An Update on the Sweet Potatoes

In the spring, I wrote about the Seattle Community Garden’s experiment with growing sweet potatoes. Although I’m not there to find out how it turned out, John sent an email out to the garden group (I’m still on the email list) with the results. I thought I’d share what he sent with you so that you can learn from our experience if you’re trying to grow sweet potatoes in a similar climate.

Although in spring we were planning to plant the sweet potatoes in the in-ground long beds, they decided to plant them in raised beds in the end. I forget the rationale for that decision, but it may have had something to do with soil temperature. I believe these sweet potatoes were planted at the end of June or beginning of July, and the garden group harvested them a little over a week ago, just before Seattle’s first frost.

Of the 15 sweet potato plants planted in those two beds, here are the harvests results:

There are a few giant sweet potatoes in the bed 13 harvest, but overall, this isn’t all that impressive.

John says: “the soil in these two raised beds was ‘not optimal’ to put it mildly… too much nitrogen to grow sweet potatoes (excessive vine growth) and poor soil consistency – ‘gooey wet’ when we planted them….then hard caked, and very difficult to dig in when we harvested.” Sweet potatoes, according to John, prefer sandier soil and need more potassium for root development. Bed 13 did slightly better than bed 14, he postulates, because bed 13 gets a bit more sun. John and Sue had planted some sweet potatoes in their own garden in a sandy, sunny bed and found that their harvest was more consistent and easier to dig up.

John also put a lot of work into curing these sweet potatoes. Apparently, they need to sit for 4 to 14 days in a warm, humid place (85F and 90% humidity) in order to sweeten up, and then they can be stored in a dry cool place (55-60F).

John built an insulated box and used an open crockpot filled with water to create heat and humidity for the space.

Here’s what they looked like after 6 days in the curing box:

Community Garden sweet potatoes are on the left and John and Sue’s sweet potatoes are on the right

Despite the mediocre results this year, it sounds like they are not discouraged and are excited to try again next year. John suggested replacing the soil in two raised beds that get the most sunlight with sandier soil.

There you have it. If you have experience growing sweet potatoes in a northern climate, I’d love to hear about it!

Can We Grow Sweet Potatoes in the Pacific Northwest?

As I’ve mentioned before, we’re attempting to grow sweet potatoes in the Community Garden. This is a first for us, and we’re not expecting much.

Sweet potatoes are typically grown in hot climates, like the Southern US. They also require a long growing season. Western Washington is a temperate climate, and we don’t have long hot summers. Good for me… not so good for sweet potatoes.

One of the members of the garden group, John, is really excited about growing sweet potatoes this year, and he’s been doing a lot of research. I ran in to John at the garden a week ago, and he filled me in on the sweet potato plans. He heard about sweet potato growers up in Canada, and figures if they can do it, we can too.

These two mounds are the future sweet potato beds.

We picked a place for them to go in the long beds at the edge of the garden. We mounded up the soil a bit, which, I am told, makes the soil warmer. John has been taking the temperature of the soil every day. He says the soil needs to be above 60 deg F (minimum for the day) to plant. The last I checked with John, we were still below that, and the days and nights haven’t gotten any warmer here since then, soooo….we might be waiting awhile.

John mentioned that, in order to warm up the soil, we could try to cover the beds with black plastic in which we cut holes where the sweet potatoes go. That would not only help to heat up the soil, but would also suppress weeds in the beds. Win-win. That seems like a no-brainer to me.

We have to get the slips in the ground soon. I believe he’s planting a variety called ‘Georgia Jet.’ (I could be wrong – he mentioned several varieties, and I might be mixing these up.)

Georgia Jets. Image from Mother Earth News

They have a relatively short growing season – 90 days as compared to 110-120 days of some other varieties – which works to our advantage here in the PNW. (Dad: You might argue that these are yams, not sweet potatoes, but I disagree. Exhibit A, Exhibit B.)

When I do a google search “growing sweet potatoes in the PNW,” I find a mixture of stories from people who had a good deal of success growing sweet potatoes (examples here and here), as well as some stories from people who had less success (here). Georgia Jet is mentioned frequently on sites discussing growing sweet potatoes in northern climates, such as Canada. The two examples that I cited that were successful used the Beauregard variety and an organic sweet potato from Costco.

Although, I won’t be around to enjoy (or mourn) our sweet potatoes harvest, I’m sure Nate will keep us updated. Right, Nate?