Start Your Own Sweet Potato Slips

Sweet potatoes were developed several thousand years ago by Native-American tribes in Central America.  Sweet potatoes are only very distantly related to “Irish” potatoes.  Sweet potatoes require a long growing season, warm temperatures, plenty of rainfall, and light soil.  They grow best in sandy, acidic soils.  They do not tolerate a frost.  In the tropics, sweet potatoes are a perennial plant that can be harvested as needed.  In temperate regions sweet potatoes are planted as an annual.  They will store for several months after harvest.  Sweet potatoes grow best when average temperatures are 75 degrees F or higher, and they require around 120 days to reach maturity.  The sweet potato puts out very long vines, 15 feet or more, so they require a lot of room in the garden.  Sweet potatoes have few natural enemies, and they can be grown without much in the way of fertilizers although a light dressing of 10-20-10 will help improve their production.

Unlike Irish potatoes, which are traditionally planted from seed potatoes, sweet potatoes are usually planted from slips.  The slips are small leafy shoots that grow out of mature sweet potatoes, and there are a number of different methods for growing slips.  The method that I am outlining here is the one that I consider to be the simplest.  It requires very little space and no special equipment.

First you will need two or three mature sweet potatoes to grow your slips from.  You can beg, borrow, or buy these potatoes from someone who already grows their own; or you can buy them at the grocery store.  Some store potatoes are treated with a sprouting inhibitor, but this only “inhibits” sprouting, it doesn’t stop it.  The sweet potatoes shown below were purchased from a local grocery store, and they sprouted without any problem.

Growing the slips takes a pretty long time, so you will want to start your slips about ten weeks before you plan on putting them in the ground.  In my area, slips are put in the ground from around mid-May to the first part of June.  Backing up 10 weeks from this date, I usually start growing slips around the first of March.

Growing the slips is simplicity itself.  Just take a wide mouth glass jar that your sweet potato will fit down into.  Hold your sweet potato upright and stick four, evenly spaced, tooth picks about half-way up the potato, and set the potato into the jar.  The toothpicks will support the potato so that it doesn’t rest on the bottom of the jar.  Now fill the jar with water to about a ¼ inch from the top.  You should now have the bottom half of your potato submerged in the water and the top half sticking up out of the jar.  Set the jar in a sunny window and wait.

And wait……and wait……..  You will be convinced that this is not going to work; you will be tempted to throw everything into the trash and forget it, but be patient.  During this waiting time the water in your jar will probably start to turn green.  When it does, empty the water out and refill the jar with fresh water.  By the way, I have a water well; so my water doesn’t have any chemicals in it.  I don’t know if treated, city water might affect the slip growing process.  If you are using city water you might need to run a bucket full and let it sit for a few days before using it on your slips; or you could catch rain water to use.

So, back to the process.  After two or three weeks you will begin to see little white spindly roots growing out of the underwater portion of the potato. The roots pictured below are already well established. 

A few days later you will notice small purple buds appearing on the un-submerged part of the potato.  Your slips are about to take off.

As the slips and roots begin to grow they will start drinking up the water in your jars.  You will probably not have the water-turning-green problem anymore, but you will have to check your jars daily and keep them topped up with water.  You don’t need to add any fertilizer or plant food to the water.  The slips are feeding off of the nutrients stored in the mother potato. 

When the slips are four to six inches tall and have several leaves growing on them, you can begin to harvest the slips.  Just break a slip off right up next to the mother potato and then place the slips in another jar that has a couple of inches of water in the bottom.  In this jar the slips will begin to sprout their own roots.

You will get many slips from one mother potato over an extended period of time.  When I have fifteen or so slips in the rooting jar, I start putting them in the ground.  

The mother potatoes will continue to produce slips, and you can continue rooting and planting them.  As long as you still have 120 days to the first frost, any slips that you plant will grow to maturity and produce potatoes. The slips pictured below have been in the ground for a little less than two weeks.  They are well established and ready to grow into good sweet potatoes.