The Society receives many gardening questions. This page was created to share answers to some of the Frequently Asked Questions (FAQs). If you don’t see your question listed here, check out the options on the Gardening FAQs page.
Start of Season Tips
What is a cold frame?
Cold frames are generally unheated, simple structures that allow you to start the growing season early and extend it later into the fall. The structures provide protection from the wind, frost, and snow, and provide a little extra warmth.
How can I make a cold frame?
Cold frames can be constructed as a bottomless box with some sort of transparent cover. Old windows, doors, shower doors, sky lights, and plastic can all be used for the top cover. The box can be built from wood or even straw bales. Another option is using arches from fence wiring or reinforcing bars and covering it with plastic. Ensure the plastic is anchored well to prevent the wind from lifting it off or having the snow collapse it.
You need to have a way to open the cold frame to vent moisture and heat, so plants don’t develop fungal issues or die due to extreme heat when the weather warms up.
Note: Products sold as mini-greenhouses are also a type of cold frame.
What can I grow in a cold frame?
Cold hardy vegetables can be started outside earlier in a cold frame. Peas germinate at temperatures as low as 4 ºC and can be grown for pea shoots. Some lettuce such as mache, mizuna, mustard, and winter purslane can survive at temperatures as low as -12 ºC. Cabbage, spinach, and green onions will also tolerate and grow at cooler temperatures. Specific varieties of these plants may have different temperature requirements.
Cold frames can also be used to grow out spring transplants, although plants may still need to be brought inside or provided extra protection when the temperature drops below freezing.
How wet should my soil be when starting seeds?
When starting plants from seed, it is important to keep the soil that the seed is planted in moist, but not wet. The surface should feel damp to the touch. The soil should be moist several centimetres into the container. This moisture level should be retained until the seedling has its first set of true leaves. At that time, the plant needs deeper watering less often. Once the seedling has reached that stage, the surface of the growing medium can dry out between waterings. For plant health and the prevention of rot, watering in the morning is recommended.
For additional tips about starting seeds, see the blog post “Troubleshooting Native Seed Germination” on our corporate member ALCLA Native Plants’s website.
What is hardening off?
Hardening off is the process of giving your seedlings or greenhouse grown plants time to transition from their controlled environments to the outdoors. Direct sunlight, strong winds, and fluctuating temperatures can stress plants. Plants need time to adjust to direct sunlight, so their leaves do not get scorched. Young plants also need time to adjust to greater temperature swings. The process thickens the cuticles on the leaves enabling them to preserve moisture.
Once outdoor temperatures are appropriate for your plants, harden them off over a period of several days to a week. Start on a warm day. Place the plants outside in full shade (in a sheltered location) and bring them back in for the night. If it is breezy, you may want to only leave them outside for an hour or two (do not try to harden off your plants on a windy day). Over the next couple of days, place them in dappled shade, increasing the amount of sun exposure each day. By the third night, they can be left outside overnight (only leave them outside if the low will be no colder than 5° C). The plants should be ready for planting in their final growing locations after day five.
How do I get compost from the City’s green bin compost program?
Compost is available for pickup from April 25 to June 11, by online appointment only, at Shepard (South) and Spyhill (North) landfills.
- Appointments will be available between 8 am to 3:45 pm, Monday to Saturday.
- To avoid line ups from high landfill traffic volumes on the weekends, consider booking your compost pickup on a weekday.
Compost pick up appointments will be released in the following time slots:
- start booking April 18 for April 25–May 14 appointments
- start booking May 9 for May 16–28 appointments
- start booking May 23 for May 30–June 11 appointments
To ensure there is a fair opportunity for all citizens to pick up compost, households may pick up compost once for the 2022 year. Remember to mix your compost with soil. Check out tips on how to use compost.
How will appointment bookings work?
- When the appointment booking tool is live, select which location you will be picking up your compost.
