HOUSEPLANTS CUTTINGS AND SEEDS - Greenhouse Vegetable Gardening (2015)

Greenhouse Vegetable Gardening (2015)



Houseplant enthusiasts—with or without interests in any specific flowers—can derive great pleasure from a greenhouse and/or outside room. Many houseplants suffer when they spend winter inside our homes, because we not only get less natural sunlight though the windows during the day, we also tend to keep our heating cranked up too high.


It was easier in the past to store or keep houseplants over winter: They were usually placed in the parlor, a room that was only heated over the holidays and at special occasions. Some homes also featured a glassed in veranda, or had a root cellar or other kinds of cold storage. In order to ensure that a plant survives winter (if there’s not enough sunlight), you need to lower the ambient temperature of the room. It follows that darkness in conjunction with higher heat is not a good combination for plants, with the exception of African violets. The best way to keep plants happy during winter is to provide a cool environment with as much light as possible. Since houseplants often require both a lot of light and a lot of heat, overwintering them in a cold greenhouse is not an optimal solution; the greenhouse can be useful, however, in rejuvenating houseplants in the spring. When the time comes to prune the plants and pot them up, a warm greenhouse is the ideal place to work in.

Tall, winter lanky plants that have been pruned and then placed in a cool and lighted area will grow many new and healthy shoots. The change freshens up the houseplants and makes them bushier. Compare the shoots grown during the winter with the new ones from summer—you’ll notice that the spacing between the shoots is shorter, the more light the plant receives. On the other hand, shoots with leaves that are few and far between, and leaves with long shafts, indicate insufficient light.

Propagation of houseplants

Shoots that are pruned off the plants can be used as cuttings for new plants. A mini greenhouse with a bottom-fed heat source is a great tool for growing new roots quickly.

How to’s—Propagation by cuttings

♦ Cut off the houseplant’s long, lanky shoots.

♦ Take the cut-off shoot, and snip off the stem right under the leaf axil. Depending on the type of plant you’re cutting, you’re left with the top bit and two to three leaves.

♦ Remove the lower leaf.

♦ Fill a pot with soil, tap the soil down, and water it.

♦ Push the stem down about an inch into the soil.

♦ Enclose the planting in a plastic bag, and place the pot in a mini greenhouse or frame.

♦ Air out the mini greenhouse regularly to remove any condensation that has accumulated. Some mini greenhouses feature small vents that can be opened; or just leave a gap between the box and the lid. Turn the plastic bag inside out, shake off the droplets of water, and replace the bag over the planting. If there’s a lot of condensation, leave the plastic bag open at the base instead of fastening it underneath the pot to seal it tight.


Saintpaulia (African violet).


A collector’s greenhouse filled with all kinds of geraniums.

A bag or a lid is necessary so the cuttings don’t dry out before they’ve had time to grow roots. Plants breathe out water through their leaves, and absorb new moisture through their roots. Cuttings don’t have any roots yet for taking up water, so they must be in a humid environment to avoid drying out. However, there is a limit to how much moisture is beneficial before the cuttings start to rot, so there needs to be a balance between cutting and soil humidity. After one or several days, the condensation will have been aired out, or the excess water wiped off the lid. When the lid shows just a slight mist, the humidity level is just right.

Leaf cuttings

Rex begonias, cape primrose and African violets can all be propagated through their leaves. One single leaf can produce lots of identical plants. African violets grow new small plants at each leaf shaft stuck into the soil. Other houseplants propagate through roots or rhizomes, such as cupid’s bow (also called orchid pansy), or tubers like gloxinia. There are plenty of houseplants from which to choose to try your hand at propagation.

Seed propagation

A lot of houseplants are propagated through division, like clivia (also called natal lily), or through the formation of small side plants, like spider plants or hen and chicks. Many plants can be grown from seed, such as coleus, parrot leaf, calico plant, and Joseph’s coat. The greenhouse is the perfect place for sowing seeds during the warmer season, as is the mini greenhouse (with bottom fed heat) during the spring. The new plants fill out, grow beautifully colored leaves, and flower earlier. Some plants take a long time to germinate, so the greenhouse is their best bet to grow strong enough during this start-up period.


Many houseplants, such as geraniums and Christmas cacti, like things cool but frost free, with temperatures around 8°C to 10°C (46.4°F to 50°F). At right: pelargonium from seed.

Persian violets, pelargoniums/geraniums, fuchsias, browallias and passionflowers are all easily grown, but need a bit of time and a lot of light to grow handsomely. Many plants can be used in different capacities, as houseplants, greenhouse potted plants, and as outside bedding plants. Their roles are fluid, and the greenhouse only increases your choice of plants’ function. Sow according to the instructions on the seed packet, and follow the instructions for summer flowers (see chapter 5, page 40).

