There are two optimal times of the year to root English Boxwood. Late February / early March is an excellent time after the major freezes of winter are over and before any new growth comes out in the spring. The other optimal rooting period is late June or early July after the new growth has matured. Our experience of rooting at English Boxwoods of Virginia has shown us that both of these times are equally effective. The timing may be based on when you pluck your plants (see “plucking”). An effective sequence is to pluck plants in March prior to spring growth, and then use these cuttings for rooting at the same time. Plucking in July will not harm plants and the cuttings may also be used at this time of the year to start new plants.
Taking these cuttings accomplishes two purposes. It thins the parent plant, allowing light and air to circulate within it, and secondly, it obviously gives the beginnings of some fine new plants. One reason to root in February is that the parent “plucked from” plant fills in very quickly, with new growth, any gaps created by the thinning process. If July is chosen as the thinning / rooting time, one has to wait a little longer before the new growth appears. A small flush may occur in the fall, but this is typically not a significant growth period nor a desirable time to encourage new growth. New growth in the fall is very easily damaged by early frost and freezes. Although this damage does not hurt the plant, it affects the appearance until the spring growth covers it up.
In the early years, we rooted by putting the cuttings in a bed heavily mixed with sand. It worked very well but the downside was that this method required the plants to be repotted in the spring from the bed to a pot, thereby disturbing the roots.
A much more efficient method is to put small pots in trays, fill with the pine bark mixture that all nursery growers use in their pots, and root right in the pots that the plant will spend the next one to two years in. We use two different size pots to root in. One is approximately 3 in. deep and the other 4 in. deep with a correspondingly larger diameter.
When preparing a cutting for rooting, take a single stem cutting and clean any branches off of the lower 3 in. or so. The cutting itself can be a total of 6-8 in. in length before planting but it must end in a single stem, otherwise you end up rooting multiple plants in one container and this will eventually lead to multiple plants in the same pot which is really not acceptable.
Rooting hormones can be used but we do not simply because of the large numbers that we propagate and the fact that they grow roots within three to four weeks anyway with about a 90 – 95% rooting rate.
To plant a cutting, grab the stem between your thumb and index finger leaving 3 to 4 inches sticking out to insert into the soil. The soil should not be real loose because you want it to be tight around the stem to facilitate moisture transfer. If soil has just recently been placed in the pots, watering heavily will tend to solidify and compact it. As you insert the stem into the soil, push down on the soil with your fingers to compact it around the stem.
If propagation is to occur in the heat of July and August the operation should be located in the shade. The cuttings should be kept moist while working with them and after being planted in the ground. In our operation, an automatic watering system mists the plants for only about a minute but it does this 6 times during the daylight hours when the heat is the most intense. This schedule is gradually reduced over time. If shade is not available, shade cloth supported by hoops, shades the plants from the direct rays of the sun which is very important.
Cuttings develop roots very quickly. In mid-summer roots are often visible on a cutting two or three weeks after they have been placed in the beds. Within six weeks cuttings are often “difficult to pull up” which indicates that they do not need to be pulled up; you know that the roots are there.
Stephen D. Southall
English Boxwoods of Virginia