Spring 2011

Spring 2011

Cover: A Wallichia disticha in Brownsville in good condition after the February freeze

Before having a chance to fully complete out the damage reports from January 2010 the state of Texas was affected by its most severe cold outbreak in decades. In far West Texas over to the southeast corner of Arizona the cold was a true generational freeze, which had not seen such a hard freeze since the 1960s or '70s. East of the Pecos River the state was spared from an '89 type disaster but it was still the most severe and prolonged airmass freeze since at least 1990 (though admittedly it has been a relatively kind two decades compared to periods past).

Before going on to list the requisite inventory of damaged plants, which will take several issues, it is worth putting last February's cold spell into some historical perspective. At the top of the list of many people's questions are just how bad this freeze ranks, what are the odds we'll see a repeat any time soon, and how much worse can it get?

Starting with the last question first, the answer unfortunately is that it can get quite a bit worse. Everyone who was here in the 1980s knows that this was in no way the severest the winter can dish out to South Texas if it's really in the mood. We've been fortunate that Mother Nature hasn't much felt like socking it to us (or anywhere else in the southern part of North America) for most of the 1990s and the start of the new millenium. But it is pretty obvious that the past two winters (actually going back to 2007 if you include the SW United States) have seen a trend towards harsher. This is surely a disappointment for those who may have believed the climate had truly changed due to general global warming - the past two years has been a kind of reality check.

Having said that, I don't think that a repeat of another '89 or '83 generational freeze is inevitable within the next few years; there were only four of them in the entire twentieth century and the period before 1990 was certainly colder than the last two decades. And, as I like to point out to people, extremely severe freezes are not totally random events and not an inevitability over a given interval. It could well be that we have another two decades before we experience something substantially worse than this. But we have to be realists here: this type of freeze occurs more often than the "Big One" and your yard should be albe to handle an event like this.

In spite of the sobering statistics, however, keep in mind that this was an unusually damaging freeze considering the relatively high minima. Duration, icing, a followup freeze a week later and (at least near the coast) little prehardening all took their toll. In some respects it more resembled harder past freezes, just without a really cold night like we had in '62 or '83. So I guess you could consider this something of a next-to-worst-case

scenario. Whatever withstood this past freeze should be pretty secure in all but the most disastrous of winters. This freeze in fact was so hard on so many commonly used plants here that it is still not possible to determine the fate of a number of plants. Many are either dead or severely injured, but while we wait on the most sluggish plants it is already possible to get a decent idea of what fared well and what had serious issues. Generally certain genera or even entire groups of plants did better than others. So for this newsletter I want to look at what so far appear to be winners and losers in this freeze, both overall as a group and what exceptions there may be. For now we'll look at the lower Valley from Brownsville and South Padre up to the McAllen area. Recovery has been a bit longer in coming to areas north of here so that'll come in later issues.

First the winners. Most notable: Fan palms - As a group the fan palms did considerably better than the feather palms (remember Phoenix is really more a fan palm with feather leaves). Even fan palms with very tropical reputations, such as Thrinax radiata or even Latania fared relatively well compared to feather palms from similarly balmy climates. In fact it's hard to find any sort of fan palm here that completely died. But there was some minor damage to many growing points, even on some tough subjects like Livistona decipiens in pots.

One gorgeous fan palm did so well it deserves its own entry: Bismarkia - while many Bismark palms that were introduced here before the late 1990s are often quite tender the newer selections from Florida are proving to be much tougher. They look even better now compared to all the dessicated leaves on so many feather palms. Really we can't plant enough of this gorgeous palm.

Archontophoenix - perhaps the best performers among the crownshaft palms, especially A. cunninghamiana.

Phoenix - as mentioned earlier the date palms are anatomically closer to fan palms but the nicest ones still give tropical feather palms a good run for their money. Especially pleasing is the very tropical looking P. rupicola, which like P. roebelenii did have their growing points injured and some leaf damage in cold areas but recovered.