Buy cuttings and small plants

There are many cuttings and small plants for sale in the spring, so it’s a great opportunity to buy many plants—from the exotic to the more elegant—at affordable prices. Set them in nutrient rich soil and place them in the greenhouse or on a glassed-in balcony or deck, and they will grow and flower profusely. When you move them from greenhouse to an in-house setting they will become deprived of a lot of light, so the best time for this move to take place is during the summer or early fall, when there is still plenty of bright light outside. The plants will then have time to grow accustomed to the lessening daylight as fall sets in. It’s much worse for them to move them directly from a bright greenhouse to a dimly lit living room, and that’s the reason why some store-bought houseplants turn pale and dismal looking only after a week or two.



Pelargonium/Geranium ‘Carmel’.

The collector’s greenhouse

Pelargoniums/geraniums and fuchsias belong to a niche of plants in which there’s an enormous range of flowers. For you, the collector, a greenhouse is the perfect environment to cultivate your own specialty plants.

Pelargoniums/geraniums and fuchsias are profusely flower-rich plants, with extraordinarily long blooming periods. Geraniums and pelargoniums are especially suited to growing in the greenhouse because they rarely suffer from insect infestations.

Many rare or exotic geraniums, like the rose geranium, prefer to have a roof over their heads—even in the summer—and are sensitive to wind damage. The stacked blooms rot easily if left in the rain, and the heavy stalks can easily snap.

Plants are usually very sturdy and hardy when they’ve spent the whole summer outside or in the greenhouse. They’ll flower long into the fall, and if they’re given an ambient temperature of 7°C to 8°C (44.6°F to 46.4°F) and a glassed-in veranda or balcony, they may continue to flower during the winter.


Fuchsia: ‘Rahees Prins’.

They can stay in the greenhouse in wintertime if the temperature is kept above freezing. They overwinter better in a light and cool environment, even if they do also make it when it’s both dark and cool. While the fuchsia is less sensitive and copes better with both dark and cold conditions, it does attract white flies easily, so you’ll need to fight them with a horticultural pesticide. Leave the pots’ soil slightly moist, and don’t let them dry out completely during the winter. There are a few cultivars that can overwinter outside in the southern regions of Sweden.

It’s easy to propagate pelargoniums/geraniums and fuchsia in the greenhouse through cuttings—the plants receive light and as they develop, they produce lots of shoots instead of bolting into lankiness. The greenhouse is also eminently convenient for messy work like potting up and pruning.

Another tempting plant for collectors is angel’s trumpet. It produces glorious flowers and green, lush foliage. These plants aren’t hardy despite their large size and energetic growth—they’re best grown in pots or boxes. Start out with a small container, and pot up several times into larger and larger containers through the season. You will soon have flowering angel’s trumpet trees in the greenhouse that can even be moved outside on the warmest days. There are many types of angel’s trumpet—color and size vary widely—and they can even come in double flowers. Something to keep in mind is that these flowers are heavily scented. They will overwinter well at 5°C to 10°C (41°F to 50ºF)—the same temperature as citrus and camellias. Luckily, they can successfully overwinter in the dark, so they can be kept in a root cellar, a garage, or a heated outside barn.


Angel’s trumpet.

Visiting houseplants

You can get more mileage out of your houseplants in summertime by letting them take a vacation in—and also add a decorative touch to—your greenhouse. Many houseplants enjoy spending their summer in the greenhouse, where they can stockpile needed energy for the winter ahead. They have no issues with overwintering, since they’ll be moved back into the house once fall arrives. They benefit from the additional daylight and humidity in the air of the greenhouse, and they’re easier to care for because you can water them without any constraints. If you happen to be taking a holiday also, it’s easier to ask a neighbor for help with watering the plants, since they’ll all be assembled in one convenient location—the greenhouse.

Evergreen plants such as ivy, golden pothos (also called devil’s ivy), cissus, rex begonia, monstera and dieffenbachia all need a growing space in part shade to full shade. They can do perfectly well placed on the floor. Flowering plants like hibiscus and wax plant like to be in a sunny spot. However, even they need a bit of shade over the first few days or else they will burn. Cacti and succulents need sun and only need to be watered sparingly.


Orchid cactus.

Take the opportunity to shower your plants often while they’re in the greenhouse so they grow healthy and look their best. If you want new sturdy growth, it’s good to prune the plants as you’re moving them into the greenhouse. Water regularly with fertilized water, but shower the plants with clean, lukewarm water. Aphids and white flies are common pests, as are thrips. The best way to get rid of them is with regular showers and a treatment with a horticultural pesticide (carefully following the instructions on the packaging). Keeping many plants in one location increases the risk of pest attacks—even troublesome slugs can crawl up sides of pots to get at the plants. Collect and kill the slugs, and spread slug bait in the pots if they become a persistent problem.

The greenhouse is a pleasant space in which to spend time, and which allows you many opportunities to develop a green thumb. If your interests pertain to a more specific area, such as orchid cultivation, you’ll need—in addition to a significant fount of knowledge—a more sophisticated greenhouse. There are many associations for enthusiasts and collectors to exchange experiences, and to seek out advice and help. In order to be used for orchid cultivation, the greenhouse needs year-round heating, proper lighting and special care—topics that are beyond the scope of this book.