The 4 Types of Plants You Should Mulch in October – And the Ones That Don't Need It

Mulching is a highly recommended fall job that benefits many plants around your garden, but not all. Whether you should mulch or not depends on the soil, conditions, and the plant.

There are many benefits to mulching in the fall. It retains residual summer or early fall heat in the soil, reduces moisture loss, and protects roots from extreme cold when the temperatures drop. Many trees, shrubs, and perennials will find this a blessing, but some plants don’t want extra moisture trapped around them.

Here we look at plants you should mulch in October – those that will thank you for the protection. Plus some plants not to mulch this month, as they struggle under a thick layer of mulch. For those plants you should mulch, use organic mulches, such as compost, chopped leaves, bark mulch, or pine straw. You can get a bag of all-natural pine bark mulch at Lowe’s that makes a perfect fall mulch.

Plants You Should Mulch in October

Perennials

At the end of the growing season, flower beds will look all the better after being thoroughly weeded and mulched. Your best perennials will have worked hard all spring and summer, growing hard and putting on a show of flowers.

A great reward for their hard work is a 2-3 inch layer of mulch in the fall to protect their roots from frost and boost the soil nutrients as it breaks down. The likes of hostas, coneflowers, daylilies, black-eyed Susans, peonies, salvias, coral bells, and more will appreciate a good mulch this month.

Mulching perennials and shrubs also prevents frost heave, where the repeated freezing and thawing lifts the crowns out of the soil. You don’t need to cut back your perennials in fall before mulching, as many are best left over winter as their seed heads and old stems provide food and habitat for wildlife.

Compost is a perfect mulch for flower beds, such as this bag of organic compost at Walmart.

Shrubs

Shallow-rooted shrubs will overwinter better with a protective layer of mulch over the soil around them. This includes azalea, hydrangea, spirea, and euonymus. Also, any shrubs planted this season need mulching, as they are not fully established and will need protection from the winter cold.

The best type of mulch for shrubs is wood chips or shredded bark, like this shredded all-natural bark at The Home Depot.

Put down a layer 2-3 inches deep, but don’t pile it too close to the plant. Wendy Hanson Mazet, a plant diagnostician for the University of Nevada, Reno Extension, warns about not leaving a gap a few inches deep around the trunk or stem.

‘When mulch is piled directly against trunks or stems, it provides both protection and easy access for rodents, which can ultimately lead to the decline or death of the plant,’ she says. The rodents affect the shrub by feeding on its bark and cambium tissue.

Strawberries

In colder climates, such as US hardiness zones 6 and below, strawberry plants require some protection from low winter temperatures. Mulching offers a simple and proven way to winterize strawberry plants successfully, as it insulates the roots from deep frosts and prevents frost heave.

When you grow strawberries, wait until the plants have gone dormant to add mulch; they lose their vibrant green color, take on a reddish tint, and start to wilt. At this stage, remove any dead or diseased foliage to prevent strawberry pests and diseases from attacking your plants.

Then add a couple of inches of straw mulch (like this garden straw sustainable mulch at Amazon) around the plants, without covering the crown, which traps excess moisture and can lead to rot.

Blueberries and currant bushes also appreciate mulching in the fall. For these fruit bushes, use wood chips.

Garlic

Fall is a time for planting garlic in vegetable gardens and raised beds. The bulbs put down roots before winter, and then start growing again in spring to give you a top garlic harvest next summer.

Garlic is a cold-hardy crop, but there are still good reasons to mulch it. Primarily, it protects the bulbs from extreme cold and stops the repeated freezing-and-thawing cycle that can cause bulbs to be pushed out of the soil and leave them vulnerable to the elements.

A good material for mulching garlic is a lightweight one, such as straw or chopped leaves, though you can use compost or homemade leaf mold. Leaves are a great free fall mulching material. Simply collect leaves from around the garden, chop them with a mower or strimmer, and spread them over the soil surface.

Plants You Should Not Mulch in October

Mediterranean Herbs

When you grow Mediterranean plants like sage, lavender, oregano, and rosemary, these classic herb garden favorites should not be mulched in the fall. These plants prefer dry, well-draining soils and dislike wet conditions.

If you mulch them this month, you’ll put the plants at risk. As Anna Fialkoff, horticulturist at the Connecticut College Arboretum, warns: ‘They can be especially prone to rot if mulched heavily since that can trap moisture and humidity.’

Mulching Mediterranean herbs encourages moisture retention around the crown and stems, which can lead to rot and fungal diseases. To avoid creating an unwanted wet environment around the herbs, put a thin layer of horticultural gravel (available at Amazon) around them rather than mulching with organic matter.

Succulents and Cacti

When you landscape with succulents and cacti, these dry-loving plants don’t want to sit in lots of moisture, especially over the colder months. Excess moisture caused by a layer of organic mulch puts them at a high risk of root rot and attracts the unwanted attention of pests.

To care for succulents in winter, hardy types like sedum, euphorbias, and sempervivum can remain outdoors in many climates, while tender ones need to be brought indoors for overwintering. Plants in borders or containers will appreciate a layer of pea stone or gravel around them to help with drainage and stop the leaves flopping into wet soil, where they can rot.

It is the same advice when growing a cactus. Mulching cacti with organic matter in the fall will trap moisture in the soil, promoting rot of both the stem and roots. Give them some pebbles or gravel around the base of the plant.

Bearded Iris

When you grow bearded irises, you must be very careful about mulching. You need to always avoid burying the rhizomes under a layer of mulch.

The rhizomes of bearded iris varieties need sun and air circulation to burst into flower next summer. They are likely to rot if mulch is put on top of them.

If you have bearded irises in your flower beds, be cautious if you usually mulch the bed and avoid piling it on top of the iris rhizomes.

Wildflowers

If you have a wildflower garden or plant a wildflower meadow, you need to cut down growth in the fall to let the plants thrive. What you don’t do is mulch the garden or meadow.

Crucial to the success of a wildflower patch is self-seeding flowers. However, a thick layer of mulch buries seeds and prevents them from getting the light they need for germination.

Also, wildflowers don’t need highly fertile soil. Adding organic mulch will increase the nutrients in the soil, and unwanted plants and weeds will take advantage of that and start to take hold.

Shop Fall Mulches

Now that you understand which plants you should mulch in October and which you shouldn’t, it might also be a good idea to learn the same about pruning. Thankfully, we’ve got you covered.

We have guides to plants to prune in October and trees and shrubs to never cut back in October to help you prune with confidence and avoid making any mistakes this fall.

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