How Chemistry Plays a Role in Plant-Insect Relations in our Gardens

July 3, 2023 peterboroughmastergardeners Leave a comment

By Laura Gardner, Master Gardener

Have you ever wondered how certain insects are able to discover a plant in your garden? How do they know it is there? Some of them may already have been hanging out there but others fly in from afar. How does a predatory insect seem to find its prey without much effort? Both insects and plants engage in the production and release of chemicals such as pheromones and allelochemicals. These can act as insect attractants and deterrents.

Last year I grew Tomatillos. I usually grow Tomatoes but I thought I would try Tomatillos instead. One of my plants was visited by Three-Lined Potato Beetles (Lema daturaphila). These insects feed on plants in the Solanaceae family such as Tomato, Potato, Eggplant, Tomatillo, and Groundcherry. From my reading, this species is not very damaging so I was willing to monitor and see if beneficial insects would step in to act as biological control agents. Sure enough, soon afterwards, when I was inspecting my plants, I found an assassin bug eating the beetle larva that were under a leaf. Just like Lily Leaf Beetle (Lilioceris lilii) larvae, the Three-Lined Potato Beetle larvae cover their backs with their own excrement called a “fecal shield,” as a means of defence. Clearly the assassin bug was undeterred. Plant volatiles had likely been released by the plant in response to the larvae feeding damage to the leaves. This has been described as an indirect defence mechanism[i].” The assassin bug responded as it detected the plant volatiles.

This spring, I planted some cantaloupe and watermelon seedlings in a raised bed. I read up on the various insects that are attracted to these plants—their life cycles and behaviours. One of the insects that favours cantaloupe and other members of the cucurbit family is the Striped Cucumber Beetle (Acalymma vittatum). Up until recently, I hadn’t seen any on my plants. Often, I will use floating row covers for protection from insect damage but these plants are currently flowering so they are uncovered so pollinators can access them. When I saw my first beetle, I thought about how it knew I was growing cantaloupe. Cucurbit plants emit floral volatiles in the air that travel. Adult cucumber beetles are attracted because the pollen of the plants makes up a part of their diet.[ii] These same and other volatiles also attract pollinators of these plants such as Squash Bees (Eucerini spp.).[iii]

Cucurbit plants also contain a chemical called cucurbitacin. This is the substance that gives some cucurbits a bitter taste. When cucumber beetles feed on the leaves and other parts of the plant, they absorb the cucurbitacin, rendering them unpalatable to many predators. Young plants produce more cucurbitacin than older plants—which make them more attractive and vulnerable to damage.[iv] Cucurbitacin is so attractive to the beetles that it encourages more and more feeding—called a “phagostimulant.”[v] (Is this the same as sugar, salt, and fat for us humans?) As the beetle feeding progresses, adult male beetles give off an aggregation pheromone called vittalactone that invites others to come and join the party.[vi] Cucurbitacin also plays a role in their reproductive activities as males transfer it to the females as “nuptial gifts.”[vii]

The beetles can also transmit bacteria via their feeding that causes a fatal wilt in the plant. What is also unfortunate is that the wilting plant gives off more volatiles that attract more beetles. The flowers of wilting plants are not as attractive as non-wilting plants—this encourages the beetles to move on to other nearby plants, thus causing further spread of the disease.[viii]

In the end, the key is to try to deter adult beetle feeding as much as possible. This can be achieved in a number of ways such as using floating row covers; delaying planting in the spring; planting more developed transplants; hand-picking beetles in early evening when they are most active; planting cucurbit varieties with lower levels of cucurbitacin,[ix] interplanting plants like radishes and nasturtium with melons,[x] and using straw mulch around plants to attract beneficial wolf spider predators.[xi] Some cucurbits like watermelon are resistant to bacterial wilt,[xii] unlike cantaloupe. So perhaps by the end of the summer I will at least have watermelon.

