Every garden has trees and shrubs as its main structure, but the best gardens don’t stop there. Nature is a complex, detailed ecosystem, and the garden ecosystem looks best, and works best, when there are many kinds of plants. Visually too, while a garden made just of trees and shrubs can be beautiful, and filled with flowers for much of the year, adding more flowers is never bad, and there is a way to do that without adding tones of work, like the bad old days of endlessly planting annual flowers. The way is to grow perennial plants, and many gardeners have discovered how easy it is to add color and interest – without adding work – to your garden with perennial plants. There is an enormous diversity of perennial plants available, from the rarest to the most common, and while some need dedication, others thrive on neglect, and grow superbly with almost no attention from you.
Perennial plants aren’t like trees and shrubs. They don’t have a permanent woody framework. Instead they grow new stems each year, dying back to the ground for the winter (or for some, the dry summer). Some are just a big, fat bud attached directly to the roots, like bulbs, iris or daylilies. Others put up stems, but these stems are ‘herbaceous’, they don’t thicken and become woody, they just produce leaves, flowers and then die back. That word ‘herbaceous’ is sometimes used as an alternative to ‘perennial’. There are so, so many perennial plants in the world, and don’t forget ornamental grasses too, which are also perennials.
A few, like Japanese spurge or periwinkle, have stems that do live for years, but they stay the same width, never thickening like a tree does. Many of our most useful groundcover plants are like this, because they are often evergreen, and so are more valuable in the garden, because they stay attractive throughout the winter months. We also group these plants with perennials.
Perennial plants can take the same role in our gardens as shrubs, particularly smaller ones, and they also offer unique features that help enrich and improve our gardens. Let’s look at some of the most important ones.
If you have spaced your young trees and shrubs correctly, you will have some pretty big gaps. It might take 5 or 10 years for them to fill in, so why not bring beauty and color in the meantime by planting perennials in those gaps between your shrubs? You can also design some permanent perennial groupings when you lay out your beds for color and different times of the year, for foliage contrast, or simply because they are beautiful. Keep an eye out that they don’t start to smother your shrubs, though. You might need to move some out of the way as the shrubs get bigger.
We often want to tie parts of our gardens together to create a greater whole. A good way to do this is to plant the same plant all around the edge of that area. We can fill a bed with a mixture of plants, and then use a continuous row of something low-growing to edge it, like a frame around a picture. It is best not to overdo this, as you don’t want everything in your garden wrapped up like that, but it can be very useful to emphasize features or accent important lines.
We could do this with low-growing shrubs and hedges, but these often need trimming or regular pruning to control their size. With the right perennial you can achieve this effect in a couple of seasons, and have it take care of itself. Outlining a patio, or emphasizing the lines of a path or driveway, is another use for edging plants. Good perennial edges will either be evergreen or have attractive foliage, and having a period of attractive flowers as a highlight is great too, so consider these two things when looking for edging perennials. This is so much easier and more permanent than the old way of edging beds with annual flowers each year.
All but the smallest gardens have lots of room to fill. You can cover it with grass – and be out mowing every week – but an alternative is to use groups of easy-care perennials to fill these areas. Even if you do want lawn, there are areas that are too shady or too hot and dry for grass to grow. Ground cover plants are ideal for them. Those few perennials that are both evergreen and shade-tolerant are top-choices – spurge, periwinkle or bugleweed for shade, or low-growing sedums for sunny spots – but any suitable low-growing plant could be used, and today we have many choices when it comes to shade.
It’s a blurry line between ‘ground cover’ and ‘mass groupings’, but usually we think of ground cover as just a few inches tall, almost a direct replacement for grass, and evergreen, while perennials of all kinds and sizes can be extended into larger groups. Think of how beautiful your garden would look with big drifts of colorful plants sprawling across it, around and between your shrubs and trees. Plants with good foliage are favorites for this – daylilies in sun, astilbe in shade, as examples – or another choice is to use late-blooming plants that won’t die down, as some spring bloomers do. As for cost, it’s great to have an instant garden, but if you are willing to wait a few years, a handful of initial plants you buy can be divided when they are large, and turned into many more, that you can then use for mass groupings.
Since so many plants bloom in spring, we are often looking for late-bloomers, and sure, there are some great shrubs that do it, like some of the hydrangeas. Among perennials, though, there are many that bloom later, including ornamental grasses, and these keep your garden looking beautiful month after month. Look at pictures of beautiful gardens that you admire and you will almost always see perennials in them. You can get the same result, and you’ll be surprised how little work they are.
Tree and shrub gardens model one kind of natural space – woodlands. In nature we find lots of other things, like open, rocky places or grassland. You can quickly turn an area of rough grass into a prairie with plants like coneflowers, butterfly weed and Agastache. These are all native to our own prairies, but you can add others, like catmint, or flowering sage, from other parts of the world. You can struggle to turn a rocky area into shrub beds, or go with the flow and decorate it with sun loving plants and sprawling evergreens. Even woodlands have plants at ground level, and these are usually perennials too, many of them native plants as well, so plant up those spaces beneath your trees. The possibilities are endless.
