With all that is going on in our world during these recent weeks, more folks than ever are feeling drawn to gardening. The confidence that comes with growing your own source of healthy food is appealing, of course, but the garden also provides a refuge through periods of anxiety. Well, this week’s episode focuses on an easy way to get growing – using the straw bale gardening method.
Joel Karsten literally wrote the book on gardening in straw bales. It’s often said that necessity is the mother of invention, and that was true for Joel. He grew up on a dairy farm in southwest Minnesota and, as a child, noticed how robustly thistles would grow out of broken bales left near the family barn. Joel also noticed that the bales would decompose into a rich soil-like material.
Eventually, Joel earned a degree in horticulture from the University of Minnesota, so when he bought his first home, he was eager to grow a garden. The problem was that the property was built on fill dirt. Having just spent all his money to buy the home, Joel didn’t have money to build raised beds or bring in lots of quality soil or amendments to get started.
So, his ingenuity and childhood memories kicked in. He decided to try establishing a garden using straw bales. By the middle of the first season, his tomato and pepper plants were thriving, and Joel realized he was onto something.
As the years passed, Joel learned firsthand that just about everything grows well in the environment of a straw bale – from root crops (like potatoes and beets) to vining plants (like cucumbers) to leafy greens. The only exceptions are sweet corn (which becomes too top-heavy for a bale to support), rosemary, and perennial-rooted plants, such as asparagus and rhubarb.
Nearly 30 years after Joel’s first experiments, the straw bale method has become popular with gardeners across the globe.
Sourcing the Bales
The most commonly available types of bale are straw and hay. If you didn’t grow up on a farm, you probably don’t know the difference, so let’s break that down first.
Straw bales are made from the stalks of cereal grain crops. It’s the material left over after the grain has been harvested. As a byproduct, straw bales are less expensive. The grain stalks are hollow, so the bales are lighter too. Straw is slow to break down, and Joel has found they tend to last for two growing seasons.
Hay bales are used to feed livestock. The grass crop – like alfalfa, fescue, or clover – is grown specifically to be dried and baled as a food source, so hay is more expensive. Hay bales are heavier and break down quickly due to their higher nitrogen content. In fact, Joel has found that hay bales typically collapse before a single growing season is over.
It’s more common for seed from a hay crop to be present in a bale, which results in grass sprouts in your garden. On the other hand, farmers want to remove all the grain before the remaining stalks are baled, so it’s less likely you’ll have any unwanted sprouts in straw.
The biggest issue between hay and straw bales is the risk of the presence of persistent herbicides. It’s not uncommon for hay farmers to spray their fields with an herbicide to protect the crop. It’s against agricultural regulations for grain farmers to use these persistent chemicals. That said, there is still a slight risk in straw, whether from overspray or a disreputable grower.
There’s an easy way to test any bale to feel confident that it will be safe for your plants. It’s called a bioassay test. Chop a little of the material into small pieces, add it to some potting mix, and plant 3 small containers with pea or bean seeds. Then, plant 3 small containers using just the potting mix.
When the seeds sprout after a few days, you’ll be able to see if the sprouts in the bale/soil containers look as healthy as the sprouts in potting soil only. If the bale sprouts look stunted or misshapen, that’s due to the presence of persistent herbicide, and you’ll definitely want to avoid planting in that bale.
So, where can you find bales for sale? Joel recommends that you look for organically-grown bales. Each state’s Department of Agriculture website includes a list of certified organic growers, the crop(s) they produce and how to contact them. If there aren’t any growers nearby; Craigslist, Facebook Marketplace, or strawbalemarket.com can be good resources.
Nurseries and garden centers often carry straw bales, and they have usually vetted the supplier to make sure the bales are pesticide-free.
Conditioning the Bales
Straw bale gardening is easy, but there are some preparation steps that you need to do before you start planting. First – be sure to place the bale with the cut side on top, as the planting surface. The folded sides can be used, but the cut (or prickly) side will make water and nutrient penetration easier.
It’s key to get the moisture and nutrients into the bale, because they will promote bacterial growth. In a healthy compost pile, bacterial growth and activity are necessary for decomposition. The same is true in a hay bale. It’s what will create the conditions for supporting plant growth and production.
Straw is high in carbon, so it’s necessary to add a lot of nitrogen to create the environment for bacterial growth. Joel recommends blood meal as the nitrogen source. Apply it to the bale by poking holes in the top and pouring the meal into those cavities. Next, add water and let the bacteria population boom begin.
Bacteria multiply by splitting in half. As it prepares to divide, a bacteria will vibrate back and forth before breaking apart. Within 15 minutes, each of the two individuals are ready to split again. All that vibrating creates friction, and the friction generates heat – a lot of heat. The interior of a bale can reach about 140 degrees Fahrenheit.
The heat is a good indicator that the bale is conditioning well and some of the internal material is beginning to decompose to be ready to support your plants. During conditioning, Joel provides more blood meal (or whatever nitrogen source you prefer) every other day.
Proper conditioning takes a little time, so Joel recommends that you begin the process 20 days before your area’s last frost date. By Day 18, the bale should be ready for seed sowing.
One of the most common mistakes in gardening is a tendency to overwater, and according to Joel, that’s just as true in straw bale gardening. A bale has the capacity to hold 3-5 gallons of water. Anything beyond that amount will drain away.
Unlike in-ground or raised bed gardening, water draining out of a straw bale is carrying with it some of the nitrogen you applied to feed bacteria growth. Early in the season, bales need no more than one gallon of water per bale per day to support plant growth. Any more than that can be detrimental to the nutrient level within the bale.
As the season progresses and plant roots take up more space within the bale, more water will be necessary, because the bale will just dry out more quickly. Rather than watering more per dose and potentially washing away nutrients, Joel recommends increasing the frequency of watering instead.
