Ask the Clark Gardener

Dear Fellow Gardeners:


September 7, 2011. Yes, we do have bananas – well, banana plants anyway – 60 of them actually. As visitors enter Clark Botanic Garden, they are greeted by a wide selection of plant varieties in Clark’s seasonal garden beds. Some have colorful flowers, some grow amazingly tall or wide in just one season, some have huge leaves that cause visitors to stop in their tracks and stare. Often, someone asks me for the name of one of these plants and jots it down on a piece of scrap paper. The next question is; “Can I just leave this plant in the ground year around?” I sigh, and once again have to explain to someone that we are looking at a plant that can’t stay out in the winter on Long Island, is not hardy, and cannot live through our winters. Disappointment crosses the questioner’s face, the pencil stub gets put away, and the scrap of paper is crumpled.

The plant that we are talking about is often tropical in origin. The impact of tropical plants in the garden is dramatic. And some are inexpensive enough to be treated as annuals, discarded at the end of the growing season (and purchased or started anew the next). Others can be wintered over indoors with just a little effort.

Here, at Clark Botanic Garden, our modest greenhouse gives us a little more flexibility in preserving our tropical plants. We will bring in some entire plants. We will take cuttings of others or plant offsets. Some have rhizomes or tubers that we will dry out and store in the basement of the Clark house over the winter. And for still others, we will gather seeds to start plants anew in the spring.

Here are a few tropical plants that you might want to start to experiment with at home to preserve from year-to-year:

First, our friend the banana. Those 60 banana plants at Clark are of the variety Musa kandarian. There are other varieties of banana plants that you can buy through catalogs, but, in my opinion, none are reliably hardy in our Long Island climate regardless of what the catalogs say. Banana plants can be kept alive indoors over the winter if you have a sunny area. That assumes that your banana plant is small enough to pot up and bring into the house, and that you have an area large enough to accommodate new growth during the winter. Bring in your plant around late October. If you are lucky, your banana might have developed an offset – a small young plant attached to the “mother” plant – which you can cut off (with some roots) and pot up. An offset is often of a more manageable size than the parent plant. If you are saving an offset, you can discard the larger parent plant. I’m seeing a good number of harvestable offsets with Clark’s Musa kandarian.

The next couple of plants are tropical plants often used by many strictly as house plants, Chlorophytum comosum, commonly called a spider plant, and Ficus elastica, commonly called a rubber plant. Bring these plants inside around late September or early October. This year, I used spider plants as border plants along one of Clark’s planting beds. I used two variegated varieties of rubber plants as taller plants in the back of a planting bed. Soon it will also be time to preserve these tropical plants indoors.

One way to over winter spider plants is to snip off the many plantlets that have arisen from the “mother” plants and pot each one up individually. These plantlets will develop their own robust root systems and will probably put out plantlets of their own before winter’s end. These, in turn, can be snipped off and potted up to root. That’s what I’ll do, and by next spring I’ll have enough spider plants to again use them as a border.

As for the rubber plants, one can pot up the entire plant and bring it indoors for the winter. If the plant is too large for your space, you can snip off a few inches from the top of the plant, including the growing point and two sets of leaves. Cut the stem just below the lower set of leaves and strip off those leaves, being careful not to injure the “nodes” on the stem that are visible where the leaf joins the stem. Cut back the second set of leaves to ˝ their size or less so that the cutting you have taken doesn’t look too disproportionate to the pot you are going to use for the cutting. Use about a four inch wide pot or even less. Too big a pot will encourage rotting of the unrooted cutting. Be careful not to injure the growing point of the stem. Insert the part of the stem with the bare nodes into a moist potting mix and over time new roots will begin to grow. I’ve found that it takes a fare amount of time for rubber plant cuttings to send out roots, so keep the growing medium moist (not soaking wet).

For immediate gratification, not much can beat wintering over efforts for Ipomoea batatus, the sweet potato vine. Prepare cuttings, in September, as I described above for the rubber plant, but the cuttings by nature will be smaller, so that you can start six in a cell pack you may have saved from your summer planting. I’ve had sweet potato vine cuttings show roots in as little as a week. In fact, I’ve had cuttings grow so well in the winter that the plants were transplanted to four inch wide pots and then became pot bound well before the spring arrived! That enabled me to take cuttings from those new plants and start even more.

Wintering over Caladium x bicolor doesn’t require much space because one lets the tubers go dormant. Around early November, caladium foliage will probably be well on its way to dying away. Dig up the tubers, clean them up and store them away in a cool place (about 50 degrees). I store the tubers in dry peat moss in a covered bucket with a few small holes punched in the cover to provide some air. And that’s it! Next spring, I’ll take out the tubers, start them in four inch pots, and in a few weeks put them in the garden for another summer. Restart the tubers in late April or May, when the weather is warm and settled. If you forget to start your caladiums in the early spring gardening frenzy, do not fear. I’ve had caladiums refuse to grow well or at all until the weather warms up.

These five plants are just a sample of tropical plants a homeowner can winter over without a greenhouse. There are many others to experiment with. Consider saving the roots of canna and colocasia (elephant’s ear); taking cuttings of hypoestes (polka-dot plant), strobilanthes (Persian shield), anternanthera, or plectranthus; preserving whole plants of cordyline, sansevieria (snakeplant), agave or brugmansia (angel’s trumpet); and saving seeds of ricinus (castor bean).

Come, visit Clark Botanic Garden as Summer ends and Fall begins. Explore our new website. And, remember, if you have a comment, horticultural question, or general question about Clark Botanic Garden, remember to send them to me at CBGardener2@gmail.com.

The Clark Gardener

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