Straw bale gardening means growing vegetables, herbs and flowers directly in a bale of straw, instead of in the ground or in a pot. The bale is conditioned — watered and fed for a couple of weeks so it begins to break down inside — and then plants are set into the top of the bale, where they root into the warm, moist, composting straw. It is a good way to garden on poor soil, on concrete, or on a plot full of weeds, because the bale sits on top of the ground and the plants never touch the soil underneath. It is also a good way to garden at a comfortable height, because a bale is about knee high, and it is a useful method for a first garden, because it needs little digging. This guide explains how to condition a bale, how to plant into it, and which crops grow best.
The idea behind straw bale gardening is that a bale of straw, once it is wet and fed, begins to compost from the inside. The composting process warms the bale, which helps seeds germinate and young plants establish earlier in spring, and it breaks the straw down into a soft, moisture-holding material that roots can grow through. The bale also drains well, so plants are less likely to suffer from waterlogged soil, and it is free of soil-borne disease and weed seeds, because the plants are growing in straw, not in ground soil. After a season, the bale breaks down into a rich compost that can be spread on the garden. A bale will usually last one growing season, though a bale that is still firm at the end of the year can sometimes be used for a second season of hardy crops.
Choosing and placing bales
Use straw bales, not hay bales. Straw is the dry stalk of a cereal crop such as wheat or barley, and it contains few seeds. Hay is dried grass and clover, and it is full of seeds that will sprout in the bale and compete with your plants. Buy bales from a farm or a garden supplier, and check that they are tightly bound with twine or wire, because a loose bale falls apart when it is watered. Avoid bales that have been treated with herbicide, and ask the supplier if you are unsure — herbicide residue can damage or kill garden plants, and it is the most common cause of failure in straw bale gardening. If you cannot confirm that a bale is untreated, do not use it for food crops.
Place the bales where they will get at least six hours of sun a day, on level ground, with the cut side up and the twine running around the sides rather than across the top, so the twine does not rot and the bale holds together. Leave a path between bales so you can reach every plant, and put the bales where they can stay for the season, because a wet bale is heavy and hard to move. A bale on concrete or paving works well, and it is a good way to garden on a patio or a driveway, though the bales will stain the surface underneath. If you are gardening on a balcony, check the weight limit first — a wet bale is heavy — and see our apartment gardening guide for balcony rules.
Conditioning a bale
Conditioning is the most important step, and it takes about two weeks. It prepares the bale by starting the composting process inside it, so the bale is warm, moist and ready for plants. The usual method is to water the bale thoroughly every day, and to add a nitrogen-rich fertiliser — such as a balanced fertiliser or well-rotted manure — every other day for the first week, watering it in each time. The nitrogen feeds the microbes that break the straw down, and the bale will warm up inside as composting begins. You can check the temperature by pushing your hand into the bale: it should feel warm, but not so hot that it is uncomfortable to hold there. If the bale is very hot, wait a few days before planting, and water it well to cool it down.
After about ten days to two weeks, the bale should be ready: it will feel warm but not hot, it will have darkened and softened inside, and it may have a few small shoots of straw sprouting from the top, which you can pull out. If the bale still feels cold and dry inside, keep watering and feeding it for a few more days. Do not rush conditioning: planting into a bale that has not been conditioned means the plants will struggle, because the straw has not yet begun to break down and the bale will draw nitrogen from the soil around the roots. If you are unsure about conditioning, check your local extension service for advice.
Planting into a bale
To plant into a bale, make a hole in the top with a trowel or your hands, fill it with a handful of potting mix or compost, and set the plant into it, firming the mix around the roots. For seeds, spread a layer of potting mix a few centimetres thick over the top of the bale and sow into that, because seeds will not germinate well in bare straw. Space plants as you would in a bed, and do not overcrowd the bale: two tomato plants, or three or four pepper plants, is enough for one bale, while a bale of lettuce or herbs can hold more. Water the bale thoroughly after planting, and mulch the top with compost or straw to hold moisture in. Our guides for growing tomatoes, growing lettuce and growing basil give crop-by-crop detail, and container gardening covers the general principles of growing in a contained space.
