Archives For spring

The late February weather in Chicago has been a glorious time to be outside and work in the garden. But the unseasonably warm weather has also raised questions about the long-term effect on plants and what garden tasks are appropriate.

It is best to hold off on doing any detailed clean up of garden beds as the mulch and leaves in the beds will provide some protection to any early growing perennials when the weather eventually turns cold again. Raking leaves off the lawn and cutting back perennials are all fine to do now providing your garden soil is not too wet.

Snowdrops are blooming at the Garden.

Early flowering bulbs like snowdrops that are in flower here at the Chicago Botanic Garden are very tolerant of the cold. Daffodil and tulip foliage is coming up; these might end up being damaged by a spell of cold weather, but this should not affect the spring flowers. You do not need to take any special maintenance steps to protect these plants.

If you have some perennials that are growing in a warm area of the garden with more pronounced growth, they might benefit from a light layer of mulch. For the most part, though, there is nothing special for most gardeners to do in their perennial beds.

This is great weather to prune but proceed with care. Spring flowering shrubs like viburnums, lilacs, and forsythia set their flower buds last year so pruning done at this time of year will remove flower buds and reduce the number of spring flowers. You can still prune—just be aware of the flower buds as you are pruning. Forsythia flowers along the stems while viburnums will have a flower bud at the ends of the stem.

The dormant season, and in particular late winter, is the best time of year to complete rejuvenation pruning, which is the aggressive pruning of overgrown shrubs to bring them back into scale with the garden. Shrubs like hydrangea (except oak leaf hydrangea), potentilla, and spirea that flower on new wood respond well to pruning now too. For instance, I cut my Annabelle hydrangea back to the ground each spring.

Any plants installed last summer or fall should have been mulched when they were planted. If they were not, then mulch them now to help mitigate the temperature swings in the soil and prevent frost heaving of any plants in spring. The freezing and thawing of the soil can push recently installed small plants such as 1-gallon perennials or ground covers that were grown in containers out of the soil as the weather transitions to spring.

If we receive a good covering of snow, the snow itself will not harm plants unless it builds up on them and breaks branches. It is a good idea to brush plants off during a storm if you observe them getting weighted down. Later snowstorms are more likely to come in wet and heavy. Leave the plants alone if the snow has frozen on them to avoid breaking branches during the removal process.

Enjoy the warm weather and the early blooms, both at the Chicago Botanic Garden and in your own backyard.

Early summer in the Dwarf Conifer Garden is all about the new growth. Everything is bursting forth with fresh new growth in vivid shades of green, chartreuse, yellow…and blue!  

PHOTO: Dwarf Conifer Garden in spring.

Layers of color draw you into hidden paths throughout the Dwarf Conifer Garden.

Many of the trees feature entirely unexpected colors. For most of the year, Spring Ghost blue spruce (Picea pungens ‘Spring Ghost’) looks like your average Colorado spruce. From early spring through midsummer, however, the tips of every branch shine with the palest yellow—nearly white—new growth. Likewise, Taylor’s Sunburst lodgepole pine (Pinus contorta ‘Taylor’s Sunburst’) is a handsome green tree for most of the year—until spring, when radiant yellow new growth bursts forth, bringing a welcome dose of sunshine to the garden.

PHOTO: Picea pungens 'Spring Ghost'.

Picea pungens ‘Spring Ghost’

PHOTO: Pinus contorta 'Taylor's Sunburst'.

Pinus contorta ‘Taylor’s Sunburst’

PHOTO: Pinus cembra 'Blue Mound'.

Pinus cembra ‘Blue Mound’

New needles aren’t the only attraction this time of year. Many conifers have cones that start out in surprising shades! Blue Mound Swiss stone pine (Pinus cembra ‘Blue Mound’) would be a beautiful plant in its own right, with its long, soft, blue-green needles. But when you throw in dusky purple cones, you get a plant that is truly a gem. As the cones age, they’ll slowly turn into the more typical brown of a ripe cone, but right now, they’re as pretty as any flower.

Red can be a difficult color to find in conifers, but Acrocona spruce (Picea abies ‘Acrocona’) has cones that start out a vivid ruby red and slowly fade to a soft tan. The cones start out upward-facing, but slowly begin to droop as they age.

PHOTO: Picea abies 'Acrocona'.

Picea abies ‘Acrocona’ has cones that start ruby red, and slowly fade to tan.

PHOTO: Abies koreana 'Silver Show'.

Abies koreana ‘Silver Show’

Another unique plant is Silver Show dwarf Korean fir (Abies koreana ‘Silver Show’). Unlike other conifers, the firs (Abies sp.) have cones that always face upward. ‘Silver Show’ is beautiful any time of the year, but its purple upward-facing cones really make it special in spring. The cones start out small and green, but as you can see in this picture, they begin to turn purple as they grow until you’re left with dozens of dark purple cones set against perfectly tiered, silvery green foliage. There really is nothing else like it in the Garden.

PHOTO: Male cones on Pinus leucodermis.

Male cones on Pinus leucodermis

On most conifers, it’s the female cones that are most showy and most often noticed, but on Bosnian pine (Pinus leucodermis), it’s the male (pollen-bearing) cones that steal the show. Arranged in groups at the end of every branch, they light up the tree like little Christmas lights. Even on a gloomy day, the bright orangey-tan color stands out against some of the deepest green needles in the garden.

