Dear Jessica: I have some cactus plants that I bought at CVS about a year ago. Each pot contains three cactuses. I've always kept them by the front window so they could get some sun each day. I've liberally been spray misting them with water every several days. Within the last several weeks, one of the plants in each pot began to decline. I'm not sure what I should do.
_ Keith Amato
Dear Keith: Your ailing plants are Acanthocereus tetragonus (sometimes called Cereus tetragona, for short) and these types of cactuses require slightly more water than most others. They also prefer smaller pots. Cactuses in general should never be planted in glazed containers, as yours are, because the glaze prevents moisture from evaporating; and pots should always have sufficient drainage holes. In addition, sometimes pre-planted arrangements (especially some found at non-horticultural retail outlets) contain groupings of individual plants that look nice together but have different cultural requirements. A shade lover, for instance, might be planted with one that requires more sun to thrive. In your case, the plants' water requirements weren't compatible.
I reached out to the Long Island Cactus and Succulent Society for more information, and a representative confirmed, "This is totally the wrong plant in the wrong place. You can't grow a plant like that in a drainless-pot or with other cactus that need very different care. The people that put these pots together are to blame for the plants dying."
Your two cactuses cannot be saved, but you should repot the other two into a smaller, unglazed terra cotta pot with a hole at the bottom for drainage.
Dear Jessica: I planted a few small arborvitaes (I think they are Green Giants) last fall. I want to fertilize them but am not sure what type of fertilizer to use.
_ David Millman
Dear David: Arborvitaes and most other evergreen trees do not typically require fertilizer once they are established but can benefit from annual applications of a slow-release product, made in early spring, in each of their first five years.
Because they don't fruit or flower, the fertilizer you choose should be mostly nitrogen, which is the first number in the nutrient ratio indicated on the package label. Look for a first number that is at least double the second and third, such as 12-6-4, 12-6-6 or 20-10-5. Apply one-third pound (2 cups) per foot of the trees' height (10 cups around each 5-foot tree, for example), working it into the top 3 inches of soil and taking care not to allow the product to come into contact with the trees' trunks or roots. Water well.
When applying fertilizer, avoid inhaling the dust and heed other precautions noted on the package label.
DEAR JESSICA: I planted a honeysuckle vine three years ago but let it get out of control. Can I prune it back and start over?
_ Kevin Winther
Dear Kevin: Honeysuckle vines bloom on the previous season's growth, so when a few branches need to be removed or shortened, it's best to wait until just after the season's flowers drop (and no later, or you'll risk removing buds that will become next year's flowers).
When the vines are neglected and become a tangled mess as yours have (no offense intended), it's almost impossible to selectively prune branches, so a rejuvenation pruning may be in order. Doing so requires cutting the entire plant down _ nearly to the ground _ and the best time to do that is now, before it breaks dormancy. The benefit is that the plant will grow back quickly and in good form, but the downside is that you will have to sacrifice this year's flowers.
