Planting Asparagus is not like planting a few lettuce seeds. If the lettuce seeds don't germinate you can always sow a few more, and if they don't grow terribly well you can experiment a few times until you get the right conditions.
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With aspargus crowns you are going to be planting asparagus now not really knowing how well its going to do until its been in the ground for several years. By then you are going to be itching to eat your produce and very disappointed if you aren't getting a good crop! Conversely if you get it right you will be enjoying the best apsaragus you can imagine (that is straight out of the ground)for years to come. So do your resaerch and get it right!!
Asparagus care starts well before you touch a crown with a decision on what varieties to plant , how many plants you want to end up with and the preparation of your asparagus bed. Have a good read of the pros and cons of the various varieties and make some choices but don't decide completely until you've read further....
Before you even think about buying or planting asparagus you need to decide where you are going to plant them and how much space you are going to need. If you are going to grow asparagus you are going to be dedicating a patch of ground to asparagus growing for a long long time (think forever is probably easiest!). You also need to consider the time of year and you may need to plan in advance probably in the autumn for a spring/late winter asparagus planting.
So how much space? Well before that comes how many asparagus plants?
How much do you want to eat! I think that 1 pound of fresh asparagus is a really nice generous serving for a family of four as a side vegetable. Lets say during the season you want to eat asparagus every other day that’s 3.5 pounds per week with an 8 week cutting season – 28 pounds of asparagus to grow. How much your plants will produce will vary according to the variety you chose, how well you look after it, how patient you are in the first couple of years (DO NOT harvest too much too soon) etc.
So if we assume an average of 2-3 pounds per plant you might want 10 to 15 crowns to plant. Note that the F1 hybrids can produce up to double what some of the lower cropping varieties produce so you need to factor this into that 2-3 pounds per plant range. When planting asparagus you need to allow for a few not to take, say 10%, and then you need to think about whether you are going to want to freeze, share, giveaway, pickle etc. any surplus. Come back and read this again when you’ve thought about asparagus varieties as this may influence your thinking.
Well after that digression I ask again how much space are you going to set aside for planting asparagus? You are going to plant your crowns about 1 foot apart (30 cm) in wide rows maybe 5’ wide. So you can do the sums but for 15 asparagus plants you will need a bed 15’ by 5’ or 8’ by 10'.
By the way if you are re-planting it is better to find a new plot than re-plant on your old bed to avoid the spread of disease.
If by now you feel you need to have a good think and do some more detailed planning to get your vegetable garden planning right you might like to follow this link for some more detailed advice.
The picture at the top of the page will give you an idea of how your plants are going to grow.
Ideally you have a patch of well drained good deep soil ph 6.5 – 7.5 which still retains the moisture in full sun, which doesn’t catch late frost and which you can dig really deep. Into this you are going to dig plenty of good compost. If only life were so easy….. of course you don’t have the perfect spot …who does?
You can get away with a little shade but there must be a reasonable amount of sun and full sun is best. If your soil does not hold moisture well dig in plenty of compost, if it is rather heavy again dig in plenty of compost….
If the ph is too low (too acidic) you can add some form of lime and if the ph is on the high side (too alkali) you can add ammonium sulphate or sulphur or wood ash. Adjusting the ph needs to be done carefully and well in advance so you might want to do a bit more research first, if you follow this link you will find more information http://www.ipm.iastate.edu/ipm/hortnews/1994/4-6-1994/ph.html . Adding compost and adjusting ph are best done well in advance of planting so getting this done in the autumn is a good idea.
If your patch is prone to frost you will need to keep an eye on the weather forecast and protect the bed with gardening fleece if you see a ground frost coming after late March - mid April.
You are not going to be able to dig this bed over for a long time once planted or you will disturb the asparagus plants roots so make sure you get all the perenial weeds out eg. buttercups, dandelions etc. You might want to cover the bed with old carpet for 6 months prior to planting asparagus to really kill off any unwelcome weeds.
So lets assume you now have a bed the right size well dug over incorporating some good compost with the right ph in a nice sunny position.
A couple of weeks before you are ready to plant dig some fertiser into the soil at about 90g/sqm.
The roots of the asparagus are rather spidery with a crown where the spears will start to grow.
Before you start planting asparagus place the crowns in a bucket of water to rehydrate.
First dig a trench about 30cm wide by 20cm deep (1' x 9") where you are going to plant the asparagus roots. You will be planting the crowns about 45cm apart and if you have 2 or more rows the trenches need to be about 1m (3')between rows.
In the bottom of the trench add a ridge of soil about 10cm high. Now carefully place the crown of the plant at the top of the ridge spreading the spidery roots down the sides of the ridge.
Cover the crown and roots with about 5cm of soil. Keep the plants well watered.
You've finished planting asparagus, and you've done it well. 15 - 20 years of asparagus gardening has just begun!!
Varieties of Asparagus