Wednesday, October 5, 2016

Overwintering Your Plants and Vegetables

Why overwinter plants?

·       Well for one thing it's fun and easy and saves a ton of money! You can save all those gorgeous border dahlias and canna lilies and they will just be larger and more beautiful next year. You can also bring those tender tropical plants indoors to use as houseplants. Indoor plants improve our well being, clean the air and actually cheer us up! Just a word of caution- some plants are poisonous to cats and dogs and children! The Ontario Veterinary Association posts a list of potentially toxic plants. 

What plants can I bring in?

  • Most tropical or tender annuals such as begonia, geranium, coleus, hibiscus, impatiens, mandevilla
  • Bulbs such as cannas, callas, dahlias, elephant ears
  • Plants that grow easily from cuttings: geranium, begonia, basil, mint, coleus, impatiens
  • Some culinary plants can be dug up and kept on indoors
Plants can be overwintered by growing them on in the house, by starting cuttings or by keeping them in a dormant state or a semi-dormant state. How you treat individual plants depends on whether they prefer to keep growing in cool or warm conditions or whether they need to be kept in a dormant state.

Growing Plants on Indoors (Warm and bright plants)

Many garden plants can be grown indoors as house plants during the winter. Bring these tender plants in before the first frost hits! You can bring in the whole plant or start new plant from cuttings. 

Starting new plants from cuttings (i.e. begonia, geranium, coleus, hibiscus, impatiens)

Sometimes there are fewer pest problems with cuttings and the smaller plant size makes it easier to manage.
  • Cut a piece of the plant about 4-5" long (12 cm). 
  • Remove the leaves from the bottom of the plant. 
  • Place the cuttings in potting soil and keep moist until roots form. 
  • You can place a cut water bottle over the pot to keep the soil moist.
  • Reduce watering once roots have formed.

A bottle over your cuttings keeps moisture in and stops squirrels from digging up your plants!
Rooted Coleus cuttings- Unfortunately, the bottle doesn't stop the earwigs from making holes in the leaves!

To bring in whole plants

  • If the plant has grown too large, cut back to half or more and trim for shape if needed.
  • Remove any dead or damaged foliage.
  • Minimize shock by getting plants acclimated before bringing them indoors.
  • Start by moving the plant to a shady location outdoors a week before you want to bring it in. Bring the plant indoors during the night if the nights get too cool.
  • Inspect for bugs on the plant or in the soil; treat for bugs (i.e. strong spray with hose, insecticidal soap spray) or by immersing the whole plant in water. Repot plants in clean pots and soil to minimize soil pests in the home.
  • Place your plant in a sunny (east, south, west) location to keep it growing on; give plants a ¼ turn per week to keep growth balanced all around the plant.
  • Find the right place for the right plant; some prefer cool/dark, some a cool/light location; house windows vary widely depending on orientation, trees, overhangs etc
  • Inspect plants weekly for pests; treat as needed by using yellow sticky strips, soap sprays etc
  • Trim and remove dead leaves as needed
  • Pinch back plants if they get to leggy
  • Water when dry;  daily spray increases humidity and reduces pests
  • When the days start to get longer, and there is new growth, increase water and then start to feed with a dilute solution of fertilizer
  • Repot (if needed) one pot size up; use a commercial mix or potting medium of good compost/organic matter and  builder’s sand (for drainage); (
  • Move outside gradually to acclimate; first in the shade in a protected area, then to a sunnier location; plant out when all danger of frost has passed; this is usually after the May 24th weekend in southern Ontario

Other plant suggestions to try:

  • Rosemary: grow under lights; water once a week
  • Many herbs will grow in a bright window
  • Passionflower, Hibiscus
  • Clivia: needs cool and bright conditions
  • Mandevilla: prefers sandy well drained soil

Keeping Plants Dormant (Cool and dark plants)

General Directions

  • Plants that prefer the cool and dark can be kept in a dormant or semi-dormant state until spring.
  • Forcing dormancy is useful if you're short on space or want to save time and effort on winter care.
  • Start to decrease watering before bringing in. Most plants are brought in before the frost hits them.
  • Most plants will need to be severely pruned back.
  • Put the plant, either potted or with newspaper wrapped around its root ball, in a cool (not below 40°F/5°C), preferably dark place for winter.
  • Allow the soil to dry somewhat but not completely.
  • Check every few weeks and water/mist sparingly if needed.
  • Remove and discard any dead leaves, diseased, rotting parts.
  • In spring, repot the plant and resume watering.
  • Place in a warm, well-lit place indoors or outside after danger of frost is past. 

Specific Plants

  • Banana plants: cut back to stump; wrap root ball in plastic bag to keep moist; leave top of plant exposed
  • Elephant’s ear (colocasia, alocasia): cut back just above soil level and shake off soil; keep moist, not wet in plastic bag/pot
  • Brugmansia (Angel's Trumpet): I cut my Brugmansia back severely leaving one main stem and pot them up. They are kept semi dormant in the basement with minimum light and water. 
  • Agapanthus, Duranta, Pineapple lily can also be kept cool and dark
Brugmansia-remove leaves and prune off a branches but the main stem.

