When to collect seed?

[NSB001]

Hello, when do I collect seeds? I know with deciduous that the leaves will drop soon. Do I take seed when there on the ground or off the tree before they dry out?
What a bout conifers and pines?

[Raniformis]

With the cupressus species you can collect at any time of year. Many of these species are serotinous (open after fire) and the cones remain on the trees for many years after the seed ripens. For this reason I've found it best to collect cones that still have a little colour (brown), the seed from these cones is more viable than seed from grey cones.

Species like cedrus and many of the common pines you see around seem to co-ordinate their years of fertilisation, for example, last year where I live pretty much every tree was sporting mature cones while this year the same trees where fertilised and won't have mature cones until the '27/'28 season. They're called mast years. They still produce the odd cone inbetween however so if you can find some ripe but unopened cones they may contain viable seed.

Deciduous trees like maple, beech, ginkgo, sweetgum, etc, can be collected now, through autumn.

Oak acorns can be collected when they start to fall on the ground but like pines they co-ordinate fertilisation, one year you'll get 1000s of acorns everywhere you look, the next year hardly any.

Elms generally flower before the leaves come out and ripen during spring but it happens fast and they're hard to catch, some parts of a cluster will be ripe while other parts will be immature.

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Ripe vs immature (cypress)

[shibui]

Different species ripen at different times of the year.
Maples ripen around the time the leaves drop but many of the seeds stay on the tree making it easy to pick ripe seed.
Oaks ripen mid - late summer and drop as soon as the seed is mature so you have to collect seed from the ground.
Chinese elms flower in Autumn and the seed ripens rapidly and is mature before the leaves drop. My Chinese elms are currently heavy with seed that should be mature in a few weeks.

In general, seed is mature when it changes colour.
Most seed is viable a bit before full ripeness. It can germinate but usually does not store well if picked before full ripeness.

Pines are ripe when the cones start to open. Most pine cones mature in Autumn. I'm currently checking my JBP each day, looking for signs they are starting to open. They generally open on a warm, dry day and usually all open over just a few days so to get best seed harvest you really need to be watching. I've noted that when the cones open the best, viable seed drops immediately. Seed that is left in the cones is often not viable.
Pine cones are also tricky because the scales open and close with changes in moisture and humidity. Later in winter the cones will look closed but the best seed dropped out when they opened earlier in Autumn. Old cones can stay attached to the tree for a year or 2 after the seed is gone.
As with other species, seed is usually viable before the cones are fully ripe so you can probably pick closed cones from now and still expect to get some good seed.
Some conifers retain the seed in the cones for a year or 2 after maturity so pick oldest, brown/black cones any time of year if they are not opened.

For more you'll need to name names as each species is different.