[i] Dicke, M. (2009), Behavioural and community ecology of plants that cry for help. Plant, Cell & Environment, 32: 654-665. https://doi.org/10.1111/j.1365-3040.2008.01913.x

[ii] Rojas, Erika Saalau et al. Bacterial Wilt of Cucurbits: Resurrecting a Classic Pathosystem. Plant Disease 2015 99:5, p. 569. https://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-10-14-1068-FE

[iii] Andrews ES, Theis N, Adler LS. Pollinator and herbivore attraction to cucurbita floral volatiles. J Chem Ecol. 2007 Sep;33(9):1682-91. doi: 10.1007/s10886-007-9337-7. Epub 2007 Jul 21. PMID: 17659427.

[iv] Rojas, p. 569.

[v] Wallingford, Anna. What Cucumber Beetles Want. Over Informed on IPM. August 13, 2020, Episode 24. https://extension.unh.edu/blog/2020/08/over-informed-ipm-episode-025-what-cucumber-beetles-want

[vi] Ibid.

[vii] Rojas, p. 569.

[viii] Alexander, Lauren Maria. Take Control of Cucumber Beetles. Growing Produce. https://www.growingproduce.com/vegetables/take-control-of-cucumber-beetles/

[ix] Ibid.

[x] Cline, G. R., Sedlacek, J. D., Hillman, S. L., Parker, S. K., & Silvernail, A. F. (2008). Organic Management of Cucumber Beetles in Watermelon and Muskmelon Production, HortTechnology hortte, 18(3), p. 444. https://doi.org/10.21273/HORTTECH.18.3.436

[xi] Striped and Spotted Cucumber Beetle: Insect Pests of Vegetable Gardens. Kansas State Research and Extension. https://bookstore.ksre.ksu.edu/pubs/MF3545.pdf

[xii] Rojas, p. 565.

Advice, Annuals, Websites

Begonias, so many Options!

June 26, 2023 peterboroughmastergardeners Leave a comment

By Christine Freeburn, Master Gardener

The choices for summer annuals seems to grow greater every year. Filler plants like geraniums, petunias, marigolds, impatiens are lovely, but the begonia has so many variations of shapes, sizes, colour, and sun requirements, they are worth a try in your hanging baskets or containers.

Begonia are generally easy care with no deadheading and different varieties can grow in sun or shade. Flowers are often smaller but there are lots on the plant. They often just fall off or can be pinched off quickly. Leaves come in many shapes and sizes, colours and textures. When you go into a garden centre, you need to know what type of begonia you are looking for.

Fibrous rooted types include the easy Dragon Wing variety which are great in window boxes and containers. They come in red, pink or white, grow about a foot tall and wide, and can take sun or part sun. There is a new variety called Canary Wing which has yellow leaves and prefers less sun.

Wax begonias Begonia semperflorens are usually sold in cell paks, prefer part shade, can have bronze or green thicker fleshy leaves and white, pink or red flowers. Often called bedding begonia, they are great in the garden as an alternative to impatiens.

Tuberous begonias include the Solenia type Begonia x tuberhybrida which can take full sun and come in a variety of colours from shades of pink to yellow and red. Great in hangers or containers.

‘Nonstop’ and ‘Illumination’ are hybrid variety of tuberous begonia that will take the heat but want shade. They come in lovely shades of pink, red, yellow, peach or white. These also work well in containers and hangers.

Reiger begonias can produce double blooms, are more upright and also prefer shade.

Gryphon Begonia is a cane type begonia with stunning foliage and upright habit which will do well in part shade in the garden bed. Although the plant rarely flowers, the maple shaped leaves on a 2 foot plant looks great.

Rex Begonias have amazing furry leaves in many different shapes and colours. They do not want any sun and are often used as houseplants. Flowers are rare on these lovely specimens, but the leaves are the showstopper.

And if you grew houseplants in the 70s, you might also remember the cute little indoor begonia called Strawberry Begonia Saxifraga stolonifera which grows similar to the spider plant having babies growing from trailing stems. These little houseplants are difficult to find but a nice addition to a houseplant collection.