Bulbs (cannas, dahlias, Caladium spp. and tuberous begonias) 

  • Wait until after the first frost; cut back the foliage to about 3 or 4 inches; leave the bulb in the ground for eyes to develop.
  • Use a fork to dig up bulbs to avoid cutting bulbs; cut bulbs are subject to disease; brush off the soil and lay them out in a dry, airy, warm place for two weeks. (Dahlias-you can wash off the soil.)
  • Divide if necessary; one "eye" per tuber; you can also divide in the spring.
  • Overwinter in dark, cool (50°F/10°C), dry, yet airy surroundings, usually a basement. Medium: newspaper, vermiculite, wood shavings. Containers:  empty pots, shallow crates, pizza/pie boxes. 
  • The storage container depends on the type of bulb, corm or tuber.
  • Gladioli and bulbs with a papery husk: place in mesh bags with plenty of air circulation. Don’t water; check once a month and discard any that show signs of rot.
  • Dahlias, cannas, caladiums, tuberous begonias:  store uncovered in trays or boxes loosely packed with vermiculite/ dry peat moss/ wood shavings. Check every month to see that they aren’t drying out; mist or sprinkle a few drops of water over the vermiculite or peat moss to keep it plump; don’t overdo the water or rot may set in.
  • If plants start to sprout in early spring, pot them up and grow them in a sunny window or a cold frame if you have one. Large plastic bottles over plants can also protect plants.

Elephant ears are a bit large to bring indoors-but you can cut them back and keep them dormant

Challenges of Growing Plants Indoors

The three big challenges to growing plants indoors are having enough light and humidity and dealing with pests. 


Fluorescent lights and reflective white panels increase light levels
  • You can increase light levels with grow lights, compact fluorescent lights or LEDs. Aim for 12-16 hours of light per day. 
  • Placing reflective material (white cardboard) around plants can also increase light levels. 


  • To increase humidity, you can place your plants on something to elevate them from a shallow water source. (I have never had luck with the recommendation to place plants in a saucer with pebbles as the bottom of the pot is too unstable on the pebbles.) I put my plant pots on inverted thick lids/clay saucers in water filled trays/saucers. When I water the plants, the water drains into the saucer under the lid.
  • Weekly or even daily misting works wonders. 
Use plastic lids, clay saucers to elevate plants-trays below catch water and increase humidity


Yellow sticky strips are effective for flying pests
  • Inspect plants weekly; treat as needed and following instructions (i.e. insecticidal soap-need to spray 3 times over 10 days and rinse after spraying)
  • Mealy bugs; little fluffy tufts; wash foliage regularly; dab fluff with Q-tip dipped in alcohol
  • Scale: roundish, flat bumps on plants; the actual insect is hiding under the “bump”. These are really difficult to remove and treat! Rub/scrape off or hand pick the scale on leaves. Prune out leaves in large infestations. Dab with Q-tip dipped in alcohol. Insecticidal soap will work on the larva, but not adult scale. Horticultural oil will control all stages
  • Aphids, white fly: wash/spray foliage regularly; treat with insecticidal soap; use “yellow sticky” tape that is found in garden centres. 
  • Spider mites; tiny sucking insects on underside of leaves; they thrive in dry conditions; make sure you are watering properly; increase humidity around plants and spray/mist leaves; prune heavily infested areas; spray with insecticidal soap. 

Other Thoughts

  • Soil: use a good quality potting soil.
  • Limit the shock: don’t dig up, spray, repot, cut back, move all in one day! Cut back once it is in the house and looks healthy.
  • Watering: Some plants like to dry out slightly. Others like to be kept on the moist side. Lift the pot-if it feels really light, your plant probably needs water. 
  • Limit the shock: don’t dig up, spray, repot, cut back, move all in one day! Cut back once it is in the house and looks healthy.
  • Leaf drop is normal for some plants due to the shock of living indoors; they could still perk up; don’t water much if the plant has no leaves; new leaves produced will be better adjusted to indoor light
  • Decline: some plants may only just survive the winter indoors, but once put outdoors again, they brighten up!
  • Have fun! The worst that could happen is that the plant could die; and that would happen if you did nothing anyways!

What to do with Herbs and Vegetables

Herbs- Growing and Drying

I've kept this rosemary growing indoors in winter for several years. 
  • Bring in any container herbs, like basil, parsley or sage to keep them in active growth in a bright, south-facing window over the winter.
  • Keep the soil just moist.
  • They’ll continue to grow, but at a slower rate than in the summer due to winter’s lower light levels.  


  • You can also dry your herbs in the microwave to preserve them.
  • Try drying leaves of mint, parsley, basil, thyme, sage.
  • Rinse herbs and check for "critters". Dry with a dish towel. 
  • Remove leaves from stems. (For thyme, you can dry the stems and all and just rub off the leaves when they are dried.)
  • Place a layer of herbs on a sheet of paper towel.
  • Cover with a second sheet of paper towel.
  • Microwave for 2 minutes.
  • Open the microwave door for 2 minutes.
  • Repeat
  • Check how dry the herb is and repeat until the leaves feel "crispy".
  • Crumble and put into air tight jar. 
  • Your dried herbs will stay green all year!

I loved using "chives from my garden" when cooking
Microwaved dried parsley keeps green all year!

Tomatoes - Ripe or Green 

 Freezing ripe tomatoes
  • Clean, remove top core and any blemishes; freeze tomatoes whole in plastic bags or cut large tomatoes in quarters
  • To use in soups and sauces, just plop them in! Skins will come off easily if you do not wish to include them in the soup.

Green tomatoes

  • If you still have lots of green tomatoes and the frost is threatening, pick them and bring them indoors.
  • Wrap green tomatoes individually in newspaper and store in shallow boxes in a cool, dark space; they will ripen slowly over the winter; use as needed. Use shallow pizza or pie boxes.
  • For cherry or other small tomatoes, place them in cardboard egg cartons!

One year I still had a ton of "black cherry" tomatoes in late September and placed them in egg cartons in the fruit cellar. I was still using fresh tomatoes in April!
My bumber crop of "black cherry" tomatoes picked just before the frost

Egg cartons are great for storing green or unripe cherry tomatoes! Sort them by ripeness.

I put them in the fruit cellar and labelled the ripeness so I'd know which ones to start with!

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