How Deep Does A Planter Box Need To Be? (With 100 Plants List)

You want to grow plants and buy a planter box. But you wonder?

How deep should the planter box be so your plants don’t have any growth problems?

A planter box should be at least 8 inches deep because most plants need 6 to 8 inches of soil for proper root growth. Leafy vegetables can grow in a planter box 6 to 8 inches deep. Root vegetables need a planter box 8 to 14 inches deep. Fruiting vegetables need planter box 12 to 16 inches deep.

This is a reference you can use when selecting a planter box for your plants. But I’ll give you a detailed list of 100 types of plants and the planter box depth that each one would need.

Why planter box depth is important for plants?

Plant roots absorb nutrients and moisture from the soil so they can prepare food. When the plant grows in outdoor soil, it has plenty of space to spread out the roots deep into the ground. But in a planter box, the depth limits the roots growth.

If the planter box has the right depth, the plant roots will get the required nutrients and moisture. Otherwise, it will cause poor plant growth. And the plants may suffer other problems like pests and diseases.

The planter box depth will depend on the type of plant you’re growing. Some plants need more depth than others. Because some plant roots can grow deeper and spread wider than others.

Some leafy vegetables like lettuce and herbs like cilantro have shallow roots. While root vegetables like carrots and fruiting vegetables like tomatoes have deep roots.

If the planter depth is insufficient for fruiting plants that grow tall, such as peppers, eggplants, and okra, they may even topple over with the weight of the plant.

Can a planter box be too deep for plants?

You don’t want to overdo and make the planter box too deep for the plants, as this can cause some problems.

If the planter box is too deep, you’ll need a lot more potting soil, which will get expensive considering the cost of the soil.

If you try to grow a small plant in a deep planter box, the roots won’t be able to absorb all the moisture. This means the water will sit in the potting soil for longer and can attract fungal problems like root rot.

Pro tip: Make sure that the planter box has sufficient drainage holes at the bottom so that excess water can drain out. Also, use a liner at the bottom of the planter box to encourage good drainage.

If the planter box is deep, the plant may not get the required stable base with the surplus of potting soil. This soil is soft and has an airy texture compared to garden soil. So the plant could topple over because of its weight as the potting soil shifts underneath.

How deep should a planter box be for leafy vegetables?

Leafy vegetables and herbs typically need less soil depth compared to fruiting and root vegetables. These include vegetables such as spinach, lettuce, and kale. Herbs like cilantro, mint, and lavender also need less soil depth.

These vegetables and herbs would do just fine if depth of planter box is between 6 to 12 inches. You could even grow different leafy vegetables in the same container.

Here is a list of some leafy vegetables and herbs and the planter box depth they would need.

Plant	Planter Box Depth (inches)
Arugula	12
Bok Choy	8
Cabbage	12
Celery	8
Chard	6
Chicory	18
Collards	12
Kale	12
Lettuce	6
Mustard Greens	6
Orach	12
Sorrel	8
Spinach	6
Swiss Chard	8
Cilantro	8
Basil	8
Lavender	12
Rosemary	12
Thyme	6
Sage	8
Mint	12
Parsley	8
Dill	12
Fennel	12
Chamomile	8
Tarragon	12
Oregano	8
Marjoram	6

How deep should a planter box be for root vegetables?

It’s obvious that many root vegetables would need a deep enough planter box so they can grow well.

Some of these root vegetables, like turnips or beets, may need less than others, but typically you want to grow these vegetables in a planter box that is 6 to 24 inches deep. I’ve also included tubers like potatoes and pods like garlic on this list.

You can grow different root vegetables in the same planter box if it’s large enough to give space for each of them.

Here is a list of some root vegetables and the planter box depth you should use.

Plant	Planter Box Depth (inches)
Beets	8
Carrots	12
Garlic	8
Horseradish	24
Jicama	12
Leeks	18
Onions	10
Potatoes	15
Radishes	12
Rutabaga	12
Scallions	6
Sweet Potatoes	18
Turnips	8
Chives	8
Lemongrass	8

How deep should a container be for fruiting vegetables?

Most of the fruiting vegetables require deep potting soil to grow tall and healthy roots.

You’ll need a planter box with at least 8-12 inches depth for growing such vegetables as tomatoes, peppers, cucumbers, or eggplants. I’ve also added vegetables like asparagus and Brussels sprouts to this list.

You should not grow different fruiting vegetables together because they will compete for nutrients and moisture, affecting growth.

Here is a list of some fruiting vegetables you can grow and the planter box depth they need.

Plant	Planter Box Depth (inches)
Asparagus	12
Beans	8
Broccoli	8
Brussels Sprouts	12
Cauliflower	8
Corn	12
Cucumbers	12
Eggplant	12
Endive	6
Kohlrabi	16
Okra	10
Peas	8
Peppers	10
Pumpkins	20
Rhubarb	20
Squash	12
Tomatoes	12
Zucchini	12

How deep should a planter box be for houseplants?

The depth of the planter box for houseplants would depend on the type of houseplant you’re growing.

Most houseplants would grow well in any planter box with decent depth such as 8-12 inches. Use your judgment to figure out how deep the planter box should be. Small plants like succulents could do just fine in a planter box with less depth, such as 4-6 inches.

If you’re growing flowering plants, note that perennials will need a deeper planter box than annuals. That’s because their roots grow deep into the soil to survive for years, unlike annuals.

Here’s a list of some houseplants you may grow and the planter box depth you can use.

Plant	Planter Box Depth (inches)
Anthurium	8
Croton	12
Orchid	6
Pothos	10
Red Aglaonema	6
Snake Plant	10
Peace Lily	10
Succulents	4
ZZ Plant	10
Ponytail Palm	8
Chinese Evergreen	8
Grape Ivy	8
Philodendron	12
English Ivy	8
Spider Plant	6
Hoya	8
Rubber Tree	10
Cast-Iron Plant	8
Jade Plant	12
Weeping Fig	8
Asparagus Fern	6
Chinese Money Plant	6
Yucca	10
Air Plant	6
Aloe	4
Dragon Tree	12
Calathea	10
Bromeliad	6
Kalanchoe	6
Crown Of Thorns	8
Christmas Cactus	6
Schefflera	10

How deep should a planter box be for fruit plants?

There are some fruits that could be grown in a large enough planter box. These include strawberries, blueberries, and even figs.

But other fruit plants grow into large trees and even if you want to grow dwarf varieties, the planter box needs considerable depth.

You may need a planter box that is at least 8 to 48 inches deep to grow such fruiting plants or trees.

Here are some fruit plants and the planter box depth you need for growing them.

Plant	Planter Box Depth (inches)
Melons	16
Strawberries	8
Blueberries	24
Pineapple	24
Cantaloupe	16
Watermelon	20
Currants	20
Gooseberries	18

How deep should a planter box be for flowers?

A planter box should be at least 8 to 10 inches deep for growing flowering plants. Perennial flowering plants have deeper roots than annuals. So I would suggest using 10 inch deep planter box for perennial flowering plants.