Category: October in the Garden

  • How to divide and store dahlia tubers

    How to divide and store dahlia tubers

    dahlias make cut flowers
    Dahlias make wonderful cut flowers. If you have a favourite, you’ll want to overwinter it and replant it next year. (Photos by Dugald Cameron)

    Colourful dahlias, native to Mexico, make a superb cut flower. They thrive in hot, sunny weather and rich, fertile soil, but they won’t survive freezing temperatures. This means you’ll need to store dahlia tubers over winter if you wish to plant them again next year.

    But before learning how to divide and store dahlias, first decide if it’s worth the effort. Unless your dahlias were a spectacular success and you simply must have these exact ones again, why not explore the incredible variety of dahlias out there and buy new tubers next spring? They’re not expensive, and nurseries, dahlia societies and garden clubs would be thrilled to lead you on your dahlia adventure.

    If you decide to keep them, next decide if you want to divide them. If you have plenty and no remaining sunny spots to plant more dahlias, skip the instructions on dividing and go straight to storage instructions.

    Lifting tubers

    The little potato-like tuber you planted in the spring has likely grown into a large, multi-stemmed plant, and the tuber has probably grown huge and multiplied, too. In fact, a dahlia continues to grow until frost turns the stems and foliage into a collapsed sorry version of its former glory. Leaving plants until they’ve been killed to the ground is critical to storage success. The tubers are toughening up and getting thicker skins (a.k.a. ripening). Tubers lifted too early won’t store well.

    Cut off the stems, leaving a few inches (about 8 cm) above the soil; the shortened stems make handy handles for carrying the tubers once they’re dug up. Start at least a foot (30 cm) away from the stem and gently lift the whole clump. It’s fragile and there’s probably some water in the stems. Carefully remove loose soil, placing the clump upside down for a few hours to dry out. A warmish, late fall morning is best. They’re less likely to fall apart if they’ve had a chance to dry out a bit.

    The second trick is to remember the variety. Record the height and save any photos you’ve taken to help jog your memory next spring. If you’re not planning to divide the clump, skip to storage instructions.

    A note about container-grown dahlias: Plants in containers freeze solid earlier than tubers in the ground. Lift these plants as soon as their foliage has been killed. Otherwise, the procedure is the same as plants grown in the ground.

    Dividing tubers

    It’s easier to divide clumps in the fall after you’ve lifted them than to do so next spring. A clump left until spring becomes as tough as wood over the winter months and hard to divide. The question now is how many more plants do you want? It’s always a good idea to have some spares, but do you need 10 more? If you just want a couple more, then divide the clump into a few roughly equal pieces.

    Start by washing the soil off with your garden hose. Cut off the remaining stem as close to the base as possible. Now, use a sharp knife to divide your clump from the top downwards through the stem base, like a pie. Each piece should have a section of the base (also known as the heel) and a single or cluster of tubers attached. Cut out and dispose of any damaged tubers; these will likely spoil in storage.

    You may notice clusters of dark bumpy spots on the tubers. These are the “eyes” that will form stems when the dahlia is planted again in the spring. Let your tuber(s) dry thoroughly.

    A whole Dahlia root in the spring
    A whole Dahlia root in the spring

    Storing tubers

    It’s most important that they remain dry regardless of where you decide to keep them. Once dry, you can wrap them in a few sheets of newspaper, taking care to label each piece. You can also put them into individual paper bags, loosely closed. An ideal location is somewhere dark, between 5 and 10 degrees Celsius. They mustn’t freeze.

  • How to store calla and canna lilies

    How to store calla and canna lilies

    Mixed calla in container (Photo by Dugald Cameron)
    Mixed callas growing in a container. (Photo by Dugald Cameron)

    In the fall, you can store calla and canna plants for next year. Both are easy to overwinter; here’s how:

    Overwintering calla lilies

    These wonderfully colourful plants are from South Africa. In their natural habitat, they grow and flower during the wet season, going dormant during the following dry season. Fortunately, these bulbs are super easy to store over the winter. They have a tough outer coat and equally tough interior, making them less likely to shrink during storage. Give them what they like and they’ll multiply like crazy.