- Select a date and time to pick up compost—appointments are booked in 15 minute slots.
- Save your confirmation email, on your smartphone or printed, as you will be asked to show it to the site attendant when you check in.
- Please arrive on time for your appointment.
If you receive an error message when booking, please refresh the page and try again.
How can I cancel an appointment booking?
If you are unable to make your scheduled appointment time, you can cancel your appointment through your confirmation email and rebook a timeslot at a later date.
Visit the City’s Green Cart Compost Giveaway page for details and to book a pick up time.
How do I winter sow?
With winter sowing, hardy vegetables, annuals, and perennials can be started outside after the coldest days of winter have passed, in late February or early March. Choose cool weather vegetables such as kale, rutabaga, spinach, or beets, hardy annuals like pansy, snapdragon, or dianthus, or Zone 4 or hardier perennials.
Four litre milk or juice containers or take out containers with enough depth and a clear or translucent lid make ideal containers to provide protection from wind and trap some warmth. Poke four or five holes in the bottom for drainage and a few holes in the top for ventilation. Leave the lids off the beverage containers. Cut around the beverage container from one side of the handle to the other. The cut line should leave room in the bottom for 10–15 cm of soil. The uncut portion at the back will act as a hinge.
Fill the bottom of container with damp, but not dripping-wet soil. Plant the seeds according to package directions. Tape the container shut with a weatherproof, such as duck tape, and label it with a weatherproof marker.
Leave the containers in a bright area, out of direct sunlight. Shelter from the wind or secure so they can’t be blown over. Shovelling snow around them can help insulate and provide moisture.
If the jugs need watering, placing the jug in a bucket of water to soak up moisture from the bottom will minimize the seed disturbance. Once the plants have four true leaves, remove the tape and start opening the jug a bit. After a week, the top can be removed when there is no danger of frost. Plants can be transplanted once they have been fully exposed for at least one week.
How do I care for an African violet?
With a few simple needs, African violets can add almost continuous colour to a room. African violets prefer to be root bound so keep them in pots that are about 1/3 the diameter of their leaf spread and ensure the pot has drainage holes to prevent root rot. A soil mix of equal parts peat moss, vermiculite, and perlite is ideal. The plants need indirect sunlight since direct sunlight can burn the leaves, however insufficient light will diminish the blooms. A location about 1 m away from a south or west window should provide sufficient light. A grow light can provide extra light in winter if less than 6-8 hours of light is available but also ensure that they receive 8 hours of darkness per day. African violets with dark green foliage will need more light than the lighter green varieties. Turn the pots often to keep the plant balanced.
They prefer warm room temperatures; in the same range as most people or about 21 °C. Water African violets by filling the saucer with room temperature water and dumping any water remaining after an hour. They can be watered from the top but avoid splashing the foliage because it can cause foliar spots and damage. Allow them to dry out between waterings. Ideally, they do better when the humidity is at least 50-60%. Fertilize regularly with a higher phosphorus number fertilizer such as 15-30-15 in the spring, summer, and fall but be careful not to overfertilize. Plants without sufficient fertilizer may have reduced blooming or paler leaf colours. Encourage continued blooming by pinching off spent blossoms and stems
Growing Season Tips
When should I stop watering the garden in the fall?
Winter can be a dry season for plants and trees. This is especially true in Calgary where the chinook winds can strip moisture away. Calgary is often dry in the fall, so keep watering trees until the first hard frost which typically occurs in late October in Calgary.
Perennials should be watered until the ground freezes as well, but decrease the watering as the temperatures get below 5 °C to help them prepare for winter.
Should perennials be cut back in the fall?