Although begonias don’t need constant deadheading like so many other annuals, removing spent blossoms will keep the plant looking fresh and encourage new blooms.

Soil should be well draining and evenly moist but don’t over water as this can lead to root rot. Begonia stems are fleshy and brittle, and can break easily, so they don’t do well in wind. Fertilizing for bloom and good health can be done weekly over the summer months.

http://www.missouribotanicalgarden.org/

https://www.thespruce.com/

Advice, Perennials, Propagation

Peonies: The Stars of the Show at Present

June 19, 2023 peterboroughmastergardeners 1 Comment

By Mary-Jane Pilgrim, Master Gardener

Peonies are like the royalty of the flower world, with their lush petals and captivating fragrances. If you’re itching to grow more of these stunning beauties in your garden, you’re in luck!

Peony plants fall into one of three categories: herbaceous peonies, tree peonies, and intersectional/Itoh peonies (modern crosses between herbaceous and tree types). This article addresses the propagation of herbaceous peonies by seed and by division.

Growing Peonies from Seeds: Starting peonies from seeds is like embarking on a rather long gardening adventure. First, collect ripe seeds from mature peony plants once the flower heads have dried. Give them a good soak in water for a day to help with germination. Then, plant the seeds in well-draining soil in a pot or tray. Cover the container with plastic wrap to create a cozy greenhouse effect.

Now, it’s time for a little winter simulation. Pop the container in a cool spot like your fridge for about three months. After the chill period, move the container to a warmer spot with indirect sunlight. Keep the soil moist, and be patient. It might take a while, but soon you’ll see those precious seedlings sprouting. Once they grow bigger, you can transplant them into individual pots or your garden. Remember, it may take a couple of years for them to bloom.

Dividing Peonies: Dividing peonies is like giving them a fresh start and making more peony magic happen. Autumn or early spring is the perfect time to divide these beauties. Carefully dig up a mature peony plant, making sure to keep as many roots intact as possible. Gently shake off excess soil and look for natural divisions or “eyes” on the plant – these are the points where new shoots will emerge.

Grab a clean and sharp knife, and cut the plant into sections, making sure each division has a few healthy roots and eyes. Then, replant these divisions in well-prepared soil in a sunny spot. Give them a good drink of water and watch as they settle in and grow. Don’t be surprised if it takes a year or two for the divided peonies to bloom, but when they do, it’ll be worth the wait!

With these two propagation methods, you can expand your peony collection and enjoy a blooming paradise in your garden. Whether you choose seeds or division, the joy of growing peonies will reward you with breathtaking blossoms and a sense of accomplishment. Happy gardening!

Bees & Pollinators, Perennials, Propagation

Why are my Columbines Changing Colour?

June 12, 2023 peterboroughmastergardeners 2 Comments

by Emma Murphy, Master Gardener

Columbines (Aquilegia spp) are lovely perennials. I have had them in my garden for many years, and they always offer a pop of colour in the late spring/early summer garden here in Lakefield, Ontario.

These easy care perennials come in a variety of colours, shapes and sizes – most are bi-coloured, ranging from pastel shades to vibrant hues. Columbines have distinctive five-petaled flowers with long backward-extending spurs as pouchlike extensions of the petals, containing nectar. Sepals and petals are brightly coloured. The leaflets of the compound leaves are usually rounded and notched.

In my garden I have both cultivars and straight species (native) columbines, but it was a query on our Master Gardener of Ontario’s Facebook page about someone’s columbines changing colour from year to year that caused me to go down the research rabbit hole to try and find an answer for them.

What Did I Find Out?

Well, apparently columbines really like to hybridize with other columbines. They really do. They are also sensitive to their soil conditions and a number of other factors.

There has been some fascinating research done at universities like UC Santa Barbara (here and here). In one study they used two columbine varieties – red columbines pollinated by hummingbirds, and white or yellow columbines pollinated by hawk moths. Apparently hummingbirds prefer medium length nectar spurs (the ‘tails’ on the columbines), while hawk moths prefer the relatively longer-spurred species.

