Suckering of Citrus Due to Cold Damage

Q. The low temperatures affected our citrus trees from last year.  Most of my new growth is on the suckers.  Should I remove them?  Or just let the tree be?

A. If you look at the trunk of the tree you should see a bend in the trunk or “dogleg” where the top was budded or grafted on to the rootstock. I doubt if it is on its own roots which would mean you would see no bend or dogleg.

Example of a "dogleg" where a fruit tree (in this case not citrus) was budded previously.

            Anything coming from or below this bend should be removed and kept off. Whenever you see any type of growth at all from these spots it should be removed. If you let this growth develop it will rob growth from the part of the tree you want to keep and eventually dwarf or kill the good part of the tree.

            Next you want to allow the lowest branches to develop from the trunk at a height you want these branches to remain. The distance these lowest branches are now will be the height they will be in ten years from now.

I did not have a pic from the reader and this is not citrus but this will give you an idea of what suckers that are coming from the rootstock might look like. The suckers are dark brown. The trunk is whitish due to painting the trunk two years prior. These suckers need to be removed by digging the soil away from the trunk and removing them as close to the trunk as possible. Replace the soil after the wound from cutting has begun healing, normally at least 48 hours.

            If these are too low then move up the trunk to a place where you want the lowest limbs to develop. Remove any of these unwanted lower limbs completely from the trunk by cutting them as close to the trunk as possible.

            You can do this now if you want or you can wait until next January or February if there is fruit on them. I am not sure which citrus you have but if it is lemon they should probably be harvested in December.

            Try to find limbs to keep which are coming from the trunk going in different directions. Hopefully you will find one limb going north, one south, one east and one west (I think you get what I mean by going in different directions as this will give the tree “balance” and reduce shading of itself).

            On the limbs coming from the trunk, remove shoots going straight up or straight down. This leaves shoots that spread out in a fan (horizontally or laterally) but remove shoots that are growing up or down. This allows for better light penetration inside the tree and helps distribute fruit production throughout the canopy rather than just on the perimeter. I hope this helps.

Nematodes Permanent Garden Problem

Q. Are these nematodes on my tomato roots in the picture I sent to you?

Picture sent from reader

A. Yes, you have them. Once you have nematodes they are a permanent pest in your vegetable garden. Your future with them is in managing their new home but you will never be rid of them.

            In the past, soil fumigants were available that would dramatically reduce their numbers and easily make them manageable. These soil fumigants are no longer available to homeowners and highly restricted even for commercial applicators due to their potential in damaging the environment.

Root knot nematode on tomato

            There are multiple approaches in managing nematodes. One way is to exclude them. You can do this by growing vegetables that are highly susceptible in pots or containers. If the pots or containers are in direct contact with the soil containing nematodes, the nematodes will move into the container eventually.

            You can impede this by putting down a layer of coarse gravel on top of the soil and putting the containers on top of the gravel.

            If you want to grow in the ground with nematodes then heavily enriching the soil with organic material such as high-quality compost will help to deter them. Keeping the soil as healthy as possible is a great deterrent. Nematodes do not seem to like heavily enriched soils.

            Another deterrent is to select plants that nematodes do not seem to like very much. There are some vegetables somewhat resistant to nematodes but it is quite lengthy. I will post this list on my blog but a few of them include broccoli, cauliflower, chives, and many mustards.

            There are other plants which nematodes really like a lot but plant breeding has produced some varieties which are resistant to nematodes and a few plant diseases. These varieties have capital letters such as V,F,T,N after their names which designate their resistance. The capital N in this case designates nematodes.

            Another method is growing marigolds in the vegetable plot. The most effective way is to grow a solid stand of marigolds for at least 2 to 3 months in the planting bed. Turn these marigolds under the soil so that they decompose. Then plant your vegetables.

            Some people grow them on the borders of the vegetable plot but it is not as effective as growing a solid stand and turning them under.

            There are some products available such as Clandosan which gives some benefit and could also be incorporated into the soil.

Large Boxed Tree Needs Extra Help

Q. Should a newly planted 36" boxed purple robe black locust tree have it's nursery stake removed? I sent you a picture of it.

Readers Purple Robe Black Locust staked.

A. Larger trees need their roots stabilized for one to two growing seasons and then the stakes removed. In your case the tree has poor trunk strength since the trunk has no taper to it and the trunk will snap in high winds.

