plastic liner for rotating your perennials. Removable liners can be found at your local garden center and typically run $5-$10 depending on length. They are nice and affordable, and if you're a nut like me, you'll buy four. One for every season.
Use a Moisture Retentive Potting Soil for Best Results
When planting your window box be sure and use a light-weight potting mix with moisture retentive ingredients like vermiculite and peat moss to help your plants aerated and your soil moist. Personally, I like to change out the soil in my window boxes every spring. A dose of fertilizer once a month will keep your plants happy and well fed.