Watering, feeding and care
A straw bale dries out fast, especially in sun and wind, so it needs watering more often than a bed — often daily in summer. Water slowly, so the straw absorbs the water rather than letting it run off, and water in the morning so the plants have the day to use it. A drip system or a soaker hose laid along the top of the bales can take over the daily watering job, and it is worth setting up if you have several bales. Feed regularly through the season with a balanced liquid feed, because a bale has little food of its own once conditioning is finished, and hungry crops such as tomatoes and courgettes need feeding every week or two. Herbs need less feeding, and they taste better for it.
Check the bales regularly for slugs, which love the damp straw, and for mushrooms, which are a normal sign that the straw is breaking down and are not a cause for concern — do not eat any mushroom that grows in a bale. As the season goes on, the bale will soften and sink, and plants may need staking: tomatoes and beans in particular need firm support, because a bale is not as stable as the ground. At the end of the season, the bale can be broken up and spread on the garden as compost, or added to the compost heap — see our composting basics guide. If you are unsure what will grow in a bale in your area, check your local extension service for advice.
What grows best in straw bales
Tomatoes, peppers, courgettes, cucumbers, beans and squash grow well in straw bales, because they are vigorous, they like the warm, well-drained bale, and they produce a lot from a small space. Salad leaves, herbs and strawberries also do well, and they are easy to pick from a bale at knee height. Root crops such as carrots and potatoes do not suit bales, because they need deep, loose soil to grow into, and a bale is not deep enough for them. Tall crops need staking, and the bale should be placed where it will not blow over in wind once it is top-heavy with plants. A bale garden is a good first garden for a beginner, because it needs little digging and the plants are easy to reach — see our gardening for beginners guide for the basics.
Common mistakes
The most common straw bale mistakes are using hay instead of straw, so the bale sprouts weeds; using a bale treated with herbicide, which kills the plants; skipping conditioning, so the plants struggle; underwatering, because a bale dries out fast; and overcrowding the bale, so plants compete and yield poorly. Another is placing bales in shade, where they never warm up and the plants grow slowly. The fixes are simple: buy straw, not hay, from a supplier you trust; condition the bale for about two weeks; water daily in summer; give each plant the space it needs; and site the bales in full sun. A straw bale garden that is conditioned, watered and fed well will produce a good crop in its first season.
Frequently asked questions
What is the difference between straw and hay bales?
Straw is the dry stalk of a cereal crop such as wheat or barley, and it contains few seeds. Hay is dried grass and clover, and it is full of seeds that will sprout in the bale and compete with your plants. Always use straw bales for straw bale gardening, not hay bales.
How long does it take to condition a straw bale?
About two weeks. Water the bale thoroughly every day, and add a nitrogen-rich fertiliser every other day for the first week, watering it in each time. The bale should feel warm but not hot inside, and it should have darkened and softened. If it still feels cold and dry, keep conditioning for a few more days.
Can I grow tomatoes in a straw bale?
Yes, tomatoes grow well in straw bales, because they like the warm, well-drained bale and they produce a lot from a small space. Plant two tomato plants per bale, stake them firmly, water daily in summer, and feed regularly through the season. See our growing tomatoes guide for the full planting steps.
Do straw bales need watering every day?
In summer, often yes. A straw bale dries out fast in sun and wind, and it needs watering more often than a bed. Water slowly in the morning so the straw absorbs the water, and consider a drip system or a soaker hose if you have several bales. In cool or wet weather, the bale will need water less often.
What do I do with the bale at the end of the season?
Break it up and spread it on the garden as compost, or add it to the compost heap. A bale that is still firm at the end of the year can sometimes be used for a second season of hardy crops, but most bales are best used for one season and then composted.