            Immobilize the roots by re-staking the tree. Let side branches develop along the trunk to improve trunk taper and strengthen it. Normally, a tree with good trunk taper can have its stakes removed after one to two growing seasons. A tree with poor trunk taper will require a longer period of staking to strengthen the trunk AND give it solid rooting into the surrounding soil.

            Allowing side branches to grow along the trunk helps promote taper in the trunk reducing its need for staking after one season.

            Ideally, the tree should have small stems growing from the trunk covered in leaves, removing them only when they reach about pencil diameter. This increases stem taper, reduces the possibility of shear or snapping in high winds. 

            Trees also need to “sway” in the wind. This swaying or movement of the trunk from side to side also helps to develop taper in the trunk. But the roots of the tree need to hold the trunk in place at the bottom.

            This tree will need to be staked for awhile to keep the trunk from snapping. Probably at least one season. I would probably restake the tree with either two or three stakes to support the trunk and keep it from bending to the point where it could snap and immobilize the roots.

Large trees usually need stakes to support the trunk. The stakes should be driven deep enough so that they are in solid soil. The support from the stakes should be low enough to allow the top of the tree to move but keep the rootball from moving.

            Two methods used for re-staking include a two to three stake method with the stakes driven into the solid soil beneath the rootball. The other way is to use guy wires to stabilize the tree. I supplied pictures that I will also post on my blog.

            This next year let small branches grow from the trunk if they develop. These will increase the strength of the trunk and help reduce sun damage to it as well. Remove older branches from the trunk when they get larger than a pencil in diameter. Cut them off flush with the trunk. Do not use pruning paint.

Container Plants Difficult to Manage for Snowbirds

Q. We winter in Boulder City in a condo RV park. Three years ago we planted a rose bush that did wonderfully well until it died last summer. The pot gets plenty of water from a drip hose. We would like to put something in the pot more capable of surviving the extremes of the high desert. I would be happy with anything that will flower or fruit when we are here in the winter and is OK with being abandoned for six months. 

A. It will be very, very difficult to grow much of anything in a pot if it is not attended to. You might be better off putting something there that will not die and, while you are here, growing something that you can dispose of when you leave such as an annual.

            The other possibility is to have someone care for your plants while you are gone. The summers here are brutal on plants as you know. We get fluctuations in our weather that are very unpredictable.

            If you insist on growing something in a container then double pot your container so that the container you are growing in is surrounded by another container or object that shades the outside of the inner container.

            Surface temperatures of containers that receive direct sunlight in late spring and summer will produce temperatures inside the container that will kill plant roots. Double potting a container with a larger container with gravel in the bottom and just airspace on the sides will help insulate the soil inside the container.

            Surface temperatures of a container will easily rise above 165F in direct sunlight. This heat transfers to the soil and cooks the roots on the side exposed.

            Another possibility will be to grow cacti in containers and watering it no more than about once every two weeks. Once a week if the container is small. Make sure the soil for the cactus drains readily. The container should still be double potted.

Oleander Shows Signs of Winter Dieback

            Reports from the weather station at the UNCE Orchard in North Las Vegas put the low temperatures on December 6 and 10 at 20F with daytime highs around the same as the inside of a refrigerator. I am sure this caused some damage to plants in that area. I posted the weather report on my blog for those interested.

Q. I believe I messed up with my one year old oleanders. I covered them with old cotton bed sheets and then plastic bags thinking it would protect them. When I uncovered them, the sheets were frozen with what I assume was condensation caused by the plastic bags. I’m hoping they survive as much of the lower foliage is still green and soft. What is my next option?

 

Freeze damage to oleander in north las vegas

Freeze damage to hedged oleander and new spring growth

A. I don’t think you made a mistake. They just froze, that’s all. 9 times out of 10 they will come back in the spring. In fact the freezing bed sheet gave the oleander a few extra degrees of warmth.

            Wait until spring and new growth before making any decisions. It is possible the oleander just got some leaf and the stem death with some of the stems still alive. You will not know until it starts growing again but I don’t think you lost them.

            The degree of damage to a plant will depend on the plant itself, its variety and how it was cared for, weather prior to the freeze, landscape microclimate, the minimum temperature reached and the duration of that temperature. It can be really difficult to predict the degree of damage done for quite some time.

            There may still be some cold coming later in the winter. Sometimes freezing temperatures in February, when plants are preparing for spring, can be much worse than the same temperatures in December or January.

            Don’t prune them back just yet. Be patient and see what spring brings.