Glandora
( glan - DOH - ruh )
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At-A-Glance InformationThese perennial flowering herbaceous plants need light shade in warmer climates and moderate amounts of water. They are native to Morocco, Algeria, Portugal, Spain, France, Italy and Greece. These plants are typically used in containers or window boxes or in mixed planting beds throughout the landscape. They are great spilling plants for retaining walls and rock gardens, and typically produce profuse shows of blue flowers in spring and summertime. Use these trailing plants in containers or in the ground as accent or small-scale groundcover plants.
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Glandora species and Varietals
The genus Glandora is a member of the plant family Boraginaceae and includes eight species. The genus was split from Lithodora in 2008. Glandora grows best in zones 5-7 and 14-17. To find your zone, click here: Zone Map.
Glandora diffusa (Lithodora diffusa, Lithospermum diffusa) (Purple Gromwell)
Used commonly as groundcover, it forms a mound 6-12 inches tall and 3-4 feet wide. It is somewhat woody and has narrow evergreen leaves. Blue and white flowers bloom in late spring. It is native to southern and western Europe. It is best suited to mild-summer climates. Varieties are outlined below.
Used commonly as groundcover, it forms a mound 6-12 inches tall and 3-4 feet wide. It is somewhat woody and has narrow evergreen leaves. Blue and white flowers bloom in late spring. It is native to southern and western Europe. It is best suited to mild-summer climates. Varieties are outlined below.
'Heavenly Blue'
A commonly grown variety with blue flowers. |
'Star' ('Blue Star')
This variety has white-edged blue blossoms. |
'Grace Ward'
This variety has blue flowers and is widely-grown. |
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Glandora oleifolia (Lithodora oleifolia, Lithospermum oleifolium) (Olive-Leaved Gromwell) This species is endemic to Spain and forms a low evergreen subshrub that reaches 8 inches tall and 12 inches (or more) wide. Leaves are silky and dark green, and look similar to those in Olive species. Flowers are sky blue. These are cultivated widely as garden ornamentals, and are great in rock gardens and other drought-tolerant landscapes. |
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Glandora prostrata (Lithodora diffusa, Lithospermum diffusa) (Shrubby Gromwell, Creeping Gromwell, Purple Gromwell) This species is native to Portugal, Spain and France, and produces small shrubby plants with bluish flowers. There are many cultivars, including 'Heavenly Blue' and 'Grace Ward'. This species is sometimes grouped in with Lithodora diffusa. |
Caring for Glandora
Glandora plants do best when planted in full sun; they ideally should be receiving between 6 and 8 hours of sun each day, with some late afternoon shade during the warmest hours. They prefer to have their roots in soil that is well-draining, moderately fertile, and that has a pH of between 5.5 and 6.0 (acidic). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Lay down 1-2 inches of organic mulching material after planting to suppress weed growth, maintain soil temperatures, and increase soil moisture retention. Water Glandora plants regularly as they develop a strong root system. Once established, Glandora is considered drought-tolerant, able to get by on few supplemental waterings during times of dry weather.
Fertilize yearly in early springtime with a application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Cut back when plants get leggy towards the end of their growing season (late spring to early summertime) and they will send out a flush of new foliage growth and flowering. If growing Glandora in a container, it may be necessary to divide plants after a few years to avoid them becoming root-bound or outgrowing their area. For instructions on how to divide Glandora plants, consult the Propagation section below.
Fertilize yearly in early springtime with a application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Cut back when plants get leggy towards the end of their growing season (late spring to early summertime) and they will send out a flush of new foliage growth and flowering. If growing Glandora in a container, it may be necessary to divide plants after a few years to avoid them becoming root-bound or outgrowing their area. For instructions on how to divide Glandora plants, consult the Propagation section below.
Propagation
Glandora can be propagated either by division or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Gromwell flowers, follow the instructions below:
Propagating Glandora by Seed
Propagating Glandora by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (12 inch pots will do, and these are only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:
Propagating Glandora by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
- In either late winter or early springtime, get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-6 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Propagating Glandora by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (12 inch pots will do, and these are only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:
- Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
- Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
- Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
- Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.
Problems and Pests
Glandora, or Gromwell, can have issues with the following pests and diseases in the landscape:
- Aphids
- Spider Mites
- Whiteflies
- Root-Knot Nematode
- Bacterial Leaf Spot
Gallery
Glandora is a classic 'spiller' plant, great for hanging over walls or the sides of containers.
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Glandora can be used as a small-scale low-traffic groundcover.
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Here, Glandora is used to frame large landscape boulders, adding color at the front of beds.
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Videos
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 418, Lithodora diffusa
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