I guess it starts as a small plant, becomes a shrub, and can be allowed - or indeed encouraged - to become a tree. Endemic to Australia, it grows well here and is well adapted to Portuguese landscapes.
Full of vibrant red bristly-looking flowers, they grow well in full sun in Portugal, mainly as they aren’t too picky about the soil, provided it is well drained.
Callistemon is its official Latin name but is called ‘bottlebrush’ as the blooms resemble the brushes used to clean the inside of bottles.
They have a long blooming season, so there will always be a blast of red in the garden, but there is another colour, yellow (C. sieberi), and several different species giving red, yellow, orange or white blooms, but the red seems to be more popular. The blossoms are actually really soft to touch, though they give the appearance of being hard and bristly like a brush.
They can be grown from seed, and in fact, each red bloom will have a collection of woody seeds hidden, which remain on the plant until it dies, or fire stimulates their release. A few species release their seeds annually, but an easier method of propagation is to take cuttings, and these should be taken from semi-mature wood. You need to pinch off the leaves on the lower half of the cutting and remove any flower buds, then dip the cut end of each into hormone powder (available from garden centres) and plunge into a pot of universal potting soil, then water occasionally until it is strong enough to be planted out, and place in a sheltered sunny position. To start from scratch, of course, you could always purchase a partially grown shrub from a garden centre, to cut the waiting time! Once established, you can start with a natural fertilizer, such as compost, round the roots.
They are slow-growers, so it could take up to 30 years to grow to a tree, and they have a wide spread, so some pruning might be necessary to keep it in shape. To do this, lightly thin out the branches so more sunlight can reach the inside of the plant, and remove any suckers growing from the roots as they appear. Also, remove forking or crossing branches. If you seem to be lacking flowers, remember that it needs at least 6 hours of sun, so it could be that some other plant or trees are giving it too much shade.
Because there are so many beautiful blooms on one of these shrubs or trees, the bees will love them, and you will find your shrub positively humming as they seek out the nectar, and it will also attract butterflies. They will suffer from one or two diseases from overwatering or really wet soil, but generally, they are pretty hard to kill! These are non-poisonous to dogs, so if you have a chewer in your canine family, it will do them no harm.