Is Pluto still a planet in astrology?

Yes. Astronomy reclassified Pluto as a dwarf planet in 2006; astrology kept reading it as it had since 1930, because the readings depend on its cycle and position, not its category. This site lists it with the planets and says plainly what it is.

Why does Pluto spend so long in some signs?

Its orbit is stretched, so it moves fastest when nearest the Sun, in Scorpio, crossed in about twelve years, and slowest at the far end, in Taurus, about thirty. Every sign between takes something in between, which is why a Pluto generation can be twelve years or thirty.

What does Pluto rule?

Scorpio, in the modern scheme, a sign Mars ruled alone before 1930 and which many astrologers still read with both. Pluto's natural house is the 8th: what is shared and what is owed, intimacy, other people's money, loss, what is kept out of sight.

Astrology basics · The ten planets

Pluto in astrology: a dwarf planet that takes 248 years

Pluto is a dwarf planet, smaller than our Moon, found in 1930 and reclassified in 2006 when bodies of its size were found beyond it. Astrology kept it as a planet and reads it as one. Its orbit takes about 248 years and is lopsided, so it spends twelve years in one sign and thirty in another. By sign it tells what a cohort had to take apart and remake.

What it is: A dwarf planet since 2006; astrology keeps it as a planet
Zodiac cycle: About 248 years, twelve to about thirty years per sign
Retrograde habit: About five to six months a year
Sign ruled: Scorpio
Natural house: The 8th
Its domain: What a cohort had to take apart and remake

A dwarf planet, kept by astrology

Pluto is about two-thirds the width of our Moon, with a moon of its own, Charon, half its size, and an orbit so stretched that for twenty years of each circuit it is nearer the Sun than Neptune. The International Astronomical Union made it a dwarf planet in 2006. Astrology did not follow; the readings had been built since 1930 and the thing itself had not changed, so every chart on this site lists Pluto with the planets and reads it as one.

Twelve years in Scorpio, thirty in Taurus

Because the orbit is an ellipse, Pluto's speed through the zodiac varies more than any other body's. It crossed Scorpio, its fastest stretch, in about twelve years (1983 to 1995); it takes about thirty years to cross Taurus, where it moves slowest. So a Pluto sign is a twelve-year cohort or a thirty-year one, and this site gives each two or three sentences on what that cohort took apart, with the years named. The yearly retrograde, five to six months, is in the table and little else.

The house: one person's remaking

Thirty years of births share a Pluto in Taurus; they do not share its house, since the houses turn once a day and the birth hour settles which one Pluto fell in. That house is where this one person takes something down to the frame and rebuilds it, and it is read at full length. A Pluto in the 4th has moved house eleven times and gutted two of them; a Pluto in the 10th leaves a twenty-year career on a Tuesday and does not go back for the plant; a Pluto in the 7th keeps the one friendship that survived the divorce and has no small ones. The remaking is the person's own, in that area.

The longest transits in the chart

Pluto is the slowest of the five planets this site's transit reading covers. Transiting Pluto aspecting a natal planet keeps its orb for two or three years and is exact three times, sometimes five, as the yearly loops recross the degree; Pluto's passage through one natal house runs twelve to thirty years, most of a chapter of a life. A reading of it names the thing being taken apart and the person's hands on it this year, not the finished rebuild. Pluto squares its own place at an age that moves with the generation, because its speed is uneven: births from about 1960 to 1975 met it at thirty-six or thirty-seven, the early 1990s meet it at forty to forty-two, the 2000s at forty-seven to fifty-five, and children born since about 2015 reach it near or past seventy.

See Pluto in your own chartA free birth chart, with the reading, from your date, time and place.

Questions

Is Pluto still a planet in astrology?: Yes. Astronomy reclassified Pluto as a dwarf planet in 2006; astrology kept reading it as it had since 1930, because the readings depend on its cycle and position, not its category. This site lists it with the planets and says plainly what it is.
Why does Pluto spend so long in some signs?: Its orbit is stretched, so it moves fastest when nearest the Sun, in Scorpio, crossed in about twelve years, and slowest at the far end, in Taurus, about thirty. Every sign between takes something in between, which is why a Pluto generation can be twelve years or thirty.
What does Pluto rule?: Scorpio, in the modern scheme, a sign Mars ruled alone before 1930 and which many astrologers still read with both. Pluto's natural house is the 8th: what is shared and what is owed, intimacy, other people's money, loss, what is kept out of sight.