Diseased plants should be cut back for winter and cuttings discarded but cutting most perennials back is a matter of personal preference. Some people prefer a neater appearance, while others like to leave most of the clean up until spring to create winter interest. Leaving plants intact can also help catch and retain more snow and provide a little protection from the freeze thaw cycles. To avoid damaging early spring plants during spring clean ups, leave their fall foliage on to indicate the plant’s location. If plants are cut back, be careful not to cut them back too early in the fall, as this can encourage the plant to send up new growth. Low growing, semi-evergreen plants should not be cut back. Hostas, irises, and daylilies are good candidates for cutting back in the fall as their foliage can be messy and harder to clean up in the spring. Peonies should be cut back in the fall to help prevent botrytis, a fungal disease.
When should I stop deadheading my perennials?
Deadheading perennials can extend the blooming time for some plants. However, deadheading should stop several weeks before the first killing frost. This will trigger the plant to start going into dormancy in preparation for winter. Allowing the plants to go to seed has some additional benefits. The seeds pods provide food for birds, winter interest in the garden, and will help trap snow and moisture for the garden.
Should I fertilize my lawn now?
Cool season grasses have two peak growing periods, early spring and early fall. Fertilizing during these growing periods provides nutrients when they are needed by the plants. Lawns should be fertilized with a high nitrogen fertilizer (for example 21-3-4) in May and July. Grass tends to go dormant in August and should not be fertilized at that time. A slow release fertilizer feeds the lawn over 6 to 8 weeks, which helps develop a healthier plant and root system better able to resist stressors. In late September, a winter fertilizer can be applied to promote deep root growth and nutrient storage for the winter. Stronger roots help get the lawn off to a good start the following spring.
Does leaving grass clippings on my lawn cause thatch?
Grass roots are the primary cause of thatch, not grass clippings. Thatch is made up of roots, stems, rhizomes and other plant materials. These materials contain large amounts of lignin (fibrous material) and decompose slowly. Grass clippings are about 80-85 per cent water with only small amounts of lignin, and break down rapidly.
To learn more about the practice of leaving clippings on the lawn, also know as grasscycling, read the information sheet from the City on the Society’s Resources page. The City also has lawn care information on their website calgary.ca.
Do I need to fertilize my containers?
Even plants growing in good quality soil need to be fertilized regularly to continue optimum growing, as the nutrients are used up by the plant and are leached out during watering. Choose a quality fertilizer that has micronutrients as well as nitrogen, phosphorus, and potassium. If you are concerned about burning your plants with fertilizer, choose an organic fertilizer as the nutrient concentrations are lower and you are unlikely to harm the plant if it is not diluted or applied properly.
Can I fertilize all my containers the same way?
Plants that bloom before producing fruit (tomatoes, peas, peppers) and root vegetables should have a fertilizer with a higher phosphorus (middle number e.g., 10-15-10) content applied. Non-flowering leaf plants, ornamental or edible, benefit from a fertilizer with a higher nitrogen content (first number). If root vegetables receive too much nitrogen, they will produce leafy growth at the expense of tuber growth.
Flowering plants in pots will stop producing flowers if they don’t have enough fertilizer. They need a higher phosphorus level to support blooming.
Liquid fertilizers get absorbed very quickly and do not last very long, so they should be applied every 2-3 weeks. Granular fertilizers release slower, but feed plants over a longer period of time. Be sure to water the container before applying the fertilizer. Follow the directions on the package for mixing the correct concentration of fertilizer and for the frequency of application. Some gardeners will fertilize more often, but with a solution mixed to a lower concentration.
How often should I water my vegetable garden?
Wind, temperature, and rain will affect the frequency of watering, but a vegetable garden generally needs about 2.5 cm (1 inch) of water per week. Water the garden when the soil is dry 2.5 cm below the surface during the growing season. If you are starting plants from seeds, watering may need to be done daily during the germination period and until the seedlings are established.
Watering is best done in the morning to ensure the plant foliage doesn’t remain damp over night. Extended periods of dampness can cause disease. However, watering in the evening is better than midday if you can’t fit in morning watering. This reduces evaporation loss.
Water deeply to encourage deep root growth. Ideally, water until the soil is damp 15 to 20 to cm (5 to 6 inches) below the surface.
