Sunday, July 1, 2012
Summer Xeriscaping Series: Part 1 of 9
Welcome to today’s edition of Lost in the Farmer’s Market. Today’s episode is the first of a nine-part series detailing a number of Xeriscaping plants and methods. In each episode you can expect to see two Xeriscaping plants, one that is a perennial outdoors and a second that is a ‘seasonal perennial’ specifically a tender perennial that needs to come indoors for the winter. Before we go into the two plants of the day, I need to cover one of the key aspects of maintaining a good Xeriscaping bed. For all of you regular readers this might sound like retread theatre but when it comes to Xeriscaping the most important thing is soil improvement and quality. Half of a plants tolerance for its surroundings comes from the soil’s ability or lack of ability to hold both water and nutrients. The other half lies within the plant’s own ability to retrieve and absorb moisture and nutrients which is a factor that you cannot change. So back to the soil, the one absolute way to improve the soil texture and quality is to add organic matter.
For those of us in the Southeast we face sand or clay dominated soils where as in the northeast the soils tend to be clay or slit oriented. Both have a similar problem, in that either the moisture or nutrient you add tends not to stay, in clay or silt soils it tends to runoff since water cannot penetrate. In effect a clay or silt soil often ends up compressed and thus is rather like a colander with holes so tiny virtually no water can pass in any amount of time to allow any actual drainage. Sandy soils in comparison tend not to retain water or nutrient as the individual sand particles are large enough to act somewhat like a colander with extra large holes basically remaining damp but not holding onto anything.
The addition of organic matter to either soil base effectively changes the soil structure. Using the prior metaphor, adding organic matter to a silt or clay is akin to filling the colander with large chunks of sponges, the water no longer sits and the lack of drainage becomes less of an issue. Those sponges present more surface area to spread out the water and allow slower evaporation. Using the same metaphor as before; in the case of sand adding organic matter is a little like lining the colander with loose layers of sponges. The effect of this is that water is slowed down in it’s drainage but its clear where you can see the difference between what you add and the parent material. The effect of these additions is better retention overall.
In short, the addition of organic matter can rapidly improve the quality of any soil as it improves the ability to hold moisture and nutrients over time. This improves your chances of success with Xeriscaping because it improves the tolerances of your plant selections. Further more soil quality can also make already durable plants that are not traditionally considered Xeriscaping plants into drought tolerant plants that can be used in drought situations. Good soil quality can in fact make normally soil-insensitive plants grow to greater dimensions and proportions and read an otherwise greater potential then noted. The easiest way to improve a garden bed is either by use of compost, as a good organic garden will have no shortage of compost. The other way to improve it is to add in high quality topsoil at a rate of two parts top soil to one part native soil. A third alternative is to topdress your existing beds with either compost or topsoil at an average depth of 1/4th and inch. With that said onto the first plants of this plant series.
As you well know climate change is a problem we face despite what certain pollution-oriented industries say, knowing this; we can skill keep beautiful gardens if we select plants for their ability to withstand drought and heat. The measures we take also can have far-reaching effects on the survivability of these plants and our gardens. Today’s plants come from the Artemisia and Aloe families.
Artemesia absinthium – Wormwood
Artemesia dracunculus - Tarragon
The Artemisia family is notorious as far as herbs go, while related to the invasive weed/herb Mugwort (A. vulgaris) these particular herbs take heat dryness and humidity and seem to laugh at it all. A well established stand of either even when planted in poor soil will do quite well forming a respectable stand about 1-2 feet high. Wormwood itself has been extensively cultivated beyond its natural form into varieties such as ‘Powis Castle’, ‘Silver Mound’ and ‘Lambrook Silver’. Despite the cultivation all wormwoods can form mounds of dense silvery-grey flower comprised of fine textured foliage. Ff cared for and provided better then average soil and additional fertilizer can form a extremely dense ‘canopy’ of growth that can block most weeds. One additional advantage to Wormwood is that you have the ability to make assorted Liquors and spirits and can with some preparation make medical remedies for parasites and worms.
