Growing willow for biomass at home

Willow is easy enough to grow - the problem is when to plant. I've spent 5 years coming to the realisation that trees have two periods of growth - spring and summer, when they grow at the top, and winter - when only roots grow. They can't really do both. So.. if you are going to plant willow whips, you need to cut them in November or December, and get them in the ground then. They sit there, apparently doing nothing, until spring. What you dont realise is that the roots are growing like mad ready for spring. We push them into the ground and cut them back to just over a metre above the ground. But then, as if by magic, new shoots appear all over the place, and they take off.  If you plant the same whips in spring, you'll almost certainly get poor root growth, and they'll turn into weak, sickly plants that never really get going - no matter how long they are in the ground. I've got 5 year old plants which went in at the wrong time, and they have never grown. Whips that went in the ground in December are towering trees by comparison. We try not to stake the trees much - we've found that staking them makes the stems thinner and taller - if they get to wave around in the wind, they become stronger - so only take them for the first year till they have some basic strength and are upright, then take the support away.

There's a rule of thumb that 5 acres of willow will grow enough wood to keep a large house going - on a 5 year rotation. From my observations, that means you'll be harvesting wood at around 2 inches average diameter - so running a 6 or 7 year rotation would create much larger timber. Just planting rows of willow around the edge of our paddocks takes hundreds of whips - so you need to be very organised to build up enough trees to become self sufficient. Problems always occur - the main ones are voles - which take the bark off the base of new plants - the little buggers totally ring bark them. Deer will rub the bases of younger trees, and chew the tops - so most whips get a 1200mm tree shelter and stake until they are properly established, and the trunk is at least 50mm diameter. At that point the shelters and stakes can come off, and be re-used on another plant. It's probably a two or three year rotation for that. I let the whips grow as they want for the first year, just rubbing off shoots at low level to concentrate growth higher up the stem. At the end of the first year, cut nearly everything off - back to a strong main stem about a metre high. The following year, it will explode into action, and you will see rapid and powerful growth.

Willow is very good to burn - it just needs to be cut at the right time. Wait for all the growth to die back in autumn, and around the time that you are planting, is also the time to harvest. The two go hand in hand really, as you can cut whips (long straight stems about the diameter of your thumb) and then cut thicker stems for firewood. I lay some poles on the ground parallel to one another, and then lay the cut timber at right angles to dry. We cut everything to a metre in length - its important to be accurate, or when you put it through the saw in the yard at home, you'll end up with logs just too long for the boiler (which takes 500mm). 

The photos here are taken in our paddock, where we've experimented with growing the stuff.  Most planting is actually in our woodland, where it grows amongst poplar, birch, hawthorn, ash and oak - the more variety, the stronger all of the trees seem to be. They like air, and light - but a bit of competition for light is good, and encourages growth upwards, which makes it easier to harvest timber for firewood - vertical growth is better than spindly stuff growing sideways!

The important thing to note here is the progression of planting:

 

Year 1 December:  Cut whips, and plant. Ideally just over a metre high when in the ground. Push one end into the ground as far as you can - at least 20 cm.  Ideally there should be no grass to compete with the new roots. We tend to mulch with grass or wood chip, so surface growth is inhibited till the new plant gets growing.

 

Year 1 - March / April: Trim the whips to a metre, and rub off any buds at low level - you want to encourage growth at the tip, not low down.

 

Year 1 - sit back and watch them grow...

 

Year 1 November / December - when everything has died back, we cut back new growth and shape the young tree - I cut back to nearly the top of the original whip.  This sets the tree up for good strong growth in the new year.

 

Year 2: Sit back and watch them take off - all you need to do now is rub off any growth below the top union - where by now there should be a cradle of branches starting to fan out at the top of the whip.

 

That's it really - once the plants are 2 and 3 years old, you'll be taking whips from them to plant more, and pruning to keep good strong leaders for firewood. We aim for selective pruning of firewood in year 6 - by that time, you should have a big top of growth, and main branches at least 50 to 65 mm diameter - great for chopping into half metre logs. They need cutting in December/January, and either splitting, or storing under cover whole, for the rest of the year. Split, they dry out a lot quicker.

 

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