Plant Spacing Calculator
Buying too few plants leaves gaps in the bed, while buying too many wastes money on plants you don't have room for. Enter your bed size and spacing below to work out exactly how many plants to buy.
Work out how many plants you need
Enter your bed size and your chosen plant spacing.
At 30cm spacing, you'll need approximately:
66 plants
That's a grid of 11 rows of 6 plants each, running along the length and width of the bed.
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Frequently asked questions
What spacing should I use between plants?
It depends on the plant's mature spread, which is usually given on the label or seed packet, but 30cm is a common default for many bedding plants and smaller perennials once fully grown.
Why not just plant as close together as possible?
Planting too close together leaves plants competing for light, water and nutrients as they mature, which can lead to smaller, weaker growth and more disease, so it's worth sticking to the recommended spacing even though the bed looks sparse at first.
Does this calculator work for vegetable beds too?
Yes, the same grid approach works well for vegetables, though it's worth checking the specific spacing recommendation for each crop, since some vegetables need much more room between plants than typical bedding plants.
Should I round the number of plants up or down?
It's generally best to round down slightly rather than cram in extra plants at the edges, since a slightly looser layout gives room for plants to reach their full mature size without overcrowding.
How this calculator works
The Plant Spacing Calculator uses the bed or border length and width that you input, along with the recommended spacing between plants for your chosen species. We utilise a simple multiplication formula: Bed Area (length x width) divided by Plant Spacing (in metres), to determine the number of plants you can fit within the space. For example, a 2-metre long bed with a spacing of 0.6m between plants will accommodate approximately 3.33 plants.
The calculator assumes a rectangular bed or border for simplicity. It also relies on you selecting an appropriate plant spacing – this is crucial and depends heavily on the mature size of the plant. Larger plants require wider spacing to allow for adequate growth, while smaller plants can be planted closer together. Always check the supplier's guidance before planting.
Plant Spacing Guidelines - UK Varieties
- **Roses:** Typically 60-90cm apart for climbing roses and 30-45cm for bush varieties, allowing for robust growth and airflow. Consider the mature spread when selecting your spacing.
- **Lavender:** Best planted 45-60cm apart to allow for good air circulation and prevent fungal diseases common in damp UK conditions.
- **Salvia:** Space salvia plants around 30-45cm, particularly ‘Black Knight’ varieties which can spread considerably.
- **Foxgloves:** Plant foxgloves approximately 60-90cm apart to avoid overcrowding and ensure healthy flower stalks. Consider the height of surrounding plants.
- **Hydrangeas:** ‘Endless Summer’ hydrangeas typically need 90-120cm spacing, while larger varieties may require 1.2m – 1.8m for optimal flowering.
- **Peonies:** Plant peonies around 60-90cm apart to allow for root development and prevent competition for nutrients.
- **Cornflowers:** Space cornflower seedlings approximately 30cm apart, providing enough room for them to self-seed successfully.
- **Dahlias:** Depending on the variety, dahlias can be spaced from 45cm – 90cm apart; check the seed packet for specific guidance.
- **Bulbs (e.g., Daffodils):** Plant bulbs approximately 15cm deep and 10-15cm apart to allow sufficient space for growth and prevent overcrowding, especially important in heavier clay soils.
- **Herbs (e.g., Rosemary):** Allow rosemary plants at least 60cm spacing to promote bushy growth and robust flavour development.
Worked example: Planning a Lavender Border
Let’s say you're planning a border that is 4 metres long and 1.2 metres wide, intending to plant ‘Munstead’ lavender – a popular variety known for its strong fragrance. The recommended spacing for ‘Munstead’ lavender is 60cm. Using the calculator, we input these values: Length = 4m, Width = 1.2m, Spacing = 0.6m (60cm). The result is 4m x 1.2m / 0.6m = 8 plants. This suggests you’ll need approximately 8 ‘Munstead’ lavender plants to fill the border effectively.
This estimate provides a starting point, but it's important to consider that these are general guidelines. You might want to add an extra plant or two for a fuller look. Furthermore, the soil type and drainage will also affect plant growth; heavier clay soils may require wider spacing to allow roots to develop properly. The cost of 8 ‘Munstead’ lavender plants from Amazon UK is currently around £12 – £18 per plant, so your initial investment would be approximately £96 - £144.
More questions answered
What happens if the calculator gives me a decimal number of plants?
Don’t worry! Round up to the nearest whole plant. It's always better to have slightly more space than not enough, as overcrowding is a far greater issue.
Can I use this calculator for irregularly shaped beds?
The calculator is designed primarily for rectangular beds. For irregular shapes, you’ll need to break the bed down into smaller rectangular sections and calculate the plant spacing for each section individually.
What if my plants have different spacing requirements?
You'll need to use separate calculations for each type of plant in your border. Consider grouping plants with similar spacing needs together to simplify the planning process.
Does the calculator account for mature plant size?
The calculator uses recommended spacing based on the *initial* size of the plant. As the plant matures, it will require more space; you’ll need to reassess your layout periodically.
What if I want a very dense border?
While this calculator provides an estimate for a standard density, achieving a truly densely planted border requires careful planning and potentially closer spacing than recommended – but be aware of the increased risk of competition and disease.
How does soil type affect plant spacing?
Heavier clay soils require wider spacing to allow roots to penetrate effectively. Sandy soils may benefit from slightly tighter spacing, provided drainage is adequate.
Can I use this calculator for containers?
Yes, you can! Just input the dimensions of your container (length, width, height) and the appropriate spacing for the plants you're using.
What if I’m planting a mixed border with different types of plants?
Use the calculator individually for each plant type in your border. Consider grouping plants with similar requirements together to simplify the process.
Is this calculator suitable for large-scale landscaping projects?
While useful for smaller gardens, for larger areas, a professional landscape designer’s expertise is recommended to ensure optimal spacing and overall garden design.
What if I want to plant a climbing rose along the border?
For climbing roses, significantly wider spacing is crucial – typically 1.8m - 2.4m depending on the variety's mature size and support system. Adjust your calculations accordingly, using the largest recommended spacing for your chosen rose.