Open Grow Guide

Mulching basics

By Open Grow Guide Updated

Roots on a newly planted tree or shrub stay close to the root ball at first. They have not yet spread into the surrounding soil. Mulch spread over the root zone holds moisture in the soil and slows weeds at the surface. Organic mulch is generally the preferred choice in gardens and landscapes. Inorganic materials, such as rock, give coverage without adding organic matter to the soil. Checking soil moisture 4 to 8 inches (10 to 20 cm) down tells you when a tree needs water. This guide covers building a water ring and setting a watering schedule. It also explains spreading mulch 2 to 4 inches (5 to 10 cm) deep while staying clear of the trunk. Keeping mulch within the depth a source recommends protects roots instead of harming them.

When: Spring and fall (Apr–Nov)

When to do it

Water a newly planted tree or shrub every day for the first one to two weeks after planting. From three to twelve weeks after planting, cut back to watering every two to three days. After twelve weeks, a weekly watering is enough until the roots are established. Skip a hand-watering only when more than one inch of rain falls that day. For an established tree, water at the first sign of wilting or once the top 12 inches of soil turns dry. Wait to mulch until soil has warmed enough for roots to start growing again. Add winter mulch to perennials and bulbs as soon as the soil starts to freeze, or any time after that. Pull winter mulch off perennials and bulbs as it thaws in early spring, so crown rot and other fungus problems don't set in. Bark mulch usually needs replacing every two to four years, while wood chip mulch needs it every one or two years.

What you need

Organic mulches are generally the preferred mulch for garden beds. They include bark, wood chips, pine straw, pine bark, and shredded or whole leaves. Shredded wood mulch is also a choice for covering the roots of a newly planted tree or shrub ahead of winter. Inorganic materials, such as rock or pebbles, give physical coverage without adding organic matter to the soil. They usually go on at a shallower depth than organic mulch. A biodegradable plastic mulch sheet is another option, though it can take up to three years to fully decompose. You don't need a tape measure for every check. The heel of your hand is a simple guide for a mulch depth of 2 to 4 inches (5 to 10 cm). For watering, keep a way to measure 5 to 7 gallons (19 to 26.5 L). That is the amount a newly planted tree needs at each watering. Soil mounded into a 3-inch (7.6 cm) ring around the root ball works as a simple water-holding tool right after planting.

Step by step

  1. Step 1

    Water the root ball right after planting

    Aim the water directly at the root ball rather than the surrounding soil, since the roots have not yet spread into it.

  2. Step 2

    Build a water ring around the root ball

    Shape the ring about 3 inches (7.6 cm) high around the root ball's edge to hold irrigation water in place. Remove the ring by the end of the second growing season if it hasn't settled into the soil on its own.

  3. Step 3

    Water on a daily schedule right after planting

    Give newly planted trees and shrubs water every day for the first one to two weeks. Each time, pack the soil down firmly. Apply 5 to 7 gallons (19 to 26.5 L) each time. Or use 1 to 1.5 gallons per inch of trunk diameter (3.8 to 5.7 L per 2.5 cm).

  4. Step 4

    Space out watering as roots settle in

    From 3 to 12 weeks after planting, water every 2 to 3 days, then shift to weekly watering after 12 weeks until roots are established. Watering may happen about twice a week, depending on rainfall, temperature, and wind.

  5. Step 5

    Skip a watering only after heavy rain

    You can skip hand-watering when more than 1 inch (2.5 cm) of rain falls in a single day.

  6. Step 6

    Check soil moisture before watering an established tree

    Dig down 4 to 8 inches (10 to 20 cm) for a new planting. For an older, established tree, dig 6 to 9 inches (15 to 23 cm) down. Water at the first sign of wilting, or once the top 12 inches (30 cm) of soil dries out. Avoid overwatering, since too much water pushes air out of the soil.

  7. Step 7

    Choose organic mulch for garden beds

    Organic mulches, such as bark, wood chips, or pine straw, are generally favored in gardens and landscapes. Inorganic materials, such as rock or pebbles, give physical coverage but do not add organic matter to the soil.

  8. Step 8

    Spread mulch at a depth that balances weed control and air flow

    Apply mulch 2 to 4 inches (5 to 10 cm) deep in most beds. Inorganic mulch, such as rocks or pebbles, can go shallower, at 1 to 1.5 inches (2.5 to 3.8 cm). Keep mulch no deeper than the heel of your hand, generally 2 to 4 inches (5 to 10 cm).