Sonoran plants - as a group they did admirably well, with the handsome Sonoran guayacan (Guaiacum coulteri), desert fern tree (Lysiloma thornberi) and palo brea (Parkinsonia praecox) taking no stem damage at all. Slight branch dieback was seen on lushly grown brazil (Haematoxylon brasiletto) and palo papel (Acacia willardiana) but recovered quickly.

Bromeliads - unfortunately bromeliads, as a group, have not been cultivated as landscape plants in South Texas as extensively as they have been in Florida. I used to think the only type that would do well here was Quesnelia quesneliana because it was all you saw. But after 15 years of growing a few in the ground and 5 years of trying many more varieties with reputations as resisting both salt and cold I can say that there are some very promising types out there such as Neoregelia cruenta and most Aechmea distichantha hybrids. These had relatively minimal freeze damage.

Bromeliads as a group fared well

Tropical foliage shrubs - a number of shrubs which are grown for their attractive tropical foliage such as pineapple guava (Psidium cattleianum) had no damage. Most yellow oleander (Thevetia nefiifolia) and the larger forms of Natal plum (Carissa grandiflora) also did fairly well.

Hardier subtropical trees - while the spectacular Delonix were severely injured in the cold the tougher subtropical flowering trees such as Jacaranda, Peltophorum dubium, Grevillea robusta, Ceiba (Chorisia) insignis, Callistemon viminalis and Lagerstroemia 'Princess' did very well. Also virtually all of the dry subtopical flowering trees being cultivated in Phoenix and Palm Springs laughed at the freeze. Caesalpinia mexicana, however, has been beat up in the spring winds but not. Senna fistula was often burned but managed to bloom. The temperature did not drop low enough to injure most Australian plants.

Now to some of the losers. Starting with the obvious: Rare feather palms - afraid these didn't do too much better than the chain store stuff, many collectors with a lot of the more unusual tropical feather palms really took some losses (time to consider a Copernicia collection?). There are some happy exceptions: Wallichia disticha fared well as did Attalea speciosa, in addition to the usual suspects like Allagoptera.

The common feather palms - except for queen palms, most commonly seen large tropical feather palms really took a hard beating, so badly that the final damage tallies aren't yet fully known. This includes the foxtails, royals, bottles, triangles, Christmas and of course coconut palms. The larger royal palms seem to have the most resiliency and the majority will survive.

Can't say the same about the coconuts or bottles.

Allagoptera arenaria

Ficus - probably one of the most disappointing group of plants. Many large trees growing for two decades here have been turned into ugly eyesores. Many need expensive pruning. There are some exceptions: a lone F. macrophylla in a warm part of Brownsville did very well as did many F. religiosa in the Mercedes area (go figure).

Still, if you want that tropical foliage look it may be better to consider Schefflera actinophylla, it's just as tender but at least you won't have to pay a tree company hundreds of dollars to take out the dead wood. Also doing poorly were trees often mistaken for figs, such as Java plum (Syzygium cumini).

Crotons - until now these had been pretty widely used landscape plants but the past winter took nearly wiped out most forms of it. In many instances they have already been replaced. Some protected plants survived, including a stressed plant of 'Stoplight' that I had growing in Olmito. Covering helped a lot.

Euphorbias, including crown of thorms - most unprotected plants were either killed to the ground or died outright. Again, simple protective measures brought many of them through. The cactuslike euphorbias also did poorly and many were totally killed, with E. royleana taking the least damage for me. The South African Portulacaria afra also had quite a bit of damage, the lower growing forms doing the best.

