Deep Rooted Plants: Why Garden Beds With Ample Depth Are Essential

There’s a saying in gardening: Healthy plants begin from the ground up. And it’s true. So many factors beneath a garden’s surface — soil conditions, the presence of nutrients, pH level, moisture — impact plants’ well-being.

And the list doesn’t stop there. Not only are plants impacted by the quality and content of their soil, but their well-being also depends on having enough soil to accommodate their growing roots. Subjecting roots to cramped conditions puts plants at risk of poor health, injury, and limited crop production.

What that means is, if you want thriving plants, you’ll need to provide enough depth for them in your garden beds.

This is particularly true for deep-rooted plants: species that naturally develop extensive root systems. These plants are equipped to do well in environments where moisture and nutrients are limited near the soil’s surface. But their roots can work against them if they don’t get the room they need to grow.

Why plants need their space: health issues

When “cramped” roots compete for space, they may not be able to explore a wide enough area to absorb essential nutrients effectively. This can lead to stunted growth and poor health. Along the same lines, cramped roots may have difficulty accessing water, especially in drought conditions. Inadequate water uptake can result in wilting, leaf yellowing, and even plant death in severe cases.

Plants that don’t get enough room for their roots are more prone to disease, too. When roots are crowded in a confined space, air circulation and drainage could be compromised. This creates favorable conditions for soil-borne pathogens. And because cramped roots put plants under stress, they’ll be less resilient, not only to diseases but also to pests and harsh weather conditions.

Risk of injury

It’s also important to remember that healthy root systems provide structural support and stability to plants, anchoring them firmly in the soil. Cramped roots may not be able to anchor themselves, which in turn, puts them at risk of toppling over in strong winds or heavy rains.

In severe cases of root crowding, roots could even begin to wrap around each other and constrict themselves. This highly undesirable situation makes it even harder for roots to absorb nutrients and water. It can impair vascular flow, and ultimately, can cause plant decline or death.

Worth the effort

Don’t let deep-rooted plants’ needs for adequate soil depth discourage you from including them in your garden. Some of your most popular vegetable and flower options, from tomatoes to daylilies, tend to be deep-rooted (we’ll talk more about deep-rooted plants below).

Not only that, but deep-rooted plants can enhance your garden’s soil environment and structure. As roots penetrate deeply into the soil, they break up compacted layers, improve aeration, and encourage nutrient cycling.

The deep crowd

So, how do you know if you’re growing deep-rooted plants in your garden? This is one of the things you should research when deciding which plants are best for your region and the conditions in your garden. That said, here are a few examples of flowers and vegetables that tend to extend their roots deep into the ground.

Flowers

Perennials, like hollyhocks and black-eyed Susans, can have roots extending up to several feet, depending on soil type, climate, and specific species. Other deep-rooted flowers include lavender, coneflowers, Russian sage, salvia, coreopsis, and columbines.

Vegetables

Veggies that grow deep roots include tomato plants, which can have roots reaching depths of up to three to five feet. And taproots like carrots, potatoes, and beets can reach depths of one to three feet, depending on their species and soil conditions.

Onions have shallow root systems compared to some vegetables, typically reaching depths of six to eight inches. But they can develop deeper roots in loose, well-aerated soil.

Herbs

Some herbs develop deep root systems, too. Rosemary, for example, has been known to send roots several feet deep into the soil in search of moisture. Other deep-rooted herbs include thyme, oregano, and sage.

How deep should you go?

If you’d like to grow deep-rooted plants, the good news is, providing the space they need is not particularly complicated. While there's no one-size-fits-all rule for garden bed depth, a general guideline is to aim for a minimum of 24 to 36 inches for most deep-rooted vegetables and flowers. 

While you can provide that depth with containers or planting your garden in the ground, raised beds offer several benefits for deep-rooted plants. They provide improved soil drainage, better aeration, and easier root penetration. Besides, since you’re the one creating the bed, you can make sure it has the ideal mix of soil and amendments like compost.

In gardening, healthy plants really do begin from the ground up. When you give your plants enough space for their roots below the surface, you’re setting them on the path to flourishing above ground.