Flower Border Planner UK

Planning a new flower border, or improving an existing one? Our free Flower Border Planner helps you measure the space, choose plants for your soil and sunlight, and create a scaled planting plan before you buy anything. Start with a cottage garden, pollinator border, contemporary planting scheme or a design for a difficult dry or shady spot.

Move plants around the plan, check their recommended spacing and eventual spread, then work out how many to buy. The planner also builds a flowering calendar, a shopping list and planting positions you can take into the garden. It is free to use and no account is needed.

How to use the Flower Border Planner

1. Measure your bed or border. Enter the length and depth in metres, or choose a circular, oval or L shaped bed. Tell the planner whether the border is seen from the front, both sides or all around. You can mark existing shrubs and spaces you need to leave clear. If you only know the area, you can estimate quantities, but a scaled plan needs dimensions.
2. Describe the growing conditions. Choose the light, soil, moisture and exposure that best describe your garden. These details help the planner identify plants likely to suit the site and flag those that may struggle.
3. Choose the plants. Pick individual species or start with a suggested design. The catalogue includes researched perennials, ornamental grasses, ferns and compact shrubs, with typical height, mature spread, flowering period and spacing guidance.
4. Arrange your planting plan. The designer lays out individual plants to scale. Move them with a mouse, touch or keyboard, add groups, and request another arrangement. Check any warnings about crowding, gaps or tall plants hiding smaller ones.
5. Get your results. View the flowering calendar and quantities, enter your supplier’s prices and pack sizes, then save, print or download your plan and shopping list.

How far apart should you plant perennials?

Planting distance depends on the species and its eventual size, not just the area of the border. A small perennial and a broad, mature shrub should not be given the same space. The RHS advises planting many perennials slightly closer together than their expected spread so they grow together into a continuous display. For example, a plant expected to spread 60 cm may be planted about 50 cm apart.

Our planner records mature spread separately from the recommended distance between plant centres. Dashed outlines show roughly how wide plants may become, while the symbols show where to plant them now. Growing conditions, cultivar and maintenance can all affect the actual size. Always check the plant label and give particularly vigorous plants room to develop.

How many plants do you need per square metre?

As a broad starting point, the RHS suggests approximately five herbaceous perennials, three small shrubs or one large shrub per square metre. These are general guides, not universal planting rates. A border full of small salvias will need a different number of plants from one containing mature hydrangeas and large grasses. This designer estimates numbers using the individual plants, their planting distances and the space available.

Designing a border that looks good as it grows

Start with the structure

Place shrubs, larger perennials and ornamental grasses first. Think about the view from a path, lawn or window, and leave space for plants to develop. A narrow border against a fence needs a different arrangement from an island bed viewed from all sides.

Get the heights right

In a border seen from one side, taller and denser plants generally sit towards the back. For an island bed, put most of the taller plants towards the centre. Slender plants with an airy habit, such as purpletop vervain, can sometimes sit further forwards without blocking the view. The planner highlights likely height conflicts, but you remain in control of the design.

Repeat plants in groups

Groups of three, five or more of the same plant often look more natural than scattering one of everything throughout the bed. Repeating a few dependable plants gives the planting a sense of rhythm. A smaller selection of suitable species can be more effective than buying many unrelated varieties.

Plan for more than summer flowers

Use the flowering calendar to check for gaps in interest. Spring flowers, summer perennials, autumn colour and winter foliage or seedheads can all contribute to an attractive border. Flowering times are approximate and can vary across the UK, so treat the calendar as a guide rather than a guarantee.

Worked flower border planning examples

Example 1: A cottage garden border, 4 m by 2 m

A rectangular border 4 m long and 2 m deep has an area of 8 m². In one tested cottage-garden layout, with full sun and moist but well drained soil, the designer arranged 48 plants across seven types. These included foxgloves and perennial wallflowers towards the fence, masterwort, catmint and Balkan clary through the middle, and cranesbill and lady’s mantle nearer the front.

That is one particular scheme produced from the selected plant sizes and spacing rules. It does not mean every 8 m² border should contain 48 plants. A planting scheme with larger shrubs or grasses would have fewer plants. Review the actual mature spreads, the warnings and your preferred maintenance level before buying.

Example 2: A circular island bed, 4 m across

A circular bed measuring 4 m in diameter has a radius of 2 m and an area of approximately 12.57 m². When seen from all sides, taller plants usually work best nearer the centre, with shorter plants towards the edge. The designer creates a scaled layout and provides setting out positions measured from a centre peg, helping you transfer the plan into the garden.