    If you’ve grown them in pots, cut off the foliage and bring them in before frost. Chances are they’re probably wet, and the tubers will be plump and full of moisture. If they’re dug out at this stage, they can be easily damaged, and the wound can cause your tuber to spoil during storage. Bulbs and tubers need to ripen in order to survive dormancy. They will slowly dry out, forming thicker, tougher coats that don’t mind handling. They like a cool, dark (but not freezing) spot.

    If you really must unpot them, carefully remove the soil and re-package them in vermiculite or ever-so-slightly moist peat moss before storage. But why bother? This is a messy job and it’s easy to accidentally mix them up if you’re keeping track of different varieties. They’ll actually store far better left alone in their pots. It’s what I’ve done successfully for years.

    If you’re wondering where to put all your pots, fear not. You can stack them once they’ve dried out. The only thing to watch for are early sprouts growing as your callas wake up. (They don’t grow too well under another pot!) This shouldn’t happen until late winter, but sometimes they surprise you. Keeping them cool helps prevent them from sprouting too early.

    Overwintering canna lilies

    These popular plants have adorned Canadian gardens for generations. Their lush, tropical foliage and non-stop flowering are one of the highlights of summer containers and gardens. They’re native to tropical Asia where they flourish in the hot, wet growing season; some species reach seven feet (2 m). Here in Canada, where our winters are hardly hot and tropical, our shorter days and cooler weather signal that it’s time to move them indoors. They hate cold weather, so bring them in when overnight temperatures get into the low, single digits.

    Early signs of yellow streak virus on canna leaf.
    Early signs of yellow streak virus on canna leaf.

    Canna virus – a bad news, good news story

    The bad news: Unfortunately, there is a nasty virus in virtually all the big cannas grown in France, Israel, the Netherlands, Australia and the U.S., which are where almost all the canna sold in Canada come from. The disease was first identified years ago but little has been done to stop its spread. It has spread throughout the large nurseries of the world, with only a handful offering virus-free, healthy stock.

    It’s known as yellow streak virus, and the name says it all. It first appears as faint yellow streaks in the foliage, increasingly spreading, eventually leading to distorted foliage and death. Like many plant viruses, it’s spread by sucking insects like aphids. There is no cure. Dispose of infected plants and surrounding soil in the garbage, not in your compost. The tragedy is you can’t see any evidence on the root or even early-season foliage. But the mature foliage in fall will show if the plant is infected, which leads me to…

    The good news: Fortunately, the majority of cannas we grow aren’t bought. They’re traded, passed on, shared with family and neighbours or traded at horticultural societies. These have likely been around long before the virus even existed. If they’re healthy they’re probably fine. In fact, several canna nurseries and collections were saved by collecting healthy rhizomes from isolated virus-free gardens. So check your canna foliage carefully. If in doubt, throw them out.

    Overwintering

    Chop the foliage off a few inches above soil level. Cannas in containers can be brought indoors. If they’re in big pots, you’re better off lifting them as you would those growing in the garden. This requires some care because a healthy canna rhizome (root) will have grown a lot bigger over the summer.

    Allow their plump, water-filled roots to ripen a bit before storage. Once ripened, you can remove any soil and place them in clear plastic bags filled with very lightly moistened (not damp) peat moss, storing the sealed bags in a cool, dark place. Check them from time to time to make sure they haven’t rotted (you’ll see a mushy area). Just cut this off, let the root dry off and re-store again in peat moss.

  • How to store tuberous begonias for the winter

    How to store tuberous begonias for the winter

    Potted Begonia waking up in late winter
    Potted Begonia waking up in late winter (Photo by Dugald Cameron)

    It seems a shame, but tuberous begonias are often flowering at their best in late summer, just when it’s time to bring them indoors. Like most bulbs, tuberous begonias need a period of dormancy – several months where it’s dry, dark and cool. My bulbs spend the winter in a dark corner of our basement. I discovered my storage trick by trial and error over the many, many years I’ve enjoyed these amazingly floriferous plants. It’s actually super simple.

    It’s best if they first get nipped by frost. Wilted foliage is fine, but the the most important thing is to not let them freeze. Better to bring them in a little early. This tells the tubers it’s time to go dormant.

