Saturday, March 9, 2013

Bud burst comes to Project BudBurst

Looking at Stages of Leafing out in Chokecherry

Bud burst stage beginning- you can see green leaves under the bud scales
Winter dormant stage

Sometimes young leaves are reddish

Leaves unrolling, this occurs within a few days of the beginning of budburst

The first leaf stage

Today we are having a snowstorm - blizzard. Here in Colorado this mostly is a welcome thing. Its annoying if you have to drive somewhere, but potentially life giving for our parched ranches, prairies and forests.  We remember all too well the fires last summer which were made possible with record droughts and low snowpack. We even had a fire start in a wet mountain valley in Rocky Mountain National Park in November. It burned most of the winter, since there was so little snow. Bizarre. 

It's been a cool but mostly dry winter and spring so far. This means the soil has stayed pretty cold, so even the winter annuals and early bulbs have been slower than usual to emerge. It has been fun to at least vicariously enjoy spring by reading all the reports coming in to Project BudBurst especially from the South and California. It will be interesting to see how plants respond to the wild weather which has effected so much of the USA this year as spring fully develops.

There is a lot more to look for in the early spring of 2013 since Project BudBurst has now added a new phenophase -- bud burst.  So bud burst finally comes to Project BudBurst. You might ask why, up to now, we have not included the bud burst stage in our protocols. The challenge is that how plants prepare for winter and make buds to protect leaf tissue varies widely - so it's a little difficult to come up with a simple consistent definition of when a plant is in the bud burst stage.  Some buds simply burst open with new leaves, others swell, then change colors then reveal brownish or reddish early leaves which will eventually emerge and turn green.  Some plants do not have any leaf scales at all, like many dogwoods and bitterbrush.  These plants have tiny rolled up leaves that usually turn brown or red in the fall, then turn green and expand into normal looking leaves sometime in the spring. It makes sense that plants have a wide variety of ways to get through the winter - this makes it possible for them to adapt to many different climates and conditions. The definition of bud burst which is being used this year (and should apply pretty easily to most deciduous shrubs and trees) is to note when you can see leaves exposed as the scales of the buds spread apart. As long as you are observing a plant that has scales on its buds this should be pretty easy to see. If the leaves are not green you will have to make sure you are seeing leaves and not just other leaf scales.

Bitterbrush winter leaves. They expand into full size green leaves in spring

The date of bud burst is a really important stage to report to Project BudBurst since scientists can use this to precisely determine the beginning of the growing season for each plant species. The timing of bud burst usually reflects the genetics and climate around the tree quite precisely so it is an important way to see how plants are responding to changes in climate or growing conditions. For many trees it is usually easier to see leaf bud burst than first flowers since you can see it on the easy to reach lower branches.

Here in the high plains the first plants to burst their buds are trees that are pollinated by the wind instead of insects. Siberian elm, Green ash, Silver maple, Quaking aspen and Red maple are usually the first ones. Their flower buds are usually quite swollen and rounded just before they burst. They often are reddish or even black in color. The "flowers" are actually just anthers on thin stalks that waver in the wind, spreading pollen far and wide. They may not have any noticeable color at all since there are no petals or sepals. The exception to this general rule is Red maple which can be bright red and can attract insects as well as disperse by wind.

Sibirian elm with male flowers and budburst stage in the leaf bud


Cherry Blossom Blitz

Don't forget about the Cherry Blossom Blitz! Any cherry tree can be used, even the odd ornamental ones. Cherries are already in bloom in the milder parts of the country and should be spreading rapidly north over the next couple of months. There is nothing more spectacular than fruit trees in full flower, turning streets and gardens or even hillsides shades of white or pink. Its a celebrated symbol of the optimism of spring. A great way to help Project BudBurst and enjoy spring at the same time.

Last year we had one of our most successful years with many observations from new observers and new parts of the country.  I am looking forward to seeing what new things will be discovered this year!

Paul Alaback


  1. Over the past week I have seen flower buds burst revealing cottony tufts on some aspens near Aspen, Colorado . Is it typically the male staminate catkins that burst first? Does this qualify as one of the phenophases to submit to PBB? It is not first flower since I only see the tuft.

  2. Great question on aspen. They have cottony buds here right now too. These hairs provide protection for the flower buds as they develop. Wait until you can see the catkins (flower stalks) emerge and see the tiny black male flowers or pollen (first pollen or first flower stage). After that happens the leaf buds will open up which is the budburst stage. Leaf buds open very quickly so it's usually easy to tell they are leaf buds, with the leaves unrolling usually within a day. Also note that aspens are either male or female, if the flowers don't have the black anthers or pollen it is a female tree which we do not keep track of, except for leaf budburst and fruiting.