A. formosa (left) is primarily pollinated by hummingbirds. A. pubescens (right) is primarily pollinated by hawk moths.

The study also noted that columbines can change from blue to red, then white to yellow. According to the researchers, the colour shift from red to white or yellow in columbines has already happened at least five times in North America.

So Why Do They Change?

There are several reasons why columbines change colours:

DNA mutation
Natural selection
Adaptive radiation
Hybridization
Changes in soil conditions

DNA Mutation

Based on the UC Santa Barbara findings, at least 34 genes produce different columbine flower colours. Because of the presence of various genes, there’s an increased likelihood that the colours will change simply due to gene mutation. It doesn’t happen because of creation of new genes, but just because of current gene mutation.

Natural Selection

In the studies and mentioned above, if most pollinators are hummingbirds, most of the columbine colours are red. However, when the population shifts and most of the pollinators become hawkmoths, there’s a potential for the colour to modify. The resulting blooms can be white or yellow.

Adaptive Mutation

Another concept explored in the study of the columbine colour changes is adaptive radiation, based on Charles Darwin’s Theory of Evolution, which assumes that living organisms change their structures to better adapt to the changes in their surroundings. For columbines, flowers develop new traits as a response to changes in their environment. In this case, the changes include the pollinators.

Research shows that columbine flowers are tailored to the tongues of their pollinators, which shows an example of how they evolve based on their environment.

Hybridization

Columbine colour change can also be due to cross-breeding, when male and female parts are pollinated. The goal? Combining the positive attributes of two species, changing the physical characteristics, resulting in a better yield and disease resistance, among others.

Hybridization can also occur non-deliberately – for example when we plant two columbine varieties near each other, this will often create colour changes from the original plants.

To prevent problem hybridization, especially with our native Eastern Red columbine (Aquilegia canadensis), the best thing you can do is plant the native species as far away from the cultivars as you – not foolproof but an important thing to consider. Or don’t have any cultivars on your property, but that doesn’t guarantee they will stay the same as pollinators move from garden to garden.

Changes in Soil Conditions

It’s common for columbine colours to shift because of slight changes in the soil’s pH, as well as the presence or absence of metal ions in the soil. A pH lower or higher than 6.0 to 6.5 can result in nutrients being unavailable, which in turn can affect colour.

Our beautiful native Eastern Red Columbine (Aquilegia canadensis)

Colour change in columbines is a fascinating phenomenon, as you can see from my “rabbit hole research”.

But here’s the bottom line – if you want to keep your native columbines from hybridizing with cultivars you have to keep them as far away from each other as possible. If you like the idea of them changing colours (for a variety of reasons) just sit back and enjoy!

Where are the weeds?

June 5, 2023 peterboroughmastergardeners 2 Comments

By Mary-Jane Pilgrim, Master Gardener

I was honoured to be part of the Lakefield Horticultural Society’s Garden Tour last summer, along with fellow MG Emma Murphy. It was a glorious day, and I loved the wide range of people who came to tour — each with different backgrounds and gardening styles.

The one question I fielded more than once is “where are the weeds”?

First of all, what’s a weed? To me, a weed is a plant that is growing where it is not wanted. My weeds could be your prized “Lubauchnia” (my hubby’s fabricated word for plants he doesn’t know the name of, which includes most plants).

Disclaimer: I didn’t inherit a bunch of the nasty weeds as there were no gardens at my house when we bought it 32 years ago. I do deal with the nasties at my gardening clients’ homes weekly, though!