  9. Step 9

    Mulch a newly planted tree with 2 to 4 inches (5 to 10 cm) of organic mulch

    Spread it over the planted area, but keep the total layer under 3 inches (7.6 cm) on a new tree or shrub. For finely textured or double-shredded mulch, cut that back to 1 to 2 inches (2.5 to 5 cm).

  10. Step 10

    Extend mulch out to the tree's drip line as it matures

    For an established tree, a 2- to 4-inch (5 to 10 cm) layer out to the drip line is ideal. Start the mulch ring 12 to 18 inches (30 to 46 cm) out from the trunk's base.

  11. Step 11

    Keep mulch away from the trunk or stem

    Don't let mulch touch the stem or trunk, since that raises the chance of stem rot. Pull mulch 3 to 5 inches (7.6 to 12.7 cm) back from a young tree. Pull it 8 to 10 inches (20 to 25 cm) back from a mature one.

  12. Step 12

    Leave extra clearance at the trunk to head off rot and pests

    Around a mature tree, leave a 6-inch (15 cm) mulch-free ring at the trunk. Keep mulch at least 12 to 18 inches (30 to 46 cm) from a tree's base. Around a shrub, 1 to 2 inches (2.5 to 5 cm) of clearance is enough. Mulch piled against a trunk can rot roots and stem.

  13. Step 13

    Time mulch application to soil warmth, not the calendar

    Wait until soil temperatures have warmed enough for root growth to begin before you spread mulch.

  14. Step 14

    Avoid piling mulch into a volcano shape around the trunk

    Mulch volcanoes are a real threat to a tree's health and should be avoided. Piling new mulch on top of old mulch year after year has the same effect as applying too deep a layer all at once.

  15. Step 15

    Check the depth of old mulch before adding a fresh layer each season

    Some of the old layer may need to come off before you add new mulch. Reapply bark mulch every 2 to 4 years, and wood chip mulch every 1 to 2 years. Add 2 to 3 inches (5 to 7.5 cm) of fresh organic mulch over the soil surface each year.

  16. Step 16

    Note that mulch temperatures can run high while it breaks down

    Temperatures inside a mulch pile can reach as high as 140°F (60°C).

  17. Step 17

    Water mulched beds deeply but less often than bare soil

    Apply enough water each time to thoroughly moisten the soil underneath the mulch. A clay soil may need about 1 inch (2.5 cm) of water weekly. A sandy soil may need about half an inch (1.3 cm) every 3 to 4 days.

  18. Step 18

    Let mulch do double duty against weeds

    Mulch mainly limits weeds by blocking sunlight from reaching the soil surface. Since some weed seeds need light to germinate, mulch can stop those seeds from sprouting at all. Mulch also cuts evaporation from the soil surface, which helps soil hold onto water.

  19. Step 19

    Mulch perennials and bulbs for winter protection

    Apply a protective layer, such as 5 to 6 inches (13 to 15 cm) of whole or shredded leaves. Add it once soil starts to freeze, or any time after that. Remove this winter mulch as it thaws in early spring, so crown rot and fungus problems don't take hold.

  20. Step 20

    Protect young trees and shrubs the same way heading into winter

    Cover the roots with 3 to 4 inches (7.6 to 10 cm) of shredded wood mulch for winter protection. A 4- to 6-inch (10 to 15 cm) layer also helps prevent frost heaving by keeping soil temperature more constant.

  21. Step 21

    Know that plastic mulch sheeting breaks down slowly

    Biodegradable plastic mulch sheeting can take up to three years to fully decompose.

Mistakes to avoid

It is a real threat to a tree's health and should be avoided. Mulch touching the stem or trunk raises the chance of stem rot. Piling mulch against a trunk can also rot the roots and stem outright. That same pile against the trunk can draw rodents that chew the bark and girdle the stem. More than 4 inches (10 cm) of mulch can harm a tree's root system. It has the same effect as piling on too deep a layer all at once. Check the existing depth each season, since some of the old mulch may need to come off before you add more. Using a finely textured or double-shredded mulch at the same depth as a coarser one is also a mistake. Cut that type back to 1 to 2 inches (2.5 to 5 cm). Leaving winter mulch on perennials and bulbs too long after it thaws in spring can lead to crown rot and other fungus problems. A water ring left in place past the second growing season should be removed if it hasn't settled into the soil on its own.

How this page was made

  • Written with AI assistance from the sources listed on this page. AI is never the source of a fact.

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