Container Gardening FAQs

The beauty of gardening in a container (or two!) is that you can grow gorgeous flowers, veggies, herbs, and fruits anywhere. Not sure where to start? We tackle our most frequently asked questions about container gardening.

Container Basics

What is the best soil for containers?

Soil for container-grown plants should be light, crumbly, and well-drained. Most container-grown plants are happiest in a soilless blend comprised of peat moss and vermiculite or perlite, with the addition of finished compost. Don't use random soil dug up from your backyard — it will be too compacted and potentially harbor diseases.

How often do I have to water my container garden?

Watering needs will depend on the plant type and weather — your best bet is to check the soil with your hand. Stick your hand about 2 inches into the soil will give you a sense of whether the soil is truly dry — just because the surface is dry, does not mean the whole container is is! Indoor plants will typically need to be watered much more frequently in the winter, when the air is dry from forced hot air. Keep in mind that soil may need a few days to dry out after a heavy rain, especially if the air is already saturated (humid).  

Do I need to cover my container gardens at all?

It depends! If you are trying to prevent insect or animal pests from eating your plants, try a simple cloche, pop-up cover, or dome. If you are concerned about extreme temperatures (either frost or heat), cover your container with garden fabric. Note that roots that fair well buried in the ground are more susceptible to freezing temperatures when in a container.

What kind of fertilizer do I need for my container garden?

Fertilizer is less about the container, and much more about the type of plant you are trying to grow. An All-Purpose Fertilizer will work for well for all plants. If you are looking to really promote bud growth on flowering plants, look for a fertilizer that has a slightly higher amount of phosphorous (P).

Should I install a vertical support in my container?

Depending on the size of the container and plant, you can certainly use a vertical support. Supports come in all shapes and sizes and can be used for tomatoes, cucumbers, morning glories, sweet peas, beans, peas, and other vining plants. Keep the scale of the trellis in proportion to the pot, and be sure to attach it securely using brackets or wires.

 

Types of Containers and Planters

What kind of container material should I choose?

Consider your budget, weight you are physically able to manage, preferred aesthetic, and the types of plants you want to grow. Terracottta has a classic look, but can be quite heavy, and are often hand thrown, therefore quite expensive. They should be moved to a protected area in the off season to prevent the porous walls from cracking with freezing temperatures. Terracotta also dries quickly so may not be suitable for a plant that prefers consistent moisture. Plastic is lightweight, can be relatively inexpensive, comes in a variety of shapes and colors, and requires minimal maintenance — but can weaken over time. Consider environmental impacts of plastic compounds. Metal is quite durable as long as maintained free of corrosion. Metal containers come in a variety of price points, and is relatively lightweight. Powder coated metals can come in a variety of colors and typically last a long time. Wood is moderately heavy, depending on the thickness, but provides a natural look in the garden. When treated regularly, wood planters can last many years.

Do collapsible planters exist?

Fabric planter pots like these Universal Grow Bags will stand freely once filled with soil, and then fold up easily when emptied out.

Are there garden containers that are universally accessible?

Many gardeners find elevated planters that are 2-3 -feet off the ground easy to access from a seated position with no bending or kneeling required.

What kind of containers are good for railings?

Railing planters and windowboxes are very popular. There are planters designed to sit on top of standard decking widths of 4-6 inches or ones that can be hung from iron railings. Because these knids of planters don't hold a lot of soil, they can dry out quicker. Look for ones with self watering features for the best results.  

Are there containers that are easily moveable?

Look for a planter or container with rolling casters or consider adding a plant caddy. Either of these solutions make it easy to move a heavy planter around; especially useful if you live in a shady spot and you want to "chase the sun". 

If using a wooden container, what kind of wood should I look for?

Cypress and cedar are both fungus- and insect- resistant. Though treatment is highly recommended with any bed, cedar may last longer than cypress untreated. Cypress is denser than cedar, and more resistant to scratches or damages. I

What are coco liners?

Coco liners are made from coconut fibers and can be placed inside wire containers and baskets to prevent soil from escaping. They allow for healthy air flow, provide a natural aesthetic, and can be composted after it degrades (unlike plastic liners).

Can I recycle old containers?

Nursery pots have a designated plastic type, discernable by the number on the bottom.  Untreated wood can be composted, however treated/processed wood cannot. Scrap metal is widely recyclable and may even be worth some money depending on the material. Always check with your local solid waste district first, and consider repurposing the container if recycling is not an option!

 

The Right Plant for the Right Container

How deep of a planter do I need for veggies?