For plants that are growing where they’re not wanted in my gardens, here’s what works for me:

Don’t wait — smaller weeds are easier to get rid of than larger ones. This applies to spring and fall when we’re often not as diligent in getting outside. Sometimes it seems like a full grown weed can appear overnight during those seasons!
Use mulch — I love my leaf mulch, and it seems to be very effective in suppressing weeds. A chipper makes short work of a pile of leaves. Mulch also conditions your soil and encourages earthworms and microorganisms, a win-win situation.
It’s especially important to weed BEFORE the seed heads develop — you’ll save yourself a LOT of trouble getting them early in their life cycle.
Cut back perennials after they’ve finished blooming, and check for the inevitable “weeds” underneath.
Weed when the soil is moist, so that the maximum amount of root comes with the weed. Weeding in dry/hard soil results in small pieces of the root being left behind, which can usually regrow. I rarely weed without my trusty Lee Valley Root Knife — loosening the soil around the root before pulling.
Watch newly planted perennials closely, especially natives. If they send out runners or if they are very proficient at casting seedlings, they get “shovel pruned” at my place. You can do you at your place.
Lastly, “know your garden“. The more time you spend out there, the fewer undesirable plants there will be.

Simple knife-in then pulling works well for most regular weeds. However, some types such as japanese knotweed, lily of the valley, bindweed, cow vetch, DSV or creeping bellflower will require more diligence as their mother-roots are buried deep underground. Eradicating those weeds involves a lot of deep digging, soil sifting, and extreme diligence. There are actually support groups on Facebook for those truly invasive plants. May actually be easier to move!

Weeds that contain viable seeds should be “solarized” — left in a black plastic bag on the driveway for a couple weeks. The heat will fry the seeds. Dispose of the bag in the garbage. Don’t put seed heads attached into your composter.

There’s a new thought process that suggests that repetitively cutting difficult weeds at soil level is more effective than pulling them. It’s true that if it’s done often enough, those roots will eventually die for lack of nutrient supply from any top growth — however the weeds are usually much more persistent than the weeders! I read that cutting bindweed every 2 weeks will still take multiple years to make an impact. Sigh.

What are your tricks?

Advice, Fertilizer, Websites

To Fertilize or Not Fertilize?

May 29, 2023 peterboroughmastergardeners Leave a comment

By Lois Scott, Master Gardener

Gardeners are typically highly invested in having a beautiful and productive garden and want to do what is best for their plants. Although fertilizers are very often considered a necessary tool in providing optimal growing conditions they should be used with care and only when a soil test says they are needed. https://www.ontario.ca/page/soil-leaf-and-petiole-tissue-and-forages-and-feed-testing-labs

Commercial fertilizers or ‘plant food’ usually list three major nutrients on their products; nitrogen, phosphorus and potassium or N-P-K. These are very important plant nutrients but according to Linda Chalker-Scott PhD, author of the book “How Plants Work” https://horticulture.wsu.edu/people/chalker-scott/ “Our home landscape soils usually have enough phosphorus and potassium to meet our plant’s needs. So, wouldn’t more be better? She goes on to explain that excess levels of phosphate fertilizer can be bad for soil organisms by inhibiting the “development of the mycorrhizal relationship between fungi and plant roots causing plants to expend more energy for root growth. Another negative aspect of excess phosphorus is that it reduces the ability of plants to take up iron, a plant micronutrient. Excess phosphorus may also dissolve in runoff water causing blooms of harmful algae, depleting waterways of oxygen. Organic fertilizers such as bone meal, guano and chicken manure can also create an excess of phosphate in the soil”. https://gardenprofessors.com/fertilizers-a-cautionary-tale/

When your vegetable garden and/or annuals are growing abundantly but you start seeing older leaves turning yellow, your soil may need a boost of nitrogen-rich fertilizer. Nitrogen can become deficient in an actively growing garden and using something like alfalfa meal can replenish it.

Slow and steady may be the best approach to providing your plants with the ideal growing conditions. According to Dr. Chalker-Scott, “using organic mulches like composts, wood chips and pine needles provide a slow feed of nutrients to the soil, the way that nature provides nutrients”.

Advice, Perennials, Pruning, Websites

Pruning Herbaceous Perennials “The Chelsea Chop”

May 22, 2023 peterboroughmastergardeners Leave a comment

By Marilyn Homewood, Master Gardener

As the spring bulbs fade and we move past our “last frost” date (or so we hope!), the perennials are starting to grow by leaps and bounds. This can lead us to consider ways to manage their size or bloom time. The Chelsea Chop is a method of pruning that limits the size of a plant, controls the flower season (which can assist in creating peak season bloom combinations) and often decreases the floppiness of a number of herbaceous perennials.

