(First published in Kitchen Garden magazine, February 2009)
Asparagus is a plant I have wanted to grow for many years and now that both of my allotments are in good working order the time has finally come! I don’t mind waiting two years for the first decent harvest because I now have plenty of fresh vegetables coming off my plots all year round. To my way of thinking the two crops you really ought to grow on your allotment are strawberries and asparagus, something exotic and special – an epicurean’s delight. My favourite asparagus recipe is the cold vinaigrette served as a starter, to be eaten on a warm June day or – simply steamed, chopped and served with scrambled egg!
I ordered ten asparagus crowns from the Cambridge grower, Marshalls. I pre-prepared the raised bed in which they will grow, to let the ground settle before planting out. I ordered a mid-late season variety (Blacklim) because the part of the country where I grow is South Cambridgeshire, which can be cold and windy right through to the end of April and even early May. My thinking is that the shoots will grow better once the warmer weather is more firmly established in the second half of May and June.
I have only ordered ten crowns to be set in a single column because space on my allotment is at a premium. Asparagus require light well-draining soil so I have chosen a spot (see photo) where the ground is slightly raised and therefore better drained – this is an important factor since the allotment site runs down to the river Rhee (or Cam) and a high water table means there may be standing water in places during the winter months. Since the asparagus bed will be permanent, this part of the plot was brought into good condition the previous year and prepared in the autumn with a top mulch of horse manure. The bed is bordered on one side by a path to allow good access for harvesting the crop.
The first step is to dig a trench (see photo) a little deeper than the depth of the spade, placing the soil in equal amounts on either side. The idea is to create a raised bed so remember, the deeper the trench the more material you will have to put back in! It needs to be sufficiently wide for the number of crowns you are going to plant. In my case a single row requires a width of about three feet. A double row of crowns would require a bit more than four feet, so as to provide a gap of 15 inches between the rows. The plants will be spaced about a foot apart.
The next task is to deposit, (see photo), a good thick layer of well-rotted manure evenly along the base of the trench. This will feed the plants in the years to come. Then the topsoil is raked back into the partially filled trench, leaving the level slightly raised, (see photo). To finish off the job, lightly skim along both sides of the bed with a shovel, shaking the additional soil onto the crown of the bed, thereby raising it a bit further. The bed should be built up to at least 6in. above the surrounding level. Finally, carefully rake over the raised bed to ensure an even slope runs from the middle down to the sides along its whole length, (see photo). The bed should be left for a couple of weeks to a month to weather down and settle before final planting out.
The crowns are then planted a foot apart with their roots well spread out (see photo) then covered over to a depth of three inches. To ensure this I have replaced the skimmed-back topsoil and added a mulch of compost as a final covering (see photo).
I ordered one year old, well-grown crowns, which should not be cut later this year (June 2009) and only sparingly in the year following (2010), to ensure optimum growth. In the meantime the plants are allowed to grow unchecked, making plenty of top growth, which is only cut back in late October, as it turns yellow. Good top growth will put more strength back into the crown through photosynthesis. Each spring the asparagus bed should be fed with a thick mulch of well-rotted manure or garden compost.
Last summer (2011) I had a very good crop of asparagus and the bed is now well established. Asparagus beetle can be a problem after the crop has finished and you are left with the thinner green stems. The only sure fire way to deal with an infestation is to pinch out the bugs with your fingers, once a week. I have read that tomatoes deter asparagus beetle and that asparagus may repel nematodes (round worm) that effect tomato plants – so you might like to try some companion planting.
I have found that the bed needs to be raked up every Autumn to maintain the crown for good drainage. Take care also when picking to cut the stems beneath the surface. Once the asparagus starts to show it grows very quickly – you will be amazed at the rapidity with which the stems shoot up. So you need to keep an eye on the situation and cut frequently. If the stems get very long you can still usually eat the top part which remains soft, cutting off the woody bottom of the stem.