Laying soaker hose over a straw bale garden is an effective way to deliver water evenly, but constant exposure to sunlight breaks down the hose material quickly. Joel recommends drip irrigation as the best option. The irrigation tube is more durable and easier to tuck out of the light. Plus, drip emitters provide better control for providing the right amount of water to each type of plant.
Put the system on an automatic timer, and you’ll be all set for water delivery to run on its own. It can provide the frequency the straw bale garden will require without overdoing it to wash away nutrients.
There’s no soil required when it’s time to plant in a conditioned straw bale – unless you’re sowing small seeds. Crops like carrots, radishes, and lettuce will be better off if you lay a thin layer of sterile soilless mix over the top of the bale and cover the seeds with a light dusting of the mix. The larger seeds of crops like peas, beans, and squash can be inserted directly into the bale to a depth of around the second knuckle on your finger.
Joel recommends following the same row spacing as recommended on the seed packet, but plant in a checkerboard pattern to make the best use of the bale’s footprint.
When planting seedlings, create a hole in the bale deep and wide enough to accommodate the roots, and insert the root ball directly into the cavity. If any of the roots are exposed to the surface, add a little soilless mix to protect them.
If you live in a cooler zone, you may want to cover the bale with plastic over a wire trellis to create a sort of tent over the bale. The cover will hold the heat developed by bacterial growth in the bale. Since heat production continues for up to 8 weeks, it can create a comfortable environment for even tender crops to thrive. Here’s a pro tip – tuck the plastic into the bale strings to keep it from blowing away in the wind.
According to Joel, five bales can provide sufficient crop production in a season to feed one person. Just keep plant size in mind when deciding what to plant in each of those bales. An indeterminate tomato, for example, will take up a huge amount of space at the height of the growing season. So, better to limit those to one per bale.
Become familiar with the mature size indicated on a seed packet or plant tag, and space accordingly.
Straw bales are unique in that you can tuck small plants into the sides. Herbs and flowers do really well inserted into those spaces.
Joel likes to maximize the use of each bale by strategically planting crops according to the age of the bale. After all, a bale that is 2 years old will be much more decomposed than a new bale. Root crops prefer that environment. So, Joel plants crops like tomatoes, peppers and eggplant in newly-conditioned bales and plants his root crops into second season bales.
After the second season, bales tend to be too decomposed for another crop, but the remaining material makes for a great potting medium for container gardening. Like the fresh bale material, the decomposed byproduct holds moisture well while still providing good drainage.
Benefits and Common Concerns
Aside from being easy to set up, there are several advantages to straw bale gardening. The height of the bale is a big bonus when it comes to accessibility. Plants in the surface of the bale are 18-22” higher than an in-ground bed, and that can make all the difference for some gardeners.
Don’t have any garden tools? No problem. All you need to garden in straw bales are pruners and a planting trowel.
Although you might have a grain seed or two that sprouts between your plants, you won’t have any weed problems, and what’s not to love about that? The heat created by bacterial activity means that gardeners in cool zones can start planting sooner. Even warm-season crops do well during cool spring days, because their roots remain warm within the bale. That means earlier crop production.
On the other hand, Joel has found that roots within a bale remain cooler during hot weather. As moisture in the bale evaporates it creates a “swamp cooler” effect that’s so powerful Joel can keep harvesting lettuce all through the summer.
You don’t need much space – or even a patch of Earth – to garden in bales. European gardeners are setting up straw bale gardens on their rooftops, and gardeners all over the world have set them up on balconies or small patios. One New Jersey community garden is built entirely in straw bales situated on a plot of contaminated land. The toxic soil has been covered up, and the bales provide space to grow food without any soil contact.
Another big benefit is the reduction in diseases. Many diseases are soil-borne, but the soilless bale will be pathogen-free, which is why Joel recommends using sterile soilless mix for sowing small seeds and covering exposed roots. However, bear in mind that disease pathogens can infect a bale environment. So if you have issues with a soil-borne disease avoid inadvertently transmitting the pathogens on work gloves or your garden trowel to the plants in your bale garden.
Gardeners often ask Joel if vegetables grown in a bale taste as good as what’s grown in soil. He says that they do as long as the bale is conditioned well and decomposing. The bacterial activity within the bale can provide nutrients for plant roots just like the soil food web in our in-ground or raised bed gardens.
Joel sometimes experiences calcium deficiency which creates blossom end rot in his tomatoes, and he’s also dealt with symptoms of magnesium deficiency on occasion. He feels these issues are far outweighed by the benefits he enjoys.
Some gardeners don’t like the look of straw bale gardens. They are definitely not your traditional beauty, but they can be dressed up with flowers planted in the sides, decorative trellis options or other creative adaptations.
It turns out that bale gardening is a great option for providing food to families in third world countries. Some Asian countries burn rice straw off the fields after harvest, but Joel is involved with an organization teaching local farmers to bale the material instead. They’re also sharing seed saving methods.
Poor families in these areas don’t need to spend money on tools or supplies, they use creative nitrogen options – like human pee – to condition bales and irrigate with greywater from cooking, bathing and washing. It’s this type of creative thinking that’s keeping many people fed in these struggling areas of the world, and that’s just one more reason that we can all feel so good about gardening.
I hope you’ll be sure to listen in to my conversation with Joel by scrolling to the top of the page and clicking the Play icon in the green bar under the page title. He’s full of enthusiasm for this gardening method, and it’s easy to understand why. Maybe it will be a good option for you to try as well this season.
Links & Resources
joegardener Online Academy Three popular online courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting!
Master Seed Starting – My newest online course teaching you how to master the art of starting your own plants from seed and seeding care! Registration closing soon, so don’t miss out!