When planning a garden landscape, it’s important to consider the root depths of different plants. Some plants have roots that spread out shallowly, while others have deep taproots. Knowing which plants have shallow root systems can help you make informed choices to create visually pleasing designs and avoid potential issues.
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Why consider root depths?
There are a few key reasons to take root depths into account when selecting plants:
- Avoid root competition – Shallow rooted plants can compete for water and nutrients. Spacing them too close together causes them to struggle.
- Prevent damage to foundations and hardscapes – Roots that grow close to the surface can sometimes crack paths, walls, and structures. Deeper roots are less likely to cause issues.
- Plan for water needs – Shallow roots require more frequent watering as they are closer to the surface which dries out faster. This is important to factor in for irrigation.
- Design visually pleasing beds – Mixing plants with different root depths and spreads creates more interesting and dynamic looks compared to uniform depths.
Taking root growth habits into account allows you to select appropriate plants for their sites and set them up for success.
Shallow rooted perennials
Many common perennial flowers and non-woody ornamental plants have shallow root systems. Here are some examples:
- Lily of the valley – Roots grow just 4 to 6 inches deep.
- Hostas – Grow roots in the top 12 inches of soil.
- Astilbe – Has roots reaching 6 to 12 inches deep.
- Bearded irises – Develop roots that go down 1 to 3 feet deep.
- Peonies – Grow taproots only 1 to 2 feet deep.
- Oriental poppies – Grow roots reaching just 1 foot deep.
- Bleeding hearts – Grow roots in the top 12 inches of soil.
- Daylilies – Spread roots horizontally about 12 to 18 inches down.
- Shasta daisies – Grow roots reaching about 12 inches deep.
- Garden phlox – Has shallow roots growing just 1 foot deep.
The perennials listed above all grow roots quite close to the surface. Give them plenty of space from trees and shrubs to prevent competition. Water them more frequently during dry periods. Plant with deeper rooted perennials to allow plants to complement and support each other.
Shallow Rooted Perennials
| Plant | Root Depth |
|---|---|
| Lily of the valley | 4 to 6 inches |
| Hostas | 12 inches |
| Astilbe | 6 to 12 inches |
| Bearded irises | 1 to 3 feet |
| Peonies | 1 to 2 feet |
| Oriental poppies | 1 foot |
| Bleeding hearts | 12 inches |
| Daylilies | 12 to 18 inches |
| Shasta daisies | 12 inches |
| Garden phlox | 1 foot |
Shallow rooted annuals
Like perennials, many popular annual flowers and plants grow roots close to the surface. Some examples include:
- Impatiens – Root depth around 6 inches.
- Petunias – Roots grow in the top 6 inches of soil.
- Marigolds – Taproot goes down about 1 foot deep.
- Zinnias – Grow roots in the top foot of soil.
- Nasturtiums – Roots grow in the top 8 inches.
- Cosmos – Have roots reaching about 1 foot deep.
- Salvia – Grows roots about 8 to 12 inches down.
- Verbena – Spreads roots about 8 inches deep.
- Geraniums – Grow taproots about 1 foot deep.
Annuals with shallow root zones need frequent watering and will compete with other shallow rooted plants if spaced too closely. Their quick growth and seasonal nature make it easy to replant them in combinations that allow adequate root space.
Shallow Rooted Annuals
| Plant | Root Depth |
|---|---|
| Impatiens | 6 inches |
| Petunias | 6 inches |
| Marigolds | 1 foot |
| Zinnias | 1 foot |
| Nasturtiums | 8 inches |
| Cosmos | 1 foot |
| Salvia | 8 to 12 inches |
| Verbena | 8 inches |
| Geraniums | 1 foot |
Shallow rooted vegetables
Root crops aside, many common vegetables grow shallow root systems. Some to consider for space planning include:
- Lettuce – Grows roots in the top 6 to 12 inches of soil.
- Spinach – Has roots reaching just 6 to 8 inches deep.
- Beans – Grow taproots about 12 inches deep.
- Peas – Spread roots out to 8 inches deep.
- Cabbage – Roots grow in the top foot of soil.
- Cucumbers – Develop roots about 12 to 18 inches deep.