Mulching around the plants reduces evaporation from the soil.
The Old Farmer’s Almanac has an interesting critical water period table for vegetables. It is usually when the flowers and fruit are forming. Visit to see their guide: https://www.almanac.com/when-water-your-vegetable-garden-watering-chart
When should I harvest rhubarb?
Rhubarb should not be harvested at all in the first year, and only lightly during the second year to ensure the plant becomes well established. Harvest stalks when they are at least 20 cm (8 inches) long and greater than 1.5 cm (3/4 inch) in diameter. To harvest, pull from the base of the stalk and twist slightly. Cutting rhubarb stalks leaves a short stub that can rot and damage the root. Leaves are toxic due to their high levels of oxalic acid, but they can be composted. Leave a minimum of 2 stalks per plant to ensure continued plant growth. Stalks from later season harvesting tend to be tougher than spring harvested stalks. Stop harvesting if the stalks become thin, or after mid-summer, so the plant can restore it’s energy for next year!
How can I attract beneficial insects to the garden?
Encourage biodiversity! Choose a variety of plants that bloom throughout the season. Plants of varying heights will attract different types of insects. Many beneficial insects prefer small, simple blooms.
How can I keep hanging baskets looking good all summer?
Soil in hanging baskets will dry out quickly, especially in windy conditions, so keep up with the watering – this is usually once per day and sometimes even more than that. Make sure you match plant selections with their site. Fertilize once every two weeks during the growing season with a water soluble fertilizer formulated for flowering plants. Deadhead spent blooms when necessary.
What can I grow underneath a large conifer?
Large conifers will compete with other plants growing beneath them for sunlight, water, and space. You need to be able to control these barriers to plant growth. The simplest, most workable solution is to set up planter boxes/containers and then plant shade-loving species in them. (Watering will have to be done on a regular basis as the plants might not receive sufficient rainfall). You are at least able to give the plants the soil and nutrition they require, without competition from the trees.
What are some herbaceous perennial selections for shady sites?
Hosta, bleeding heart (Lamprocapnos spectabilis), bugloss (Brunnera spp.), Ligularia, Astilbe, ferns, queen of the prairie (Filipendula rubra), among others. Visit the Perennial Plant of the Year page under Resources for more plant information. Society Members may visit the Society’s Plant Database under the Members Only section of the website.
How can I design my yard to conserve water?
Select water-wise native plants. Grow less lawn. Use mulch. Make sure your soil is healthy. Use compost. Install a rain barrel. Water only when needed. Sign up for a Design Your Yard workshop to learn more.
End of Season Tips
What plants can I overwinter?
Many tender perennials can be overwintered indoors. Plants that are geophytes (plants that propagate from bulbs, corms, tubers, or rhizomes) which we frequently all call bulbs, can be gently cleaned of soil and stored in a cool dark place over the winter. Usually, they are lifted (dug up) after a light frost, their leafy growth is removed, and stems trimmed to about 2 cm. After air drying for a few days, the can stored in dry potting medium in a cardboard box or unsealed bag. The challenge is to keep them dry (to prevent mould growth) but not so dry that they become desiccated. The stored plant should be checked once a month to watch for mould, provide a air circulation, and add a bit of water (if required). In the spring, they can be potted up, or when warm enough, planted outside.
A few of the common plants that can be stored this way are begonias, canna lilies , crocosmia, dahlias, and gladiolus.
How do I overwinter my geraniums?
Pelargoniums, commonly call geraniums, are related to our hardy cranesbill geraniums but are not hardy in Calgary. These plants can be brought inside and overwintered. They can be grown as a houseplant, have cuttings taken for starting new plants that are grown over the winter inside, or stored dry and dormant.
