Question
QUESTION: My wife has planted some flowers right against our concrete slab foundation and I am concerned about moisture problems in that area.  I did put some block against the foundation to make somewhat of a barrier between the soil and foundation but those blocks are only 2 inches thick probably and a couple inches tall and I asked her to try not to splash the wall but just soak the plants for a short while when watering.  Do you suggest we move the flowers a distance away from the house and if so how far?  The thing is even if flowers werent there, there was grass before, so it was getting wet anyways when grass is watered.  Not sure what to do...

ANSWER: Hey, James.

You did well to install some block against the foundation. The actually make vapor barrier plastic which is what is normally used.

I'm presuming by "flowers" you mean things like petunias, snapdragons, pansies, marigolds, and other small plants that flower seasonally, also called annuals. Generally, the amount of water that they require won't affect your foundation.

If she planted bushes -- like ligustrum, natal plum, oleanders -- they require more water and have a more substantial root system. Generally, though, if you keep them pruned, their energy will go into regenerating growth rather than expanding the root system. If you let them grow wild, the roots could cause some damage, although it still would be a little unusual.

Definitely soak the plants rather than the exterior siding. I like to use soaker hoses in my foundation planters. I just roll the hose out, turn the water on, and come back in 15-30 minutes. They are pretty inexpensive, although some people -- including me -- find joy and relaxation in actually going out to water the plants. It's just that I water the plants away from the house and let the soaker hose water the plants next to the house so that I don't splash water and soil everywhere.

I don't think you have anything to worry about specifically, but I also don't know where you're locaed -- so I don't know the soil types and weather there -- and I don't know what flowers you're talking about. If you'd like to send me some pictures, send them directly to [email protected], and also tell me where you live.

Hope that helps.

Russel

---------- FOLLOW-UP ----------

QUESTION: She planted a hibiscus right against house.  She also planted bird of paradise plants right against patio concrete but a couple feet from foundation slab.  We are in az, so only rains few days a year.  I will make sure to prune if they get too big as you mentioned.  How big should we allow them to grow?  They will only be able to spread a couple feet horizontally due to space, but what about vertically and width from house too?

Answer
Hey, James.

Neither of those should cause any problems over there in Arizona if you take care of them.

The giant bird of paradise could, but I'm presuming that you have the standard bird of paradise. The bird of paradise does like to spread via new shoots so be aware of that. I have seen one plant that spread and became so big that it did cause foundation damage, but it took about 40 years.

The hibiscus requires quite a bit of water to keep it looking good and flowering, and over here in San Diego it is quite susceptible to white fly. White fly don't like to be wet, so most of us water the leaves each time we water the hibiscus, or set the automatic irrigation sprinklers to spray the bush, too.

In both cases, though, to protect your siding, keep the bushes pruned so that there is 6-12 inches of air space between the bushes and the exterior siding. Bushes brushing up against the siding can create mini- and micro-environments that hold moisture against the siding and causing moisture damage.

The hibiscus and standard bird of paradise will only get so tall, so they shouldn't be a probably vertically next to the house. If you have a giant bird of paradise, they can get very tall and really shouldn't be planted in a foundation planter.

Hope that helps.

Russel