Xtremehorticulture

Xtremehorticulture of the Desert

Some Houseplants Need Their Roots Pruned

Leave a Comment / propagation, root pruning, root to shoot ratio /

Q. We repotted a house plant that was constantly wilting and that seems to help. Is it possible that the plant is too large and needs a “haircut”? A. Potted plants benefit from root pruning as well as top pruning if it is possible to do so. I guess we could call this a “haircut”. Both the top of the plant and its roots should be “in balance” with each other. We sometimes refer to this as a plant’s “root to shoot ratio”.             More about root to shoot ratios Not all plants can be root pruned and top pruned to make them smaller so they perform better in their container. Some plants will need a larger container. Some plants are made smaller by “dividing” the plants. Plants that require division are removed from their container and separating a “clump” of plants into individual plants with a sharp, sanitized knife or pruning saw. The cut ends are dipped into a fungicide before replanting. Some plants require renewal through propagation. Typically these plants are propagated using methods such as stem cuttings, leaf cuttings, root cuttings or layering. These specialized propagation techniques are specific to certain plants. The Internet is a good source of information on propagating interior or houseplants. Propagation of Houseplants

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Pruning Roots of Plants Gives Added Control

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Did you know that the roots of plants can be pruned? This is called root pruning and dramatically alters the root to shoot ratio of plants. Root pruning, what is it? As the name suggests, root pruning is the cutting of roots. It is done for different reasons than pruning the tops of plants. We have total access to the tops of plants. Axis to the roots of plants is much more limited. Roots grow differently from stems. Roots do not have buds. You can virtually cut anywhere on a root and it will “sucker” unlike many of the stems of trees and shrubs. Why root prune? The most common reasons for root pruning include controlling the size of the plant, slowing the growth of plants, initiate flowering, keep the roots closer to the trunk, keep the roots out of problem areas or creating problems. This is a root pruning machine used in nursery practices for undercutting trees growing in the field under production.This machine is driven so that the young trees are undamaged as they pass under and between the tracks. The U-shaped blade is pulled behind this machine and undercuts the roots…root pruning… to make a bare root fruit tree that will transplant to the field with fewer losses. Photo taken by me at Dave Wilson Nursery www.davewilson.com  Root pruning is commonly done in the nursery operations where trees and shrubs are grown to be transported for planting in a new location. Root pruning is common in bonsai to reduce the growth of plants and keep them small. Root pruning is done in some greenhouse operations for similar reasons to nursery operations. If root pruning is not done and the top of the plant dies or is severely pruned back, then the top regrows again very quickly to its original size. Once it reaches this size, growth slows again. This is the plants way of reestablishing what we have called the root to shoot ratio of the plant. The plant “recognizes” the difference in size between the top growth and undisturbed root size. The plant directs its growth, the flow of carbohydrates and hormones, to the top of the plant at the expense of growth in the roots. How can I use Root to shoot ratios? If a plant is growing too rapidly and you want to slow it down, root prune it. Take a sharp shovel and sever the roots by pushing it through the soil and through the roots as deep as possible. Do you want to keep the roots of plants from entering the septic tank or other problem areas? Root prune between the plant and the problem area. Root prune every 2 to 3 years. Some diseases are transmitted from plant to plant when the roots fused together and what are called “root grafts”. This commonly occurred in American elm with the transmission of Dutch elm disease. Root pruning can isolate plants from trees that are carrying the disease. If an Apple or Pear tree dies from fire blight, root prune the area around the dead tree to prevent the transmission of the disease through root grafts. When Retrofitting trees and shrubs from a lawn area to drip irrigation, consider root pruning these trees and shrubs to generate roots closer to the trunk were the emitters are placed. Having trouble with the tree flowering? Try root pruning to create a new root to shoot ratio that might slow the top growth and induce flowering.

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Air Pruning of Roots Another Form of Root Pruning

