Spring mulching is one of the highest-value jobs in the garden. A layer of mulch applied in spring suppresses weeds, holds moisture in the soil through the dry months ahead, feeds the soil as it breaks down, and protects the soil surface from heavy rain. It also saves work: a well-mulched bed needs far less weeding and watering all season. But mulching in spring has rules of its own — mulch too early, while the soil is still cold, and you lock the cold in and slow the plants down; mulch too thickly, or piled against stems, and you cause rot and give slugs a hiding place. This guide explains how to mulch in spring, and how to do it well.
When to mulch in spring
Wait until the soil has warmed and plants are starting to grow before mulching in spring. Mulching cold, wet soil in early spring keeps it cold and delays growth, which is the opposite of what you want. The right time is usually mid-spring, once the soil has dried a little, the first weeds have been removed, and the plants are showing new growth. Water the bed thoroughly before mulching, so the mulch locks moisture in rather than locking dryness in — mulching dry soil is a common mistake, and it means the soil stays dry all season.
Weed the bed first, because mulch suppresses new weeds but does not kill established ones, which simply grow through it. Remove perennial weeds with their roots, and clear the bed of debris. If the soil needs feeding, apply compost or fertiliser before mulching, because the mulch then covers and protects it — see our spring fertilizing guide and spring soil preparation guide. Check your local extension service if you are unsure when to mulch in your area, because the timing depends on your climate.
Which mulch to use
Organic mulches are the best choice for most of the garden, because they break down and feed the soil. Garden compost is the best all-round mulch: it feeds, holds moisture and suppresses weeds, and it is free if you make it yourself — see our spring composting guide. Well-rotted manure suits hungry plants such as roses and vegetables. Bark chips last longest and suit shrubs, trees and paths, but they are low in nutrients and should not be dug into the soil. Straw suits vegetable beds, especially strawberries, because it keeps fruit clean and dry. Grass clippings can be used in thin layers, but a thick layer of fresh clippings mats down, smells and becomes slimy.
Inorganic mulches have their place too: gravel and stone suit Mediterranean plants such as lavender that like dry conditions, and they do not break down, so they last for years. Landscape fabric under a mulch suppresses weeds but prevents the soil from being fed by the mulch above it, and it makes the bed hard to plant into later. For most beds, an organic mulch is the better choice. Use the mulch calculator to work out how much mulch a bed needs.
How to apply mulch
Apply mulch two to three inches deep — enough to suppress weeds and hold moisture, but not so deep that it smothers the soil and stops air reaching the roots. Spread it evenly, and keep it away from the stems and trunks of plants: leave a gap of a few inches around every stem, because mulch piled against a stem holds moisture against the bark and causes rot. This is the single most common mulching mistake, and it kills more plants than any other mulching error. The same applies to trees: mulch should never touch the trunk, and it should never be piled into a volcano shape around the base.
Mulch around vegetables once they are established, not when they are tiny seedlings, or the mulch will smother them — see our spring vegetable care guide. Mulch around flowers and shrubs once they are growing, and mulch containers with a thin layer of compost or bark to slow drying. Water after mulching if the weather is dry, and top up the mulch during the season as it breaks down. A mulch that has thinned to less than an inch is no longer doing its job.
Mulching different parts of the garden
Vegetable beds do best with compost or straw, applied once the plants are a few inches tall, which keeps the soil moist and the vegetables clean. Fruit bushes and trees do best with compost or well-rotted manure, applied in a wide ring around the plant but kept away from the stem. Flower beds do best with compost or bark, which looks tidy and feeds the soil. Paths and seating areas do best with bark chips or gravel, which last longest and need the least topping up. Lawns are not mulched, but grass clippings left on the lawn after mowing act as a light mulch and feed the grass — see our spring lawn care guide.
Roses benefit particularly from spring mulching: a layer of compost or well-rotted manure around the base, kept away from the stems, feeds them through the flowering season and holds moisture during dry spells. Newly planted trees and shrubs need mulching most of all, because their roots are shallow and the soil around them dries fast. Always mulch a new planting in spring, and keep the mulch topped up through its first summer.
Mulching mistakes to avoid
The mistakes, in order of damage done, are: mulching against stems and trunks, which causes rot; mulching cold, wet soil too early, which delays growth; mulching dry soil, which locks the dryness in; mulching too thickly, which smothers the soil; using fresh manure or fresh wood chips, which rob the soil of nitrogen as they break down; and mulching over weeds, which simply grow through. Fresh wood chips are fine as a surface mulch on established beds, but they should not be dug in, and they should not be used around young plants. Slugs love the damp, sheltered conditions under mulch, so check under it regularly in spring and remove any slugs you find — see our spring pest control guide.
Mulching around trees, hedges and new plantings
Trees and hedges benefit from spring mulching as much as flower beds do, and the technique is slightly different. For a tree, apply mulch in a wide ring around the base, two to three inches deep, extending as far as the drip line — the edge of the canopy — if you can, because that is where the feeding roots are. Keep the mulch well away from the trunk, leaving a clear gap of several inches, because mulch against a trunk holds moisture against the bark and causes rot. Never pile mulch into a volcano shape around a tree: it is one of the most common and most damaging mistakes in gardening, and it kills trees slowly by rotting the bark at the base.
Hedges should be mulched along their base in the same way, keeping the mulch off the stems, which feeds the hedge and suppresses the grass and weeds that compete with it. Newly planted trees, shrubs and hedges need mulching most of all, because their roots are shallow and the soil around them dries fast in spring sun and wind. Mulch a new planting in spring and keep the mulch topped up through its first summer, watering the plant regularly while it establishes. A tree that is mulched and watered in its first year grows far faster than one that is left to fend for itself, and the mulch pays for itself in saved watering and weeding.
Frequently asked questions
When should I mulch in spring?
In mid-spring, once the soil has warmed, weeds have been removed and the soil has been watered. Mulching cold, wet soil too early delays growth.
How deep should spring mulch be?
Two to three inches. Less than that does not suppress weeds; more than that smothers the soil and stops air reaching the roots.
Should mulch touch plant stems?
No. Keep mulch a few inches away from every stem and trunk, because mulch against a stem holds moisture and causes rot.
What is the best mulch for vegetable beds?
Garden compost or straw. Compost feeds the soil as it breaks down, and straw keeps fruit clean and holds moisture well.
Can I mulch with grass clippings?
Yes, in thin layers that dry quickly. A thick layer of fresh clippings mats down and becomes slimy. If you are unsure, check your local extension service for advice.