All of these colors are a seasonal show that is best appreciated before things start to heat up for the summer, so now is your best time to come see them!


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Sure, it snowed just three days into spring—it’s Chicago! This week we’re set to hit the magic temperature, 45 degrees Fahrenheit, and here’s what it will trigger in your garden.

ILLUSTRATION: How trees set buds in spring.


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Have you heard the sounds coming from nearby lakes, ponds, and puddles this month? The American toads are singing!

PHOTO: female toad looking directly at the camera

This female American toad may be listening for the enchanting song from a handsome male toad.

Every spring, the toads emerge from hibernation in wooded areas and hop to the nearest standing water to breed. The sound you hear comes from the males, who are singing to attract a mate. You’ll hear the sound of hundreds of toads at the Kleinman Family Cove for the next week or so, maybe longer.

The toads will pair up and lay a string of eggs in shallow water where it is warmest and rich in food for their offspring. After laying eggs, the adults will return to the woods or shady gardens to look for food, leaving their babies to fend for themselves.

PHOTO: the toad pair are together in the water with a string of black eggs she has laid around the algae.

The black lines of dots in the water are strings of eggs that were laid by the toad on the right.

The black embryo inside each egg will grow into tiny tadpoles and hatch in about a week. They will grow and develop into half-inch toadlets over the next few weeks. Then they will leave the water and join their parents in the shady gardens and woods. With any luck, some of them will survive the next two years, developing to full maturity, and return to the Cove to breed.

This is the only time of year to hear the toads singing, so visit the Cove this month. If you visit over the next four weeks, maybe you’ll see some little black tadpoles swimming in the water.

Please resist the urge to collect them to take home. You won’t be able to provide enough of the right kind of food for a growing tadpole or toadlet, and they will die. Watch them grow up successfully in their natural habitat at the Cove throughout the month of May and early June instead!


©2013 Chicago Botanic Garden and my.chicagobotanic.org

This year, it sure felt like spring was a long time coming — especially compared to last year when it seemed that we went straight into summer! I wonder how the wildflower timing of spring compared to previous years in the Chicago area…

Mayapples, April 25, 2012

Mayapples, April 25, 2012

Mayapples, May 2, 2013

Mayapples, May 2, 2013

For several years now, I’ve been working on a web-based citizen scientist project, called Project BudBurst, with colleagues at the National Ecological Observatory Network (NEON). We study the phenology — the timing of natural events like blooming, fruiting, and leaf fall — of plants around the country. Our participants track when plants bloom in their area, and we compare the reports to records from other parts of the country.

You can help us collect data! Sign up to help at Project BudBurst.

For instance, I’ve been tracking when the first forsythia flower opens on the plants near the Garden’s front gate since 2007. The earliest bloom I have on record in that time was last year, on March 15, 2012. The latest first flower for this specimen was this year, on April 20, 2013. In 2007 and 2008, however, we also had first flowers in mid-April (April 16, 2007, and April 17, 2008, respectively). So, as we look back in time, this year’s bloom time doesn’t feel quite so late. In the graph below we show the variation in flowering dates (using Julian dates, which standardize for differences in dates between nonleap and leap years).

forsythia data

In the Chicago area, we have a wealth of phenology data collected by the authors of our local flora, Plants of the Chicago Region by Swink and Wilhelm (1994). While they were gathering data for their book, they recorded when they saw plants in bloom from the late 1950s to the early 1990s. They record the forsythia bloom period as April 25 to May 5. So, when we look still further back in time, our “late” spring is much earlier than it has been in the past.

I took a similar look at several other species, both native and nonnative, for which we have both Project BudBurst data and data from Swink and Wilhelm’s book. About 70 percent of the species have earlier flowering dates in the last six years compared to those recorded by Swink and Wilhelm. Some of the species that have advanced their flowering dates are in the table below.

Species Earliest First Flower Observations
Common name
Genus species
Swink & Wilhelm
1950s – 1990s
Project BudBurst
2007 – 2012
Days
Advanced
Forsythia
Forsythia x intermedia
April 25 March 15 -40
Spiderwort
Tradescantia ohiensis
May 14 April 12 -32
Dogtooth violet
Erythronium americanum
April 6 March 20 -17
Red Maple
Acer rubrum
March 20 March 6 -14
Mayapple
Podophyllum peltatum
May 1 April 17 -13
Lilac
Syringa vulgaris
May 3 March 20 -44
Black locust
Robinia pseudoacacia
May 9 April 20 -19
Bradford pear
Pyrus calleryana
April 15 April 13 -2

Plant phenology, particularly when plants leaf out and bloom in the spring, is remarkably sensitive to the annual weather. Looking at phenological records over much longer periods of time can tell us a lot about how the climate is changing. Many scientists are comparing contemporary bloom times with historic bloom times recorded by naturalists like Aldo Leopold in the early 1900s, and Henry David Thoreau in the mid 1800s, as well as records kept by farmers, gardeners, and others interested in the natural world. Two of the longest phenological data sets are those maintained for cherry blossoms in Japan (dating back to 900 AD) and for grape harvest dates by winemakers in Switzerland (dating back to 1480 AD).

Plants have so much to tell us, if we take the time to listen!


©2013 Chicago Botanic Garden and my.chicagobotanic.org