    Be gentle with them at this time of year as their fragile, water-filled stems and swollen tubers are easily damaged. Begonia tubers have thin skins and a tiny nick or scrape can become an entry point for infection that will rot your tuber; minimal handling is best. Bring them inside, pot and all, if they’re potted. If you planted them in the garden, leave as much of the root ball as you can manage. Cut the plants back a bit if they’re huge, but try to leave as much growth as you can.

    Leave potted begonias in their pots. Those planted in the garden can be carefully cleaned of their surrounding soil and stored in dry vermiculite, sawdust or peat moss in open paper bags. A cool, dark spot is best. Now you let them dry out, and then remove the stem and foliage. By leaving your tuber unmolested, it can dry (ripen) slowly, forming the thicker skin that helps it retain the moisture it’ll need when it begins to sprout again.

    Our modern, thermally efficient accommodations tend to be extremely dry in winter. Indoor humidity varies so check on your tubers from time to time. Give your potted tubers a bit of water if they’re starting to shrivel. Bagged tubers can be removed from their bags (media and all) and given a light misting of water.

    Another good reason for these checkups is that your begonias may well start to wake up in February or March which is a good thing. I’ve all too often heard sad stories from begonia lovers with neglected tubers that have grown tall, thin white stems while in storage. This won’t kill them, but will give a poor performance that summer. An early awakening tuber can be restarted early indoors. Remember, with tuberous begonias, the earlier they start the sooner they’ll commence their superb, summer-long display. Besides, aren’t we all dying to get something growing in the depths of winter?

    By now some of you may be wondering if this is worth all the bother. Well, you’ll know if your begonias were properly grown if the tuber is larger at the end of the season than when you started. If not, then they were missing something they need. An important lesson that, if acted upon, will make you a better gardener. If it has grown bigger it may be big enough to divide into two. Even an undivided tuber will produce a larger plant with more flowers. Like potatoes, begonias grow from tubers, can be divided provided each piece has an “eye”.    

    More on tuberous begonias

     

  • Protect evergreen shrubs and trees in winter

    Protect evergreen shrubs and trees in winter

    Soon it will be time to protect evergreens from winter stress. (Garden Making photo)

    Despite the surprisingly warm days this week, it’s smart to consider what we can do to protect needle and broadleaf evergreen plants from winter injuries. Evergreen shrubs and trees might give the impression that they’re tough and resilient, but the truth is these plants require as much consideration as tender perennials, and need regular watering and an annual feeding to keep them in good condition. With good care through the growing season, they’re much better prepared to withstand severe winter cold. Regular watering during the growing season is the single most important factor in strong winter hardiness for all plants, including evergreens.

    When plants are growing within their hardiness zone, cold air temperatures are unlikely to cause winter damage. However, the weight of crushing snow and ice is one hazard for coniferous shrubs; chronic exposure to extreme wind chill in exposed locations is another. When conifers accumulate large amounts of snow during winter storms, it’s worth getting out there with a broom to lightly push the accumulation off to reduce the weight on frozen branches. This is easy to do by putting the flat side of a broom on the underside of branches and gently bouncing them upward to dislodge snow. Never press downward on branches, as they are brittle and easily snap when frozen.

    Where conifers are constantly buffeted by winter wind, a windbreak will offer significant protection. A living windbreak of trees, such as spruce and juniper, are better able to withstand the blast, and can form a shelter belt for more susceptible evergreen species. A more immediate and still reliable solution is to tie evergreen branches and discarded Christmas trees to the exposed sides of evergreens susceptible to wind damage, providing them with some insulation.

    By far the most common winter injury is desiccated foliage (the loss of internal moisture in foliage tissues) on plants growing in locations with exposure to south and southwest sunlight and wind. Evergreens with lots of black or brown dead spots in spring have most likely been exposed to strong winter sunlight, sufficiently warm for a few hours at midday to stimulate biological activity in foliage and in the cambium layer under the bark. When the sun goes down, air temperature rapidly drops and tender tissues are caught in a sudden deep freeze. With a frozen root system unable to pump water, tissue death and split bark are the resulting injuries. This process of quick warming and sudden freezing is repeated every sunny day, and consequently damage to plants can be severe.