Leave a Comment / Pruning roots with air, root pruning /

Q. I read about air pruning the roots of potted plants using either fabric pots or drilling holes in pots and lining with landscape fabric.  Supposedly, air pruning keeps the roots in “check” so that they do not outgrow the pot.  The idea sounds logical, but with our extreme heat and hot winds, could this work in Vegas? A. Air pruning is allowing the roots of plants are exposed to the air and die. It is normally used in greenhouse production with potted plants. It can be used for plants growing in containers as well. It is popular where other types of root pruning may not be practical.             If plants grown in containers are allowed to rest on soil or gravel, the roots of these plants can grow out of the holes on the bottom or sides of the container and into the wet soil beneath it. Once the roots leave the container and grow into the soil, the tops of these plants typically have big growth spurts.             In the past, if these pots or containers were given a quarter turn twist, this would sever young roots and prevent them from getting anchored in the soil beneath them. This is an older method of root pruning.             Another older form of root pruning was using chemicals such as copper sulfate applied to the surface of the soil or gravel just under the pots or containers. The concentration of copper would kill the roots of plants growing into it but would hurt the tops of the plant.             Air pruning is another form of root pruning where the bottoms of containers are pots are suspended in open-air. Roots exposed to the open-air will die without moisture. As roots leave the container through drainage holes, the roots die and become “root pruned” by the air.             This would work in our climate as well. However, in our hot desert climate I worry a bit about pots or containers left in full sunlight. The soils in these containers can heat up quickly and the roots “roasted” on the side of the container facing the sun.             If pots or containers that you are using for root pruning are in full sun make sure they are white or shiny and reflect as much sun as possible. It would be best if they were shaded. Water the plants in the containers just before the heat of the day.

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Air Pruning Will Work in the Hot Desert with Some Precautions

Leave a Comment / hydroponics and pruning roots, Pruning with air, root pruning, will air pruning work in the desert /

Q. I just read about air pruning of roots in potted plants using either fabric pots or drilling holes in pots and lining with landscape fabric.  Supposedly, air pruning keeps the roots in “check” so that they do not outgrow the pot.  The idea sounds logical, but with our extreme heat and hot winds, could this work in Vegas? I know that pots kept in the sun will overheat and kill roots.  If the pot is large enough, would it only kill the outer roots, similar to the action of air pruning? I have some large pots and as I get older, it is going to be very hard pulling the plant, cutting the roots and re-potting with fresh compost. Any thoughts would be appreciated. A. Air pruning is a form of root pruning. There is nothing new about root pruning. Root pruning is used in growing bonsai to help keep the plants small and reduce the amount of top growth. Root pruning is used in nursery production to restrict the size of the roots and increase the survival of field grown trees that will be harvested and sold as bare root, containerized or balled and burlaped. Machines like these are used in commercial nurseries for root pruning young trees before they are harvested as bare root or transferred into containers. Root pruning concentrates the roots close to the plant so they can be transplanted with a higher percentage of success. You can use air pruning in our hot desert with high light intensities if you regulate the solar radiation heating the soils inside the containers during summer months. Container plants should be repotted every 2 to 3 years as you know. You might be able to skip the part about cutting off some of the older roots but if you do not replenish about one third of the soil it will eventually be like growing a plant in sand or hydroponics. You might be able to use compost tea as a soil drench for the plant in the container. That, and the addition of a good fertilizer plus micronutrients, might get you by. Hopefully good management of plant root systems can help prevent girdling or circling roots, a huge problem in the nursery industry and passed on to the homeowner and not discovered for many years later. Just as you stated, air pruning is allowing tender roots to come in contact with dry air thus killing them. This is usually a greenhouse technique. In the nursery trade we used to use copper sulfate to control plant roots. When plant roots in they did a space treated with copper sulfate, they died back from copper poisoning. Copper did not travel back inside the plant but stayed localized where it came in contact with roots. This was sometimes used in what is called pot-in=pot culture or “double potting” where a plant is grown in a container and that container put inside of another container that had a shallow layer of gravel at the bottom to prevent the two of them from lodging. We used pot-in-pot culture when growing ornamental trees for a research project in the 1990s. The container inside of the container that was buried into the ground helped keep the container soil cool. This reduced the risk of high temperatures in the soil surrounding the roots and root damage. Growing plants in black nursery containers in the hot Mojave Desert runs the risk of root damage due to high soil temperatures. The outside pot was buried in the ground nearly up to its rim. The outer pot acted as a “sleeve” for the inner pot and helped prevent potted plants from blowing over in the wind. This was a big problem in the nursery trade and required many man-hours to “right” the plant after a wind.  If copper sulfate was not used on the gravel between plants or the inner pot was not twisted every couple of weeks during the growing season, the roots from the plant in the inner pot would grow through the gravel and through the second pot into the ground and the plant would be ruined. Air pruning is similar but without the harsh chemicals. When plants are grown in black nursery containers in full sun, one half to two thirds of the root system of that plant can be killed during summer months due to high soil temperatures. Surface temperatures of black nursery containers can reach 170° F in direct sunlight in just minutes. High temperatures spread through the container soil on the sides facing the sun. Damage is worse if the soils are dry. What to do? •           Paint nursery containers white. This helps to lower the surface temperature 6 to 10° F. •           Keep nursery containers shaded during summer months by double potting them, placing a son barrier on the outside of the container on the South and West sides •           Grow nursery plants in partial shade; 30 to 40% shade is best. •           Water nursery plants just prior to the heat of the day so that soils are moist. Moist soils do not gain heat as much or as rapidly as drier soils.

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