Yard & Garden: May 22, 2020

This is the Q&A for the Yard and Garden show for May 22, 2020. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through July 31, 2020. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.

Guest Host: No guest host due to COVID-19 and social distancing

1. The first caller of the show wants to know how much manure he should apply on his garden?

A. Manure should not be applied to a garden during the growing season. For food safety reasons, it should only be applied in the fall. The guidelines recommend waiting 120 days after adding manure before vegetables should be harvested from the garden if the edible portion of the plants come into contact with the soil. If fertilizer is necessary, general fertilizers for a garden would be sufficient. If unsure how much to add, a soil test should be done so that you don’t apply too much fertilizer.

2. This caller wants to know if castor beans are poisonous? She is mainly concerned for her dog who may eat the plant if she plants it.

A. Yes, the seeds of castor beans are poisonous. If she can ensure to pull the bean pods off throughout the season, it should be ok. However, it would be best to double check with her vet to be sure for the dog’s safety.

3. Is it too late to plant potatoes? How about sweet potatoes?

A. It is getting a bit late to plant potatoes for this year. Sweet potatoes are still fine to plant, though. They should be planted in mid-May to early June for best success.

4. A caller has an Empress clematis that is not blooming after 3 years of growth. Why is that?

A. This could be from cold weather damaging the blooms. If the blossoms were just about ready to open up as the snow came or cold temperatures, it could have injured them. It does take a few years for the flowering to reach its full potential, so that could be part of it as well. Finally, make sure that the clematis is not getting too much Nitrogen fertilizer overflow from a lawn. Too much nitrogen can make the plant very healthy but not produce flowers.

5. This caller is looking for a plant to place on the south and west sides of a brick house that only get 1-2 feet wide. What can be planted in this location?

A. This is a difficult location due to the heat, it is in full sun and will receive reflective heat from the brick house. Also, the size will be hard to fit into. She could look at some sedums, there are some smaller varieties and they like hot, dry locations. Salvia may be ok, but it would have to be pinched back through the summer to keep the plants smaller. Daylilies also could work, but may grow too large. Missouri primrose or penstemons could be a smaller choice that would grow well in this location.

6. A caller has cedars that have poison ivy and virginia creeper, also called woodbine, growing up through the trees. What can he do to control the vines?

A. You can’t spray the vines as they are growing on the cedars, it will harm or possibly kill the cedars. It is best to cut them off near the ground and then treat the stump with a brush killer. Do not use Tordon, it is not labeled for use there and it can spread to the roots of the cedars. If you cannot get to the poison ivy or are highly sensitive to the plants, you may want to call a lawn spray company to spray it for you to keep you from developing a rash.

7. This caller started tomatoes inside and they have now been transplanted into the garden but the bottom couple of leaves are turning yellow. What is causing this?

A. This is likely due to environmental conditions. It has been cool for tomatoes. As long as the top of the plant is maintaining healthy, green leaves, the plants should be fine. If the bottom leaves die back, they can be removed.

8. A caller has noticed that the bagworms are just emerging from their bags and it looks like they have started to chew on the needles of his trees. Should he wait a little longer to spray them or should he do it now?

A. Give them a little more time to ensure that all have hatched before spraying. If you spray too soon, you will miss those that are later to hatch. Watch for very small bags to begin to form on the tree, that is a good time to start spraying, before the bags are more than 1/2 inch in length.

9. This caller has a weeping willow tree that is 4 years old and still isn’t growing well, it is planted in full sun. What is wrong with it?

A. Be patient, it may take a little while to get over the transplant shock. Also, be more diligent when watering the tree. It should be watered once a week with a slow trickle for about 20-30 minutes. If the tree isn’t receiving this, it could be part of the problem.

10. Why are the peonies not blooming yet? They usually are blooming by now.

A. The cold weather is pushing back their bloom time. Also, the snow or freezing temperatures in late April to early May could have damaged the buds. Give them time to bloom a little later this year.

11. A caller has tomatoes that were damaged in the freeze this year. The leaves wilted and fell off but the stalk is still green. Will they come back or should they be replanted?

A. It would be best to replant. Those plants have no leaves to build sugars to grow, it is likely that they won’t live through this.

12. When should you stop harvesting asparagus?

A. When the spears start to get very spindly, it is best to stop harvesting your asparagus. Also, the spears will start developing the ferns quickly on those spindly spears, that is another indication to stop harvesting to allow the plants to grow for the rest of the season.

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Winterkill on Arborvitae

13. The last question of the show this week was from a man who is struggling to get American arborvitae to grow here. He planted some last year, some more this spring, and is watering every day but some are not greening up. What is the problem?

A. Watering could be an issue. Rather than just watering each tree a short period of time every day, it would be better to water slowly for longer periods of time, but less often. We need to encourage the roots of the trees to grow deep for best longevity. Water the trees once a week for 15-20 minutes each time would be better. Also, add mulch around the trees to help with competition and root growth. Some of these trees may have had issues with winter desiccation, which is common in arborvitae trees. Watering over the winter, once a month on warmer days, will help them get through. Evergreen trees still transpire through the winter, if transpiration is more than the water they take in through their roots, desiccation can occur. Anti-desiccant products can be sprayed on the trees through the winter to help as well.

*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.

Wild Cucumber

Windbreaks are very important to many acreage owners throughout Nebraska. A windbreak is used to block the wind, as the name implies. Winter winds can be very strong and a windbreak will help to reduce those winds, which will in turn reduce heating bills. Windbreaks can be built from a variety of trees and shrubs which are typically fairly tolerant of many problems. However, we do still see problems from bagworms, some fungal diseases, and weeds growing around the trees. A windbreak weed that is quite prevalent this year is wild cucumber or burcucumber.

About Wild Cucumber

Wild cucumber is an annual weed that grows up and over our windbreak trees. Due to all the rain we saw this spring, it is growing voraciously over our trees across the Nebraska countryside. It vines and has leaves similar to cucumber plants. The leaves are arranged alternately along the stem and have five triangular-shaped lobes on the leaves. The leaves are large, 4-10 cm long and 4-13 cm wide. If left on the trees long enough, a fruit will develop. The fruits of wild cucumber resemble a shorter, stouter cucumber with spines all around the outside. The plant climbs up onto our desired trees through the use of tendrils that twist around small branches to hold the plant up as it grows.

There is also a burcucumber plant which is closely related to wild cucumber. Burcucumber is also an annual weed that vines up and over windbreak trees. The leaves of burcucumber are more rounded and the lobes are not as deep as the lobes on the leaves of wild cucumber. Also, the fruits of burcucumber are much smaller and held in a groups. Wild cucumber and burcucumber are similar enough that management for both plants is the same and the names are often used interchangeably.

Managing Wild Cucumber

Wild cucumber is a plant with a shallow root system, so it pulls very easily. At this time of the year, this is really the only way to manage wild cucumber. Don’t spray 2,4-D or any other herbicide on the vines because anything that would control the wild cucumber can damage or even kill the trees that wild cucumber is vining up on. It would be best to pull it off and kill the plant before any fruits are produced to reduce the seedbed. However, at this time of the year they have already begun to produce fruits.

Since wild cucumber is an annual plant, it can be controlled with a pre-emergence herbicide in the spring. Products containing simazine will work to control this weed before it emerges next spring. Early May would be a great time to apply the chemical around the trees in your windbreak to make sure it is in the soil before the wild cucumber germinates. If you are having troubles with this weed this year due to the excess moisture, it would be beneficial to use the simazine next spring or you could have a similar or worse problem next year.