We have all seen the juice commercials where the actors are standing waist deep in water, cranberries floating around them. Doesn’t everyone know cranberries grow in a bog? Well NO, they don’t. Cranberries, are awesome ovals packed with vitamins, antioxidants, and a tart punch. It is a shame they only make their fresh appearance at Thanksgiving, but I have really enjoyed craisins since they came on the market and wanted to try my hand as growing cranberries at home. They are one of my secret foods that I love. I try to make a homemade cranberry sauce each year. Since we have been doing plant profiles on my gardening favorites and temperate perennials I thought we should profile the lowly cranberry next! (Affiliate links may follow)
Tell me more about Cranberries
What? You want me to tell you more about a cranberry plant and how to grow them?! I thought you would never ask. Vaccinium macrocarpon (aka Cranberry: Yep, being all fancy and Latin again) grow naturally in damp areas on tiny evergreen vines. Unlike many vining plants, cranberries, grow as an evergreen ground cover and not up a trellis. Like blueberries they enjoy slightly acidic soil but need more dampness to thrive. We planted ours late summer before last and though the foliage is considered evergreen it did not necessarily mean it stays green. Ours turned a pretty reddish hue; spring saw the tiny leaves turn dark green again.
Cranberries are native to North America, specifically the North Eastern area. Cultivars have expanded the zones that you can successfully grow cranberries. So my zone 6b-7a should still technically allow me to grow cranberries and it proved true. We did leave them at the prior house (sniff, sniff) but I have been waiting for the local vendor to put their plants on end of summer sale so that I can add cranberries back into our home mix. The suggested growth zones are 2-7. Cranberries grow best in areas where glaciers, during the ice ages, left pockets of minerals and silt. Mixed with years of damp organic matter piling on top and you have a perfect place for smaller vining ground cover.
One of the things I find most fascinating about cranberries is the size of the berry in comparison to the vine. We bought vines that were already bearing fruit, which means they have to be 3 years old already. If your only experience with a cranberry is from a can, then allow me to explain. The berries themselves are oval shaped and probably 3/4 of an inch long. In comparison the leaves are maybe half that size. It looked way out of proportion to me! Additionally the berries are a light green to almost white before the ripen to that dark cranberry red.
The plant is very long lived. There are estimates that some cranberry vines can be 100+ years in the North Eastern US. Though commercial vines are replaced much more frequently, you are likely to get many years out of any plants you grow. Temperate perennial food FTW!
How to Grow Cranberries
I am going to cry foul on the traditional cranberry advice. We bought ours at the end of the summer, plunked them in the ground and mulched heavily. We have thick clay soil, so with mulch everything tends to hold water like nobody’s business. I guess we were in luck as this is NOT the recommended way to plant them. Luckily they spread on runners, like strawberries, so I plan on remedying my planting mistakes around the plant and give it more favorable conditions as they spread. So, you know, do as I say not as I do, but note that I have found cranberries relatively easy to plant and keep alive. (Not like my kiwis *sigh*)
If you want to go with traditional planting methods then here is what I should have been doing. Depending on what type of soil you have you are going to want to dig 5-6 inches of top soil out. I know this is probably going to kill gardeners everywhere, but cranberries do not want all that lovely top soil. Excavate soil in all the places you want the vine to spread. Remember they can grow up to 7 feet in length creating runners the whole way.
So what are we going to replace all this soil with? Mostly peat (1/3 or more), some top soil, and sand. Pretend you are trying to mimic a shallow wetland and add lots of peat. I’m not sure how well the new peat substitutes work. Knowing how peat needs to be somewhat conserved I might be tempted to try one of the new eco-friendly faux-peats if I was going to cultivate a large area. BUT! Cranberries need that slightly acidic soil, so make sure to supplement if you do not go with traditional peat. FYI, traditional peat is acidic in nature. Interestingly enough, once you cultivate your cranberries you have technically created a ‘bog’. A bog is what they call any field created for cranberry production. It does not have to be a flooded field. So I guess I lied in the title, since as soon as you plant them you are putting them in a cranberry bog. Please forgive me!
After you complete your soil prep you will want to plant the plants about 1 to 3 feet apart and add a thin layer of sand. Some sources disagree on whether or not the sand is necessary. Since, mine seem to be thriving in mulch I would say probably not necessary, but I will be raking the mulch back and trying it with sand next year for one very important reason. WEEDS! Cranberries hate weeds, but if you want them to produce runners and spread they need to be able to touch bare soil. Bare soil is weed country! So the sand will work as a mulch to keep the weeds down but allow all the runners to root out.
Okay, this next piece is IMPORTANT for what you are trying to achieve with your cranberries. If it is year 1 or 2 then you are trying to achieve runner growth because they are not going to produce much fruit anyway. Which means fertilize lightly with nitrogen throughout the growing season. In year three it is time to decide, do you want more growth or fruit? Fruit grows in 6-8 inch upright branches that grow up from the runners. A plant that has plenty of food grows lots of runners. A cranberry that has less nitrogen will focus on growing uprights to produce fruit. The choice is up to you. A good mix of runners and upright growth is what you are going for since this plant is around for a long time.
Other than making sure the soil is optimal and has a bit of food, the only other major piece will be to make sure they stay evenly damp. Again, this is not the flooded bog you see on TV, but just making sure the soil does not get dry for days on end.
So Why The Flood?
Cranberry farmers flood cranberry bogs for a couple of reasons. They will flood the vines with water to protect them from severe freezing in the deep winter. They will also flood them in the early spring as pest management. But mostly they flood them for harvest. See, cranberries float… Which means you can flood a field of ripe cranberries, have them float to the top and skim them off. It is not only easier, but leads to less bruising and prettier fruit. Home growers like me aren’t going to need to flood the cranberry bog. Just make sure it has nice consistent water throughout the growing season. So if you are zone 7 or above give this cute cranberry ground cover a try!