Copyright © 2005 Tammy Clayton
The end of Februrary already? My how time does fly! The sun has already become more readily available than in the past few months. Perhaps more cold and clear, but those candle-hours are important to the sleeping natural world; it is their built in clock. You cannot lie to a plant, it knows what time it is. Far more intelligent than one gives them credit for.
As you plan what to add to your garden this winter, I am sure you are paying attention to the light and water requirements all good perennial vendors attatch to each entry in their catalog. This is very important to your success with each plant. But it is possible to mix more drought loving plants with those that require more moisture in the same planting with good results. The secret lies in the substructure of each given plant's area in the bed.
Drought lovers do like some water, they will reward you with a much more beauty with some weekly water...in a drought bed. But what if you want to put say - lavender and phlox in with lobelia and ligularia? Those water requirements can really hamper one's creativity! So some knowledge of drainage engineering will give you the ability to try mixing them in the same planting area. Lavender and Phlox like drier conditions. Not that the Phlox will die in a spot where daily overhead watering is recieved. It will survive and grow huge, and flower excessively, but be stricken with fungus that makes the lower leaves yellow, icky looking and then become half defoliated. Ground watering is it's preferred daily moisturizing treatement. One can place it in a corner the sprinkler doesn't hit and water that section by hand once or twice a week and it will reward you very nicely indeed. Since Phlox is rather tall, this avenue of placing it in the back corner works out well. It likes the moisture but not on its leaves. Roses fare better this way as well, especialy since one cannot control what the heavens will pour down. Less black spot and such other marring problems will occur, if ground water is used vs. overhead.
Lavender on the other hand loves it hot and dry. It doesn't mind what heaven pours down IF there is a good drainage structure where the roots are. Too much water retention and it will slowly die. To conteract good soil water retention where one would like to plant the ever so beloved lavender row, a blind drain is required. It is called "blind" because on the surface you do not know that it is different from the rest of the area. In a planting area that is scratched once or twice a month some of the substructure will mix into the top surface and change the color of the topping soil. But once the bed fills no one will see this. (Surface scratching, by the way will put much needed air tunnels to roots, create more water availability to roots, and lessen the amount of weeding one must do, if it is done twice a month.)
The smaller the particle size of soil, the moisture it will retain. Clay having the most minute pieces and sand having the largest. Each person's garden area will have a totally different soil structure. If you are in hard clay, I would advise that either you excavate 6" of clay and fill with 7 inches of peat/topsoil 50-50 fill OR raise the bed at least 6 inches above the harsh environment of the clay. Raising it is much less labor than excavating! Not too many things will do nicely in clay. The only way around it is correction. Once you have nice workable soil, with good moisture retention, yet good drainage - you can go about planning what goes where and how to amend each area for certain plants.
To get good drainage, you need to go down at least 4-6 inches, depending on the plants requirements. SHARP drainage is engineered with pea gravel in a 2" layer, followed by 2" of coarse sand, topped off with 2" of your rich garden soil. In times of extreme moisture the worst of it will lay in the gravel bed. The gravel there also holds more heat than the moisture retaining soil, therefore using the warmth to do away with excess water faster. Variegated irises planted with a bed of road gravel 4" beneath the surface will grow three times more lushly than those in average garden soil - they love that heat! Heat and drought loving plants are much happier in that environment when regular water is recieved. It is the retention that causes decline and not what comes from above. More moderate drainage would be created using 3" of sand and 3" of soil on top. Since each plant has different needs, your engineering of drainage will require a bit of working on. But it opens doors to what you can put in a planting as happy bedfellows that no drainage field would never allow you to attempt.
Plants such as Ligularia need loads of moisture. To truly enjoy these types of plants you must keep the soil moist at all times. So to plant these in a happy spot, average garden soil (50/50 peat-topsoil mix) must have good composted humus worked in and layed on top as a mulch. This holds water and coolness where it is needed for the roots to stay wet enough. Another neat trick I have seen that might aid in keeping these hungry types lush would be a water reservoir or two at their bases. Using an inverted 20 oz. pop bottle with the cap on and bottom cut off. Then 3/4 of the way up the bottle poke a small hole every inch. The water in the reservoir only leaks out when the water in the soil is depleated. So it slowly oozes moisture where it is needed. Refilling it would depend on the heat index and the amount of rainfall or irrigation in a given spot. To keep the soil from filling the bottle, a peice of landscape fabric, a hunk of old polyester fabric, or even the foot of an old nylon stocking, rubber banded in place allows moisture in while keeping most of the dirt from washing into your reservoir.
If tulip bulbs are rotting in an area due to heavy spring and fall moisture a more aggressive drain system is needed that will carry the water down and out more quickly. Water runs down hill, so an incline to your drain bed is needed. The more water, the more layers of decreasing size fill is needed and the deeper one must go to drain the area. BEWARE! Sometimes you can over do drainge and even daily watering will not keep things moist enough! If that problem occurs, excavate and change your "recipe" to lessen the sharpness of draining. As with all things, experience is good guidance as to what is enough and what is too much. Heavy water problems can be solved with this system. The bigger the area, the bigger your drain field. Using successive layers of 1-2" roofing stone, pea gravel, coarse sand and topsoil or garden soil. Some drains go down a whole foot or more. The layered field can also be used with slotted tile pipe in a sock, attatched to solid pipe in some severe situations. A one to two inch decline over many feet can take a "pond" in your lawn or garden out to the woods or curb; to an area that it is no longer a detriment to whatever you are trying to grow in that spot. This same system was used repeatedly over the coarse of decades by my father who specialized in "corrective drainage" while in the landscape contracting field in. We employed it in many planting areas of customers yards with much greater success of what we could grow in any given customer's yard. (It was also used to correct basement flooding.) This will widen the choices of what you can grow together under "normal" garden conditions quite a bit, no matter what your limitations are at the moment.
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About the Author
Raised by a highly respected & successful landscape contractor in the metro Detroit area, Clayton wanted a career in anything but landscaping! Now an award-winning landscape designer, Clayton runs Flowerville Farms, a mail-order nursery in Michigan. Read more at LostInTheFlowers.com.