How to Feed Perennial Beds for Healthy Flowers Next Year

Leafy green flower plants with brown shredded leaves covering the soil.
Perennial peach-leaf campanula plants mulched for the winter with shredded leaves
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Caring for soil is one of the most complex gardening topics. Once your perennial flowers are planted and growing, good soil care is essential to healthy and abundant flowers next season.

But it’s really not complex at all. Or difficult.

That’s because nature takes care of it all. As long as you supply what nature needs: some raw materials.

Roots are very active in fall and winter  

For perennials, shrubs, and trees, roots are very busy growing in the fall and winter. Even though they don’t look like it. They’re growing and taking up nutrients in the soil to prepare for their burst of growth in spring.

Soil is in the best shape when it has an abundance of soil organisms. This includes microorganism (microbes) like bacteria, fungi, amoeba, protozoans, and many more. And it includes macroorganisms like earthworms and insects.

All these organisms create a healthy soil that feeds the plants in it.This may be surprising, but…

A plant’s roots dictate what nutrients the soil organisms make

Each root ends with a tip that exudes a lubricating gel to help the root push through the soil. But this gel also contains additional exudates. These exudates provide food for soil microorganisms. But each plant’s exudates feeds the organisms that generate the nutrients that plant needs. So, the plant is directing its own microbe community to feed itself.

To say that again, different microbes generate different types of plant nutrients. And the plant roots attract and foster the microbes that produce the ones they need.

All the organisms live together in a checks and balances ecosystem where the dead and decaying feed the living, and the “good” guys keep the “bad” guys in check. This is called the soil food web, and it was discovered and elucidated by Dr. Elaine Ingham, who started a school for learning and practicing this knowledge (see the Soil Food Web School here).

The soil organisms need organic material to break down to become available to the microbes in the soil and on to the microbes. This increases the soil food web. That’s where mulching comes in.

Mulches are the best food

Many gardeners recommend laying a mulch on perennial flower beds. But not always for the same reason.

Mulches protect the soil from erosion from driving rains, from drying out, and offer some protection from cold temperatures.

But a mulch can be a long-term food source for soil organisms, if you use the right ones.

A good mulch for feeding the soil for perennials plants is different from that of annuals. Annuals need amendments and mulches that have a higher nitrogen content to feed their microbes. Perennials (and shrubs and trees) need a mulch with a higher carbon content.

What mulch has good carbon content?

Tall tree in fall with with lots of leaves turning brown.
One of our tall sycamore trees in November with lots of big leaves turning brown and falling.

The best mulch is very simple and abundant… in fall.

Leaves. All the fallen leaves that you see people sending off through the waste collection trucks, or burning (if that’s still allowed), or dumped onto the back forty to slowly degrade, or better, mulched on the spots they fall on, are perfect. (With a few exceptions, see below.)

We’re now encouraged to leave our leaves on the soil and lawns over the winter. It’s good for the soil and it lets the butterfly eggs that get laid on leaves hatch in the spring near their preferred food source. This is a very good thing!

But sometimes there are too many leaves for the space you have for them, they may smother your plants.

This is when you can cart them to your perennial flower beds and lay them on the soil. The winter weather will flatten them down and the earthworms from below will come up and start eating them and bringing them sown into the soil where the whole network of soil organisms can break them down.

They’ll feed the soil food web and that will feed your roots. Nice and easy, right?

Are your leaves too big, or too bulky?

I’ve just moved into a new (old) house with two mature sycamores. The leaves are big, bulky, and they fall on the lawn below and on the patio and walkways. I’ll leave them on the lawn (I haven’t tried this before so it’s an experiment). But what we collect from the hardscaping I’ll add to my new perennial beds.

But the problem is that the leaves are big and bulky. I just moved my perennial flowers with me and planted them, but they’re small. I want to be able to see them. And I need fast action in the soil.

Machine to load leaves in the top funnel and shredded leaves end up in the bucket below
This Flowtron leaf shredder takes leaves in the top funnel and shreds them into the bucket below. It makes quick work or reducing a pile of bulky leaves and turns them into the perfect mulch/food for perennial flower beds.

A tool for the job

But I have a tool. It’s a leaf eater. It makes quick work of breaking your leaves down to smaller, more manageable pieces that are easy to apply and stay on the beds more readily.

The leaf eater I use and recommend is the Flowtron LE-900 Ultimate Mulcher Electric Leaf Shredder. It’s lightweight and works like a string trimmer to shred leaves as you load them in. (Please wear ear and eye protection!)

You can use it to shred leaves to mulch all your shrubs and trees, too. I’ve used it for many clients I’ve worked for.

What should not be used for mulch?

Aged pine needles can be used but not fresh ones. It’s not an acidity thing, it’s the terpenes in the needles. They need to dissipate into the air first.

Wood chips are good, too. But results have been much better with leaves in comparison experiments. But not cedar chips, eucalyptus chips, and most likely walnut or redwood chips. And I would not use walnut leaves.

How About Fertilizer?

The beds I just transplanted my perennial flowers into is a soil that was used for a garden many years ago. But now it lacks organic matter. There are some earthworms, though. I dug the beds quickly and amended with some purchased compost. I also added a little organic fertilizer.

Just to jumpstart the microbes with some food, I’ll be sprinkling more of the organic fertilizer over the beds, then I’ll pile my shredded sycamore leaves onto the soil.

Only use organic fertilizers, please! They feed the soil food web with raw materials, so they’ll do their work. Fertilizers feed the roots directly, and bypass the soil food web, and the web starts to break down.

Once the microbes multiply, the only food I’ll give them is leaves.

So save your good compost for your vegetables, not your perennial flower beds. But feed the soil with the right kind of food and they’ll do well for you.

Additionally…

  • If you’re interested in learning more about the soil food web, read the book I read that really opened my eyes. It’s Teaming with Microbes by Jeff Lowenfells and Wayne Lewis. You can get it here. And Jeff Lowenfells has a newer book I haven’t read (the first one sold me!) called Teaming with Fungi (which is what our perennials want most) and Teaming with Nutrients.

Tending annual flower and vegetable beds is different. Read about soil care for annuals here.

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