Gardening with containers to attract wildlife

 

 

Why would you put native plants in containers?

Containers are what people have to use when they want to beautify a balcony or a patio. A patio can look so much nicer with some plants thoughtfully installed and if you are running out of room in the garden, then an empty patio is a wasted opportunity to attract more pollinators. Containers also will allow gardeners to try plants that will not survive in their gardens. In a container, you can easily control the moisture and nutrient levels to provide an environment for other plants that may be too delicate or need special treatment. A container is also a good way to confine a plant that would spread fibrous roots throughout a mixed bed. Containers heat up faster in the spring and can be insulated easily over the winter. They therefore have a longer growing season.

Containers can also be problematic because the watering requirements are higher. They can easily limit the depth of the roots. Plants growing in pots are exposed to greater and more rapid variations in moisture and temperature. You have to choose plants that can handle these conditions. With containers there is a lack of soil development and there are always going to be issues with drainage, aeration and compaction.

 

Soil

As noted below, drainage is important in plant containers. It is best to avoid using heavy soils. Be prepared to buy a good quality container soil with water retention capacity. These soils will be much lighter and stop many of your plant from rotting in situ over the winter. Some plants, such as Liatris, are particularly prone to this. If you buy heavier soils, the soil will retain more water, but will have less air space and so the roots of most plants will not be able to get enough oxygen. For plants with wet feet, a heavier soil is appropriate since they need the water retention more than the drainage. For acid-loving plants, buy a soil from your local nursery that is specifically formulated for these plants. For big containers, I put in a 6-inch layer of compost beneath the potting soil, which does not have much organic matter. Another way to increase the porosity of the soil is to dilute it with sand and you might consider this if you are trying to use plants that grow in dry sandy prairies.

 

Watering, fertiliser and drainage

All outside pots must have drainage and this includes pots with water reservoirs. Without drainage, a single rainfall event will completely flood the pot; even after draining, the soil will have lost a lot of the soil structure that helps in allowing the movement of air and water throughout the medium. For pots with no reservoir, the drainage hole is in the most obvious place, at the bottom. Make sure that the holes are large enough or drill some more if necessary. Quite often, there is no hole for pots with reservoirs in case you are using them indoors. If you are using them outdoors, you need to place a hole in the side of the pot a little bit above the level of the reservoir.

If you are watering using tap water, drainage will be necessary to avoid a build-up of salts in the soil, which will eventually affect the ability of the plant to grow. This can be done naturally with rainwater or if you are highly reliant on tap water, you can pour extra water in to flush the salt through. I fertilise my container plants just once when I see the plants beginning to grow properly and I reduce the recommended dosage by over 75%. Native plants do not need much fertiliser, so only use a low dosage. Some gardeners prefer a slow-release fertiliser instead.

 

Container size

You have to choose the material from which your container is made. Ceramic containers look better than plastic and this may be important if your plant is going to be part of a designed element on your patio or balcony. Ceramic pots that are not glazed lose water much faster because the ceramic is porous. If you are not worried about the aesthetics, then a plastic pot loses less water, is lighter and is cheaper. Round containers often look better than rectangular containers, but the latter might be a better fit when placed against a wall.

There are many rules about container size that one can consider, but the first one should be the type of plant that you intend to use. Plants that need water, such as wetland plants, need large containers whereas xerophytic plants with shallow rooting systems can be grown in much smaller containers. Putting a plant with high water needs in a small pot with low water retentive capacity creates a management headache. In the heat of the sun, you would have to water the plant several times each day just to keep it alive. So, if the space allows, I would go with larger containers. Containers with water reservoirs built in resolve many of these issues and are essential for water-loving plants. If you have a beautiful pot that you want to emphasise, then plant something that is about half the height. If you want to emphasise the beauty of the plants, then choose a thrill plant that is twice as high as the pot.

	It is very difficult to kill Ohio Spiderwort, which makes it a great plant for containers.

 

Design

If you are using one pot, then the most common design is the three-fold thrill, fill and spill technique. This involves planting a central plant surrounded by shorter plants and then outside of those, plants that grow over the edge of the pot. Any 2 of these would actually work quite well. This technique assumes that the pots will be viewed from all directions. If the pot is against a wall, or in a corner, then the technique is adjusted so that the thrill plants are at the back and the spill plants are the closest. Plants in the same container should have similar soil and cultural requirements. Do not put plants in the mix that spread out with fibrous roots systems because you will end up having to tear out the whole pot to remove a plant. All plants in a mixed container should have clumping root systems.

Designers tend to choose thrill and fill plants that are close together on the colour wheel, but it is certainly possible to have more garish combinations. If the pot is in shadier conditions, think less about colour and more about foliage texture.

