Basics:
Blackberries grow from a crown.
The crown sends up a stalk or cane in the first year. No berries will form on this cane the first year. If you head this cane at 3-4 ft, it will promote branching and leaves. The branched vines should be loosely tied to a trellis wire for support.
The second year, this cane will produce flowers and berries. These should be harvested during the summer months. At the end of this second season, the cane is spent and will eventually die. The dead canes should be removed as soon after harvest as practical.
At the same time this second year, the crown will send up a new cane, which is green and growing and has leaves, but will not produce any fruits this year. In a two wire system, this new cane should be headed at the height of the second wire and the resulting branches should be guided along the second wire. Next year, this cane will bear fruit.
Two wire system.
A two wire trellis system simply helps keep the two cane years separate. In year one, the primocane grows and is headed to the lower wire. All the branches are guided along the lower wire and all the fruit is on this same level. For the second year, when the lower wire is fruiting, the new primocanes are allowed to grow up to the higher level wire. The unfruitful branches will be guided along the upper wire and will not mix with the fruiting branches of the lower wire.
When the time comes to prune and remove canes, the system makes it very ease to tell which vines are primocanes and should be saved, and which are the spent fruited canes that need to be removed.
Pruning
The main stalk should 4 feet tall. The laterals are about 20 - 24 inches. Longer canes just get in the way.
Keep the ground under the brambles mowed. Don't allow the grass to compete with the crowns for resources. At the same time, mulch around the base of the blackberries, as much as a foot if possible with straw or grass clippings. (wood chips are not recommended because they prevent new shoots from coming up through it.) Needed to retain moisture.
This is a raw research page for planting potatoes in containers.
Typically, potatoes take a lot of space in the garden and a lot of time to grow to maturity. Dedicating a large portion of one of my beds and tying it up for a long period of time is usually not practical and doesn't get the most use out of my garden space. In addition, harvesting potatoes can sometimes be labor intensive and the rambling vines can crowd out other plants growing near them.
However, a system that uses containers has none of those problems. They can be placed wherever there is open space for them, away from the rest of the garden if necessary. And harvesting involves nothing more than tipping the container onto a tarp and sorting out the tubers. A properly prepared potato container involves little work beyond the initial set-up, and it quietly grows by itself during the season, multiplying each potato about five fold. This is the promise of container gardening. So let's see if it can actually be made into a reality.
Step One. Preparation
Containers
The first step is gathering the containers you are going to use. You can use something as small as a 5-gal bucket, but the easiest thing is to use fabric grow bags in the 10 to 20 gallon size. You can order these off of Amazon. Plastic greenhouse containers are fine, as well, but can be a little harder to store.
I find that the 5 to 8 gal. size containers limit the number of potatoes that each seed potato would normally produce but are great for moving around, if that becomes necessary. They would be perfect for succession planting on a porch or patio. The 20 gal and larger pots are great for growing space but very heavy to manage once they are fully planted, making moving and harvesting more difficult. For me, the 10 to 15 gal size, about 18" in diameter and 12-14" high, is the happy medium.
Growing Mix
We'll also need a bag of potting mix and a bag of compost as the growing medium. Along the way we'll need access to a leafy mulch such as grass clippings, straw, shopped leaves, or shredded paper.
The potatoes use a slow release fertilizer, possibly organic.
Potatoes prefer an acidic soil with a lower pH.
We'll want a higher potassium and phosphorous content, with lower nitrogen in this mix. Something like a 3-4-3, or 3-6-8. Don't use an alfalfa-based fertilizer that is high in nitrogen. This will produce great leafy growth, but the tubers will be small and underdeveloped. Consider using bone meal for added phosphorous.
Seed Potatoes
Finally, you'll need to source your seed potatoes. Just to be perfectly clear, potatoes are not grown from seed. Instead, potato plants are grown by sprouting existing potatoes, which will grow stems and leaves above ground, as well as additional potatoes below ground. There are two sources for these starter potatoes. You can buy specially grown potatoes from a nursery or you can grow regular potatoes that you buy from a grocery store.
The current price for nursery seed potatoes is 5 lbs for $20 from a seed house. These potatoes assure us that they are "certified" disease free, and haven't been sprayed with "growth inhibitor." This is all good and designed to build confidence in the spud.
Another alternative is to use organic potatoes from the grocery store. In theory, these are identical potatoes to the ones from the nursery, except in two respects. First, grocery store potatoes have typically been sprayed with a sprout inhibiting chemical, to keep them from sprouting in the produce aisle. This inhibitor will keep the potato from sprouting at home, and may even persist in keeping them from growing well, even after they have sprouted and been planted. The second negative is that grocery potatoes are designed for eating, not sprouting, so they may harbor diseases like potato blight that you will accidentally introduce into your garden.
The use of grocery seed potatoes has generated a lot of consternation among the homestead gardeners. Every potato gardener has an opinion on the subject. Some doubt the value of "disease-free" seedlings, while others take it as gospel. It's hard to know what value to place on that claim, because any plant you bring into your garden has the possibility of harboring some pest or disease, despite the certification.
