The Essential Guide to Straw Bale Gardening

At first glance, straw bale gardening may appear to be a fad or an overly optimistic idea, but this method has been practiced for years, with many gardeners swearing by its effectiveness. Joel Karsten, the author of Straw Bale Gardening Complete (which is actually a series of four books), developed the concept when he lived on a property with insufficient topsoil for growing crops.

Having grown up on a farm, Karsten observed how plants naturally sprouted from bales as they decomposed, prompting him to wonder if he could plant directly into straw bales. After over fifteen years of perfecting his approach, Karsten published a self-made pamphlet on the technique, which later led to a publishing deal in 2013. Since then, Karsten has become the leading figure for this innovative method, though he does not claim to be the sole inventor of straw bale gardening.

We reached out to Joel Karsten and Gail Pothour, a UCCE Sacramento County Master Gardener with over a decade of experience growing vegetables in straw bales, to learn more about this unique gardening technique. Below are their tips for starting your own straw bale garden.

What is Straw Bale Gardening?

Straw bale gardening is a technique that uses straw bales as the planting medium. It’s a simple, cost-effective, and temporary solution for creating vegetable beds. This method is especially helpful in situations where traditional soil is unsuitable, either due to contamination or poor growing conditions.

Karsten shares that he has received photos of straw bale gardens from across the globe. “People are using straw bales to garden in places where you wouldn’t imagine, like Abu Dhabi, Egypt, Israel, New Zealand, and even north of the Arctic Circle,” he notes. In Northern California, Pothour explains that the head gardener at the Fair Oaks Horticulture Center was inspired by hearing Karsten on the radio after his book was published and decided to try straw bale gardening. Since then, they’ve used straw bales to grow part of their vegetables.

How to Start a Straw Bale Garden

Starting a straw bale garden requires more than just the bales themselves. First, choose a location with full sun exposure. Pothour recommends also considering the aesthetic aspect of your garden. “Eventually, they can become quite unsightly. I wouldn’t place them in my front yard because they can look pretty rough by the end of the season,” she advises.

Besides straw bales, you’ll need fertilizers to help condition the bales, sterile potting soil, and seeds or seedlings for your plants.

Both Karsten and Pothour recommend setting up an automatic irrigation system for your garden, even if it's just for a one-season experiment. Options include a soaker hose or a more advanced drip system with an automatic timer. If you don't opt for an irrigation system, be prepared to water by hand every day, and twice daily during peak summer heat.

Be sure to purchase a straw bale—not a hay bale, which contains many unwanted seeds (and will “sprout like a Chia Pet,” according to Karsten). Position the bales with the cut side facing up, with the strings around the sides. If you end up with a bale that has the strings running along the cut side, still place the bale so that the strings are around the sides. You’ll just have to work a bit harder to plant your seeds or seedlings, cutting through the straw crosswise.

How to Condition Straw Bales

In his books, Karsten explains two methods for conditioning the bales—organic and conventional—which is essentially a process of partially composting the bales before planting. The moisture and nitrogen from the fertilizer accelerate the natural decomposition process. Pothour mentions that the Fair Oaks Horticulture Center uses the organic method, as they are committed to organic produce, but homeowners may find the odors from organic fertilizers unpleasant.

“If you choose the organic method, keep in mind that it takes longer to condition, it’s more expensive, and it does have a smell,” she says. “So don’t place it near your patio or kitchen door where the odor might be offensive.”

For the conventional method, Karsten suggests using 1 lb. of lawn fertilizer that contains no pesticides or herbicides, along with a bag of 10-10-10 organic fertilizer for each bale you plan to plant. For the organic method, you'll need much more: 5 lbs. of blood or feather meal, plus an organic source of Phosphorus and Potassium.

Conditioning the bales using the conventional method takes about 10-12 days, depending on the temperature. Following Karsten's approach, you’ll alternate sprinkling ½ cup of fertilizer on Day One and watering with warm water the following day for a total of six days. On Days 7, 8, and 9, reduce the fertilizer amount to ¼ cup and water it in, and on Day 10, add the 10-10-10 fertilizer. Complete instructions can be found in his book Straw Bale Gardening Complete.

What Can You Plant in a Straw Bale Garden?

A wide variety of plants can be grown in straw bales, but there are a few crops to avoid. Karsten suggests skipping sweet corn, as it yields poorly and the bales could tip over.

Pothour also advises against growing very tall plants, like certain tomato varieties. However, most tomatoes do well in straw bales, especially dwarf varieties. Karsten hasn’t had success with onions in Minnesota, but believes gardeners in warmer southern climates might have better luck.

Avoid planting perennial crops such as asparagus, artichokes, and rhubarb, since they regrow each year and your bales won’t last more than two seasons. Also, skip rosemary, as it prefers an alkaline environment.

Karsten shares, “Tomatoes, peppers, and cucumbers thrive, as well as the entire squash and cabbage families, which particularly benefit from the bale method, helping to prevent issues like cabbage worms that lay eggs in the soil.” Pothour has had excellent results with sweet potatoes, which turn out significantly less damaged compared to those grown in traditional garden beds.

How to Plant in a Straw Bale Garden?

Once your bale is conditioned, it's time to start planting. To transplant seedlings (also known as starts), you’ll need a hand trowel and sterile potting soil to give your young plants a comfortable environment (Karsten recommends about ½ cubic foot of potting mix per bale).

Use the trowel to make a hole in the bale, spacing your plants according to the recommended guidelines. Place the seedling in the hole, water it, and then fill the hole back in with your potting mix. For planting seeds, create a thin 1-2 inch layer of planting mix on top of the bale and set your seeds into it. Be sure to follow the spacing instructions on the seed packet.

How to Care for a Straw Bale Garden?

Your straw bale garden will need regular watering to stay moist. However, Karsten warns, “The biggest mistake people make is overwatering their straw bale gardens. It’s very easy to do.” Once the bale is moistened, a gallon or two a day is usually enough to keep it from drying out (more in extremely hot weather). “Hose-end timers that you set like an alarm clock are a game changer,” says Karsten, who typically sets his timer to run for three minutes every 12 hours. “During the peak heat of summer, you can adjust the frequency,” he adds.

Once your seedlings have their third set of leaves, it's time to start fertilizing your straw bale garden. Apply a liquid or soluble fertilizer every few weeks to keep your plants well-fed. Organic gardeners may opt for a foliar fertilizer like fish emulsion, which Karsten humorously notes, 'smells bad but works wonders.'

Troubleshooting Common Problems

One of the most common issues gardeners face is that their bales begin to slump and look untidy as the season goes on. 'As the straw bale decomposes, it shrinks. You need to keep those strings tight,' says Pothour. She and the team at the Fair Oaks Horticulture Center use a technique they call the 'tourniquet method,' where they twist the baling twine tighter with a stick to prevent the bales from collapsing.

Both Karsten and Pothour suggest adding a physical barrier, such as a small fence or a board, to help keep the bales from collapsing too much. Another occasional issue Karsten mentions is ants, which don’t harm your plants but are attracted to the straw. His advice? 'Just ignore them.'