- Tomatoes – Grow roots about 18 to 24 inches under the surface.
- Peppers – Spread roots out about 1 foot deep.
- Summer squash – Roots grow just 8 to 12 inches down.
- Eggplant – Grows taproots about 18 inches deep.
Vegetable plants with shallow root systems do best when watered regularly. Space them apart appropriately and don’t plant under trees or shrubs that will compete for water and nutrients.
Shallow Rooted Vegetables
| Plant | Root Depth |
|---|---|
| Lettuce | 6 to 12 inches |
| Spinach | 6 to 8 inches |
| Beans | 12 inches |
| Peas | 8 inches |
| Cabbage | 1 foot |
| Cucumbers | 12 to 18 inches |
| Tomatoes | 18 to 24 inches |
| Peppers | 1 foot |
| Summer squash | 8 to 12 inches |
| Eggplant | 18 inches |
Shallow rooted herbs
Many popular culinary and medicinal herbs also grow roots quite close to the soil surface. Some examples include:
- Chives – Grow roots about 6 to 8 inches deep.
- Parsley – Has roots in the top 6 inches of soil.
- Cilantro – Grows taproot about 1 foot deep.
- Thyme – Spreads roots out about 10 inches down.
- Lemon balm – Roots grow about 1 foot deep.
- Chamomile – Grows roots about 6 inches under the surface.
- Mint – Spreads shallow roots about 12 inches down.
- Oregano – Grows roots about 12 inches deep.
- Sage – Develops roots just 10 to 12 inches down.
- Rosemary – Roots grow about 12 to 18 inches deep.
Give herbs adequate space to prevent tangling of shallow roots. Water shallow rooted herbs frequently, especially in hot and dry weather.
Shallow Rooted Herbs
| Plant | Root Depth |
|---|---|
| Chives | 6 to 8 inches |
| Parsley | 6 inches |
| Cilantro | 1 foot |
| Thyme | 10 inches |
| Lemon balm | 1 foot |
| Chamomile | 6 inches |
| Mint | 12 inches |
| Oregano | 12 inches |
| Sage | 10 to 12 inches |
| Rosemary | 12 to 18 inches |
Shallow rooted grasses
Ornamental grasses provide texture and movement to gardens and landscapes. Some types grow roots quite close to the surface. These include:
- Blue fescue – Grows roots about 8 inches deep.
- Maiden grass – Roots grow about 1 foot deep.
- Fountain grass – Taproots grow about 1 foot down.
- Feather reed grass – Roots grow about 1 foot deep.
- Ribbon grass – Grows roots about 8 inches under the surface.
- Japanese blood grass – Roots spread about 8 inches down.
- Tufted hair grass – Roots grow about 6 inches deep.
- Common rush – Grows roots just 4 to 6 inches underground.
Plant ornamental grasses with shallow roots where their irrigation needs can be met. Leave plenty of room between them and other plants to prevent tangling and competition underground.
Shallow Rooted Grasses
| Plant | Root Depth |
|---|---|
| Blue fescue | 8 inches |
| Maiden grass | 1 foot |
| Fountain grass | 1 foot |
| Feather reed grass | 1 foot |
| Ribbon grass | 8 inches |
| Japanese blood grass | 8 inches |
| Tufted hair grass | 6 inches |
| Common rush | 4 to 6 inches |
Conclusion
Many common garden plants grow their roots quite shallow, rarely reaching more than 1 to 2 feet under the soil surface. When planning gardens and landscaping, take root depths into account to give plants enough space, meet their irrigation needs, and design attractive and sustainable plantings. Choosing a variety of plants with different rooting habits also allows gardens to be more dynamic.
Shallow rooted plants require care and consideration to grow successfully. Their roots are easily impacted by environmental factors and competition from other plants. Take simple steps like:
- Providing adequate spacing for shallow roots to spread out.
- Watering frequently to keep surface roots hydrated.
- Using mulch to conserve moisture in the root zone.
- Avoiding planting under large trees and shrubs.
With a little planning and care, gardens full of thriving shallow rooted plants can be achieved. Their diversity of colors, textures, and forms make them well worth the extra effort.