It was once thought that potatoes labeled organic have not been sprayed with growth inhibitor so they with readily sprout. However, there are natural sprout inhibitors that some organic producers use.
Some gardeners use only grocery potatoes every year and report continued success. Others swear by certified seed potatoes, and some grow both kinds. One of the problems with certified seed potatoes is that, while they may be readily available at the start of the year, they can be hard to find later in the season. Grocery stores have organic potatoes year-round, so the gardener who started their first crop in April with certified sprouts may turn to grocery store potatoes for their second crop in June.
Even at the best of times, certified seed potatoes can be expensive, particularly for a crop that is relatively inexpensive to buy at the store at any time.
The consensus is that when growing grocery store potatoes, to make sure that they have really sprouted before planting them underground.
Potatoes can be a variable crop. One year abundance, the next year a few golf-ball sized volunteers. One year, they taste sweet and crisp; the next they are "bitter". Much of this variability is due to nutrient deficiencies in the soil, and uneven temperature and moisture levels. Nitrogen promotes abundant leafy growth, which can actually cause the size of potatoes to shrink as energy is drawn from the potato to fuel the stem and leaves. The answer is to develop consistent cultivation practices in preparing the soil and watering.
3 lbs might be $5. Look for potatoes that are starting to sprout or have more pronounced eyes, if possible. This is a viable option later in the season if you want to plant a fall crop in August and the seed potatoes are out of stock.
Potatoes should be sprouted before planting. (Some gardeners don't bother with this step and just plant the seed potato into the ground, but for the highest confidence it can be useful to see that the potato is actually growing.)
Step Two. Succession planting
This system allows for, and emphasizes, succession planting. You don't want all your potatoes to be ready at the same time if you don't have a root cellar to store them. For me, this means that some are in danger of spoiling before I get a chance to use them all, particularly in the summer when the temperatures are so warm.
This system of succession means that we start with 5 containers and plant one on the first of each month, starting in April, with our last potato start in August. Each container planted will grow for 90 days (three months). At the end of the final month, we'll harvest the container. The results of our 3 month growing season are on the smaller side, about the appearance of new potatoes or a little bigger. We could let them go longer and they would probably grow larger. However, harvesting at 90 days will often mean that we can fit a second crop into the growing season.
Our first container is planted in April and grows through the end of June. Our second container is planted on May 1st and grows through the end of July. Its similar for the June container. In July, we can re-use the container we harvested at the end of June. At the beginning of August, we should plant two containers to be ready for the end of October, to help build up a stockpile that will carry us into the winter months.
Step Three. Planting the container
To plant the potatoes, select 5 sprouted seed potatoes for a 15 gal container. The base mix is a 50/50 mix of potting soil and compost. Put 4" of this base mix into the bottom of the container. Mix 1/2+ cups slow release fertilizer at this level. Then place your 5 potatoes in an equidistant pattern, one in the center and four others spaced around it.
Next cover the potatoes with 4" of potting soil only (no compost). If it feels especially heavy, add in peat to lighten it. Water thoroughly. Over the next week, allow the potatoes to grow up through the potting mix and put out leaves. When the leaves are about 4" tall, mulch the surface of the soil with the dry mulch you identified (grass clippings, chopped leaves, straw, shredded paper). As the potato plant grows up to the rim of the bag, continue adding dry mulch up to the rim and let the leafy growth spill out over the top.
Step Four. Growing
The potato plants can grow on their own, at this point, provided that the soil remains evenly moist. Potatoes will rot in waterlogged soil, but the fabric grow bags will cause more rapid drying of the soil so the opposite problem, dry soil, may be more of a danger. Check soil moisture and be ready to water every 3-4 days.
Use a double watering technique to ensure that the soil is evenly moist. Water until you see it leaving the bottom of the bag. Then let it rest for 10 - 15 minutes. Then, come back and water again to give the soil time to absorb the water.
During the growing phase we will be looking for several milestones. After several weeks, the potato plant will flower and then the petals will drop. It is at this time that the tubers begin to enlarge. Some growers like to add additional fertilizer at this point.
As we reach the end of the 90 day growing period, observe the leaves of the potato plants. They should begin to turn yellow. Eventually they will die entirely, although you will usually harvest the potatoes before this point.
At the very end of the growing season, however, things are slightly different. At the start of August, you will start two containers of potatoes. As usual, they will run for 90 days, taking them through the end of October. These will be our keeper potatoes that will last in storage a short ways into the winter.
This time, we won't automatically harvest them. Instead, as long as there isn't any danger of frost, we will watch these two pots instead. The leaves will turn yellow and finally die. Once that happens we're going to let them sit for up to two weeks, still in their pots. During this time, the skins will toughen making them more suitable for storage. The temps in the garage during Nov and Dec will be slightly cooler and more suitable for a root crop storage bin.
