Thursday, December 5, 2002

Brown Dieffenbachia Leaves

My Dieffenbachia is turning brown and losing leaves. What am I doing wrong?

Dieffenbachia
If we have some knowledge of where a house plant originates, we can then try and duplicate those conditions in our home, thus providing an environment favourable to the plants health. 'Dieffenbachia' or Dumbcane, as it is commonly called, is native to tropical America (Costa Rica and Colombia, for example) as well as the West Indies. Dieffenbachia is named in honour of Herr J. F. Dieffenbach, a German botanist who supervised the imperial gardens at Schonbrunn Castle in Vienna in the 19th century. The common names of the plant, 'Dumbcane' and sometimes 'Mother-in-laws-Tongue', are derived from the effects the toxic or poisonous sap of the plant has on a person's mouth and throat if it should be eaten or chewed. The sap contains calcium oxolate crystals which causes swelling and pain of the mouth and throat, as well as speechlessness in many cases. It is for this reason, very important to keep the plant out of reach of children and pets, and to wash the hands after handling the plant. Dieffenbachia belongs to the Arum family, 'Araceae'.

Dieffenbachia plants are easily recognized by their large, brittle, oblong or ovate, often drooping, variegated leaves. The green leaves are either spotted, blotched, or streaked with cream, white, yellow, gold, silver, or a combination of these colors. Depending on the species or cultivar, the leaf size ranges from 8 inches long to over 2 feet long. If the leaves should be bruised or cracked, which they do very easily, they often give off a skunk-like odor. Be careful when handling or moving the plants so as not to damage the leaves. The leafstalks sheath at the base of the plant and encircle the normally non- branching stems (like a tree, not a shrub). Although some plants can reach a height of 6 feet or higher, they usually end up looking like a palm tree by this time due to the fact the bottom leaves drop off the plant as they mature. This is a good time to rejuvenate the plant, and perhaps start a few more plants using various methods of propagation to do so. The top part of the plant can be air-layered, and once it has rooted and been removed from the plant, the stem can be cut back to 4 - 6 inches from the pots rim to stimulate new growth from the short stub. The remainder of the stem can then be used to make cane cuttings. To make cane cuttings, cut the bare stem into 4 - 6 inch long pieces, being sure each piece has at least one node (a small green swelling on the cane). Lay the pieces of cane horizontally in moist sand or any rooting medium with the majority of the nodes facing upwards, and bury only the lower half of the cane in the media. Once the new shoots reach approximately 2 inches high, cut them from the cane with a small piece of the cane attached, and root these shoots in moist sand. Once rooted, they can be potted up in 3 or 4 inch pots in proper compost or soil. Alternatively, insert the pieces of cane upright (vertically) in the moist sand. Bury the bottom 1/3 of the cane, being sure to bury the end which was the lower part of the stem. This is the method used to produce a 'Ti-plant'.

Dieffenbachia
Because these are tropical plants, they require a warm, humid environment to succeed. Daytime temperatures of 75 - 85 degrees F, and nightime temperatures of 65 degrees F (no lower) are ideal. If temperatures are too cold or the plant is subjected to cold drafts, the leaves will either develop brown edges, turn completely brown and drop, or the lower leaves will turn yellow and wilt. Extreme or fluctuating temperatures can kill some delicate varieties. Along with warm temperatures, a high level of humidity should be maintained. If the air is too dry, the young leaves will often fall. Place damp peat moss around the pot, use pebble trays, or set basins of water near heat registers to increase humidity levels around the plant. Mist the leaves in the morning hours of each day if humidity levels are very low. Wash the leaves at least once a month with warm, soapy water to clean them and also remove any insects which may be harbouring on the plant. Rinse with clean water. Never use leaf shine products on the leafs.

Dieffenbachia camille
Provide 400 foot candles of light for Dieffenbachia plants. This is a bright, indirect light, such as a curtain-filtered south window. Direct sun shine can bleach or fade the leaf coloring, whereas, too dim a light will either cause the plant to lose its variegated colors and revert back to green, or, the lower leaves could dry up and fall.