In England, the time for this type of pruning is carried out now which is around the same time as the Chelsea Flower Show is held, hence the name. In our neck of the woods, timing would be most appropriate in late spring or very early summer when the plant has a fairly substantial amount of vegetative growth. When I am going to do this, I like to have it done before the onset of our hotter, drier weather so that it does not stress the plant overly (on average by mid June).

Phlox chopped in front to extend blooming season

Plants that have received the Chelsea Chop are not as tall or leggy, so that they may not need supporting. Flowers are smaller but are more numerous (removal of top shoots encourages branching of laterals).

It should be noted that you can not chop all summer blooming plants. Woody sub-shrubs do not respond well. If the spring has been dry, drastic pruning could shock your plants so a light hand is recommended in those years.

Many summer and autumn flowering perennials are good candidates for the chop. These plants include:

Garden phox (Phlox paniculata)
Yarrow (Achillea spp.)
Bellflower (Campanula spp)
Aster (Symphyotichum spp)
Coneflower (Echinacea spp)
Black-eyed Susan (Rudbeckia spp)
Upright Sedum Hylotelephium spp)
Penstemon (Penstemon spp)
Goldenrod (Solidago spp.)
Shasta daisy (Leucanthemum superbum)

This list is not complete. Try experimenting with some of the vigorous plants in your garden. I have a cultivar of catmint (Nepeta “Six Hills Giant”) that is large and spreading. In one area of my garden, I prefer it to stand a little more to show the blooms to effect so I chop it back by about one third in the last week of May.

Nepeta more upright and floriferous due to chopping

The chop is done in two ways depending on the effect one desires. In the first method, clumps of perennials are cut back by one third to one half. This will delay flowering and keep plants shorter and more compact. The second method involves cutting back only half of the stems on a plant, this has the effect of extending the flowering season over a longer period. I commonly used the second method on my Garden Phlox keeping the plants in bloom for a longer time. Pruning can be done with sharp shears or with secateurs. Garden shears are often faster when there is a large volume of pruning to be done. Try out the chop and see if you can alter the form or flower of some of your favourites!

Resources

https://www.gardenersworld.com/plants/11-plants-to-chelsea-chop/

https://www.bethchatto.co.uk/discover/our-blog/guides/the-chelsea-chop-how-to-do-it.htm

Advice, Garden Design, Vegetable Gardening

How to Make Your Vegetable Garden Beautiful

May 15, 2023 peterboroughmastergardeners 1 Comment

By Cheryl Harrison, Master Gardener

I was recently browsing through a hard copy April, 2009 issue of the “Fine Gardening” magazine. I came across an article, “Who Says Your Kitchen Garden Can’t Be Beautiful”… to see the full article check the link here. The author, Jennifer Bartley, planted her raised vegetable garden for the edibles that it produced but in such a way that the garden was also beautiful!

This appeals to me because vegetable gardens are definitely not my passion. However, I do love to eat my own fresh veggies and so I have a vegetable garden.

I have raised vegetable beds where I have intermittently practiced square foot gardening (see square foot gardening for more information). I have also planted marigolds and nasturtiums amongst my vegetables which are pretty but also serve a purpose….the marigolds for insect control and the nasturtiums because they are edible. For more information on flowers for your vegetable garden check the link here. I have been inching towards trying to make my vegetable garden more visually appealing without realizing it.

Ms. Bartley talks about using “four simple design tips” including:

Arrange bunches of bold colour.
Plant snug beds.
Smooth out the edges.
Define your space.

Arrange bunches of bold colour – I do a planting plan ahead of time every year. Try grouping your vegetables, flowers, fruits and herbs together so that you have lots of colour and texture (different leaf shapes). For example, you may edge the bed with the leafy fronds of carrot followed by beets and parsnip, maybe you plant some asparagus in the centre for the height or an obelisk in the centre and plant runner beans to climb it. You could use yellow, green or purple bush beans to fill in the blanks. I grew some purple Brussel sprouts last year and the leaves were spectacular!

