Archive for the ‘Garden Tips’ Category

Growing Sweetpotatoes in N.H.

Written by UNH Extension Specialist Becky Sideman (, 603-862-3203). Updated June 2013.

Sweetpotato (Ipomoea batatas) is a member of the morning glory (Convolvulaceae) family. The sweetpotato is not related to the Irish potato, which belongs to the nightshade (Solanaceae) family. Unlike potatoes, which are tubers, sweetpotatoes are roots.

Growth Requirements

To produce a crop, the sweetpotato requires 90-120 frost-free days. The plants and roots are very sensitive to chilling. They grow best if the soil temperature is above 65F before planting. Sweetpotatoes prefer well-drained loam soils that are not too fertile. Over-fertilization causes vigorous leaf growth and long, skinny roots. If grown in heavy clay soils, roots can be small or misshapen, and will be hard to dig. A soil test will identify any major nutrient deficiencies and recommend how to correct them.

Starting Materials

Sweetpotatoes are started from ‘slips’, or plants, rather than from pieces of roots. Slips can be purchased from many seed companies or other plant suppliers. While you can start your own slips, roots from a grocery store are not usually identified by variety, so you don’t know what you are starting with.

To produce your own slips: Place sweetpotato roots on their sides in trays of soil 6-8 weeks before you want to transplant them outside. Cover the roots with 2 inches of moist sand and keep the soil in the trays between 75-80 degrees F. When the sprouts are 4-6 inches long, remove them with a twisting tug. The root will continue to produce more sprouts. Sprouts can be planted directly in well-prepared ground, or you can place them in a jar of water for a few days to produce a rooted slip and/or to delay planting.

If you purchase slips, you will have to specify the ship date. In Durham, soil temperatures under black plastic mulch are typically 65F by June 1. If your site is cooler or if you are not using plastic mulch, you may want to delay this date by 1-2 weeks.

Transplanting conditions are important for success. If poorly rooted slips are planted in sunny, hot conditions, a large number of slips may dessicate and die before roots can establish. It’s best to wait until overcast conditions, and to make sure to water slips in immediately after planting. If slips arrive long before you are able to plant them, place the entire bundle of slips in a pot and pack potting mix loosely around the bundle, and water as any other plant. This ‘heeling in’ can successfully hold slips for a week or more prior to planting.


Sweetpotatoes respond well to ground-warming black plastic mulch. The sheet of plastic is laid tight against the soil, and slips are planted into holes cut in the plastic. It is possible to produce good yields without plastic mulch, but the warming mulch extends the growing season by a few weeks, which can increase yields dramatically.



Typical pests of potato (Colorado potato beetle, potato leafhopper, etc.) do not bother sweetpoatoes. However, they do have some pests:

  • Deer love sweetpotato foliage, and will browse it to the ground. While this won’t kill the plants, it will reduce yields significantly. Since there is plenty of other food for deer in midsummer, a lightweight electric fence may successfully keep the deer at bay.
  • Voles also love sweetpotatoes. Some NH farmers have reported that voles have eaten their entire harvest. Keeping weed populations under control and keeping the area around the planting mowed and/or tilled can help reduce vole damage.
  • Scurf is a soilborne fungal disease. It discolors the skin of the root, so that the root is covered with rough black patches, but does not harm the root. Some varieties are more susceptible than others.
  • Wireworms can be an issue for sweetpotatoes grown in fields that were sod (or that were weedy with perennial grasses) in the previous year.

Harvesting and Storing


Sweetpotatoes should be dug as late as possible in the fall, but before a hard freeze. The vines can tolerate a light frost. It can be helpful to mow and remove the vines before digging, to provide easier access to the roots. After digging, sweetpotatoes should be ‘cured’ by placing them in a warm (80-85F) place for 4-7 days. This heals any wounds on their skins, and increases their storage life. Sweetpotatoes should be stored in moderately warm (55-60F) and humid conditions. The roots are easily damaged by temperatures lower than 50F.

For best eating quality, it is important to wait a few weeks before eating roots once they have been dug. Our research has shown that percent soluble solids (primarily sugars) can increase over 4% in three weeks, and then starts to taper off once most of the starches have converted to sugar.



Sweetpotato varieties perform very differently, so it’s important to test performance in your situation. Varieties that are well adapted to New England conditions include the following:

Beauregard –Orange flesh and copper skin, good flavor. Early, produces high yields. Highly recommended.

Covington – Orange flesh and copper skin, excellent flavor. More uniform shape, higher marketable yields and better flavor than Beauregard. Highly recommended.

Georgia Jet – Orange flesh and rose colored skin. Very susceptible to cracking and storage losses. High yield potential and good flavor. Cracking may depend on moisture level in soil. Better for home gardens than for commercial use.

Japanese –White flesh with purple skin. Unique smooth texture, good flavor. Non-uniform size and shape.

O’Henry and White Yam –  White/cream-colored flesh and skin. These are both high yielding, with good flavor.

Carolina Ruby – Deep orange flesh, garnet-colored skin. Skin has unusual rough texture. Moderate yields, average flavor.