Many perennials are important plants for pollinators like bees and butterflies. Some are visited by our magical hummingbirds. Others, the coneflowers for example, and some grasses, produce edible seeds that can be important winter food for birds like goldfinches and others. Your garden can make a valuable contribution to your local ecology by making green space and providing food. You can help by leaving stems standing for winter, and choose bee-friendly plants over ones that don’t produce pollen or nectar (like some double flowers for example). Planting flowers in a rough piece of land is a way of restoring some of what we have lost.
When choosing your perennials, there are different aspects to think about. Here is a ‘checklist’ of what these plants can give you:
Consider the overall shape of the plant, and how it will fit into your beds. Is it tall and upright, or mounding? Does it arch out like a fountain or have a shrubby form? Just as we think of these things with shrubs and trees, we should think of them with our perennials, when deciding where to place them, and how they will look. Ornamental grasses are especially good for this, but big, fat, silvery mounds of catmint are striking, even before those lovely blue flowers open. The reliable foliage of daylilies make them great weed-suppressors, and peonies have gorgeous leaves, complete with fall color. Consider too whether you want an evergreen look, or are OK with a plant disappearing over the winter
You might choose them for flowers, but even the best have periods when they are just leaves, and some are grown for their leaves as much, or more, than for their blooms. Some plants, like coral bells (Heuchera) come in amazing shades and rich tones. Grasses and catmint add silvery and blue tones – colors that work wonders in any garden. Even the greens of perennials are different, often brighter and lighter than many shrubs, so they stop your garden looking gloomy.
This is an obvious aspect, and working with color needs some thought, but it isn’t as tricky as you might think. Some colors – white, blues and silvers – fit in anywhere, and are great for calming down riots of many shades. Reds get tricky, and try to distinguish orange-reds from burgundies and pink-reds – they make one of the few serious color clashes in gardens when such plants are beside each other. Put those orange-reds with real oranges and yellows, and add a touch of blue for contrast. Keep the pink-reds for mixing with pinks and purple. If you love purples and pink, add a touch of pale yellow or greenish yellows – it doesn’t sound obvious to do, but it really makes those other colors sing, and stops them looking too bland.
Just as with shrubs and trees, building a garden with the longest possible season when something is blooming is an important goal. There are perennials that bloom in every month of the year (at least in some zones), so there are lots of choices. Some of the most useful are summer and fall blooming, because that is when many shrubs are least likely to be flowering. You can choose to develop an area where everything blooms together – it makes a spectacular display, but may look drab the rest of the year – or spread the blooms around for a steady, all-over display. A lot depends on the size of your garden, and with a small garden getting an all-over look is best.
Many people avoid flowering plants because they feel they are a lot of work, but the best perennials are no more work than shrubs, and sometimes even less.
Like all plants, some work at the beginning pays the biggest dividends. Soil preparation and watering young plants regularly during their first year is vital for success. Just because a plant is tough doesn’t mean it won’t give much more with a little care. We want these plants to fill their chosen spaces quickly, so fertilizing, and watering during dry periods when they are young, will mean that later you can more-or-less ignore them.
Almost all the deciduous kinds of perennials – ones that die down in winter or summer – need to be taken care of when they die down. This is only an annual job, so even if it takes a while, it is much less than weekly lawn mowing. In milder parts of the country the dead stems of plants like grasses and coneflowers look lovely through winter, and feed birds, so cut down in spring – but do it early before things start to grow again. In colder areas it is likely that snow and storms will flatten plants early in winter, so the value is not so great. Plus, winter cold and ice, trapped under piles of dead foliage, can lead to rots and you end up losing the plants. Cutting down in late fall and leaving clean beds really makes a difference to winter survival if you garden in cold zones. It also makes mulching the beds much easier.
Removing flowers when they fade is a valuable way to extend blooming and encourage reblooming. Snip or snap off the dead flower, or remove a whole stem, without damaging surrounding buds or stems. If there are many leaves on the stem, just cut back to the first ones, don’t cut down the whole stem. By preventing the plant’s energy going into seeds, you encourage it to keep on blooming. Some people find this job tedious, but think of it as an opportunity to be right among your plants and enjoy them up close. Many modern varieties are sterile, so they don’t make seeds, and dead-heading might not be necessary at all.
Overall, perennials seem to have far fewer problems with pests and diseases than many shrubs or trees. They rarely if ever need spraying, The most likely problem, in hot and humid summer weather, is a whitish powder on the leaves, called powdery mildew. This disease is harmless, and your plants come back the next year clean and fresh. Diluted milk, sprayed on plants where you have seen it before, and before you see much sign of it, is a good and safe control if its presence bothers you. We always note in our plant descriptions when a plant is safe from rabbits or deer, although these animals are unpredictable, and if they are hungry enough they will try anything once.
Because there are so many different perennials, and because our catalogue keeps changing, a list of them all here wouldn’t be very useful. Use our search function to check for blogs on plants that interest you, and get even more information than you can find in our detailed descriptions. The best way to get to know perennials is to grow them – you’ll be so glad you did.