I recently went to an OHBA lecture given by John Nielsen-Gammon, Texas’ state climatologist and professor at Texas A&M. His lecture helped me have an even deeper understanding of our climate here in Houston. I am sure many of you have seen long term damage from all the rain we have had in the last year. I have lost many bulbs and have hardly any earthworms left. As a landscape designer that works towards sustainable landscapes I make sure I study the effects of climate on plants. Some of the information in his lecture was speculative, as we can’t know the real outcome of all the forces at work here in Texas. It is especially challenging if your job depends on it. Understanding more about the years of drought that hasn’t actually ended in some areas was useful. Learning more about the strong El Nino in the Pacific ocean and how it affects us was also helpful. It contributed to our milder winter and the above normal rainfall. It can also contribute to a more active hurricane season. Houston’s unique climate is pretty rough on plants with huge temperature extremes. We have several weeks in the summer with temperatures as high as 108, then down to lows as low as 20 degrees during the winter. We have tight clay soil, fondly known as gumbo. The annual average rain fall is 52” (79” the last twelve months). We have brutally hot summers with 98% humidity and no chilling breeze in the evening to cool down the soil. Some wonder if the changes are due in part to global warming. Going back in history gives us and understanding of the range of changes in Texas climate before the effects of environmental pollution. In each hardiness zone, climate zones and region (elevation, or lack thereof, as well as ocean influence) plants act and grow very differently. Houston is generally broken up into cold hardiness zone 9a and 9b but there are pockets or micro-climates like here in the Heights we have conditions similar to zone 8b. We are also considered sunset zone 28.Climate parameters in the gulf coast of Texas vary as you drive west and north or south with variation even in Houston itself. This means what grows fabulously in Austin or Dallas may not thrive in Houston with its own unique climate. As you drive south to Corpus you find it is more humid with no freezes and tropical plants thrive. Drive west to the Hill country and Austin, they get much less rain with long dry spells and have areas with a thin layer of poor soil on top of limestone. Dallas to the north is part of the Great Plains and gets snow and long hot dry summers.
Even though we have nutrient rich soil and plentiful rainfall you will find plants act differently than in other regions. In my designs I use a lot of native plants. Here in Houston we have two main Ecoregions . The Piney Woods from the north meet the Gulf Coast prairies and marshes weaving in and out along the horizontal line created by Interstate Highway 10. The Heights has qualities of both with pockets of pines and oaks surrounding grassland meadows. Of course these are being replaced by houses and there are few open spaces left. But the conditions remain the same for growing both tall trees and perennials and grasses.
In this last year a weather map like the one below appeared much to often and caused damaged to homes, people and wild life. Understanding what standing water does to our clay soil is a new area for me. The water can suffocates the plants roots and it also can compact the soil. Compacted soil contributes to flooding. This is the street outside of our house. I am originally from southern California. The annual rainfall in San Diego is 12″. Learning the climate of our Bayou (alluvial coastal plain, river city) took time, research and local training. For more information about the Texas-Louisianan Coastal Plain environment here is an excellent website. It has been seventeen years now and I felt I was pretty well versed but there continue to be surprises, like 80 inches of rain in one year. The learning curved started when I first moved here and planted my front beds with annuals in May. That June it rained every day and it never got below 85 degrees day and night (think sauna)…everything rotted. In some descriptions we are considered sub-tropical but in fact during our winter it is not unusual to get hard freezes, it may skip a year but must be considered when choosing plants. This all means plants have a lot to deal with. Here is a link to a Houston Flood Mapping Educational Tool, that can give you more information on the area of Houston you live in.
Colorado River just west of Houston on Memorial Day 2015
In the seven years we have been in the landscape installation business, averaging about forty to fifty projects a year for the past five years, I have come to have my list of reliable low maintenance, drought and frost tolerant plants. Now they must also be able to deal with ‘wet feet’. Drainage is the key to this. I will add that subject to my list of blogs I want to write : ) Even with this new challenge I feel confident in my choices as we see our gardens suffer less than 1% plant loss. I have collected some information on these plants on our Pinterest Board Plants for Houston. There are several things you can do to help plants thrive. One is to use an all-purpose organic fertilizer at least seasonally to help naturally aerate the soil. I will elaborate more on this in my next blog. I will follow that with a blog on watering and drainage. Below you see one of my test gardens were I used very drought tolerant plants that I am happy to report also survived all the rain. By working on our soil health this area doesn’t hold water more than an hour.
May 2016 at Ravenscourt Gardens