Gardening in Grow Bags | Answers to All Your Questions

Gardening in Grow Bags | Your Comprehensive Guide

For gardeners with limited space, grow bags offer an incredibly convenient solution, while also providing benefits to all types of gardeners. In this week’s post, I will address frequently asked questions regarding grow bag gardening, covering both the pros and cons, along with strategies for overcoming the challenges. Recently, we asked our social media followers what they wanted to know about grow bags, and the response was overwhelming—with plenty of questions answered in this blog.

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Even though I maintain a large garden with 16 significant raised beds, I have incorporated grow bags into my layout. They prove to be useful and practical for various reasons, as I will outline in this article. I continually seek opportunities to experiment in my garden beyond the confines of my raised beds. Grow bags act as temporary mini raised gardens, allowing me to expand my growing area. Once I no longer need them, I can easily empty and store them away.

While grow bags are beneficial for all gardeners, those in urban or small-space situations stand to gain the most. They are ideal for gardening on decks, patios, or stoops.

Amy Prentice, the Director of Marketing and Communications at Agrivana Media® joins me in this discussion. This is her first season using grow bags, and she shares popular inquiries regarding best practices for utilizing them.

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Advantages of Utilizing Grow Bags

Extra Growing Space: When planting crops in my raised beds that require time to mature, my options for succession planting become limited. However, by adding grow bags, I can create additional opportunities in my garden. Grow bags come in various sizes, allowing you to select an appropriate size for anything you wish to cultivate.

Convenient Harvesting: One of my favorite features of grow bags is the ease of harvesting root crops. When it's time to harvest sweet potatoes or new potatoes, I avoid disturbing the tubers with a garden fork. Instead, I simply pour the bag out onto a sifter, preserving 100 percent of what has been growing underground while allowing the soil to be saved and reused. Some grow bags even feature side flaps, making it easy to access only the tubers you need for dinner.

Attracting Pollinators: Grow bags can be scattered throughout your garden to entice pollinators and add a splash of color by planting flowers inside them. If you need to relocate the bags for better positioning, they can be easily lifted by their handles or placed on rollers.

Crop Rotation: As I tend to grow several crops within the same family, enforcing a proper crop rotation in my 16 raised beds can be quite challenging. Ideally, crop families should rotate annually in a four-year schedule, shifting beds before returning to their original locations. With some soil-borne pathogens developing in my raised beds, it's become essential to discover new spots for growing crops like tomatoes and peppers (both belonging to the nightshade family). Grow bags provide an excellent solution without the need for additional costs associated with building more raised beds.

Amy also benefits from utilizing clean soil in her grow bags. After battling tomato and pepper diseases and persistent poor growth in her beds, she shifted to grow bags with potting soil. She observed that her plants became bushier, yielded greater fruit, and encountered fewer disease issues. The clean soil not only eliminated pathogens but potentially offered more nutrients compared to her raised bed soil. This revelation highlighted areas needing improvement in her gardening approach.

Grow Bags vs. Plastic Containers

Podcast listener Belinda inquired whether she should switch to grow bags after experiencing success with plastic containers. My take is if something is working, there’s no need to change it. Nevertheless, you might find that grow bags can yield even better results.

The primary distinction between plants grown in rigid plastic containers and those in grow bags is how their roots grow. In plastic containers, roots will grow in a circular pattern when they reach the edge, risking becoming root-bound. This condition may restrict access to vital water and nutrients. However, in grow bags, once the roots reach the edge, they stop growing due to the porous nature of the bags that delivers essential air. This process, known as air pruning, promotes healthier root systems due to increased air circulation.

Choosing the Right Grow Bags

The strongest materials for grow bags are heavy-duty landscape fabrics—commonly made from polypropylene or polyethylene (derived from recycled plastic bottles). Regardless of the material, look for spun-bond fabrics which are proven to be durable.

Quality matters when shopping for grow bags. If you purchase based purely on price, you might not find the most robust options. Choose bags featuring handles for ease of mobility, taking care to select bags with handles that are part of the bag and not merely sewn onto it, as Amy discovered that cheap handles may break by the end of the season.

Research reputable manufacturers and sellers, such as Root Pouch, Smart Pots, and Spring Pots, which are all trusted brands. However, feel free to explore options that align with your preferences.

Environmental factors will deteriorate any material you choose. Although you can craft your grow bags from burlap or cotton, consider their durability if you need to move fully filled bags often.

Color of Grow Bags: Black vs. Colorful Options

Mark, a participant in my Beginning Gardener course, asked if the color of grow bags makes a difference. Although black options are the easiest to find, there are alternatives featuring vibrant colors or those that blend seamlessly with your garden.

The key concern regarding color is light exposure. Roots require darkness, so light-colored bags should be avoided unless the material is sufficiently thick. Personally, I favor darker bottles as they retain heat, protecting roots during colder nights, which ultimately leads to more fruitful plants.

Determining the Right Size of Grow Bags

Many listeners sought advice regarding the ideal size of grow bags for various crops. Not only does the volume of the bags matter, but their dimensions do as well. Some bags are deeper while others are wider.

For shallow-rooted plants like onions, garlic, and lettuce, opt for a wide and shallow bag. In contrast, deep-rooted plants, such as carrots and tomatoes, will benefit from taller bags.