Another possibility is to use several containers together. It you want your container plants to look good on your balcony, you have to think about the arrangement of the containers even before you put any plants in. Your arrangement of containers will look a lot more personal and homely if they are of different sizes. Choose a size that is appropriate for the space. Large pots look good on patios, but a bit awkward on small balconies. Also, do not surround large pots with tiny pots. Choose your smaller pots based on the size of the largest one. Give your pots some space and try to avoid turning your balcony into the local nursery because it is always just so tempting to add one more native plant to your list.

The principles outlined for a mixed container apply to a multi container approach. Put the largest plant in the largest pot and place the pot at the furthest position away from the viewer. The smallest plant goes into the smallest pot and should be closest to the view. The multicontainer setup has some advantages. With each plant isolated in its own pot, you do not have to worry about what the roots are doing. It is much easier to have shrubs in their own pot. You can also switch out one pot with another when something goes out of bloom or if just want to change things up.

 

Plants in containers need to be rated hardier than zone 5. Plants with deep taproots as commonly found on the prairies are not going to do as well in containers. Plants in wetlands tend to have shallow root systems as do plants on alvars and in woodland habitats. Avoid planting spring ephemerals as the space left behind becomes obvious in a container. Even when plants are not in flower, you want the container to look full. Some small trees and shrubs do well in containers too as long you have the space for them. Do not just let shrubs grow untamed in a container because they will look out of shape. Prune them down to get the correct height and prune all the main branches to encourage the axillary buds to start growing. This keeps the tree or shrub reasonably compact and gives them a fuller look. Another possibility is to use a container to start a vine up a wall.

 