If you’re bringing your pelargonium in to be a houseplant, before the first frost trim the plant back about one third. Let the wound heal. Dig up the plant and clean the soil off the roots. Soak covered in water with a drop of dish or horticultural soap for about an hour or two to remove potential pests. Rinse off the plant, then pot in a clean container with fresh potting medium. Keep the plant isolated from other plants for two weeks. Ideally, the plant would be covered with a plastic bag with a few tiny holes (for air circulation). Check it regularly for pests. The plastic bag will contain the pests if they appear and should prevent their spread to other houseplants. If no pests are found, it can be moved to its winter growing location. Shoot tips may need to be pinched periodically during the winter to promote branching.
Take cuttings from plants growing outside. Cut a 10 cm length of stem from the tip. Remove flower buds. Let it dry overnight. The next day, brush a bit of soft tissue rooting hormone (#1) on the side of the stem. (Rooting hormone is not required, but it does help encourage root growth.) Plant the cutting in a pot with a soilless potting mix and water. Do not overwater or the cutting will rot. Pelargoniums prefer a drier environment.
Lift your pelargoniums before the first frost. Gently shake off excess soil. Stack them like cord wood in a cardboard box or hang them to dry. The plant should be stored in a cool dry dark place. They can survive this way due to their thick moist succulent-like stems. Periodically inspect the plants. Remove leaves that dry and fall off. You may need to soak the roots in water (1 to 2 hours each month of storage) if the stems lose any plumpness. The stems should remain thick and firm. If the stems shrivel, discard the plant. In late March, pot up the plant and water thoroughly. Place the potted plant in a sunny window to trigger growth. It may take a few weeks before you see new growth. Trim off any dead stems.
Seasonal Décor Tips
Christmas cactus (Schlumbergera x buckleyi) care
Christmas cactii are epiphytic succulents native to the tropical rain forests of Brazil. Many Christmas cactii sold are actually a hybrid of Thanksgiving and Christmas cacti which typically bloom from November to February.
Christmas cactii should be placed in bright, indirect light. While the plant will tolerate low light, it will bloom more readily with brighter light. During the periods of active growth in spring and summer, water well once the top 1/3 of the soil is dry. Don’t let it sit in any excess water or it may rot. Fertilize every 2 weeks. The plant prefers temperatures between 15 and 21°C (60 – 70°F) and average to high humidity.
Blooming is triggered by cool temperatures and long nights. To make your cactus bloom, provide a 6 to 8 week period with average temperatures between 10 and 15°C (50-55°F) and about 14 hours of darkness each day. Reduce watering during this period, although if the plant dries out too much once it starts flowering the buds may drop. Fertilize monthly in the fall and winter. Keep the plant away from drafts, warm or cold.
Prune the cactus by removing up to 1/3 of the plant after blooming to encourage branching. The cactus flowers from the ends of the stems, so more stems means more flowers!
How do I keep my seasonal greens fresh?
Fresh cut greens make a great addition to Christmas and seasonal décor for both indoor and outdoor projects. Materials, sunlight, humidity, and heat will all contribute to how long they last. Pine, cedar, spruce, and juniper last much longer than cut flowers. To keep seasonal greens looking good for as long as possible, there are a few simple tricks. Choose materials that are fresh. Fresh evergreens are fragrant, have firm well-adhered needles, and are flexible. Rehydrate greens before using them by trimming the ends and submerging the greenery in water for at least 24 hours. If you can’t submerge the whole piece, soak the cut ends and as much of the stem as possible. After soaking, spray the greens with an anti-desiccant to help lock the moisture in. After the arrangement is made, check the water reservoir daily and top up as needed. If possible, every couple of days move the arrangement to a water-safe location and spritz. Avoid placing the arrangements near fireplaces, heating vents, drafts, or in direct sunlight as these environments will accelerate moisture loss. If the projects are displayed in a warm location, placing them in a cooler area at night will help keep them fresh. Wreaths and arrangements displayed indoors will last up to three weeks. Outdoors they can last for three to six weeks.