Seed Cone Prediction and Evaluation

Evaluations of the seed crop development and seed maturity are needed throughout seed development. Predictions of crop size are needed during the late spring to plan for funding and the actual collection. Cone surveys continue throughout the summer and intensify when ripeness is predicted. Surveys may continue even when cones are being collected.

If there will not be a seed crop worthy of collection, you will save time and money by deciding early in the planning process not to collect cones. Cone crop forecasts help managers make these decisions and allow collections to be planned when a crop is expected.

Early Forecasts

The first signs of a possible cone and seed crop are when branch terminals bear cone flowers and conelets. These flowers and conelets generally can be seen early in the spring. It’s easier to spot cone flowers and conelets if you climb a hill so you can look down on the treetops.

True firs, spruces, Douglas-fir, cedar, and other non-pine species—1 year crops Reproductive buds form 12 to 16 months before ripe seed is shed. Flowers and conelets appear early in the spring. The conelets in Douglas-fir are easy to see during midspring, depending on the locale, and will cover the middle of the tree in a good cone year.

In true firs, if there is a large crop, you can see upright conelets 2 weeks after the pollen has been shed. When the pollen flies, red fir and white fir conelets are 1 and 2 inches long, respectively. Failure to see cones soon after pollen has been shed indicates that conelets were destroyed or there was not much of a crop.

All pines—2-year crops

Reproductive buds in the pines are formed 24 to 28 months before ripe seed is shed. You can see cone flowers in the pines during spring or early summer, depending on the species and locale. Two to five cone flowers on the end of the branches throughout two-thirds to three-fourths of the crown indicates that a good crop is developing. The forecast for an impending cone crop can be estimated the summer a full year before the collection, but many things can reduce the crop before it reaches maturity.

By fall, cones are about one-eighth to one-fifth their final size and are large enough to be seen from the ground, particularly when viewed through binoculars. Be sure not to confuse mature or recently opened cones with developing cones that will be ready for collection the following year.

Forecasts during the Summer before Collection

By early summer, the cones that mature in 1 or 2 years will be visible from the ground. If you suspect a good crop and need the seed, you should conduct cone crop surveys and sample collections throughout the summer season to validate the cone crop, select desirable trees or areas for collection, and monitor cone ripeness.

Avoiding Collections When Cone Crops Are Poor

It is important to make collections only during good cone crop years to ensure higher quality seed. Problems associated with collecting cones during poor cone crop years include:

• Insufficient cones per tree to justify the expense of climbing (or other collection method)
  
  
• Low percentage of sound seed per cone because less pollen is available for pollination.
  
  
• Large proportion of self-pollination and inbreeding depression (lower seed set, lower survival, slower growth, less insect resistance, less genetic diversity).
  
  
• Trees of lower genetic worth may be selected because many trees lack cones.
  
  
• Larger proportion of seed destroyed by insects
  
  
• Reduced cost effectiveness for cone processing and seed sowing (the same or similar fixed costs produce smaller seed lots).