A Little Bit More
Don’t get the impression that fire-adapted pines NEED fire to open all of their cones; some cones will open eventually without fire. But those species that use fire to start a mass seed dispersal - Pitch, Jack, Knobcone, Table Mountain, Lodgepole, and Longleaf Pines - are all well-adapted to living where fires often occur.
Fire greatly improves the chances of pines’ ability to reproduce. Any of you who may have tried growing pines, quickly learned that they need lots of sun to grow. Without adequate sun, seedling pines soon weaken and die. Landscapers certainly know this and plant pines in open, sunny locations, not in close proximity to other trees that might shade them. This pine requirement that demands plenty of sunshine for healthy growth can be a liability though; pine seeds that fall among dense grasses, trees and shrubs are never going to grow into mature trees.
Recently burned Lodgepole Pine area in Yellowstone National Park © John wiessinger
For those species that do “wait” for a fire to prepare the surrounding landscape, they have the field almost all to themselves. Seeds dispersed after a fire have little, if any, competition from other plants and the ashes of the burned material acts as a real fertilizer giving seedling pines a boost in growth. Once the pines attain some size and can maintain their position above other plants in the area, they can grow into healthy, mature individuals.
Activities
Science – Cooking Pine Cones
Objectives: Simulate the action fire has on sealed pine cones
Materials: Tree field guide, cones from one of the fire-friendly pines
If you’re able to acquire fire-friendly cones –called serotinous cones by biologists - you can see for yourself how heat works to open their scales and release seeds. This is an easy exercise that should prove interesting and will help to cement what the students learn about pines.
- Check out the range maps for these following “fire-friendly” pines (Pitch-Pinus rigida, Jack-Pinus banksiana, Knobcone-Pinus attenuata , Table Mountain-Pinus pungens, Lodgepole-(Pinus contorta), and Longleaf-Pinus palustris Pines) to see which one(s) of these might be growing in your area.
- If one of these does grow in your area, see if you can obtain a few unopened cones (possibly a parent or local nursery can help with getting these)
- Put the cone(s) on a cookie sheet and place in the oven. Set the temp at a low setting for a short time (Pitch Pine cones need at least 130°F before they’ll open). Look to see that some of the resin sealing the cone is melting onto the cookie sheet
- Once the cone has begun melting its resin, you should be able to turn off the heat in the oven and allow the cones to cool down. Once cool, remove and allow the scales to pull back (I’ve had these pull back within a few hours but yours may take longer) As the scales open, the cone should release its seeds (you may need to shake the cones a bit to get all of the seeds out)
- If you wish, you can plant these seeds in potting soil that has good drainage. The seeds are small so plant just below the soil surface. Keep the seeds at room temp, moist but not too wet, and see what happens.
Even if you don’t have a fire-friendly pines nearby, you can look for pine cones and allow their scales to open a bit - they’re probably already open but the scales will pull back even more in a dry environment. As the cones dry out (dry, winter homes are perfect for this) if you’re lucky, a remaining seed or two may drop out.
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