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Ask the Garden Guru—

This feature of Down the Garden Path invites you to submit questions relating to ornamental gardening.  Submit questions to info@zilkergarden.org, subject “DTGP Guru”.

Question from Brent H:  I hear that some citrus plants can be successfully grown in the Austin area. I would like to give some a try but what varieties do you recommend?

GURU:  Citrus can be successfully grown in out central Texas areas providing you stick to the more cold hardy varieties recommended below. Growing any other citrus plants will be very risky in our area. Most citrus that will endure the Central Texas area winters are grafted on trifoliate orange (Poncirus)  root stock. Citrus must also have a slightly acidic, well drained soil (not limestone/alkaline based as is found in Texas Hill Country) and can be container grown if roots are protected from winter freezing. If you can give any citrus plants a protected but sunny area, that would be best. The best time to establish citrus is in spring so they have an entire growing season to adapt before the challenging weather of winter returns.

  • Satsuma Orange (most any variety can withstand temps to 25 degrees). Owari, Big Early, Armstrong, and Arnolds are some variety names found in local nursery trade. 
  • Variagated CalamondinCalamondin Orange: (Citrofortunella mitis) - this small tart seedy orange is grown more for ornamental value than for fruit value. This makes a great potted plant with fragrant citrus bloom and ornamental small fruit. The variegated plant is most attractive. These oranges can be squeezed into iced tea to add a great flavor. This plant can be grown as a shrub or small tree and is ideal for small residential yards. Pictured here is the variegated Calamondin foliage and fruit.
  • Tangerine: Changsha tangerine is even more cold hardy than Satsuma orange and can be grown true from seed. Clementine and Fairchild Tangerines are also listed as very cold in cold tolerance. 
  • Kumquat: (Fortunella spp)  Nagami and Meiwa are the best varieties. Nagami is a very tart fruit.  Meiwa is very sweet and great to eat (skin and all). Kumquats take a tree form but remain very small in size – ideal for small residential yards  
  • Limequat: this cross between a lime and kumquat can be grown in Zone 9 with good cold tolerance. The fruit can be used for the same purposes one would use a lime.   
  • Meyer Lemon:  (not believed to be a true lemon but a cross between lemon and satsuma orange), has fair cold tolerance and would need a very protected area for in-ground growing.  Other lemon varieties are NOT cold tolerant to Central Texas area and need winter protection.
  • Most grapefruit and orange varieties:  All are not cold tolerant to the Central Texas area. There may be some exceptions, or a sufficient microenvironment might protect less hardy varieties from winter cold. 

 

Agave Beetle & AgavesFrom John D: Help! Some of my Agaves have rotted at the base and collapsed, only to find a mushy and decayed mess. What is causing this?

Guru:  Sounds like you have been attacked by the Agave Snout Weevil (Scyphophorus acupunctatus). This is a nasty little creature, ½ to 1” long, black, wingless, with a typical weevil snout that bores holes into the base of more mature agave, yucca and other related plants with a base diameter of 2” or more. Then it introduces bacteria which is necessary to cause rapid tissue decay in the plant to feed its white legless grub larvae at the same time it lays its eggs. Once hatched, the larvae feed on the rotting and bacterial rich inside tissue of the agave plant causing it to eventually collapse. It then pupates from larva to adult in the surrounding soil.  If this pest is not discovered early on, there is little one can do to save the plant. 

What you may need to do to prevent this nasty creature from destroying your Agave and Yucca plants is apply a systemic insecticide (liquid or granular form) that is effective on grubs. Bayer Advanced Tree & Shrub Insect Control, with the active ingredient imidacloprid (under the trademarked name Merit) has been used effectively.  Recommended treatments should be in spring and once absorbed into the plant, should protect your plant for up to a year. Treating the surrounding is also necessary. Diazinon is also used to combat this pest. Other systemic insecticides can be used if they are recommended for treating grubs. Always follow the directions on the product labels. 

As much as I hate to use any chemical product, this unfortunately is the only effective way to combat the Agave Snout Weevil once discovered.  Observation and immediate removal of infected plants and soil around them is also effective in combating this pest. Agaves grown in containers with sterile soil are much less susceptible as the weevil is soil borne during it’s development. This weevil is doing much damage to commercial Agave crops in Mexico (Tequila, Sisal), therefore is having an economic impact as well.  Ironically, it is this grub that is often placed in the bottom of a bottle of Tequila. The picture below shows the adult and the grubs which were embedded in a Yucca aloifolia plant and the damage they cause. 

 
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Austin Area Garden Council
512.477.8672
info@zilkergarden.org