Tips for Making Spring Plant Observations

Professor Lois Stack serves on the Signs of the Seasons Advisory Team. We talked to her about her horticulture work and asked for advice about collecting plant phenology data in spring.  

As we head into the second monitoring season, do you have any general advice for trained SOS volunteers?

People should make note of the second year and how it’s different from the first year.  Look for plant stages you may have missed in the first year. You can also anticipate things you’ve already seen. Also, now that you have plants staked out, you don’t need to spend as much time setting up your site and learning about the forms and the online data entry.  You can concentrate on closely observing the plants!  Phenology dates may change slightly from one year to the next, but I don’t think they’ll change dramatically.

Let’s talk about the 8 plants on the SOS Indicator Species List. Are there any special features or peculiarities people should watch out for?  

Wild Strawberry

This plant is deciduous but retains greenness in the leaves throughout winter. People might not be sure if they see “initial growth” or last year’s leaves.  In early spring, when the snow is receding and before the grass turns green, nothing much is growing.  If you see strawberry leaves then, they’re probably last year’s.  Check back the next week to be sure.  As the grass starts to green up you’ll probably see strawberry greening up about the same time.  Look for new fresh growth from underneath the old leaves.  “Initial growth” (on the data sheet) will be leaves, flowers will happen sometime in May, and then fruits will appear in June.

If you have it staked out from last year that’s good because you might not see the leaves coming out among the blades of grass in the lawn. It will produce a new rosette of foliage from the same roots in the same spot. New foliage grows up over the old foliage. The new rosette looks like tips of leaves with a flower bud in the middle.  Leaves will elongate and the flower will start to open—that first flower is often very close to ground.


This plant has a strong and extensive rhizome system.  Although it’s perennial, the shoots won’t necessarily come from the same place as last year’s shoots.  So, in this case, it would be a challenge to follow one plant from year to year. The first thing people will see is a fairly sturdy stalk with leaves folded up—like a stalk of asparagus.  It might be interesting to take a square meter plot and flag all milkweed stems at the end of one year and see where the new shoots come up the following year.

Rugosa Rose 

This plant will be easy to identify because it has one of the most thorny, stout rose stems around. There will be an obvious stem from last year and look for apple-green leaf buds that are big and bright. Note: Flowers and fruits will appear before colored and falling leaves. The data sheets list flowers and fruits after colored and falling leaves—this might be confusing for people.


This shrub has stems with yellow lenticels (bumps). People generally aren’t aware that almost all plants, like forsythia, that flower in early spring (before mid-June) set their flower buds the previous year and the buds overwinter. The flower buds are separate from leaf buds. Flower buds are bigger than leaf buds.  On most forsythia, flowers open first, then as they’re fading leaf buds begin to open.  The data sheets reflect a different order so watch out for that. People should check back frequently to confirm things: “Oh yes that was a flower bud not a leaf bud” etc.


Like forsythia, this is planted in landscapes and also has separate leaf and flower buds. The leaf buds are much smaller and more pointed than flower buds, which are big, round, chartreuse buds.

Red Maple and Sugar Maple

The trickiest part with the maples may be that leaves and flowers can be high up in the tree.  Take field glasses (binoculars) out with you so you can see the flowers, which are beautiful dark red, with yellow stamens (Red Maple). Pollen release is easy to tell—look at the ground for yellow powder.

Some people may not think of maple “samaras” as fruits but they are the fruits of maple trees. To a botanist anything that contains seeds is a fruit, but to homeowners those may be just “spinners.”  Remember, those are the fruits!

A note about Maple ID—Observe Carefully!

It can be hard to tell them apart from just looking at new leaves. It’s easy to confuse Red and Sugar Maple; look at the leaf serration (Red is toothier).  Red Maple fruits mature earlier than Sugar Maple (maple fruits generally drop off by September). Red Maple flowers are redder than those of Sugar Maple.

Do you have any other general advice for volunteers as they begin their phenology monitoring this year?

First, I recommend people read the data sheets before they head out into the field so they’ll know how the phenophases are defined. Also, add your own comments explaining what you saw when you recorded something in “full flower,” for example. Also, I only got a handful of questions last year and they were all good questions. I love the questions and people should ask more!

Tell us about your background and the work you do now.

My job is two-fold. As a professor of sustainable agriculture I teach a plant science course. I’m also a Cooperative Extension specialist in ornamental horticulture. I’ve been here about 25 years and I’ve seen a lot of changes over that time. When I first came, I spent a lot of time with nursery/greenhouse/garden centers on crop selection, crop production, and crop pest management. Now a lot of that information has moved into the private sector. That industry has matured to the point where nobody asks me for that information anymore because they can get all of that from whomever supplies the plants.

Now I find myself working more on issues. For example, I still do pest management  but I spend a lot more of my time on issues like invasive species and how they impact people’s gardening habits and the “green industry.” Native plants are a big issue now, too. People are concerned about invasive species and the environment and they want to garden for butterflies and birds. I’ve also seen a tremendous maturation in the knowledge level within the green industry and among their customers—people know a lot more about these things than they used to. I see this in the Signs of the Seasons program as well.  People come to this program with a lot of background knowledge and interest.