Autumn has not arrived so late, as far as I remember. October passed with the leaves staying on the trees – and staying mostly green – right until the last week.
It is likely that we will become more used to November and not October as a month filled with fiery display from our hedges, shrubs, and trees.
Many leaves seem to become yellow during autumn. However, it is only a hint of their true base colour which is then overlaid by the green pigment created from chlorophyll. The yellow becomes visible when the autumn chlorophyll is gone.
But to go from yellow to orange or red depends upon the weather as well as the ability of some trees – such as maples – to create sugars.
Monty Don gave advice on how to convert a leaf from a leaf mold. Pictured: Monty with the fiery autumnal leaves of Rhododendron luteum
Leaf colouration is more severe the further apart the temperatures are in the late summer or early autumn. The starch in the leaves converts to sugar, but the cold nights prevent it from moving the sugar from the leaf into the roots.
This is what causes the red pigmentation. This process is slowed down by our milder and wetter summers that have less temperature variation between night and day.
Leaves fall as cells are broken down in the layer of abscission between leaf stalk and branch. This causes a corky scar that protects the tree against infection.
Trees that cannot make this scar tissue are not able to drop dead leaves. They wait until spring when new leaves will be ready to replace them. This is why hornbeam and beech have their russet leaves through winter.
All deciduous leaves, regardless of their color, can be turned into leaf mold once they have fallen. It is a wonderful thing to have leaf mold. It is an excellent component of potting soil, and it can also be used as a mulch for all types of trees.
Leaf mould, unlike good compost which requires regular turning to stimulate the bacterial digestion that is the main action in the product’s conversion, is nearly entirely created by fungal activity. This is why it doesn’t require heat or oxygen.
Moisture is the most important thing in turning a leaf from leaf mould to leaf leaf within a season. Dry leaves can take longer to fall down.
My method is to brush the leaves in long rows, then rake them and finally mow them. The leaves will rot faster when they are cut into smaller pieces, and require less space.
They are then mowed and placed in a container with chicken wire. In this part of the country, they are not much trouble but it is necessary to thoroughly wash them each layer.
We then have perfect leaf mould the next October. We then empty the bay so it is ready for this year’s leaf harvest and put the leaf mould into reused compost bags ready for use throughout the coming year as part of our potting compost.
Because it’s slightly acidic, it makes a great peat substitute and is ideal for bulb like lilies as well as rhododendrons.
It is not practical to install a large, permanent wire cage for leaf mold in large gardens. The solution is to place the leaves inside a large black bag with the top left open and not tied.
You should make sure your leaves are wet. To drain any excess water from the bag, poke a couple of holes into the side. The leaves can slowly become mouldy if left to rot.
MONTY’S PLANT OF THE WEEK: CRAB APPLE ‘EVERESTE’
Monty Don said Crab Apple ‘Evereste’ (pictured) makes a beautifully delicate and clear jelly
One of many crab apples that make ideal small garden trees, Malus ‘Evereste’ was introduced in 1980 and won the RHS Award of Garden Merit in 1993.
There are four of them in my Paradise Garden. They all bear fruits.
Even though the fruits can be quite small, you can still make delicious jelly from them. This is true if they are available before birds.
THIS WEEK’S JOB PLANT TULIPS
Bulbs must be planted to a minimum of twice their height. Good drainage is essential for tulips. If your soil is too heavy to grow them, you can add grit or use a potting compost that’s peat-free and has horticultural grit. Pack them in tightly but not to the extent that they’re touching.