Warm April days, with longer hours of daylight, herald the approach of a new growing season for plants. Some of your houseplants may be showing signs of new growth and may be ready for repotting. For most houseplants, early spring is the best time for repotting. The roots are in a state to meet the challenge of new conditions and the change to fresh potting soil is stimulating.
A plant usually needs repotting when its roots fill the pot. If roots show on the soil surface, or if roots are growing through the drainage hole, repotting is indicated. If new leaves produced are smaller than average, that is another sign that the plant needs a larger pot or fresh soil.
Some slow-growing plants, such as Ficus, Schefflera and palms, can remain undisturbed for several years if they are well taken care of. It a plant has already grown as large as you want it to be, you need not report it. Just remove some of the soil at the top of the pot and replace it wish fresh mix. Or transfer the mature plant to a clean pot of the same size, replacing some of the old soil with fresh.
Get set for your repotting project by assembling clean pots, drainage material and fresh potting mix. New clay pots should be soaked overnight in water so that when they are used the porous clay will not draw moisture from the potting mix. Old plastic or clay pots should be washed and scoured to remove old mix or deposits of fertilizer.
When repotting, use the next larger size pot. Do not use a pot that is too large. The roots need to be fairly snug in the pot; roots will rot in too much soil, which tends to retain more water than the plant can use. Some foliage plants, such as Ficus species, do very well when their roots are crowded. Many flowering plants tend to bloom better when slightly pot-bound.
Indoor gardeners are coming to rely more and more an prepared potting mixes sold in packages at garden centers, variety stores and by mail order. If you have only a few plants it is simplest to rely on one of these mixes, such as Black Magic, Pro-Mix, EnVee. Almost all are composed of sterile ingredients; those of coarse texture and high percentage of organic matter are best. The mix will be more manageable and less "dusty" if you moisten it lightly with warm water before using it.
Place pieces of broken pot or some gravel over the drainage hole in the new pot. A thin layer of sphagnum moss over this drainage material will help to prevent the mix from washing throught the drainage hole and will further ensure a free flow of water from the pot. Then start to fill the pot. Pour in a layer of mix deep enough so that when you set the roots of the plant on it the plant will be at the same depth in the new pot as it was in the former pot. The new soil level should be about an inch below the rim of the pot, to allow space for watering without overflow.
Next, start filling around the root ball, tamping with a potting trowel or applying gentle finger pressure to ensure good contact of the roots with the new soil mix. Keep adding mix until all exposed roots are covered.
Next, water. Really drench. Always use tepid water.
Newly repotted plants should have less than normal light for a day or two. Do not fertilize a newly potted plant for about a month. Be especially careful about frequency and amount of water; remember that initial drenching. Wait until the soil has dried a bit, then resume watering.
Thus invigorated, the plant will respond with new growth in a short time. Oxalis sources
I want to thank my readers whowrote friendly and appreciative letters about the column on Oxalis.
I have located only one local source of the Oxalis discussed in March 17 column. Bittersweet Hill Nursey, Davidsonville, Md. (telephone 301 798-0231) has plants of most of the kinds listed.
Mail order sources are Merry Gardens, Camden, Me. 04843, and Logee's Green houses, Danielson, Ct. 06239. As I recall, the catalogs of the two latter nurseries cost $1 each. Bulbs of some other kinds of Oxalis are carried by Behnke Nurseries, Beltsville, Md. (telephone 937-1100) and are listed in the catalog of Geo. W. Park Co., Greenwood, S.C. 29647.