Example 3: Planting in dry shade

A bed measuring 5 m by 1.5 m contains 7.5 m². Dry shade can be especially challenging under trees and close to walls, where roots and rain shadows compete for moisture. The tool can suggest researched plants such as barrenwort, rock cranesbill and Mrs Robb’s bonnet, while warning when a sun loving or moisture demanding plant is a poor match. Even drought tolerant shade plants need attention while becoming established.

Example 4: Buying plants in packs

If your planting plan needs 23 plants of one species and the nursery sells them in packs of three, you need eight packs, giving you 24 plants and one spare. Enter your supplier’s pack sizes and prices to produce an estimated shopping total. Prices are not looked up automatically.

When should you plant a new flower border in the UK?

Spring and autumn are usually the best periods for establishing most hardy perennials and shrubs, when the soil is workable and moisture is more reliable. For many perennials, the RHS recommends spring from March to early May or autumn from late September into October. The exact window depends on your location, the plants chosen and the weather.

Avoid planting into frozen or waterlogged soil. Summer planting is possible with container grown plants, but establishment can demand more watering. Check individual plant requirements, especially for less hardy species and gardens in colder or exposed parts of the UK.

Before planting, remove perennial weeds, check drainage and improve the soil where appropriate. Put the pots on the ground in their planned positions before digging, so you can judge the spacing from the path or lawn. Water plants thoroughly after planting and during dry spells while roots establish. Use mulch where suitable, keeping it clear of plant crowns and woody stems.

Taking your plan into the garden

The overhead diagram uses measurements so that the plant positions can be set out using a tape measure. Rectangular plans reference the front left corner, while circular beds can use a centre peg. The printout includes planting information and a setting out table. Check dimensions on the ground before digging, especially around existing roots, paths and drains.

The dashed circles show an approximate mature spread, not the size of each plant at purchase or an exact prediction of its eventual shape. A new border may initially look sparse. Filling every gap immediately can create overcrowding as the plants mature.

Frequently asked questions

Is the Flower Border Planner free?

Yes. The designer is free to use and does not require an account. You can plan a border, review plant quantities and use the export options without paying a subscription.

Can I change the plants after creating a plan?

Yes. You can move plants, remove them, add individual plants or groups, and generate another arrangement. The plan and shopping list use the plants actually placed, so the quantities remain consistent.

Can I add plants that are not in the catalogue?

Yes. You can add a custom plant with its height and spread. Use figures from the plant label or nursery. The planner will not invent flowering dates or suitability information for a plant it has not researched.

Will every suggested plant grow in my garden?

No planner can guarantee that. Recommendations consider light, soil, moisture, exposure and hardiness, but local conditions and aftercare still matter. Read suitability warnings and check the individual plant’s requirements before ordering.

Does the planner account for mature plant sizes?

Yes. It treats a plant’s mature spread and its recommended planting distance as separate measurements. The plan can flag crowding and overlapping growth, but real plants do not all develop as perfect circles.

Can I use it for a shaded or wildlife friendly border?

Yes. You can describe shaded conditions and select styles including pollinator planting and dry shade. The planner flags poor matches rather than assuming every plant is suited to every garden.

When will the plants flower?

The calendar shows approximate UK flowering months for the researched plants included in your layout. Weather, variety, growing conditions and regional temperatures may shift flowering by several weeks.

How do I save or print my design?

You can save named plans in your current browser and download a plan file for safekeeping. You can also export the planting diagram and shopping list, and print a plan with planting positions. Browser saved plans may be lost if you clear that browser’s data, so download a backup for important projects.

Are the plants safe around children or pets?

The planner displays recorded warnings where its horticultural sources identify them. An absence of a warning is not proof that a plant is safe. Check toxicity information for individual plants before planting where children or pets may encounter them.

More help with your garden project

Planning to add bulbs between the perennials? Use our Bulb Planting Planner to work out planting positions and quantities. For compost, bark, topsoil or mulch, use the Garden Materials Calculator. You can also browse all our free Garden Tools or check what to do in your garden this month.

Sources and further reading

Plant details and general planting advice are informed by the Royal Horticultural Society’s guide to planning a border, its guide to creating a border and its perennial planting guidance, together with RHS plant records and BBC Gardeners’ World plant profiles. Individual plant entries in the designer link to their supporting sources.