Abundance of flowers indicates time to harvest potatoes

A: Start harvesting young potatoes when plants are full of flowers. Most of these potatoes will be small and full of sugar. Most tubers require about three months to fully mature and get some size, but you can start harvesting anytime after you see lots of flowers.

Potatoes can be planted sometime in October or about late February or early March, depending on the weather. Check your weather app on your phone and use a soil thermometer, pushing the tip in about an inch. The soil must be warm, somewhere in the high 50s or low 60s and getting warmer (spring) or still warm (70s) and cooling down in the fall. If the soil is too cool when planting, the seed pieces will just sit there and eventually rot.

Seed pieces (quarter-cut tubers with a clean knife) can be planted directly into fertile soil, or they can be sprouted (preferred) and then planted. Sprouting takes about two weeks. Plant them 18 inches apart and about 3 inches deep in a raised bed.

When they have sprouted to about 6 inches above the ground, pull soil from the surroundings so that an inch of the green leaves is showing. Leave the soil loose. Roots will grow from the buried stems. These roots produce potatoes.

This technique is called “hilling” and is very important for a good crop of spuds. Hill your plants like this every three weeks while the plants are growing.

Potatoes are sensitive to a killing frost so cover the plants if there is danger of even a light frost. Don’t be afraid to fertilize plants. They like a light fertilizer application every four weeks after the plants are growing.

As with all vegetables, the soil should be amended and high in phosphorus before planting. Remove weeds when small as soon as you see them. Weeds spread insects and diseases as well as steal fertilizer and water.

Q: You have mentioned several times the orchard in North Las Vegas. Is that open to the public to come and pick fruit and if so, what fruits are available and when?

A: The Master Gardener Research Orchard is open to the public on Tuesdays, Thursdays and Saturdays. You can get just-harvested fresh fruit and vegetables there. It is located in North Las Vegas, 100 yards east of the corners of North Decatur Boulevard and Horse Drive. It is located about 1½ miles east of the Gilcrease Orchard and just down the street from Shadow Creek High School.

It is not a “pick your own” operation like the Gilcrease Orchard. You must be qualified to pick the fruit and vegetables when it is ready. That is where training comes in. You must be a qualified volunteer to pick the fruit and vegetables made available to the public.

For more information about this learning-and-doing opportunity, call 702-257-5555, the master gardener helpline.

Q: How and when do you cut back an ocotillo to get it to fill out?

A: As it gets older, it naturally fills out as the plant gets wider, older and matures. The only place to prune, or cut back, ocotillo is very close to the base of the plant. The only time to do it is in the early spring.

Once the branch or “wand” is cut, it can be cut into smaller 18-inch sections and planted with one-fourth of it below the soil. Don’t let it dry out. Use rooting powder to encourage root formation at the buds.

You can somewhat speed up the filling-out process of established plants by making sure they get a light application of fertilizer in the spring and again in the fall. Fertilizing more often than this, or using higher levels of fertilizer, will not give you faster results and may be detrimental.

Q: I noticed browning at the bottom of both of my 10-year-old barrel cactuses. Is this from too much water? They get water every 28 days for 28 minutes unless we receive a lot of rain close to watering days.

A: I don’t think you are watering too often. However, the water might not be draining from around the cactus. It is best to check the soil for moisture before applying more water.

To drain water from the plant, put four postholes (vertical chimneys) around the cactus, about 2 to 3 feet deep, about 2 feet from the cactus. This should sump water from the roots. An alternative method is to replant them on a hill.

To be on the safe side, pull the rock away from the cactus a couple of inches to help it dry. I don’t know how the cactus was planted, but it should be the same depth as it was in the container. If it is planted too deep, it can cause rotting where the soil is in contact with the barrel.

Q: I have a silk tree with branches that look like they are dying.

A: A major problem with mimosa or silk trees is a disease problem that plugs the water-carrying vessels or “tubes” that carry water from the roots to the leaves. Once these tubes or vessels get plugged, this plant disease gets out of control.

This problem is so inevitable in silk trees that I tell people to enjoy their mimosa or silk trees for 15 to 20 years and then plan to replace them. There is really nothing you can do to help these trees if they are in fact infected with mimosa wilt disease. The wilting eventually turns the branches into dead branches.

All you can do is prune out the dead branches, making sure to sterilize or sanitize your saw or pruning shears every time you are making a new cut. You do not want to take the chance of transferring this disease from one dead branch to another branch in the tree or another tree.

To be on the safe side, plant the new tree in a new location to minimize any problem of reinfecting it from this disease.

Q: We have three bird of paradise plants in our backyard. They were in bloom when we planted them five or six years ago, and they bloomed the following year as well. They look beautiful and healthy, but they have not bloomed again. Is there something we can do to encourage them to bloom?

A: The most frequent problem is planting them where there is not enough light. They need at least eight hours of sunlight every day. In the nursery, this is not a problem because they are in full sun all day long.

If low light levels are found to be the case, move them to a new location where there is more light. Another possibility is that the smaller containers may force the plant to grow twisted and cramped roots. This overly compact condition for the roots may lead to earlier flowering. They usually need about three years after planting to begin flowering.

There is a lot of confusion about these plants. As I see it, there are three types of bird of paradise: Mexican bird of paradise, desert bird of paradise and tropical bird of paradise. The first two have a common genus and look similar. The last bird of paradise belongs to a different genus altogether.

The bird of paradise, which has the greatest chance of surviving our climate because of the cold winters, is the type that is more open and produces nearly all yellow flowers. It may be called the Mexican bird of paradise and grows up to about 12 feet tall and across. It is probably the least attractive of this group. It can be pruned treelike or left bushy.

The type sold most frequently in our location (because it is fuller and has more red flowers) is the desert bird of paradise. It may drop its leaves in a show of less cold tolerance so be careful.

However, if they do die back during the winter or look hammered, cut the stems close to the ground (within about 2 inches) and let them grow back in the spring. Use a bit more water and fertilizer to get them to grow back.

The last in the group of three is the tropical bird of paradise, or Strelitzia, with fleshy leaves. The bird of paradise most touchy about winter cold temperatures (and many other things) is the tropical bird of paradise.

Each bird of paradise has a different winter threshold temperature, with the one that is open and mostly yellow flowers, the most tolerant of our winter cold.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.