Dieffenbachia compacta
Watering can be a touchy subject with this plant. While the plant is actively growing, keep the soil moist to moderately dry. The media must never be soggy wet, as overwatering will cause the lower leaves to drop. In winter, or the dormant period, the plant will need to be watered more sparingly, especially if room temperatures are on the cool side. The plant is very susceptible to crown and stem rot disease when a combination of overwatering and low temperatures co-exist. If the soil is allowed to dry out, the leaves will develop brown edges.

Dieffenbachia tiki
Dieffenbachia generally require fertilizing only every 2 or 3 months while they are actively growing. Use a plant food such as 5-10-5 diluted to 1/2 the strength recommended on the fertilizer containers label. Never feed the plant while it is dormant.

The most common pests of Dieffenbachia include mealybugs, aphids, red spider mite and scale. A humid atmosphere helps in detering these insects. If an insecticide is needed for control of a heavy infestation, choose one that is recommended for use on Dieffenbachia as listed on the containers label. These insecticides can be found at most garden centers or hardware stores. Diseases common to the plant are leaf spot, stem, crown and root rot, anthracnose and Dasheen mosaic virus.
Dieffenbachia Tropic Breeze
The genus 'Dieffenbachia' contains over 12 species, as well as over 50 introduced cultivars. A few of the more common species include: D. amoena - dark green to blue- green leaves feathered with white; D. bausei - yellowish-green leaves with green margins and white spots (a hybrid plant); D. bowmannii - large green leaves with white spots; D. chelsonii - deep, satiny green leaves marked with gray feathering; D. exotica (arvida) - a good smaller plant for the home, dull green leaves variegated with creamy white; D. fournieri - almost black-green leaves with white spots; D. fosteri - green leaves, a short dwarf variety; D. hoffmannii - velvety green leaves blotched with cream or white and prominent white mid-ribs (the main vein of the leaf); D. imperialis - bright green leaves with soft yellow blotches; D. leonii - green margined velvety yellow leaves; D. longispatha - light midribs, dark green leaves; D. memoria-corsii - gray colored leaves with ivory spots and green veins; D. oerstedii - dark green leaves with prominent white mid-ribs; D. parlatorei - shiny, deep green leaves; D. picta - green leaves blotched with white; D. picta barraquiniana - green spotted white leaves with prominent white center veins; D. picta jenmannii - green leaves with white veins in a herringbone pattern; D. picta superba - green leaves spotted or blotched with cream, a very compact form; D. sequine liturata - velvety green leaves with white center veins; D. splendens (hybrid) - bronzy-green velvety leaves spotted with white and white mid-ribs.

Dieffenbachia Tropic Marianne
A few of the many cultivars include: 'Alix' - green and white variegated leaves; 'Camille' - creamy white leaves edged with green and green mid-rib; 'Rebecca' - compact, creamy white leaves splotched with green and yellow; 'Rudolf Roehrs' - white blotches on gold- green leaves with dark green leaf edges and dark green mid-rib; 'Compacta' - creamy white leaves with green spots; 'Tropic Star' - bright creamy-yellow with irregular green splotches; 'Silver' - silver and green leaves; 'Nelly' - green leaves with cream, slow growing and compact; 'Pittieri' - emerald green leaves with white and ivory patches; 'Wilson's Delight' - large, solid-green leaves with white mid-ribs; 'Perfection' - green and cream variegated leaves.

Tuesday, December 3, 2002

Improve Soil for Arborvitaes

I have 10 emerald green arborvitaes of 12 ft in height which were planted in spring of 2001. They were bright green until this past summer where in Rye, New York we experienced a drought problem and they started to brown. Even with all the water we recently gotten, they still don't look healthy. I'm planning to retransplant them to a anothert location for esthetic reasons but I'm afraid that they may not survive. Can you let me know what I can do to improve the conditions of the trees and if its possible I can retransplant them and what kind of soil and fertilizer do I need to do this.


