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Planting bulbs in shallow soil over concrete

#1 · 3rd October 2021, 9:59 am

Hi, just wondred if anyone had any luck planting anemone, sparaxis or crocus bulbs in shallow (7-8inch) of soil over a concrete slab. In our new house we have a lovely large raised flower bed but unfortunately a large part of it is over a concrete slab and I am worried the bulbs will rot. Would it be worth putting some gravel over it and then cover with soil. Any advice will be appreciated!

#2 · 3rd October 2021, 9:47 pm

I am not an expert but I think that bulbs would require at least a depth of planting to be about 4 inches, but if you think on it, bulbs can be grown in containers, therefore is it worth considering covering your concrete slab with a decent looking gravel? you could then include in this space a few good sized rocks for effect, treat yourself to a nice terracotta container plant a japanese maple in it, then obtain complimentary containers for your bulbs, or get some nice small grasses, to go with the maple. Have a look on Lee's You Tube channel, there's a video on grasses, you could end up with a japanese style area, a prairie style area, or a very colourful area of Daff's, Tulips, Crocus etc.

Best of luck

#3 · 4th October 2021, 8:42 am

Quote from Lee Garden Ninja on 4th October 2021, 8:42 am
Hi Guest!
You're right to worry that the bulbs would rot. All planting with the exception of aquatic and bog plants will need drainage if not they will pretty much drown then rot. Any water needs someplace to go rather than sitting at the bottom of the planted container or area. Also, bulbs need a good depth of soil/compost to help them stay upright and be protected from excessive frosts.
bulbs can be grown in containers, therefore is it worth considering covering your concrete slab with a decent looking gravel? you could then include in this space a few good sized rocks for effect, treat yourself to a nice terracotta container plant a japanese maple in it, then obtain complimentary containers for your bulbs, or get some nice small grasses,
The suggestion above is a really good idea to help distract the area using containers and give it purpose which is really clever. When I've had to deal with large amounts of concrete, and a client can't afford to have it excavated I've used containers in this way too. If you want to plant directly into the ground you will need to break through this concrete to allow proper drainage and really improve whatever soil you use!
The thing to remember about bulbs is to plant them 3x their size in the ground. They for the most part hate to be sat in water and will rot. If you plant them in containers you will need to feed them in the second year then replenish the compost completely the year after. This is because compost is not soil but a portion of organic food for soil or in lieu of soil. So over time it depletes and will need either topping up or replacing every few years.
Planting bulbs in the green can be a good way of ensuring slow-growing spring bulbs, like Snowdrops and Winter Aconites get off to a good start. If you've never seen that before then have a look here!
https://youtu.be/gBwkna77UqM
Ornamental Grasses can be a good idea to soften the area as well and here's that guide that the poster above mentioned.
https://youtu.be/SeJaCgSfBrE
Other than the tips above the sky is the limit in the way you set out this area and create something wonderful! Good Luck!
Lee

Hi Guest!

You're right to worry that the bulbs would rot. All planting with the exception of aquatic and bog plants will need drainage if not they will pretty much drown then rot. Any water needs someplace to go rather than sitting at the bottom of the planted container or area. Also, bulbs need a good depth of soil/compost to help them stay upright and be protected from excessive frosts.

bulbs can be grown in containers, therefore is it worth considering covering your concrete slab with a decent looking gravel? you could then include in this space a few good sized rocks for effect, treat yourself to a nice terracotta container plant a japanese maple in it, then obtain complimentary containers for your bulbs, or get some nice small grasses,

The suggestion above is a really good idea to help distract the area using containers and give it purpose which is really clever. When I've had to deal with large amounts of concrete, and a client can't afford to have it excavated I've used containers in this way too. If you want to plant directly into the ground you will need to break through this concrete to allow proper drainage and really improve whatever soil you use!

The thing to remember about bulbs is to plant them 3x their size in the ground. They for the most part hate to be sat in water and will rot. If you plant them in containers you will need to feed them in the second year then replenish the compost completely the year after. This is because compost is not soil but a portion of organic food for soil or in lieu of soil. So over time it depletes and will need either topping up or replacing every few years.

Planting bulbs in the green can be a good way of ensuring slow-growing spring bulbs, like Snowdrops and Winter Aconites get off to a good start. If you've never seen that before then have a look here!

Ornamental Grasses can be a good idea to soften the area as well and here's that guide that the poster above mentioned.

Other than the tips above the sky is the limit in the way you set out this area and create something wonderful! Good Luck!

Lee

#4 · 4th October 2021, 11:14 am

Hello Guest,

On your post in the forum you said “In our new house we have a lovely large raised flower bed” the rest being a large slab of concrete.

My reply to you was to think about gravel, rocks, a Japanese Maple in a nice container, with complimentary containers and plants etc.

Another thought, how large is your existing raised flower bed? Would it be possible for you to put in place another raised bed similar to the existing? But it does not have to be the same size, the space you have decides this.

I was thinking about making a raised bed using Sleepers, placing this on the concrete slab,but doubling up on the sleepers so that the depth of the bed will be twice as deep, a sleeper on top of another sleeper.

You could make this square or oblong, say for instance its oblong, you could then, a couple of foot from the end install width wise another 2 pieces of sleeper, so in effect you have two areas within your sleeper, one bigger than the other.

The possibilities are, in the smaller section you could install a nice small tree or shrub in a container and fill around this with gravel, slate or mini chipped bark, just to make it look nice, in the larger section of the sleepers you could line this area with fleece and a pond liner and give yourself a water feature?

Of course you could reduce the size of the middle section and have two planting areas one at either end, as in the centre section, line one end with pond liner, make a few holes in it, and make a little bog garden.

Again Good Luck