Written by davethetreecenters • April 29 Flowering Shrubs for Planters and Boxes

With smaller gardens, town homes and condominium living so much more common, many would-be gardeners find themselves with not much more than planter boxes and pots to work with. When most people think about planter boxes, they normally think annual flowers. But in these busy times flowering shrubs offer great alternatives that can be colorful and interesting for months, and that also need a lot less work. The range of flowering shrubs available to us has increased enormously in recently years, and many now come with colorful leaves too, meaning that even when not in flower these plants are attractive. They also add height, which is an important component in creating an attractive look in planters.

You can mix it up in larger planters, with a variety of different plants in different colors and blooms, but you can also do some effective modern planting with just a single plant. A variety of smaller pots lets you move things around to enjoy them at their best, and then put them more out of the way when they are not in bloom. Some flowering shrubs are more suitable than others for planters, so let’s look at the things to consider when making choices:

How Big are They?

It might seem obvious, but just as over-sized plants end up in small spaces in gardens, we regularly see over-large shrubs growing in planters. Too large for the space, and too vigorous for a limited soil volume, they end up as embarrassments, and distort or split the containers too. The hard trimming needed to keep them in scale prevents or reduces flowering, so the reason for growing them in the first place is lost too.

Consider roses – some easily grow 6 feet tall or more, with long stems, and simply look untidy, with few blooms, when planted in boxes. But newer types, most notably the Drift® Roses, grow low and spreading, and they are great ways to fill planters to about 18 inches tall with a continuous profusion of blooms from late spring to fall.

Other plants too, like Hydrangeas and Crape Myrtle, today come in lower varieties that are ideal for planters and bring these fabulous shrubs out of the garden and onto a terrace or patio.

Length of Flowering Season

Many flowering shrubs look fabulous for a couple of weeks and then they are over. This is fine in the garden, where they become background to later-flowering shrubs, but in planters they can look simply boring. There are exceptions – the smaller varieties of Evergreen Magnolia, like ‘Teddy Bear’, have such wonderful foliage that they look great all the time, and in fact they do flower over an extended period, although often only with isolated blossoms.

So when browsing for suitable plants, take particular note of plants that flower for a long period. We already mentioned Hydrangeas, and they are well-known for literally blooming for months. There is a whole range of sizes available today, including small ones perfect for large pots, and they can form the backbone of a flowering terrace. But today there are plants that we wouldn’t have considered in the past, because their bloom season is too short, that today exist in forms that bloom for months. We already mentioned the Drift® Roses, but they are so great it bears repeating, and they come in a fabulous range of colors too.

Then there are the amazing Encore Azaleas, that quickly return after their spring flowering, to bloom from mid-summer right to late fall. Just remember with them to use compost and fertilizer for acid-loving plants. You could make great all-year planters putting Encore Azaleas around a taller Camellia Bush – they too are acid-loving, so they’re a perfect match. The azaleas will take care of spring, summer and fall, and then if you choose a winter-flowering camellia it will be smothered in wonderful large blooms all through the rest of the year.

Use Colored Foliage Too

If you love shrubs with shorter flowering seasons, many today have colored leaves, so even if the blooming is over, they are still colorful. Thinking of acid-loving plants, the remarkable Everred® Rhododendron has beautiful bright red flowers in spring, but it  also keeps giving us color for the rest of the year with its deep red evergreen foliage.

Even plants that flower over a long time can add extra punch when they also come with colored leaves. the great ‘Magic’ series of Crape Myrtles are small enough for big planters, and they also have rich purple-red foliage that sets of their range of flower color perfectly.

Although we are talking here about flowering shrubs, we can’t pass up the wonderful modern Nandina plants. A few do flower with modest blooms in spring, but it is foliage that is the big attraction. Whether you want yellow, gold, pink or red, there is a Nandina that will give it to you, either as a burst in spring, or through winter, or all year round. Adding these to mixed planters of flowering shrubs gives you ‘off-season’ color, which is vital if you are looking out at the boxes from an apartment or town house every day, whatever the season.

Consider Care

Finally, avoid ‘choosy’ plants, that can’t cope with a touch of dryness now and then, or that need just the right drainage to survive. Planter boxes can sometimes become too wet, especially during long rainy periods, or too dry, when you slip away for a week’s holiday. So your plants need to be able to cope. One big thing to remember is fertilizing. Lots of people make that mistake. You need a regular feeding program to get the best from planters, no matter what you grow in them. Today there are slow-release granules that can be scattered on the top of pots in spring and that will then feed all season. These are great if you are busy and can’t keep to the traditional ‘liquid food every month’ routine that flowering shrubs thrive on from spring to fall.

Remember also to prune for maximum flowering, at the right time of year. It’s not much good planting flowering shrubs and then trimming them incorrectly and losing most of the blooms. Roses, for example, should be tidied up and trimmed in early spring, before new growth, and so should hydrangeas. Oh, and speaking of those roses again, in planters they always do better and have a longer life if you add about one-third garden soil to regular potting soil for planting, as they enjoy a heavier soil than most container plants.