Raised beds are usually associated with vegetables, but they are an excellent home for flowers too — and for a cutting garden, they are the best home of all. A raised bed gives you a defined, workable space with soil you control, drainage that is better than the ground, and a height that saves your back when you are sowing, weeding and cutting. A bed of zinnias, cosmos and dahlias, or a bed of roses and lavender, is a garden that looks deliberate and cared for, and it is easier to keep that way than a bed at ground level.
A raised bed for flowers is a simpler build than a raised bed for fruit, because flowers are mostly annuals and perennials that are replanted or divided every few years, so the bed does not need to last a decade untouched. Eight to twelve inches deep is enough for annuals such as marigolds, zinnias and cosmos; twelve to eighteen inches suits perennials such as peonies, lilies and hydrangeas, whose roots go deeper. A bed four feet wide is the standard, because you can reach the middle from either side without stepping in, and it can be as long as you like.
The other reason raised beds suit flowers is that they make a cutting garden practical. A cutting garden is a bed grown for cutting, not for display, and it needs rows you can walk between, soil you can work, and flowers you can cut without spoiling a border. A raised bed gives you all three, and a bed of zinnias, dahlias, sunflowers and cosmos will keep a house in flowers from midsummer to the first frost. If you are unsure about a variety, a spray, or a diagnosis, check your local extension service — its advice is matched to your climate and soil.
Building a raised bed for flowers
Build with rot-resistant timber such as cedar, or with stone, brick or metal, and avoid treated timber that is not rated safe for garden use. A bed four feet wide and eight to twelve inches deep suits annuals; for perennials, build twelve to eighteen inches deep, or build the bed on good ground soil so the roots can go down into it. Fix the corners firmly — a bed full of wet soil pushes outwards — and leave the bottom open so worms can come up and water can drain down. If the ground is heavy clay, fork the base before filling so the bed drains. Place the bed in full sun, with a path beside it wide enough for a wheelbarrow, and leave access from both sides. A bed against a wall is a good place for tall flowers such as sunflowers and dahlias, which can lean on the wall, while a bed in the open suits a cutting garden with rows you can reach from both sides. The raised bed soil calculator can work out how much soil a bed needs.
The right soil mix for raised-bed flowers
Fill a flower bed with a mix of topsoil and compost, roughly in equal parts, with a little grit or perlite if the soil is heavy. Flowers want a fertile, moisture-retentive but free-draining soil, and a mix with plenty of compost gives them that. Dig the compost in before planting, and top up with a mulch of compost each spring. Roses and peonies want a rich soil and benefit from well-rotted manure dug in before planting. Dahlias want a rich, moisture-retentive soil and will not thrive in a poor, dry bed. Lavender and other Mediterranean flowers want the opposite — a poor, sharp, free-draining soil — so give them their own bed or their own corner, with grit mixed in and no rich compost. Test the soil pH if you are unsure: most flowers want a pH between 6.0 and 7.0, slightly acidic to neutral, and a simple test kit is cheap. The soil volume calculator can help you work out quantities.
Which flowers suit a raised bed best
Annuals are the natural raised-bed flower: marigolds, zinnias, cosmos, sunflowers and petunias all grow fast, flower for months, and are easy to sow or plant in a bed. A cutting garden of zinnias, dahlias, cosmos and sunflowers will give you armfuls of flowers all summer, and the more you cut, the more they flower. Perennials suit a raised bed too: peonies, lilies, hydrangeas and daylilies will live in a bed for years, and a bed keeps their roots out of waterlogged ground. Roses grow well in a raised bed, provided it is deep enough and the soil is rich, and a bed of roses with lavender at the edge is a classic combination. Bulbs — tulips, daffodils and lilies — are easy in a raised bed, because you can plant them at the right depth in soil you control, and they will come back year after year. Avoid planting tall, thirsty flowers next to small ones that will be shaded out, and give every flower the space its mature size needs.
Layout: rows, drifts and the cutting garden
A raised bed can be planted in two ways: as a border, with drifts of flowers that look natural, or as a cutting garden, with rows you can walk between and cut from. For a border, plant in groups of three, five or seven of the same flower, with tall flowers at the back, medium flowers in the middle and low flowers at the front — the eye reads a group as a single mass of colour, and a single plant looks lost. For a cutting garden, plant in rows, with a path between them, and plant one variety per row so you can cut a bunch without hunting through a mix. Leave room to walk: a bed you cannot reach into is a bed you cannot deadhead or cut. Use the plant spacing calculator to lay out a bed before you plant, and draw the plan on paper first — a bed drawn to scale will show you at a glance whether the tall sunflowers will shade the low marigolds.
Watering, feeding and deadheading in a raised bed
Raised beds dry out faster than the ground, so flowers in beds need more regular watering than the same flowers at ground level — especially in the first weeks after planting, and while they are flowering. Water deeply at the base of the plants, in the morning, and mulch with bark or compost to hold the moisture in. Drip irrigation or a soaker hose laid along the bed is the most efficient way to water flowers, because it puts water at the roots and keeps the leaves dry. Feed with compost in spring, and give heavy-flowering annuals such as dahlias and petunias a liquid feed every two weeks through the summer. Deadhead every few days — roses, zinnias, marigolds, petunias and dahlias all flower longer if the faded flowers are removed, and in a raised bed the deadheading is easy because the flowers are at a comfortable height. The watering calculator can help you set a routine for beds in your climate.
Long-term care: renewing a flower bed
A flower bed is not a plant-and-forget project. Annuals are cleared at the end of the season, composted, and the bed is replanted in spring. Perennials need dividing every three to five years, when the centre of the clump dies out and flowering fades — lift the clump in autumn or spring, divide it with a fork or a knife, and replant the healthy outer pieces. Bulbs need little care, but they should be left to die back naturally after flowering, so the leaves can feed the bulb for next year — do not cut the leaves off, and do not tie them in knots. Roses need pruning every winter, dahlias need lifting in a cold climate, and peonies resent being moved, so plant them where you want them to stay. Every autumn, clear the finished annuals, top up the soil level, which sinks as the compost breaks down, and mulch the bed for winter. Keep a note of what grew where, and rotate the annuals so the same flower does not grow in the same soil year after year.
Frequently asked questions
How deep should a raised bed be for flowers?
Eight to twelve inches is enough for annuals such as marigolds and zinnias. Twelve to eighteen inches suits perennials such as peonies, lilies and hydrangeas, whose roots go deeper.
What flowers are best for a cutting garden in a raised bed?
Zinnias, dahlias, cosmos, sunflowers and roses — all flower for months, and the more you cut them, the more they flower. Plant them in rows so you can cut a bunch easily.
Do raised beds dry out faster than the ground?
Yes. Raised soil warms and drains faster, which is good for flowers, but it needs more regular watering in dry weather and a mulch to hold moisture in.
Can I grow roses in a raised bed?
Yes, provided the bed is deep enough and the soil is rich. Dig well-rotted manure in before planting, and give each rose room for air to move around it.
How do I lay out a raised flower bed?
For a border, plant in groups of three, five or seven, tall at the back and low at the front. For a cutting garden, plant in rows with a path between them, one variety per row.
A raised bed is a flower garden with edges: a defined space, good soil, and flowers at a height you can work with. Start with a bed of zinnias and marigolds, add a dahlia or two, and plant bulbs in autumn for spring. For the individual flowers, see the growing guides, including zinnias and dahlias, and check your planting calendar for timing in your zone.