Arracacha: A New Beginning

Arracacha (Arracacia xanthorrhiza) is just the sort of plant that I normally try to talk myself out of growing.  It is delicious, but a real challenge to grow in most climates.  It originated in the middle elevations of the Andes, a Goldilocks climate where temperatures are neither too hot nor too cold, but just right.  Frost is rare in the regions where arracacha grows, but so is heat, particularly at night.  So, it won’t grow well in North America where we have frosts, but it also won’t grow very well in most places where we don’t have frost because it gets too hot.

I live in a pretty good gateway climate for Andean plants, because it doesn’t get hot in the summer and it doesn’t get very cold in the winter.  But we do have frosts and, less commonly, real freezes.  This is OK for most of the Andean root crops, since they can be grown as annuals and are out of the ground by the time real cold weather arrives in January.  But arracacha stands out: it wants a growing season of about 13 months.

So, if I want to grow arracacha, I have to put it on life support.  My best results so far have come from transplanting it out to the garden in early June and harvesting about now (April).  To do this, I need to grow it in a tunnel through the winter and the weather has to cooperate by limiting freezes to overnight.  That usually works, as it did this year, but it limits the potential for arracacha on this continent pretty severely.  I would really like to do some breeding with this plant, as has been done in Brazil, to shorten the growing season.  Unfortunately, as is true with many of the Andean clonal crops, arracacha doesn’t like to flower.  No flowers means no seeds and no seeds means no breeding.

Arracacha is really unusual among crop plants.  It is a vegetatively propagated member of the Apiaceae, a family that is almost exclusively propagated from seed.  (Skirret and yampah are some other examples of plants in this family that can be propagated vegetatively, but both are comparatively rare in cultivation.)  Like many plants that are propagated clonally, arracacha has become pretty bad at sexual reproduction.  Reliable sexual reproduction is typically a low priority in the development of clonal crops and it tends to get lost over the course of domestication.

With every other Andean crop, I have had to produce my own seeds to get started with breeding, but friends were able to collect some true seed of arracacha this year and were nice enough to share them with me.  So, now I have a real opportunity to start working on this plant.  Arracacha seeds have been reported to have pretty poor germination, even when fresh, so I was worried about starting them.  It would be a shame to try the wrong conditions and spoil them.  I put 100 seeds in a flat at 65F/55F day/night, temperatures that should be reasonably close to spring conditions where arracacha is grown in the Andes, and hoped for the best.  The first seed germinated in two weeks.  I now have six seedlings coming up from a sowing of 100 seeds.  This is really exciting!  I planted the seeds about 1/4 inch deep and I think I will increase that to 1/2 inch next time.  The seeds are large and the seedlings look pretty rebust.  More planting depth will probably reduce problems with the seed coat sticking to the seedlings, which has been a problem with all of the seedlings so far.

Arracacha is a clonally propagated plant, so it will not grow true from seed.  Each seedling is going to be different.  In addition, arracacha is tetraploid, so the depth of the genetic differences between the seedlings will most likely be much greater than they would in a diploid.  These seeds were collected from a single variety with white roots, but a variety with purple roots was flowering at the same time, so there is some possibility of cross-pollination.  Most likely though, most of these seeds would have been self-pollinated.  Even self-pollinated seeds of a single variety can provide a significant amount of genetic diversity, which is exactly what you need for breeding.  The breeding program in Brazil, which has produced a large number of varieties, was reportedly started with self-pollinated seeds from a single clone.  Perhaps I will find among these seedlings a few that mature a little earlier.  If so, that would be a big step forward.

An even better outcome would be to find among them some plants that flower more readily.  Plants that flower and set seed in this climate are the key to continued breeding.  It is especially important to find some that flower regularly, even if they aren’t good for anything else.  My two existing varieties are bound to flower someday.  I need another variety that will flower in close enough proximity that I could at least collect pollen and cross pollinate them.  That would unlock a lot more genetic diversity (presumably – I don’t really know how distinct these varieties are genetically).  So, any variety that can flower regularly is a very high priority for seed propduction.

There is a long way to go yet, but those seedlings are a beginning… in more than one way, I hope.