    Yew, cedar and hemlock, and broadleaf evergreens such as boxwood and rhododendrons are most susceptible to desiccation. Anti-desiccant sprays provide a protective waxy coating and can be applied in late autumn. These aren’t entirely effective, sometimes flaking off before winter is over. The best solution is to provide shade from direct sunlight on foliage and bark by erecting a shade barrier with stakes and burlap. Surround the plant on three or four sides, without letting the burlap touch the branches, and without covering the top. Wrapping plants tightly in burlap will cause more problems by cutting off circulation and compressing frozen branches.

    Protect tree trunks in late autumn by wrapping them with any light-coloured material or reflective wrap (available at garden centres). Remove wrappings in late spring. The idea is to keep plants cold and shaded, so foliage will remain dormant and inactive.

    It’s a good feeling to know vulnerable plants are suited up and ready for their winter exposure. Needless to say, the gardener should be well wrapped and parked by a toasty fire for the duration.

  • Beautiful pumpkins — warts and all

    Beautiful pumpkins — warts and all

    ‘Knucklehead’ pumpkins (Photo from Veseys.com)
    ‘Knucklehead’ pumpkins (Photo from Veseys.com)

    The arrival of the first seed catalogues has coincided with the end of pumpkin season. My friend Clare had a bumper crop of pumpkins (Curcurbita spp.) at her farm garden in Ontario, and her cold cellar is full of the smooth, round globes waiting for winter pies. She gifted me with a lovely specimen that sat on my porch Halloween night, and now is on the dining-room sideboard. Its smooth surface and orange glow tempt me to run my hand over it frequently, and reminds me that such perfection isn’t entirely natural.

    Plant hybridizers have worked for decades making traditionally attractive pumpkins such as ‘Connecticut Field’ (damseeds.ca) in sizes from mini to monstrous, with blemish-free skins, shell colours ranging from ghostly white to blazing red, and thick meaty interiors. But it’s news to me that breeders are now working to make ugly pumpkins with all manner of warts and bumps.

    The dramatically warty, pale beige French heirloom pumpkin ‘Brode Galeux d’Eysines’ (seedsavers.org) comes by its wart-covered exterior naturally. The prominent, peanut-shaped warts almost entirely cover the surface of this reportedly delicious pumpkin. The ‘Red Warty Thing’ pumpkin (gurneys.com) is vivid scarlet-orange with full wart covering, though the warty lumps are less raised and more under the skin (and that may be the effect of some breeding work).

    Tampering with pumpkin genetics has drawn on warty genes and produced hybrid strains with colours, shapes and surface textures that were previously bred out of cucurbits, but now considered desirable. The Knucklehead strain (veseys.com) is tall and dark orange, with a smooth surface interspersed with irregular dark green warts on a 12- to 16-pound (5.5- to 7-kg) squash. ‘Goosebumps II’ (stokeseeds.com) is globe-shaped, eight to 12 pounds (3.5 to 5.5 kg), with a bright orange shell and generous clusters of orange and green warts. (The large wart clusters might be hard to carve around, but ‘Goosebumps II’ would be quite a conversation piece on your verandah.)

    Plant breeding and marketing over the past century has encouraged the perception that all pumpkins are shades of orange. But heirloom species (and new hybrids) now more readily available show us that there is quite a lot of diversity in pumpkin colours. ‘Fairytale’ (territorialseed.com) is an open-pollinated, deeply lobed, pale oak to mahogany brown pumpkin squash with a squat shape and meaty interior. The heirloom Cinderella pumpkin, ‘Rouge Vif D’Etampes’ (damseeds.ca), is almost tomato red, while F1 hybrid ‘New Moon’ (stokeseeds.com) is eight to 12 pounds (3.5 to 5.5 kg) with smooth, rice-white skin and firmly attached dark green handles.

    And then, there is the deep category of pumpkin sizes. Suffice to say, there is a pumpkin to fit every nook and cranny of your garden, from ‘Dill’s Atlantic Giant’ to the compact F1 hybrid ‘Windsor’ pumpkin (both from halifaxseed.ca), small enough to grow in a patio container, and producing short vines with six-inch (15-cm) orange fruits.

    Well, beauty is in the eye of the beholder, and warts are back on the pumpkins. I’m for anything that gives us more choice and greater selection.

    More that may be of interest:

    Pumpkins as groundcover

    Dreaming of a giant pumpkin

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