Your advice will be greatly appreciated.

Arborvitae
It is best to plant the trees directly in the type of soil you have in your yard or garden. It is a mistake to dig a hole and fill it with soil that has a different soil structure, as well as a mistake to spread a layer of soil with different structural texture over the existing layer of soil. These methods create problems with water moving through the soil, and the trees will surely do poorly, if they survive at all. The first thing to do is remove the topsoil from a three foot in diameter circle for each tree and set it to the side. Loosen the subsoil with a spade to a depth of about 2 feet and chop it up finely so as there are no large lumps. Mix a little loam soil, peat moss, sharp sand and bone meal into this subsoil layer to improve drainage and texture. (You may have to get rid of a few shovels full of this subsoil before mixing in the ingredients, or you'll end up with too much soil upon completion). After doing this, return the topsoil (even if is clayey) and thoroughly mix in some loam soil, more peat moss (a layer that is at least 3 or 4 inches thick when spread over the soils surface), sharp sand (unless of course your soil is very sandy or gravelly, in which case omitt the sand), and a cupfull of bonemeal. The bonemeal is high in phosphorous and promotes healthy root growth. The end result should be a loose, friable soil (like a garden soil that you could easily plant small seeded veggies like carrots or lettuce, for example). There should only be enough soil in the planting hole so that after the tree is planted, there is still a 2 inch depression around the tree so that water will soak into the soil around the tree as opposed to draining away from the trees roots due to a build up of soil around the tree. I always carefully remove 2 or 3 inches of soil from the plants rootball so that some of the plants roots are already surrounded with this fresh soil when the tree is planted. This also enables one to spread out any roots that were circling the rootball (if it was container grown) or prune off any broken roots. It is important to cover the root ball of the planted tree with at least one inch of your soil, otherwise, if the root ball is of a different soil type, and it is higher than the surrounding soil, it can act as a wick and dry out quickly, killing the trees roots. The soil must be kept moist when establishing newly planted trees or shrubs, never soggy wet, or allowed to dry out. The soil around the trees should than be mulched with a 4 to 6 inch layer of organic matter to prevent loss of soil moisture, maintain even soil temperature, keep the soil loose and help prevent the growth of weeds.

Once arborvitae are fully established, all that is generally necessary is a sprinkling of 5-10- 5 fertilizer around each tree in early spring to keep them growing healthy and green. If this does not appear to be doing the job, a soil test may be necessary to find out which macro or micro-nutrients are lacking in the soil.

I do not know if your trees were balled and burlapped, or container grown when they were purchased, but if they were ball and burlapped, they will have naturally lost alot of roots when they were dug up. If the 12 foot high trees did not receive adequate water during the dry spell, along with a reduced amount of roots needed to absorb moisture, (even though it is a year later) the direct result would be browning of the needles caused by dessication. Another possibility of browing needles could be a heavy infestation of spider mites or other insects. It won't hurt to examine the trees carefully for pests. If the trees are located near roads, and salt is used for de-icing the roads, splashing salt water will cause browining of the needles. Pesticides will also kill evergreen needles if the pesticde were used in high concentration and close to the trees. (Just some other possible causes of browning).

The only way to help the trees at this time is to keep the soil moist (providing the ground is not frozen) and if possible, provide shelter from the prevailing winds by placing burlap in front of the trees. Spraying the foliage with water from a garden hose during warm spells will also help reduce further dessication of the needles.

It would do the trees more harm than good to try and transplant them at this time of the year. Early spring is the best time to transplant arborvitae, at least in the colder regions of our continent. If the trees must be moved in the spring, it will be best to try and dig up a larger root ball in order to try and save any new roots the tree has produced over the last two seasons. A further loss of roots at this time when the trees are already stressed will definetly do more harm than good.