Asparagus is a delicious perennial vegetable that delivers crops for up to twenty-five years if cared for correctly. Here’s everything you need to know about pruning asparagus to ensure many years of healthy crops.
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Before you start pruning your asparagus, it’s important to understand how it grows. The edible spears that we love to eat emerge from ‘crowns’ in the ground and, once your plants are established, these spears can be harvested for six to eight weeks each year.
At the end of the harvest season (in June) you’ll need to stop harvesting the spears to allow the tall ‘ferns’ to develop. This leafy foliage is how the plant gathers energy for next year’s crop. Eventually this fern-like foliage will die and need to be cut back, but not until it has done its job and the crown has become dormant.
Asparagus season is just two months long, from April to June. After midsummer's day, when you’ve stopped harvesting the spears, they’ll quickly start to grow into tall, leafy ferns. It’s important to let these grow, as they gather and return energy back down into the crown for the following year. The ferns will grow throughout the summer, reaching a bushy height of about 4 feet high.
At the end of autumn, the ferns will turn yellow or brown which is a good indication that they’re ready to be pruned. This job is best tackled in late winter (November or December) or early spring while the plants are dormant.
When pruning asparagus ferns, start by cutting them all back to a height of around 4-6 inches. Then remove all of the old, yellowing, brown and damaged foliage at the base of the plant. Next, cut back any spindly shoots that aren’t producing spears. Finally, gently rake the soil to remove all the debris. This helps to prevent disease and stops pests from overwintering in the bed.
Remember that newly planted asparagus crowns need time to get established, so the spears shouldn’t be harvested at all in the first two years. Let all the spears that emerge grow into ferns. Once the ferns turn brown, cut all the foliage down to 10 cm above the soil level and apply a thick layer of mulch.
When your plants are three years old, you can start harvesting some of the spears to eat. Remember to stop harvesting in mid-June and allow some stems to develop into ferns so the plant can build up energy reserves for the next year’s crop.
Pruning your asparagus helps to keep pests and diseases at bay, and makes weeding and mulching easier. But it’s important to wait until your asparagus ferns have turned brown before you cut them down to the ground. Read our full article for more advice on how to grow asparagus including how to prepare your trench and plant the crowns.
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