Best Mulch for Flower Beds

For a broader overview of every mulch type and technique, see our complete mulching guide.

Quick Comparison: Flower Bed Mulch Types

Choosing the right mulch for flower beds depends on three things: the plants you’re growing, the look you want, and how much maintenance you’re prepared to do. A cottage garden packed with perennials has different needs to a modern gravel garden or a formal rose bed. Let’s look at each option in detail.

Composted Bark: The Best All-Rounder

Composted (or aged) bark is the mulch you’ll see in well-maintained National Trust gardens and RHS show gardens. It’s different from fresh bark chip — the composting process darkens the colour, reduces nitrogen lock-up and creates a more uniform texture.

• Appearance: Rich dark brown, even texture. Looks neat and professional in any border style
• Weed suppression: Excellent at 5–8cm depth. Creates a dry surface layer that prevents most weed seeds from germinating. For the best results, lay cardboard underneath for a double barrier
• Soil benefit: Slowly releases nutrients and improves soil structure. Attracts earthworms and beneficial fungi
• Limitations: Not cheap in large quantities. Top up every 2–3 years as it breaks down. Avoid piling against plant stems

Apply in spring after the soil has warmed, or in autumn to protect roots over winter. For more on timing, see our guide to how often to apply mulch.

Decorative Gravel: For Low-Maintenance Beds

Gravel mulch is a permanent option that works brilliantly in the right context:

• Best plants: Lavender, rosemary, sedums, ornamental grasses, alpine plants — anything that prefers sharp drainage and dislikes damp crowns
• Weed suppression: Good initially. Over time, wind-blown soil and leaf debris accumulate in gravel, creating a seed bed. You’ll need to weed or use a gravel-safe weed killer periodically
• Heat reflection: Light-coloured gravel reflects heat upward, which Mediterranean plants enjoy but shade-lovers and moisture-loving perennials won’t tolerate
• Depth: Apply 3–5cm. Too deep and plants struggle to self-seed (which you may want for naturalistic plantings)

Gravel is a poor choice for traditional herbaceous borders, cottage gardens or beds with lots of annual planting. In these settings, you’ll be constantly fighting the gravel when planting and replanting.

Garden Compost: Free and Nutritious

Garden compost (or well-rotted manure) is the soil-building champion:

• Nutrient release: Steady supply of nitrogen, phosphorus, potassium and trace elements throughout the growing season
• Soil structure: Dramatically improves both clay and sandy soils. Clay becomes more workable; sand holds more moisture
• Weed suppression: Moderate at best. Compost is fine-textured and can contain weed seeds itself. Better used as a soil feed with bark on top for weed control
• Application: Apply a 5cm layer in spring. Worms will work it into the soil within a few months

The best approach for demanding flower beds is a two-layer system: apply 5cm of compost directly on the soil as a feed, then top with 5cm of bark mulch for weed suppression and appearance. This gives you the nutritional benefits of compost with the weed control of bark.

How to Mulch Flower Beds Properly

Regardless of which mulch you choose, the application technique matters:

1. Weed first. Remove all existing weeds by hand or treat with weed killer and wait for them to die back. Mulching over active weeds just hides the problem temporarily, particularly stubborn weeds like bindweed
2. Water the soil. Mulch locks in existing moisture, so water thoroughly before applying if the soil is dry
3. Apply evenly at the right depth. Bark: 5–8cm. Compost: 5cm. Gravel: 3–5cm. Use a rake to spread evenly across the bed
4. Keep clear of stems and crowns. Pull mulch back 5cm from the base of every plant. Damp mulch against stems encourages rot — especially on herbaceous perennials that die back in winter
5. Don’t bury low-growing plants. Alpines, heathers and ground-cover plants can be smothered by deep mulch. Apply a thinner layer around these, or use gravel instead
6. Edge neatly. A clean edge between mulch and lawn or paving makes the whole bed look maintained. Use a half-moon edger to cut a crisp line

What to Avoid in Flower Beds

Frequently Asked Questions

When is the best time to mulch flower beds?

Spring (March–April) is ideal for most UK flower beds. The soil has warmed up enough for plant growth, and mulching now locks in spring moisture for the summer ahead. Autumn mulching (October–November) also works well — it protects roots over winter and is ready to feed the soil when spring arrives. Avoid mulching when the ground is frozen or waterlogged. See our full guide on mulch application timing.

How deep should mulch be in flower beds?

For bark mulch, apply 5–8cm. For garden compost, 5cm is plenty. For gravel, 3–5cm. Going deeper than these recommendations wastes material and can smother plant crowns. Going shallower reduces weed suppression effectiveness.

Should I remove old mulch before adding new?

With organic mulches (bark, compost), no. The old mulch is decomposing and feeding the soil — simply top up to maintain the correct depth. With gravel, rake it level and top up thin spots. Only remove old mulch if it’s become compacted, waterlogged or has developed significant weed problems that need clearing.

Will mulch stop self-seeding plants?

Thick bark mulch will reduce self-seeding significantly. If you want plants like foxgloves, aquilegia or verbena to self-seed naturally, use a thinner layer (3–4cm) or leave gaps in the mulch where you’d like seedlings to establish. Gravel is better for plants you want to naturalise, as seeds can lodge in the gaps between stones.

Is bark mulch or wood chip better for flower beds?

Composted bark is better for flower beds. It has a more refined appearance, doesn’t rob nitrogen from the soil (the composting process resolves this), and breaks down into finer particles that improve soil texture. Raw wood chip is better suited to woodland gardens, paths and informal areas where the rougher texture looks appropriate. For weed suppression specifically, see our guide to the best mulch for preventing weeds.

Can I mulch around bulbs?

Yes, and it’s beneficial. A 5cm bark mulch layer helps regulate soil temperature and moisture, which bulbs appreciate. Most spring bulbs (tulips, daffodils, alliums) push through mulch without difficulty. Plant bulbs at the correct depth below the soil surface, then apply mulch on top. In the first year, use a slightly thinner layer until you’re confident the bulbs are established.

You might also find it helpful to read about glyphosate for persistent weeds.

You might also find it helpful to read about tough weeds like bindweed.

You might also find it helpful to read about a pet-safe weed killer.