Ficus macrophylla in Brownsville

Some groups of plants had mixed results: Philodendron corcovadense

Aroids - for the bread and butter tropical look it's hard to beat the standard Philodendron bipinnatifidum (P. selloum), the larger forms of which performed very admirably in the cold. Some of its smaller forms, however, such as 'Xanadu', suffered heavy leaf burning in most areas. The hybrid Philodendron 'Evansii' and climbing philodendrons were defoliated and took some stem loss. Recovery so far has been so far slow on more injured plants. One of my favorites, Philodendron corcovadense, had yellowed foliage but damage was not as extensive as with the climbers.

Among the other aroids, both the common yellow and the rarer green pothos (Epipremnum pinnatum) again were defoliated and stem loss is apparent, though many did not die totally to the ground. The rather ordinary Syngonium podophyllum was also defoliated but is returning more quickly and looks like it will have less stem damage. The best performing of the commonly seen climbers has to be Monstera deliciosa; in warmer areas it only had partial foliage burn and stems are alive.

Columnar cacti - it was expected that tender cacti such as Acanthocereus, Pilosocereus and Hylocereus would be injured or killed in the cold and they were. The stockier thicker tree cacti also did well except perhaps for Pachycereus pecten-aboriginum in all but very dry areas. What was a bit disappointing, however, was the poor performance of generally tough cacti such as Harrisia and especially most of the true Cereus, including the naturalizing population north of Edinburg. The near-native Stenocereus pruinosus and the iconic Mexican fence post cactus (Pachycereus marginatus) did better. A Myrtillocactus cochal near Edinburg also had little damage.

Cycads - while I can't think of any that are totally dead or even took trunk loss there is a pretty big gap between the hardier ones (Cycas revoluta, Ceratozamia, some Dioon and the zamias from Tamaulipas and Florida) and ones that badly scorched (most Encephelartos, Cycas circinalis/rumphii, tropical Dioon and the ever-popular cardboard palm Zamia furfuracea). Recovery should soon be complete on damaged plants.

Pachycereus pecten-aboriginum was severely injured or killed

New growth on Encephelartos gratus

Dracaenas and ti plants - ti plants and dracaenas rank right up there with crotons as standard issue tropical plants and most did about as poorly. The one notable exception were the traditional "true" ti plants Cordyline fruticosa (C. terminalis). Where most others were killed at least to the base the true tis only had superficial foliage injury. The plain green form was the toughest but the large black forms and the tried and true cultivar 'Hilo Rainbow' also did well. I have not returned to some Cordyline 'Glauca' post-freeze to see how they did.

Cordyline fruticosa in Brownsville

Acanthus family - surprisingly many shrimp plants (Justicia brandegeana) did very well, the ones in the backyard not even scorching. Just as surprising was the injury of usually hardier acanthus members such as desert ruellia (Ruellia peninsularis) or even in some cases chuparosa (Justicia californica), though both quickly replaced injured wood. The old standby Mexican honeysuckle (Justicia spicigera) did fine.

Bamboos - on the whole they did pretty well. Most types seen here are the more tropical clumpers and pretty much all survived with little to no damage. The most tropical species, such as Bambusa lako, however, did go to the ground.

Tropical fruit - lots of variation here. Citrus, the king of tropical fruit here, did better than I thought given the duration of the cold. Sugar apples were another surprise. Mangos were hit again, worse that last year in urban areas, though few appear dead. Damage to avocado trees ranges from virtually none to fairly severe, presumably depending on the variety. The few longan trees I know of had some branch dieback.

Hopefully more detailed articles will be forthcoming about damage to both the bamboos and tropical fruits (they're not an area I'm all that familiar with).

Tropical vines - usually not the hardiest group and most did freeze to the ground unless in protected areas. Modestly surprising was the near- weedy rubber vine (Cryptostegia grandiflora), it didn't seem to mind the cold at all and is in full bloom this spring. The allamandas and mandevillas suffered heavily though I have seen a few wild allamanda (Urechites lutea) that look good, mostly on the south sides of buildings. It takes our soil and drought very well.

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Palm Society of South Texas 7317 Pepper Ridge Road Corpus Christi, TX 78413