Tag Archive | overwintering

Bringing Hibiscus Indoors

Over-wintering large, flowering tropical plants like Hibiscus rosa-sinensis is always a challenge. They never thrive in the living room the way they do outdoors. Leaves turn yellow and drop, flowers seldom appear. Assorted pests do appear — in droves. No wonder gardeners dream of exiling these shrubs to the basement, where they can be out of sight and out of mind until spring.

This kind of hibiscus never sleeps, however, and trying to store yours as though it were dormant may give you a rude awakening. If you want to try it anyway, keep the plants cool, 45º to 50ºF. Expect them to drop all their leaves. They will likely get bugs. And they will still need to be brought into light well before summer planting time.

A better choice is a room that gets lots of light and is cool enough to slow growth, 60º to 65º. If you must put hibiscus plants in the living room, keep them in the sunniest place, away from direct heat and far enough from the window so they don’t suffer big temperature swings from night to day. There is no point in misting, but if you don’t have a humidifier this would be a good excuse to get one. Keep the soil barely but consistently moist, and don’t feed unless flowers appear. Watch out for aphids, whiteflies, and red spider mites. If you see them, treat promptly with insecticidal soap.

Hibiscus is tough. The plants will not be glorious inside, but they will survive. Cut them back in late April, removing leggy branches and working to create a pleasing shape. New growth should start almost at once. It is tempting to set the plants out as soon as the danger of frost is past, but hibiscus is a heat lover that will be happier inside until it is warm out day and night — late May or early June.

Alternatively, treat hibiscus as an annual indulgence. While they are still beautiful, give your plants to somebody with big windows and no qualms about getting rid of ailing ornamentals. Enjoy a carefree winter, and get new ones next year.

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Keep your Kale thru Winter

Once the days are short and cold, you can’t expect kale to keep growing. But you can help it survive almost indefinitely. The trick, which also works for Swiss chard and other hardy greens, is to keep the soil around the roots from freezing.

Start by applying a thick blanket of organic mulch — straw or shredded leaves. That will be enough if you are in zone 7 or the warmer parts of zone 6. If it’s colder, use bales of straw and old windows (or clear plastic) to build a lean-to cold frame.

Place a row of bales close to the long side of the kale row. They should be to the north if the row runs east-west, to the east if it runs north-south. Put another row on top so you have a wall about 3 feet high. On each short side, make a sloping wall by butting single bales firmly against the back wall, then topping them with partial bales.

Now use the windows (or clear plastic sheeting) to cover the front, making sure the cover does not touch the plants. At the top, windows can just lean against the straw. Plastic should be draped and held in place on top of the bales by rocks or a heavy board. At the bottom, where the cover touches the ground, mound on a few inches of soil to hold it and seal out drafts.

At this point, you should have a structure whose sloping, clear roof faces south or west. Use loose straw to fill in any gaps in the walls. That’s it. Throw a heavy blanket over the cover when night temperatures are predicted to fall below 20ºF; and open the frame at the top on warm, sunny days or you’ll cook your kale before you bring it indoors. Don’t try this with root crops; mice and voles will colonize the bales of straw if you feed them beets and carrots!

Summer Bulbs

Overwintering Summer Bulbs

by Diana Alfuth, horticulture educator for Pierce & St. Croix County UW-Extension

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Tender summer gladiolus

Summer bulbs cannot make it through our cold Wisconsin winters. If you want to plant them again next year, tender bulbs must be dug and stored once the foliage begins to yellow or is killed by frost. Cut the foliage to about 2 inches, dig the bulbs with a spading fork and knock off most of the soil. Don’t wash canna, dahlia or caladium bulbs, but hose off others, if needed. Discard any bulbs with spots or sunken areas, which may indicate the presence of disease.

Once bulbs are dry, pack them with some peat moss, sawdust, perlite, vermiculite or sand, or put them in thick paper bags and place them in a cool, dry place for winter. A root cellar, unheated basement or extra refrigerator can be used to keep temperatures between 50 and 65ºF, or 35 to 55ºF for gladiolus. Don’t store bulbs with ripening fruit, such as apples. The fruit gives off ethylene gas, which can damage bulbs.

Check the bulbs periodically over the winter. If mold is present, spread the bulbs out to dry or otherwise reduce humidity. Separate the bulbs prior to planting next spring.

Planting Summer Bulbs

from The New York Times column ‘Garden Q&A’

Summer bulbs are tropical types that want summer conditions. They will start sprouting when the soil is still less than toasty, but if it is downright cold, they’ll sulk, and if they sulk in soil that is damp as well as cold, they’re likely to rot.

So people in short-season areas have two options: the first is simply to wait for warm weather and then wait for flowers; the other is to give plants like crocosmias, acidantheras, and dahlias a short head start indoors.

Since you don’t want to have to worry about providing greenhouse conditions, wait until it’s near the frost-free date, then plant your summer beauties in a free-draining seed-starting medium like Pro-Mix. Water well, then set the pots (or for small bulbs, plug flats) where they will be warm but not hot, 60º to 65ºF. Add water only as necessary to keep the soil barely moist, and do not fertilize.

It should take a couple of weeks before sprouts show above the soil and start needing light, by which time the weather should be warmer. Set the plots outside in a sheltered spot where they will get plenty of sun but be protected from cold winds, and be prepared to move them indoors if the temperature threatens to go below 55ºF. Once you’re sure the weather has settled in a warm direction, transplant into the garden.

