Raised planter containing bamboo with concrete base best way to provide drainage?

Dannyboy334

I intend to create an L shaped raised planter bed. A large proportion of the planter will have bamboo planted within it. The other smaller section will have climbers attached to trellis.

The trellis section will have a 173mm gap in the foundation which will allow drainage to the soil.

My question really is how will I provide drainage for the Bamboo considering I want to contain the roots. I was thinking of placing a weep hole as close to the foundations as possible which would drain directly to the subgrade which you can see on the second image on the right-hand side.

Many thanks

Plantminded

I'd be inclined to reconsider this @Dannyboy334. I'd use the design intended for the other section throughout the planter, with direct access to the soil below for drainage. The weep hole will inevitably become blocked by roots or debris over time, resulting in unsightly overflow on to your paved area.

Provided you choose the correct variety of bamboo, it will be easily contained in that solid planter.  Look for one of the clump forming or non invasive types like Fargesia.  Bamboos have a rather negative reputation in this country but that's because they have often been incorrectly selected by quick fix contractors and makeover gardeners to provide instant screening for their impatient clients!  If researched properly and managed correctly bamboos can provide a delightful evergreen presence in your garden.

Use a soil based compost like John Innes No 3 in your planter, mixed with about a third of horticultural grit to ensure adequate drainage.  I hope this helps.

Dannyboy334

Plantminded said:

I'd be inclined to reconsider this @Dannyboy334. I'd use the design intended for the other section throughout the planter, with direct access to the soil below for drainage. The weep hole will inevitably become blocked by roots or debris over time, resulting in unsightly overflow on to your paved area.

Provided you choose the correct variety of bamboo, it will be easily contained in that solid planter.  Look for one of the clump forming or non invasive types like Fargesia.  Bamboos have a rather negative reputation in this country but that's because they have often been incorrectly selected by quick fix contractors and makeover gardeners to provide instant screening for their impatient clients!  If researched properly and managed correctly bamboos can provide a delightful evergreen presence in your garden.

Use a soil based compost like John Innes No 3 in your planter, mixed with about a third of horticultural grit to ensure adequate drainage.  I hope this helps.

That certainly does help. I will listen to your advice and leave the opening on the bamboo side of the planter too. Much simpler.

Do you think I need to line the planter with any plastic sheeting or is the John Innes No 3 mixed with the horticultural grit enough for drainage?

I should also mention that the garden is north facing so hopefully the Fargesia does not take too long to reach my desired height of 2 metres.

Is the 500mm depth of my planter enough for the bamboo to grow properly?

Plantminded

If you want to line the inside of the planter to protect it, I'd use geotextile membrane, not plastic, as it allows air and water to move through it, but I wouldn't put it in the base of the planter as it is only semi-permeable and does not allow adequate drainage unless you pierce it with holes.  The Fargesia in my garden is in front of my neighbour's tall laurel hedge and gets less than an hour's sun in the morning, it seems quite happy and has reached about 1.5 metres in two years.  Try to buy the biggest plants you can afford and if possible view one in a garden centre or nursery to satisfy yourself that you are happy with the colour and growth habit.  Some Fargesias are upright, others cascade slightly.  The depth of 500m is fine, they are grasses and not deep rooted.

Dannyboy334

Thanks for your helpful advice. One last question, how deep should I plant the bamboo from the top of the soil, is 400mm down deep enough? I want to have it sitting as high as possible to give the best possible screening.

Loxley

You should plant the bamboo so the top of the compost in the pot is level with the surrounding soil surface. 

Plantminded

I would fill the planter up with compost to about 2 inches from the top and plant the bamboo with its compost at the same level as the compost in the planter. This gap of 2 inches allows you to water when necessary without it spilling over and you will have room to change the top few inches of compost every year to refresh it.  

Below is a photo of the Fargesia nitida in my garden. (The leaves on the upright canes will become fuller in spring which is why it looks a bit bare now!)  It took a couple of years to reach this height from a single plant of about half a metre.  But, check before you buy!