Tarragon in respect is coarse and rangy looking, with its large flat needle-like foliage. Unlike wormwood tarragon is more upright, rangy and lacks the neat mounding form that is trade mark of the above herb. While tarragon has its use as a cooking herb and that fact cannot be discounted and it’s a darn good herb when accompanied by rosemary and savory it also has a unique use in the garden as an ornamental. Few realize that a healthy tarragon plant can reach between 1 and 2 ½ feet tall in a growing season forming an upright flame shaped plant with fine green lacy foliage not unlike an entirely upright fern for full sun.
Aloe vera –Medicinal Aloe
(Aloe vera is sometimes listed as: A. barbadensis, indica, perfoliata, vulgaris And yes this one is quite pot bound.)
Aloe quicksilver x 'Rare Flare' - Silver Ridge Aloe
(For note this specimen is VERY pot-bound.)
Aloe haworthioides var. aurantiaca – Faux Haworthia
(This little guy was repotted into the above 4" round recently from a 2" round in which it was pot bound. A special thanks goes out to Jen Smith at CFBG for giving the test gardens this specimen.)
The Aloe family is noted in the eastern climates as a houseplant and this reputation is absolutely deserved. For most of the eastern coast and with most of it’s cultivars it cannot tolerate winter freezes. In USDA hardiness zones 9-11 a select few aloes are full outdoor perennials year round but may need some special considerations for unusual weather fluctuations. Our first aloe is without a doubt the most well known, there is no shortage of skincare products that incorporate Aloe in their mixtures. There are even beverages based on Aloe gel on the market. Few realize this useful herb can be kept outside in full sun after the last frost date in spring up until the first frost date in fall. Even then aloe can be kept in an unheated but glass-enclosed sun porch for most of winter if one keeps an eye out for exceptionally cold conditions. In the garden for the purposes of Xeriscaping aloes can be utilized in pots or in temporary plantings amongst other Xeriscaping plants to add sharp angles and unusual colors. Normally most aloes are thought of as glaucous grey-green plants with elongated triangular leaves but when exposed to full sun they often take on a reddish cast that disappears once returned to the indoors.
In the case of the Silver Ridge aloe it is known for its corky ridges on the leaves and a pale silver-grey coloration. Unlike medicinal Aloe, Silver Ridge forms dense contained clusters of small offsets that as the picture above will attest are quite striking, appearing like silver-speckled stars when viewed from above. In a Xeriscaping setting its best paired with plants with darker more rounded foliage that are trailing or low-growing.
The third and final aloe of note in today’s post is a rare one. In respects the Faux Haworthia or Aloe haworthioides var. aurantiaca this particular species has been heavily selected and hybridized to the form you see in the picture. It looks like a haworthia but is actually an aloe. In truth there are few examples of the originating plant, as it is apparently somewhat rare in nature and rarer in cultivation. For note the common name listed above is one I’ve stuck on this plant due to a lack of a common name in any reference to the plant. In the garden it’s an excellent contender for use in ornamental planters such as cement urns when paired with certain types of sedum and other succulents.
As a final note to the Aloe family, these plants are some what fond of being pot bound. The moment they are heavily confined for any length of time they immediately begin to produce flowers. The flowers are borne on 6-12" long stalks in clusters and are usually any mixture of red, pink, orange and yellow in color. Generally the more heavily pot-bound an aloe is the more often it will flower. Though I would not expect an aloe to bloom more then twice a year. Additionally, it is important to note that all aloes are susceptible to root and crown rot, so their potting medium should have excellent drainage or if it is not limit watering as much as is possible. A recently watered aloe will have swollen looking leaves where as a dry one will have emaciated slightly curled leaves that are thin and rubbery feeling. During the winter make sure to only water an aloe when it is dry, and allow the soil media to dry out until it is light and the plant seems heavy between individual watering times. Avoid wetting the crown of the plant and avoid watering at night to reduce the risk of any rot setting in.