characterized by a lightly pert and exuberant quality
"Pert" also means "impudent" but the robin's rudeness is characterized more by an exuberant ("joyously unrestrained") love of life. Ben describes it this way: "He likes to hear folk talk about him. An' curious--bless me, there never was his like for curiosity an' meddlin'. He's always comin' to see what I'm plantin'..."
Very soon she heard the soft rustling flight of wings again and she knew at once that the robin had come again. He was very pert and lively, and hopped about so close to her feet, and put his head on one side and looked at her so slyly that she asked Ben Weatherstaff a question.
(botany) a plant lasting for three seasons or more
It was bare of flowers because the perennial plants had been cut down for their winter rest, but there were tall shrubs and low ones which grew together at the back of the bed, and as the robin hopped about under them she saw him hop over a small pile of freshly turned up earth.
hinder or prevent (the efforts, plans, or desires) of
"Baffle" also means "be a mystery or bewildering to"--both definitions fit the situation because Mary is wondering what's underneath all the ivy, and she is disappointed to see nothing but leaves. The wild ivy, in addition to being a sign of the secret garden's neglect, is meant to prevent people from finding the locked door.
The ivy was the baffling thing. Howsoever carefully she looked she could see nothing but thickly growing, glossy, dark green leaves.
slender stem-like structure by which some twining plants attach themselves to an object for support
There were other trees in the garden, and one of the things which made the place look strangest and loveliest was that climbing roses had run all over them and swung down long tendrils which made light swaying curtains, and here and there they had caught at each other or at a far-reaching branch and had crept from one tree to another and made lovely bridges of themselves.
"Hazy" means "filled with fog or mist"--the gray or brown branches give the appearance of fog or mist, and the use of the adjective "hazy" for the noun "mantle" emphasizes the mysterious nature of the secret garden. To prevent this hazily mysterious, somewhat dead garden from seeming scary and hopeless, there is this description: "The sun was shining inside the four walls and the high arch of blue sky over this particular piece of Misselthwaite seemed even more brilliant and soft..."
There were neither leaves nor roses on them now and Mary did not know whether they were dead or alive, but their thin gray or brown branches and sprays looked like a sort of hazy mantle spreading over everything, walls, and trees, and even brown grass, where they had fallen from their fastenings and run along the ground.
She had been actually happy all the time; and dozens and dozens of the tiny, pale green points were to be seen in cleared places, looking twice as cheerful as they had looked before when the grass and weeds had been smothering them.
filled with the emotional impact of overwhelming surprise or shock
The adjective "astonished," the noun phrase "breathing space," and the verb phrase "cheer up" personify the bulbs, which strengthens the connection between Nature and the human natures of the gardeners. The more Mary works in the garden, the better her nature becomes. Even Ben, who's surly because he's lonely, is joyfully proud of his gardening and the robin. And the sweetest character in the novel is Dickon, who has the closest relationships to all forms of nature.
The bulbs in the secret garden must have been much astonished. Such nice clear places were made round them that they had all the breathing space they wanted, and really, if Mistress Mary had known it, they began to cheer up under the dark earth and work tremendously.
the trait of acting unpredictably and more from whim or caprice than from reason or judgment
Ben is punning on the word "flightiness"--while he is focused on its unpredictable appearances and proud flirting with many females, he is also talking about a bird that has the power of flight.
"That's like him," snapped Ben Weatherstaff. "Makin' up to th' women folk just for vanity an' flightiness. There's nothin' he wouldn't do for th' sake o' showin' off an' flirtin' his tail-feathers. He's as full o' pride as an egg's full o' meat."
And on the trunk of the tree he leaned against, a brown squirrel was clinging and watching him, and from behind a bush nearby a cock pheasant was delicately stretching his neck to peep out, and quite near him were two rabbits sitting up and sniffing with tremulous noses--and actually it appeared as if they were all drawing near to watch him and listen to the strange low little call his pipe seemed to make.
He moved so slowly that it scarcely seemed as though he were moving at all, but at last he stood on his feet and then the squirrel scampered back up into the branches of his tree, the pheasant withdrew his head and the rabbits dropped on all fours and began to hop away, though not at all as if they were frightened.
He moved quite close to the bush with the slow movement Mary had noticed before, and then he made a sound almost like the robin's own twitter. The robin listened a few seconds, intently, and then answered quite as if he were replying to a question.
"I've lived on th' moor with 'em so long. I've watched 'em break shell an' come out an' fledge an' learn to fly an' begin to sing, till I think I'm one of 'em. Sometimes I think p'raps I'm a bird, or a fox, or a rabbit, or a squirrel, or even a beetle, an' I don't know it."
There's naught as nice as th' smell o' good clean earth, except th' smell o' fresh growin' things when th' rain falls on 'em. I get out on th' moor many a day when it's rainin' an' I lie under a bush an' listen to th' soft swish o' drops on th' heather an, I just sniff an, sniff.