Xtremehorticulture

How to Care for Lilacs in the Desert

Q. My lilacs have bloomed and the flowers are gone. Is now the time to prune or do nothing? How do you prune or care for the lilacs. Lilac planted in rock mulch with brown scorched leaves Shrub pruned with heading cuts close to the ground A. Most people don’t know that low-chill varieties of common lilac will grow here as well as the Persian lilacs. Plant them in plenty of sunlight but in places which avoid the hot afternoon sun. All lilacs must be planted in a composted soil with a wood chip mulch. Rock mulch will not work. Low-chill varieties do not need as much low temperatures to produce flowers. Lilacs that are not low chill will not produce as many flowers in our warm winter climate. Some plants require long periods of time when temperatures are cold so that flowers will be produced the next year. Persian lilac may be a better choice for our climate and in smaller yards than common lilac. Persian lilacs are smaller in stature than common lilac, with smaller flower clusters and a lower winter chill requirement. Hopefully local nurseries and garden centers that sell lilacs for our climate are selecting low-chill types such as an old time favorite here called “Lavender Lady”. I believe this, along with “Angel White” were the first low chill lilacs available that would grow in the desert Southwest. Many of these low-chill varieties are referred to as the “Descanso Hybrids”. Lilacs are not desert plants so they require lots of compost mixed in the soil at the time of planting with the soil covered in wood chips that decay over time. They should not be in rock mulch. A very nice article appeared in Sunset Magazine and you can read it here http://www.sunset.com/garden/flowers-plants/mild-climate-lilacs As with any seasonal flowering shrub or tree the best time to prune them is soon after flowering. If pruned later than this, the flowers for next year may not be produced. First, remove the dead flowers before they form seeds by cutting them off at the base. Next, if needed, cut back branches or stems. To increase the number of flowers you should increase the number of new branches it produces. Use a “heading cut”. This type of cut is made somewhere along the length of the branch, usually just above a leaf on the outside of the branch. Heading cuts grow three or four new shoots for every one that is cut that is made. This is an excellent way to make a shrub denser with more flowers. If the shrub is getting too large, remove one third of all the longest stems back to within a couple of inches above ground. New stems will grow from just below these cuts. A radical way of pruning this plant is to totally cut it off just above the soil surface. With plenty of water and some fertilizer new shoots will grow from these very short stubs resulting in an all-new plant. This is pretty radical but if the plant is overgrown with lots of wood showing, this may be your only alternative. Remember, after pruning give it plenty of water and fertilize it with an all-purpose fertilizer.

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Chinaberry Damage Probably Carpenter Bee, Not Borers

Q. I have a 25 year old Chinaberry tree that I like because it has aromatic flowers in the spring but I also hate it because it is messy. Parts of the tree recently broke from the wind. There were still lots of leaves on the tree but the inside was dry and dead. How long do these trees live and is what I described normal? A. Chinaberry is also called Persian Lilac and here in the United States we sometimes call it the Texas Umbrella Tree. I like the tree because of its form, fragrant flowering and fruit clusters but many local horticulturists do not. Carpenter bee damage to dead palm frond remnants. Note the perfectly round holes the size of a quarter or about 2cm in diameter.             The leaves and fruit can be poisonous to humans but not to birds. It is a native to parts of Asia where the leaves and fruit have been used as a natural repellent of pests when drying food. The poisonous chemicals inside leaves and fruit are related to the natural pesticide Neem. The tree is a fairly close relative of the Neem tree.             Just like you said, it can be messy and the wood is brittle and can break easily in the wind. For these reasons, they do not last very long in landscapes.             The inside of any older tree is all dead wood. It is just the outside cylinder which is alive. Insects that tunnel or build homes in dead wood can cause damage to the tree if they get access to the inside. Wood rotting fungi however is seldom a problem since the wood resists decay. It is also a relative of teak and the wood is actually very pretty.             Boring insects feed on the living parts of the tree, not the dead parts. However insects such as termites and carpenter bees can utilize the dead wood inside the tree if they can get in there. If they do get in they can weaken the tree further where it will fail in strong winds.             I have never seen boring insects in this tree but I have seen Carpenter Bee damage to the interior dead wood. If you look closely I would suspect you’ll find large holes in the interior wood about the size of a nickel. This is a good sign Carpenter Bees were actively nesting in there.             You are probably better off replacing the tree with something else.

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Persian Lilac Can Be Different Things to Different People

Q. I believe you made an error last week about the Chinaberry tree. You said it “is also called Persian lilac and in the United States we sometimes call it the Texas umbrella tree.” I do not believe that the Persian lilac is related at all to the umbrella tree. We had both in our yard years ago, and they were quite different. A. Thanks for your comment and you are right, there is more than one plant called “Persian lilac”. This is where the common names can be confusing.              The Chinaberry tree (Melia azedarach) can also be nicknamed the Persian lilac because of the very perfumy flowers it produces in spring. You can google any of these names on Wikipedia. Melia azedarach on Wikipedia              There is another plant, also called Persian lilac (Syringa x persica), a hybrid lilac very closely related to common and Chinese lilac which is probably what you were growing.  Image of Syringa x persica              We have the same problem with another plant we call mock orange. Locally, our mock orange is a Pittosporum tobira (Wheeler’s Dwarf). This is not the same mock orange known by most of the country. When I was in school, mock orange was a totally different plant with the scientific name Philadelphus coronarius, a flowering relative of hydrangea whose flowers were used for garlands because they have a strong citrus fragrance. Image of Pittosporum Wheelers Dwarf aka Mock orange   Image of Philadelphus coronarius aka Mock orange             I do not to use scientific names in my newspaper column but common names can be confusing for this reason. I appreciate these comments because I’m sure others were thinking the same.

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