It depends on the vegetable. Leafy greens (lettuce, spinach), radishes, and small herbs can easily be grown in 6 inches of soil. Deep-rooted plants (tomatoes, peppers) need at least 12 inches of soil, but preferably more.  Perennial edibles like asparagus and rhubarb require at least 24-36 inches of soil and are better candidates for raised beds.

I have a lot of shade — can I still have some hanging baskets?

Yes! There are plenty of gorgeous shade-loving plants out there. Try begonias, fuschia, browallia, impatiens, for bright blooms, and sweet potato vine, caladium, and coleus for fantastic foliage.

Can I grow trees and shrubs in containers?

With some careful selection, trees and shrubs can be grown in containers. Know your grow zone, and choose a species that is well within that hardiness zone — roots will not be as insulated in a container as they are underground. Choose a compact or dwarf variety that won't mind a snug growing environment, and be consistent with watering as roots may dry out faster than those planted in the ground.

What size container is good for growing a tomato plant?

A container that holds at least 20 quarts of soil is best. Tomatoes get big so generally speaking, the deeper the better. The more soil there is, the more root space there will be — and the longer your plants can go between waterings.

Can I grow herbs in containers?

Starting a herb garden can be done using a container in as little as 5-6 inches of soil. Basil, chives, parsley, dill, coriander, and oregano are excellent candidates for planters, pots, and other containers. Add more of your favorites and you will soon be taking your culinatry skills to the next level!

What size container should I repot my houseplant into?

Houseplants generally only need to be repotted when their roots have begun to reach the edges of the container and are looking for more space. Sizing up to a pot 1-2 inches in diameter larger at a time is ideal — with too much room, open soil is left to harbor rot or fungal growth instead.

 

Container and Planter Care

How do I clean a wooden planter?

First, empty the planter. Remove any soil first with a dry brush, then wash with water and soap. To sanitize and prevent disease spread, use a 10% bleach solution. Rinse and allow to air dry completely (may be multiple days) before applying any wood treatment. After that has dried, add fresh soil!

How do I care for a metal planter?

Some metals will perform better when used for planting than others. Galvanized or powder coated metals will withstand the elements and are resistant to rust. Using a smaller plastic pot or liner inside and keeping the metal as a decorative outer later may help preserve the material further. Coatings may be weakened and peel or chip when exposed to freezing temperatures, so bring them to a protected area in the winter.

Can I leave my containers outside for the winter?

If you live in an area where there are regular hard frosts through the winter, there will be wear and tear on your containers no matter the material. Unglazed ceramic containers are at the highest risk of damage or cracking, since the porous material holds moisture that will expand and crack the vessel when frozen. Plastic becomes brittle and breakable when frozen. Wood (especially if waterproofed) or galvanized metal should do well outside for multiple seasons, and fabric grow bags will fare best. Your best bet? Just bring your containers inside!

Can I use a grow bag more than once?

Yes! Just clean thoroughly to make sure bacteria doesn't hang around. Empty the grow bag at the end of the growing season and clean off any debris. Wash with a mild, diluted bleach solution (1:10 bleach:water) and hang to air dry. Your grow bag is now ready for a new garden.

How do I prevent water stains from forming under my container gardens?

Water stains can be prevented by either raising the pot up slightly off the ground (ex. pot feet or on a small stand), allowing air flow to dry out any water runoff, or by using a saucer to collect excessive water from sitting on your surface.

 

Self-Watering Containers

What is a "self-watering" container or planter?

A self watering system is essentially a reservoir at the bottom of the planter that holds extra water. As the moisture in the container is used up by the plant, the extra water below will wick upwards towards the soil, keeping your soil consistenly moist. Some self watering systems use a cloth strip to help the wicking action. Most reservoirs are large enough to supply water for several days or more depending on the weather. These containers can generally be used both indoors and out. Some systems also have a water fill tube with a water level indicator that bobs up when the reservoir of water runs dry.

Why would I chose a self-watering container?

Self-watering systems come in many different forms and they can help provide consistent water to your plants. When used correctly, self-watering planters and containers prevent both over- and under- watering by regulating the uptake of water. They are super convenient for gardeners, especially when you are aren't able to water frequently or are heading out of town. For plants that like to dry out a bit (succulents, cacti, etc.) a self-watering planter may not be the right container choice.

Can I leave a self-watering system outside year-round?

If you live in an area with hard frosts/long winters and using containers that are made from plastics, you want to make sure you drain your planters before it freezes to prevent damage.