Choosing bags with a volume of at least 5 gallons is critical, as smaller sizes won’t provide enough space for adequate root development. When cultivating larger plants, allow a minimum of 5 gallons per plant. However, avoid growing two indeterminate tomatoes together in a single 10 or 15-gallon bag due to root competition.

Budget considerations apply when using larger grow bags since they are not only pricier, but filling them with premium soil also incurs extra costs. When planting singular crops like a cabbage or small quantities of spinach, smaller bags are justifiable.

Amy utilized a 25-gallon bag, which resembled a medium raised bed, planting a tomato at its center with onions arranged around the perimeter. However, filling such a large bag with soil can be costly and challenging to relocate once planted. A sizeable grow bag works well for small fruit trees or sweet potatoes that thrive with ample growing space.

Crop Suitability for Grow Bags

Listeners commonly wondered which plants are best suited to grow bags. Nearly any crop appropriate for containers or raised beds can thrive in grow bags, provided they have the right environmental conditions, well-draining soil, and proper watering. However, it's advisable to choose quickly maturing plants to minimize risks during shorter growing times.

Optimal Surfaces for Grow Bags

Students from my Master Seed Starting course had inquiries about the ideal surface for placing grow bags. Sherry noted her tomatoes didn’t thrive as well in bags on her deck compared to those on her lawn.

The surface underneath grow bags significantly impacts growth. On solid surfaces, bags can only access water from rainfall or manual watering, while bags on grass can draw moisture from below. Additionally, a hard surface may lead to staining; consider using liners or positioning the bags on bricks to avoid this issue. However, keep in mind that removing the bottoms from the bags will expose roots, potentially leading to faster drying.

Spacing Plants in Grow Bags

While most grow bags are cylindrical, Cindy from the joegardener Facebook group points out that plant spacing guidelines often align with square designs. Visualize the equivalent square within the circular shape of a grow bag, allowing for additional semi-circular space on the edges to accommodate any extra plants.

Soil Recommendations for Grow Bags

Using well-draining soil in grow bags is essential so that roots do not dry out between watering. Opt for products labelled as potting soil or container mixes.

Many potting soils consist of peat moss, but increasing numbers of brands are incorporating coir as well. Perlite and vermiculite—lightweight mineral products—are excellent for moisture retention and contribute to lighter soil mixtures. Additionally, some soil mixes may include wood fines.

So long as soil-borne diseases haven’t infiltrated your grow bag, you need not replace the soil yearly. To refresh soil, transfer it to a larger container, eliminate clumps or woody roots, then mix in compost, constituting about 25 percent of the original soil volume. The compost will replenish nutrients and beneficial microbes essential for plant success. You may also consider adding slow-release organic fertilizers.

Many question whether compost alone suffices for planting. While effective, compost lacks many vital nutrients plants require. Enhance your compost with minerals and nutrients or blend it with necessary amendments for the best results.

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Fertilization in Grow Bags

Over time, nutrients and fertilizer will leach from grow bags, presenting a challenge. I consistently apply organic liquid fertilizer, whether in soluble or liquid forms, including options like fish emulsion. Paired with compost in the soil, these fertilizers help ensure plants receive adequate nutrients.

Watering Responsibilities for Grow Bags

A downside of grow bags is their tendency to dry out rapidly. Regularly automated watering through a drip irrigation system can counter this problem. These systems are user-friendly for assembly and can be set up with an automatic timer, ensuring your plants stay consistently hydrated.

To retain moisture, applying a layer of organic mulch—such as shredded leaves or straw—around the bags can be effective. Mulch will also suppress weeds while providing essential nutrients as it decomposes.

Sunlight Requirements for Grow Bags

Vegetable crops generally necessitate full sun exposure, receiving 6-8 hours of direct light daily. Some gardeners rotate their grow bags to optimize light exposure. While constant movement is ideal, it isn’t always feasible; plants can endure occasional shading without severe impact.

Pest Management for Grow Bags

Grow bags experience no more pest-related challenges than raised beds, and in some instances, issues may less frequently arise since it's more difficult for pests to access them. If pests are present, respond with integrated pest management practices similar to traditional gardening.

Occasionally, you may discover ants or other insects when opening side flaps on grow bags. Typically, ants aren't harmful, serving more as beneficial organisms unless they are fire ants, so avoid unnecessary intervention.

Supporting Plants in Grow Bags

When a plant requires support, there's no need to overthink your solution. Tomato cages may puncture the bottom of grow bags, but this poses little risk as the bags are porous. Custom cages or stakes integrated around the bag can provide adequate support. Personally, I’ve positioned grow bags along a fence and affixed livestock panels to serve as a sturdy framework for plants like tomatoes.

Winter Care for Grow Bags

Before the winter season, you can either empty and sanitize your grow bags for storage or leave them in use with soil. Some crops—like potatoes—can be overwintered in grow bags, providing convenient access through the colder months. However, overwintering can be challenging for most crops due to root exposure to freezing temperatures.

If opting to store empty grow bags, rinse them thoroughly, sanitize them with soap, and air dry before stowing them away until spring.

If you have more questions regarding gardening with grow bags, let us know in the comments below!

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