I have a large magnolia tree in my front yard that has lots of surface roots, some getting close to the house. I’ve read that it’s okay to cut small roots, an inch in diameter or so. Some ten years ago, my gardener dug a trench on two sides and placed a hard plastic barrier to prevent root growth close to the house and sidewalk, but I don’t think that is still doing any good. I would like to keep this beautiful tree, but I need to care for it properly as well as the rest of the lawn.
I was thinking about putting in a semi-circular bench around the canopy line to mark off the tree area vs. the rest of the lawn and giving it less frequent but deeper water. I will probably dig up all the terrible-looking grass, half-dead Kikuyu, I think, and put in large concrete stepping stones next to the driveway, and adding a brick trim to the sidewalk, as well, to reduce the amount of grass and update the look. What do you think?
Karen Neuman, Rolling Hills Estates
Magnolias are botanical curiosities for more than one reason. They are among the most primitive of all flowering plants and their flowers, rich in pollen but lacking nectar, resemble the slightly more ancient water lilies (Nymphaea spp.), to which their lineage may be traced. They are also unusual in having two habitats on opposite sides of the globe, stretching from North to South America on this side, and including East and Southeast Asia on the other. Furthermore, there are both evergreen and deciduous magnolia species, as there are both evergreen and deciduous oaks. Among trees whose flowers are both ostentatious and fragrant, however, magnolia may be the only group of trees that includes both evergreen and deciduous types.
Magnolias were flourishing twenty million years before bees and butterflies appeared on earth so they are not pollinated by these insects but rather by beetles.
The roots of magnolias are also unusual since they do not branch but grow out in ropy fashion from the base of the tree. Especially in young trees, magnolia roots are highly succulent and they need consistent moisture to get off to a good start. They prefer a somewhat acid pH and for this reason benefit from a mulch of pine needles or pine bark. As for cutting off tree roots, no matter how small, I would avoid it if at all possible.
Because their roots do not branch, transplanting magnolias must be done with great caution and, if a magnolia tree trunk is more than four inches in diameter, it may not survive being moved from one garden spot to another.
Magnolia roots are shallow but they are known to expand over an area four times as wide as the canopy diameter so you are correct in being concerned about their traveling where they are not wanted. You are also correct in wanting to put down a root barrier. A barrier at a two foot depth along a sidewalk or a driveway, made of either plastic or concrete, should be sufficient to contain magnolia roots for fifty years or more.
As long as your bench does not rest on magnolia roots, which typically rise above the soil surface, you could put it under your tree. On any tree, it is not a good idea to install a bench that literally circles the trunk since, as you suggest, the bench should, at a minimum, be located along the canopy perimeter.
If you want to keep some sort of lawn around the tree, I would not be hasty about removing the kikuyu grass since, given regular water, it just may spring back to life. Kikuyu is not a thirsty grass and in these droughty times it is a premier candidate for a lawn. In the same water saving context, reduction of lawn size by placement of stepping stones and brick, as you plan to do, makes sense.
I have a problem with yellow squash. They grow about an inch and then dry up. What can I do? Also my strawberries (in pots) remain small and then ripen and dry up. Help!
Nancy Rosen, Chatsworth
There are a number of reasons that squash and strawberries may not size properly but common to both is inadequate pollination. If bee activity is not as it should be due to wind or cold or colony collapse, fruit size will be affected. Squash fruit will grow without pollination — there is an embryonic fruit at the base of every female squash flower — but they will be very small and fall off before sizing properly. Where bee activity is minimal or absent, you can pollinate with a small artist’s paint brush by moving pollen from male to female flowers. Female flowers tend to grow in the middle of squash plants and display that incipient fruit bulge below. Male flowers are larger and located on thin stalks all around the plant. Squash size will also be affected by pollination. When many bees pollinate a squash flower, a fruit will grow larger than when it is pollinated by a single bee.
Unlike squash, strawberries are self-fertile so you can get fruit without any bee activity. However, as in the case of squash, the more bees that pollinate your flowers, the larger the fruit will become. When bees are not present, the fruit will be rather small. Where strawberrries are concerned, water availability will also affect fruit size, so you want to make sure they get the water they need in hot weather without overwatering them. When plants are over three years old, you should also expect a decline in strawberry size.
To increase honeybee activity around your plants you might want to consider increasing the presence of plants in the mint family (Lamiaceae) such as culinary and ornamental sages (Salvia spp.), rosemary, bee balm (Monarda spp.), lavender (Lavandula spp.) and lemon balm (Melissa officinalis). The flowers of all of these are attractive to honeybees.