Overwintering Geraniums

8387268_origSometimes you have a perfect summer with conditions that have contributed to the most beautiful container of geraniums you’ve ever had. What to do in the fall — let them die off and try again next year, or attempt to keep them over the winter? If you’re tempted to keep them, you have some options.

The perfect solution would be a cool, damp basement (can you say cellar?), where you could just hang them upside down. Shake the excess dirt from the roots, but leave all that clings. Loosely tie a string around the neck area, where the stem meets he roots, and use this to hang them from a rafter or beam. They should get good air circulation; be sure they don’t touch each other or anything else.

A dry basement — as long as it is cool (35º to 45ºF) — is a distant second choice. In that case, you will need to pot them up and they will need a place that’s light. They should be watered thoroughly about once a month, but let them go dry in between — they’re hardly growing.

No matter which way you store them, remove buds and flowers, where the disease botrytis hides, and any leaves that turn yellow. Cut the plants back to 6 inches after planting them outside next year.

Even thought your geraniums appear healthy, they could have picked up at least one of the many diseases that affect geraniums during the summer. When they are ready to go back outside, the geraniums will be stressed from their winter treatment, but any disease organisms will be just fine so the plants may not be as healthy as you expect. Keep a little extra in the gardening budget for replacements.

Keep your Dahlias

dahlia-173799_960_720Dahlias will not winter over in places where the ground freezes, but they are easy to store if you have a cool place to keep them. Start by making labels while the plants are still blooming, so you remember which color is which. Wait until frost kills the top growth, then as soon as there is a dry day, cut off the dead foliage leaving stubs 2 inches long. Use a digging fork to lift the tubers; turn the clumps upside down.

Let the tubers dry a few hours, then gently remove as much soil as possible. Don’t wash them off, as the last thin layer of clinging soil will help protect them from shriveling. Line a large box with a plastic bag; then add a 4-inch layer of coconut fiber, dry shredded leaves, styrofoam packing peanuts, or sawdust. Place tubers stem side up on this bed, keeping them well separated. Nestle the labels into the clumps.

Completely surround the tubers with additional packing material, and loosely close the bag. Store in a dark place, ideally at 35º to 45ºF. When storage temperatures climb to the mid 50s, the tubers will start sprouting. Ignore short sprouts; they’ll be buried when you plant. Clumps that come from storage with long, pale stems, however, should be hardened off before being set out into the garden.

Dahlia tubers

Dahlia tubers

In the spring, as long as there are a couple of healthy-looking eyes (the buds from which the plants grow, located up near the old stem), even rather shriveled tubers will make decent-size plants. If shoots have started to grow, evaluate them before planting. If they are still small (less that 2 inches long), just bury the tubers as you would normally, a couple of inches below the soil.

If the shoots are long and pale, they will be too far along to bury completely; they’ll also be brittle and vulnerable to sunscald, so handle carefully. Toughen up the shoots by putting the tubers with their new growth in the shade for a week or so before planting. Plant the tubers at the normal depth, with the long shoots above ground, and continue to protect the shoots with a light sprinkling of straw for the next week or 10 days. The idea is simply to shade the bleached growth until it turns green, so don’t smother it with a heavy layer of mulch.

Plant Spinach Now

There’s a certain sadness about autumn cleanup and shutting down the garden. But one of the things to lighten a gardener’s heart is to seed some cold-tolerant varieties of spinach in the fall and let the young plants overwinter. By giving them a head start, you ensure that you will be eating fresh spinach salad next spring while your friends are still waiting for their seeds to germinate.

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Delicious spinach waiting for harvest

‘Fall Green’, ‘Vienna’, and ‘Winter Bloomsdale’ are varieties recommended for overwintering. Planting them up to the second week of October gives them a chance to develop a few leaves and roots before winter. They don’t need to be mulched; the leaves will get ratty through the winter, but the root system will be fine. When spring arrives, new leaves will sprout from the established root system.

If you have saved seeds, make sure they’re a variety that is designed for overwintering. If not, you can hold onto them until next spring. Theoretically, spinach seeds remain viable for three years if stored cool and dry, but germination rates often start falling by the second year.

Keep your Caladiums

Starr_071024-9740_Caladium_bicolorAre your caladiums so beautiful this year that you can’t face the thought of getting rid of them when the summer is over? Why not try to keep them until next summer?! They can be left in the garden into fall so that the leaves can continue working and the tuber can continue to grow larger. However, once frost is in the forecast, don’t wait — just dig, taking up the whole plants or only the tubers.

To winter over a caladium, put the tuber into storage immediately or pot up the whole plant and place it in a brightly lighted windowsill. By late January, the caladium is going to look tired and will need to rest before the tuber is repotted in the spring or planted in the garden after the soil has warmed up. Chop off the foliage, knock off the soil, and let the tuber dry at room temperature. Any condensation will encourage bacterial rot. Store the tuber in dry vermiculite or in a mesh bag (like an onion bag) in a dry place, ideally at 70º to 75ºF but never below 50º, making sure there is good air circulation. Remember: it needs to be stored dry!!

Caladium is an extraordinary foliage plant. Its leaves can be white with narrow green borders or combinations of white, green, and rosy pinks, in pale to outrageous patterns that approach a third grader’s first attempt at stained glass. Most caladiums are hybrids of Caladium bicolor or C. picturatum, native to the tropics of the Americas and the West Indies. Plants can be costly, but tubers are inexpensive so you can just say goodbye at frost time if you like.