Straw Bale Gardening.

Straw bale gardening is not something I’ve tried before, but it is on the cards for this year. The technique has been around since the Sixties, if not earlier. An American horticulturalist, Joel Karsten, has been honing his cultivation techniques using this system for 22 years and now grows almost all his vegetables and herbs this way, using 25 bales to supply his family’s needs.

He is evangelical about the technique. In many ways it is like growing in raised beds without having to make the raised beds. BBC Radio 4’s Gardeners’ Question Time has had numerous queries from schools and clubs hoping to grow crops on hard surfaces or flat roofs, and this is possibly the least expensive and most effective system without having to lift the concrete or tarmac.

Karsten reckons that veg and fruit plants are about 25 per cent more productive in bales than they are in the ground. This can be attributed to more oxygen to the roots (we are increasingly realising the importance of this), together with unlimited water (straw is like a sponge and holds an amazing quantity of water) and nutrients. Added to this, heat from decomposition of the straw means that crops are produced earlier, the cropping period is extended later in the year, too, and the produce is generally larger. Karsten calculates that 75 per cent less labour is involved – bales never need weeding.

My reservations are the aesthetics – bales do not age gracefully. Otherwise, I think the system is impressive, especially where you have no soil or poor soil. You cannot overwater and there are no problems with soil-borne diseases. Compared with the cost of a grow bag, at about £1 for a small bale (source them locally online), it is about half the cost.

In response to my reservations, Karsten says that he grows herbs and annuals up the sides of the bales to disguise them. Alternatively, many growers partially conceal them. Panels of reed fencing are especially reasonable (4  x 1m panel, £9.99;, and can be cut down easily to fit and conceal. Some have simply slotted the bales into galvanised water container.

For my first year I will use them for half my tomatoes and cucumbers in the greenhouse. The increase in humidity should help with red spider and, as I usually grow tomatoes in baseless pots on soil, it means the existing soil will have a rest.

I am following Karsten’s instructions to the letter. The bales (straw, not hay) will be positioned vertically with the string still in position. I will move them into place about two weeks before I intend to plant them, bearing in mind that the heat generated by decomposition allows you to plant between two and four weeks earlier than in the ground.

The most labour-intensive part is the initial “conditioning” – adding water and fertiliser so the bales start to decompose inside, which takes about 10-14 days. On the first day you spread 4oz of a nitrogen-rich lawn fertiliser evenly over the top before gently washing it in with 1-2 gallons of water (this takes a minute or so). The fertiliser does not need totally washing in. When water is coming out of the bottom, stop. For the next nine days or so you carry on, some days adding fertiliser, some days not. If you are organic, you can add organic fertiliser instead but increase the quantity six fold (and source organic straw). After the fifth day use water from a butt or water that has been left in a bucket overnight so it is not as cold as from the tap. Finally, immediately before planting, add a seep hose along the top (if you don’t want to hand water) and on the 11th day plant or sow.

Sowing involves spreading a 1-2in layer of multi-purpose compost along the entire top of the bale, before sowing the seeds. As for planting, you just stab the immediate area with a trowel to make a hole wide enough to receive the plug/pot and push the plant in. Remove a small bit of straw if necessary. I plan to plant three tomato plants per bale and will probably add some marigolds to help deter whitefly, and might well plant parsley up the sides, too.

Baling us out: straw makes growing vegetables easy (Streeter Photography / Alamy)

Karsten even grows potatoes this way (three plants per bale) – they are clean on harvesting, extremely easy and highly productive, so I am tempted. My thin, limey soil means potatoes are prone to scab, but the bales’ moisture-rich environment will help prevent this. Sweetcorn, however, is not ideal – this is a huge plant and can only be grown two per bale, so it is hardly worth it. Perennial vegetables are out of the question, too, as the bales will last for a maximum of two years. After this they become mushy but are great for compost or adding to borders. Otherwise, parsnips, turnips, lettuce – indeed, just about everything – will grow. As to watering interval, a grower in North Carolina applied only a gallon a week per bale during drought periods and nothing suffered. Soluble fertiliser is added every few weeks.

The other straw-related product that I am trying this year (after glowing references from Arabella Lennox-Boyd) is strulch. This mulch was developed at Leeds University and patented by soil scientist Geoff Whiteley in 2004.

Jackie, his wife, runs the business. Strulch is made from chopped and treated wheat straw, with added iron minerals that preserve it so that it lasts a good two years. Strulch is light in weight and reduces weed growth dramatically, blocking the light to prevent weed seeds from germinating. It also deters slugs and snails as the iron sticks to them.

Trevor Jones, head gardener at Alnwick, is a fan: “Each year we apply a layer of strulch over beds to protect the emerging delphinium shoots and leaf spikes of our hostas. Our delphiniums grow away to make strong healthy plants and our hosta foliage remains intact through the summer rather than looking like lace curtains by early summer. Strulch also helps to retain moisture in the beds and improves the soil as it decomposes,” he says.

Worm populations increase markedly, as with many organic mulches. Strulch is also ideal for last-minute titivating to borders before a garden opening or party.