Name	Notes
Actaea sp.	Both Red Baneberry and the closely related Doll's Eyes produce pollen that may be used by bees to some extent. The fruit are eaten by various birds.
Adiantum pedatum	A beautiful fern that is hardy enough to grow in containers. It could work as the centrepiece in a protected shady area or as a fill and spill plant around something larger.
Agastache sp.	These plants are really too tall to sensibly plant them in a container but there are smaller cultivars of Agastache foeniculum that might be suitable.
Allium sp	These are tough plants that do well in dry rocky areas so they are suitable for small containers with plenty of drainage.
Amelanchier	The smaller species such as Saskatoon, Running and Round-leaved serviceberry will do well in containers. They like a well drained loamy soil.
Amsonia sp.	This is a native to much of the USA and not Canada. Likes moist sandy soil. Blooms in spring and better suited to larger containers
Antennaria sp.	The common species on Ontario will do well in dry shallow containers.
Aquilegia (Columbine)	It does well in a range of conditions but moist soil with some shade will bring out the best foliage. Canadian Columbine is pollinated by hummingbirds.
Aronia melanocarpa	An upright shrub for larger containers.
Asarum canadense	A plant that is grown only for its foliage. It needs drainage.
Asclepias sp.	Smaller milkweeds are suitable for containers. These include A. ovalifolia, A. tuberosa, A. verticillata and you could get away with A. incarnata.
Aster sp.	Choose the shorter asters such as wood asters, heath asters, large leaved aster and alpine aster.
Athyrium felix-femina
Blephilia sp	This plant does not hit many lists, but I think it would do well in a container.
Calamintha arkansana	A low growing plant with tiny flowers that will happily fill in around other plants.
Campanula rotundifolia	A smaller delicate looking plant that does well in dry conditions.
Carex sp.	Sedges are much overlooked and gardeners miss out on the spectacular greenery that they can provide in containers. Choose a sedge that clumps. My absolute favourite is Carex muskingumensis.
Carex muskingumensis
Ceanothus americanus	A dwarf shrub that survives drought well.
Chasmanthium latifolium	A grass native to the USA that does well in part-sun and is a good size for containers. The seedheads really do show off.
Chelone sp.	Does well in moist soils and attracts bumblebees. It is a host plant of the Baltimore checkerspot.
Clethra alnifolia (Summersweet)	Grows well in part shade with moist, but well drained soil. The flowers are quite fragrant and attract bees.
Coreopsis lanceolata	Does well in dry soil and has a long bloom season. Also consider the annual C. tinctoria.
Cornus canadensis	It may be technically a shrub, but it only grows high enough to be treated as a filler plant.
Dicentra sp.	These species generally need moist soils and will grow in full shade.
Diervilla lonicera	Hard to kill plant. More suitable in its own container as it spreads by rhizomes.
Echinacea sp.	Do well in large containers.
Elymus sp.	A nice grass for a container.
Eupatorium sp.	Most species tolerate part-shade and do well in moist soils. Eupatorium rugosum tolerates dry shade and is one of the last plants to flower. Many species are too big for containers, but they attract bees and butterflies.
Euthamia sp.	Euthamia graminifolia is a bit leggy for containers but E. gymnospermoides will do well.
Fragaria sp.	They will tolerate full shade and feed both insects and birds. They will fill the container.
Gaultheria procumbens (Wintergreen)	This plant will handle dry shade and feed the birds with its berries.
Gentiana andrewsii	This plant will do well in a larger pot as a fill plant as it prefers moist soil.
Geranium maculatum	A spring plant that can handle quite a bit of shade and drier conditions.
Heuchera sp.	The foliage will provide interest more than the flowers. For Ontarians, H. Richardsonii is recommended.
Helenium sp.	Grows in larger containers quite well. A large plant suitable for very large containers. For mid-Atlantic states and further south, Helenium amarum is a short plant that will do well in containers with dry soil.
Helianthus sp. (Sunflower)	The shortest sunflowers will work. Certain cultivars of annual sunflower are only 2 feet tall and great for children. Perennial sunflowers are not recommended, but you could try H. occidentalis which is native to the Eastern USA.
Heliopsis sp.	The cultivar "Lorraine Sunshine" would work well in a container. The species is suitable for large containers.
Hepatica acutiloba	Would probably grow in a larger container with moisture retentive soil.
Hypericum kalmianum	A small shrub with large yellow flowers that are attractive to bees. It likes a moist soil.
Impatiens capensis	Jewel weed grows in moist soils in lightly shaded areas. It is pollinated by hummingbirds. The seed pods are fun for kids.
Liatris sp.	Liatris need good drainage, but still a good amount of moisture. The drainage prevents root rot over the winter. The species of Liatris that like dry soils are not recommended because they develop a deep root system.
Lilium sp.	These plants will grow in larger containers with water reservoirs. Consider using sedges to stop animals from digging up the bulbs.
Lobelia sp.	They flower well in part-shade and in moist soils. They attract hummingbirds. The have a short lifespan but reseed well even within containers.
Lonicera sp.	The vines do well in containers.
Maianthemum racemosum	Needs part-shade and moist soil.
Mitchella repens	Partridgeberries grow in dry shade and attract birds.
Monarda sp.	Monarda is sort of on the large size. Try Monarda bradburiana and Monarda punctata in containers. Alternatively consider a nativar of beebalm that is not a dwarf, but shorter than the species. It will attract hummingbirds.
Oligoneuron sp.	Both stiff and Ohio goldenrod should grow well in pots. Ohio goldenrod is slightly preferred due to its shorter stature.
Penstemon sp.	Penstemon hirsuta is particularly recommended for dry soil containers. All penstemons should do well in containers.
Polygonatum biflorum
Phlox divaricata	Woodland phlox flowers in late spring and grows in moist well drained soil. It provides nectar to insects with long tongues. These include butterflies and some of the larger bees. It grows easily as a filler plant in containers.
Prunus pumila	The sand cherry is easily grown in a container due to its drought tolerance. It is another shrub that does double-duty with flowers for pollinators and fruit for birds.
Pycnanthemum sp.	These are tough plants. They should do well in containers.
Ranunculus fascicularis	Grows well in dry soils and will do well in smaller containers.
Rudbeckia sp	Rudbeckia hirta is particularly recommended for its size and tolerance to drought conditions. It is short lived but reseeds easily. In moister containers, Rudbeckia fulgida is a good size.
Sanguisorba canadensis	It does will in moist and well drained soils.
Sisyrinchium sp.
Smilacina sp.	A woodland plant that grows in full shade and moist soils. It attracts birds with its fruit. It is best planted in its own container.
Solidago sp.	Any shorter species is recommended and any of the following are worth trying. Avoid planting goldenrods in mixed containers due to their fibrous root system. Early, gray, stiff, or stout. For shade, S. caesia or flexicaulis.
Spigelia marilandica	Grows in full shade in medium moisture. It attracts hummingbirds.
Symphoricarpos albus	The snowberry is an adaptable small shrub with distinctive white berries that feed birds and show off in winter.
Symphotrichum sp.	Choose the shorter asters such as wood asters, heath asters, heart leaved asters, large leaved aster and alpine aster.
Tradescantia ohiensis	A very adaptable plant that will do well in containers. It will spread in the container if given a chance so pair with a strong rooted central plant.
Vaccinium angustifolium	A small shrub that could easily be put in a mixed container. If given a well drained soil, it is adaptable. The flowers come early for spring pollinators and the fruit for the birds appear in the summer.
Verbena sp.	Any species will grow but V. simplex and V. stricta have much lower watering needs.
Veronicastrum viginicum	It is a tall plant and needs a large container.
Viola sp.	Woodland violets tolerate part shade and are host plants for fritillaries.
Zizia sp.	Try Z. aptera is drier and shallow containers while Z. aurea will do well in larger containers with moist soil.