Vardaman – Light orange flesh and skin. Excellent flavor. Produces small slender roots, and low yields.


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Gardens Don’t Wait On Whim

Gardens don’t wait on whim, or even on convenience. It’s a lesson new gardeners have to learn and experienced ones are reminded of every season. Gardens have to be tended And–their tending does not always conform to our schedules. Think of a garden a bit like a pet. It is a living, growing, changing organism. Just as you reconcile yourself to your pet’s needs for attention and care you must also be aware of your garden. If you are too busy to walk your dog or are planning a vacation, you find someone to care for your pet . You should do the same for your garden. That is one of the great benefits of belonging to a Community Garden. There are lots of people available and willing to pitch in. Get to know the gardeners around you and don’t forget you can contact me, the garden steward at any time for help.

Getting Started At Wagon HIll

Dear Gardeners, It’s been a slow, cool spring, which I do prefer to “sudden summer”. We get to enjoy the bulb flowers and bright green leaves and grass. Cool temperatures have delayed planting in the gardens at Wagon Hill for many gardeners. However, they have not delayed the growth of weeds! I was in the garden yesterday and noticed many beds full of rapidly growing, robust weeds.

Even if you do not intend to plant in your beds immediately, please come out and take a look at your plot and remove the weeds. The grasses are already starting to go to seed and that is just what’s happening above the ground. Below, roots are finding their way into the beds of your neighbors.

The moist soil does make it easier to pull up the weeds so it should not take long.
Once the weeds are removed, check the soil depth in your bed to be sure it is at least 1″ below the top of the bed rail. Add more soil, if necessary. This will help to prevent the field grass from growing up through the bottom. Especially important if you have one of the older raised beds.

Remember to dispose of weeds in the open compose pile not in the bins. Do not leave them in the paths. Oh—some of the paths need weeding as well.
Garden Steward

Hummingbird Migration


It’s time to put those hummingbird feeders out.  The Ruby Throats have arrived in Rhode Island and Connecticut  this week and will continue north as long as the weather is mild.

Can’t wait to see them again!  Ellen

Garden Prep

At our meeting last month, I mentioned that I would try to use pictures to illustrate different gardening techniques,  so here goes.  Let me know it you find it helpful.

This week I laid black plastic around my Heritage Plot bed to keep the field grass from invading.  I used this method several years ago and it worked really well. One of the mysteries of gardening for me it why I don’t keep doing things that work, like staking tomatoes?  Why do I suddenly “forget”  that I had a good idea?  It’s not as though I have so many I can’t keep track of them.  But, to continue, If you have a bed like this that is not raised, it is so helpful to prepare the edges before things get started growing.  I bought this plastic at WalMart in their garden department.  It is not the most expensive stuff.  I also bought 3 bags of garden staples.  Make sure you get enough of those.  I only needed one roll to edge my Heritage bed and I had a little extra.  After I laid the plastic I covered it with wood chips.  It took 4 wheelbarrows full to do it.  It is not a deep layer but it does cover the plastic to keep any light out and to hold down the edges.  I will probably add more chips and /or hay as the season progresses.  This plastic will have to come off at the end of the season and all the staples will need to be retrieved.  You could also use wet cardboard and newspaper to do this if you are really opposed to using plastic.  I used plastic because it is faster and I really wanted to get it done now while the grass is still flattened out from the snow.  So there you have it.  Please feel free to use my good idea and be sure to remind me of it if I forget next season!  Ellenphoto-53photo-54

The Joy of Spring Garden Maintenance

April at the Community Garden

I broke my first ” garden sweat” of the season this morning. I went up to Wagon Hill to put the plastic covering over my hoops to start heating up the soil. I am hoping to get a little head start on some lettuce, spinach, kale etc. But, I discovered that the sod was very soft and easy to pull up or dig out around the edges of the bed. So, before I knew it I was flat out digging and hauling wood chips to pile around the edges. I realized that I was actually enjoying it. It’s too early to really do any fun stuff yet but I am so anxious to be outdoors doing SOMETHING that I didn’t mind and it is still so cool that working up a sweat isn’t uncomfortable. It felt good to be exercising those gardening muscles. I recommend taking advantage of spring enthusiasm!

What’s up Doc? Can you grow carrots (and other root vegetables) in a raised bed?

 What’s up Doc?  A  question was asked  about growing carrots in the raised beds.  The short answer is “yes, you can grow carrots.” But a longer answer may help you better understand the garden.
The raised beds are just frames placed onto the ground. So there is no “bottom” on the beds that would impede the growth of carrot roots. The bed is placed on the ground and several layers of wet newspaper and cardboard are laid down to cover the bottom, then the beds are filled with soil. Over time the newspaper decomposes, along with the sod and worms come up to the surface and work the soil. The soil you put into the beds is contiguous with the ground. It is important to keep your beds full of soil to an inch below the top to prevent the grass from growing up again. There are varieties of carrots that are shorter. If you have a newer bed you might try those.   So grow those carrots!  And let me know how they do.  Ellen