Plant snug beds – This tip works well with raised beds. There is no need to plant your vegies in rows. Instead, group the vegetables together close enough to cover the soil when they are grown but not so close that they will crowd each other to prevent proper maturity. Covering the soil helps with moisture retention and weed suppression. Thinning your carrots allows them to mature properly and provides the delicious “thinnings” for your salad.

Smooth out the edges – Just like your flower beds, vegetable gardens are at their best when they are clean and pathways are clear. I use straw in my pathways because it is available and my garden is wet in the spring so the straw covers the mud between the raised beds. You could use bark mulch, gravel, brick or whatever you have.

Define your space – We humans like a certain amount of order and proportion in our world. If a space is too big, or too small, it can make us feel uncomfortable. The edges of a raised bed help to define the space. In our garden, we have several raised beds so have a defined entry to the garden and a wooden cedar fence to further define the space. You might choose to use a pot filled with herbs at your entry, a rock or cedar stump on either side or a berry producing shrub.

It is also a great idea to have a bench in the garden where you may rest and admire your work. Also, don’t stop with just a scarecrow … you may choose to add other garden ornaments in order to make your own beautiful vegetable garden!

Garden Design, Grass, Native Plants

Mulling about Mulches

May 8, 2023 peterboroughmastergardeners Leave a comment

By Laura Gardner, Master Gardener

At the beginning of February, the snow had melted on the grounds of the native plant garden at the Peterborough Public Library. This garden is an ongoing project between the library and the Peterborough and Area Master Gardeners. I noticed a few weeds in areas that did not have a thick enough layer of wood mulch. Ideally, they would have been removed in the fall, but I didn’t get that opportunity. Being situated downtown, the library garden is open to many types of plants that arrive via wind-blown seeds. As the intentional plantings continue to grow and fill in the empty spaces, weeds will become less of a concern.

However, it may be a good idea to consider incorporating living green mulch such as low sedges and reducing or eliminating the wood mulch in the garden to minimize weeds and to develop a more natural aesthetic that mimics nature. Benjamin Vogt of Monarch Gardens defines a green mulch as a lower plant layer that covers more than 90% of the ground. Vogt talks about how sedges, short grasses, and other low-lying forbs can be used as an initial base layer in a garden with taller plants interspersed throughout. They can also be used to plug in holes in between existing plantings. Vogt also mentions that wood mulch can inhibit the growth and spread of the plantings—which reduces the overall natural aesthetic.

Incorporating green mulch does have an initial cost but over time will cost less than wood mulch as the latter needs to be constantly replenished as it breaks down. Native plant nurseries may have smaller plugs that can be purchased in bulk at a lower cost than larger potted plants. In addition, sedges and grasses can be divided and replanted. Wood mulch is also not as environmentally friendly as it needs to be transported to the site.

Green mulch offers the same benefits as wood mulch—the ability to provide organic matter to the soil when it dies back in the fall; it helps to regulate soil temperature and moisture levels; it shields weed seeds from the light exposure they require to germinate, and it prevents soil erosion. One thing I have noticed about a particular area in the garden is that despite the heavy application of wood mulch, invasive perennial weeds like Canada Thistle (Cirsium arvense) and Field Bindweed (Convolvulis arvensis) still have the strength to poke through. The long-term and more practical solution to managing these perennial weeds here is to encourage dense plantings of green mulch and the spread of existing plantings. These weed species thrive in the sun but will weaken if shaded out by other plants.

Green mulch provides support to various wildlife species. For example, unlike traditional turf grass, sedges grow with a space around them, thus providing access for ground-nesting bees. If wood mulch is too heavily applied in the garden, it inhibits pollinator lifecycles. Sedges and grasses also serve as host plants for some Lepidoptera species and produce seeds that are valued by birds.

