Practice No. 5. Revitalizing Beds and Borders
Many of our landscapes are already in place or have been in existence long enough where some revitalization needs to take place. Revitalizing unamended beds and borders presents a more difficult task than if one started a bed from scratch. It would be ideal to incorporate 3 inches of compost for low water-use zones, 4 – 8 inches for medium water-use zones and 6 – 12 inches for the high feeding, high water-use zones, such as vegetable beds and bluegrass/fescue turf. This is much easier to do in beds of annuals or vegetable gardens where one starts fresh each spring (or fall) than in shrub and herbaceous perennial beds. Revitalizing established beds and borders that haven't previously been amended is a longer term project, not a quick fix.
Adding organic matter throughout a bed is admittedly difficult in heavily planted beds and borders. Carefully digging or aerating around established plants is necessary, so as to minimally disturb the roots. If your bed has plants that can be dug up before revitalization and replanted after amending the soil, do so.
Pull back or scrape off and save the mulch cover. Depending on the amount of clear ground and maturity of the remaining plants, either dig with a garden fork loosening the soil and apply 3 inches of compost, carefully digging this into the soil, trying not to disturb roots. If you find this isn't practical, scratch the surface of the soil with tines before laying down the compost or compost blend. Even just plunging the fork into the soil will begin to aerate it, with compost or wormcastings falling down into the holes just created with the garden fork. Adding organic amendments in this manner may need to be made over a period of years.
Compacted clay and caliche soil will benefit with the addition of inorganic material. I recommend adding an inorganic amendment such as Turface® (calcined clay), Tru-Grow® (expanded blue shale), Ecolite® (Zeolite) or Axis® (diatomaceous earth) for heavy clay soil, and Profile® for sandy soil or other brands of the same materials. Follow the recommendations on the bag for quantities to add per square yard. Other inorganic amendments with much more limited ability to retain water and nutrients are crushed granite, granite and lava sand, greensand, glass sand, and finally, regular sand. Be careful in adding inorganic amendments with low water and nutrient holding capacities to soils with low organic content, such as sands; organic matter must be added in conjunction with them. Otherwise you could end up with worse soil, mimicking brick.
In bed revitalizations, renovations, makeovers, and annual beds, the ideal time to add the compost is in the fall, giving the microbes the winter months to repopulate and grow. If the plants suffered root damage in the revitalization process, they will have the cooler winter months to recover before the major stress of summer is upon them. Monthly foliar spraying during the growing season with fish emulsion, liquid humate, molasses, and/or kelp/seaweed, trace minerals, aerobically activated compost tea, worm tea and other microbial stimulants are beneficial when getting started.
If you find you are unable to do any digging or scratching of the top of the soil, mulch yearly with a top quality compost blend from 2 to 3 inches thick and make at least three foliar applications during the growing season. Monthly, for three years, would be better (April through September). Better results will be realized sooner with the incorporation of solid organic matter into the soil. Replenish the mulch cover as needed.
Whenever replanting in beds or borders, refurbish the plant hole with Yum-Yum Mix®, compost and/or other inorganic and organic amendments.
My low water-use beds that were amended in 2000 are just as vigorous years later as at the first. The only revitalization I do is broadcasting Yum-Yum Mix® and granular humate to the top of the bed once a season. I include these beds along with the others when doing any foliar spraying.
Let the leaves fall and remain in place to decompose in the beds adding to the soil's richness. If the leaves are large and thick, rake them into the lawn and mow, returning them to the beds and borders chopped and shredded. They will decompose quicker and not mat down. For spring clean up, if you wish a tidier look, rake the leaves that have blown in over the winter, mow, and return to the beds and borders.
I've practiced this procedure of leaf recycling throughout my garden. One day after about 5 to 6 years, I dug into a shrub bed that included a tree to see what the soil felt like. Having grown up in Wisconsin and walked the forests floor, I was surprised to find this border floor nearly as soft and porous, filled with life. It can be done if you give nature a chance.