Gardening with Gary

Gardening Advice from an Expert

Mountain Laurel

Q. Do I need to soak these mountain laurel seeds in order for them to germinate? I live in south Georgia. Do you think they'll survive here? My gardening book says zone 8 and that is our zone. Any information you have will be helpful.

A. The Mountain Laurels are hardy in your zone. The flowers, appearing in late spring to early summer, of the species which you have seeds are pink, looking as though painted by a cake decorator! They prefer a humus-rich, well-drained soil and part-shade. Plant them where they will be spared the hot PM rays of the Texan sun.

The usual propagation method is by either stem cuttings or layering. But, the seeds can be used to produce new shrubs. It is quite time-consuming though. Yes, they need soaking to loosen that rough exterior shell. Usually within 24 hours you will see a softening and then they are ready to be sown in a light mix and given only morning sun. Keep the tray moist, but not drippy wet. You may wish to cover with clear plastic or a pane of glass. Lift it regularly to avoid steam buildup.

The shrubs do not require any particular special care. They grow wild throughout the US from Alaska down to California and Texas. Fertilize them once a month with a general garden food, as a 20-20-20, Scotts, Peters, Hyponex or Miracle-Gro.

Julie writes~ The leaves on my mountain laurels (I think the genus is Kalmia) are turning brown and drying up, starting on the tips and continuing up the sides of the leaf. It occurs gradually, all over the plant. The plants are in compost-enriched soil (for acidity). What is wrong and what should I do? They are planted in raised beds that are made of somewhat dense clay. However, each was planted in a very large hole containing 50% topsoil 50% compost.

A. Mountain-Laurel (Kalmia latifolia) is prized as an ornamental shrub not only for its exquisitely beautiful flowers but also for its attractive evergreen foliage, which adds color to the landscape year-around.

Your leaf symptoms may be due to drought or winter injury. They differ from those of leaf blight in that individual lesions and a zonate pattern are not apparent. But, do consider a fungus and read through the proper culture of these trees below.

Maintaining vigorous, healthy shrubs is of utmost importance. Soil that is acid (pH 4.2 to 5.2), high in organic matter, and well drained but moist is ideal for mountain-laurel. If the soil reaction is alkaline, slightly acid, or neutral (above pH 5.5), addition of sulfate as iron sulfate or ammonium sulfate to the soil will lower the pH. Aluminum sulfate is not recommended. If the soil reaction is proper and symptoms of iron chlorosis appear, add iron to the soil either as iron sulfate or chelate. Follow directions on the package label.

Watering during dry periods in summer and fall and applying an organic mulch will help prevent drought and winter injury. Recommendations for reducing winter injury include protecting bushes exposed to winter sun and wind by erecting burlap windbreaks, or growing bushes in a more protected location.

Dead or diseased leaves should be removed from the bushes and soil surfaces and destroyed by composting or burning. If only a light infection of leaf spot or leaf blight is detected, removal and destruction of diseased leaves is often sufficient.

Heavy or recurrent infections of leaf spot and leaf blight can be controlled by applying the fungicide benomyl (Benlate) 50 percent wettable powder, at the rate of 1/2 pound of product per 100 gallons of water (2 teaspoons per gallon). Because of the waxy coating on the leaves, a spreader-sticker should be added. A teaspoonful of good-quality liquid detergent per gallon of spray mix is often useful in reducing surface tension and improving foliage coverage. If leaf spot or blight was serious last year, spray when new growth starts, and repeat applications at approximately two-week intervals throughout the spring growing season. If the weather is very humid or rainy, shorten the spray interval to 7 or 10 days.

Assistance from Nancy R. Pataky, Extension Specialist of Turf and Ornamentals, Department of Crop Sciences, University of Illinois at Urbana.

Mary writes~ I read on your site about soaking Mountain Laurel seeds before planting. My question is, soak them in what?

A. Water. The seeds for this plants must be collected while the pod is still green to be truly viable. Nick deeply the seed coat; soak seed for approximately 24 hours [some growers soak for as long as two weeks, changing the water so it is fresh, not murky and full of bacteria.] If the seed swells, it will probably germinate. This plant dislikes being transplanted because of its long tap root, so use a deep container for starting seeds. Please note: Seeds can take up to 6-8 months to germinate.