When considering sedges, note that many prefer at least partial shade and moist soil conditions and so the right ones need to be selected. For the library garden, the area that is sunny and dry could accommodate Short-Beaked Sedge (Carex brevior), Ivory Sedge or Bristle-Leaved Sedge (Carex eburnea); while the partially shaded but dry areas could be home to Pennsylvania Sedge (Carex pensylvanica). A low-lying grass that could be used is Blue Grama (Bouteloua gracilis). When sourcing these, it is best to check area native plant nursery catalogues this spring for available stock. The ones to check locally are Natural Themes in Frankford, Grow Wild in Omemee, GreenUp Ecology Park Nursery in Peterborough, and Native Plants in Claremont. Ontario Native Plants is an online mail order provider. For hard-to-find sedges, Prairie Moon in Minnesota has a wide variety available to ship to Canada as seed.

Patience in the Garden

May 1, 2023 peterboroughmastergardeners Leave a comment

By Chris Freeburn, Master Gardener

When spring finally arrives, gardeners are outside daily looking for signs of life in our flower beds. Snowdrops, crocus, tulips and daffodils along with many other spring bulbs give us that pop of colour we have missed. Hellebores, primula, magnolia, Iris reticulata, lungwort are all beginning to bloom. Spring perennials like ground phlox, poppies, pasque flowers, daylilies are showing their green shoots and will soon be flowering. Bleeding Hearts, trilliums, lupins and salvia are all growing in leaps and bounds.

This past April, we experienced a week of abnormally hot weather that encouraged plants like peonies to jump up. Note to self – get peony rings up. The return to “normal” temperatures is better for all the plants. And it reminds us that spring is an unpredictable season and we can’t rush it.

As gardeners, we need to practice a bit of patience. We need to leave our gardens to thaw, give the soil time to warm up and give the overwintering insects time to awaken from the garden litter we are so excited to “clear up”. We also need to be aware that not all perennials show life at the same time.

Hostas show their poking dark shoots just as we are getting into the flower beds, so we need to watch when stepping around or moving mulch in those gardens. Perennial Hibiscus are probably one of the the later showing perennials that will look dead until mid June. Be patient! When Hibiscus decide to begin growing, they grow quickly, inches in a day. Lilacs are making buds and maples are leafing out, but hydrangeas are still looking asleep. Although early flowering clematis like Blue Bird and other group 1 types will be popping up, later bloomers with still be sleeping. Don’t despair. Be patient!

Grasses can also be deceptive. Cool season grasses begin to grow in early spring and have reached their best by mid summer. Karl Foerster, which is a Calamagrostis or feather reed grass is a well known cool season, zone 5 grass that grows 5′- 6′ tall. It likes sun, will take it wet or dry and tolerates poor soil. Overdam and Avalanche are two other feather reed grasses that will be showing green now.

Warm season grasses do not come up until June and are at their best in fall. They will look dead until the weather warms up. Patience! Because they will not show green until later in the spring, you can plant warm season grasses behind other earlier growing perennials to hide their brown bottoms.

Miscanthus grasses are warm season types and are available in different heights from 3′ to 8′ tall. Miscanthus sinensis & M. Sacchariflorus are classed as invasives, spreading by rhizomes and seeds. Other warm season grasses include Japanese Forest Grass or Hakonechloa, Japanese Blood Grass and Sedges. Panicum or switch grass is a warm season grass with many varieties native to North America. ‘Northwind’ is the most commonly know variety and it is drought resistant, will grow in any type soil and likes full sun.

Native grasses like Little Bluestem (Schizachyrium scoparium), Big Blue Stem (Andropogon gerardii) and Indian Grass (Sorghastrum nutans) are warm season grasses. These are beautiful additions to your garden, but will not green up until the weather warms.

May is the most active month in the garden. Sometimes we forget to enjoy the moments, slow down, breath deeply and have patience. New wonders will be happening for many days ahead. Enjoy them!

https://landscapeontario.com/perennials-in-bloom-month-by-month

https://www.invadingspecies.com/

The Peterborough & Area Master Gardeners