From midsummer to early autumn, Eryngium planum bears many rounded umbels, 1/2 to 3/4 inch long, of light blue flowers with spiky, blue-green bracts, to 1 inch long. The basal leaves on this clump-forming, evergreen perennial are toothed, egg-shaped, dark green, 2 to 4 inches long, and the stem leaves are spiny and blue-tinted, with heart-shaped bases. If the flowers are cut before they are fully open, they can be used for arrangements. ‘Silverstone’ produces thistle-like umbels of white flowers.
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Size: Height: 1.5 ft. to 2 ft.
Width: 1 ft. to 1.5 ft.
Plant Category: landscape, perennials,
Plant Characteristics: low maintenance, round, seed start,
Foliage Characteristics: small leaves, coarse leaves, evergreen,
Flower Characteristics: long lasting, showy, unusual,
Flower Color: whites,
Tolerances: deer, drought, pollution, rabbits, slope,
Bloomtime Range: Mid Summer to Late Summer
USDA Hardiness Zone: 5 to 9
AHS Heat Zone: Not defined for this plant
Light Range: Sun to Full Sun
pH Range: 7 to 8.5
Soil Range: Some Sand to Some Clay
Water Range: Dry to Dry
FertilizingHow-to : Fertilization for Established Plants
Established plants can benefit from fertilization. Take a visual inventory of your landscape. Trees need to be fertilized every few years. Shrubs and other plants in the landscape can be fertilized yearly. A soil test can determine existing nutrient levels in the soil. If one or more nutrients is low, a specific instead of an all-purpose fertilizer may be required. Fertilizers that are high in N, nitrogen, will promote green leafy growth. Excess nitrogen in the soil can cause excessive vegetative growth on plants at the expense of flower bud development. It is best to avoid fertilizing late in the growing season. Applications made at that time can force lush, vegetative growth that will not have a chance to harden off before the onset of cold weather.
How-to : Fertilization for Annuals and Perennials
Annuals and perennials may be fertilized using: 1.water-soluble, quick release fertilizers; 2. temperature controlled slow-release fertilizers; or 3. organic fertilizers such as fish emulsion. Water soluble fertilizers are generally used every two weeks during the growing season or per label instructions. Controlled, slow-release fertilizers are worked into the soil ususally only once during the growing season or per label directions. For organic fertilizers such as fish emulsion, follow label directions as they may vary per product.
LightConditions : Sun
Sun is defined as the continuous, direct, exposure to 6 hours (or more) of sunlight per day.
Conditions : Light Conditions
Unless a site is completely exposed, light conditions will change during the day and even during the year. The northern and eastern sides of a house receive the least amount of light, with the northern exposure being the shadiest. The western and southern sides of a house receive the most light and are considered the hottest exposures due to intense afternoon sun.
You will notice that sun and shade patterns change during the day. The western side of a house may even be shady due to shadows cast by large trees or a structure from an adjacent property. If you have just bought a new home or just beginning to garden in your older home, take time to map sun and shade throughout the day. You will get a more accurate feel for your site's true light conditions.
Conditions : Full to Partial Sun
Full sunlight is needed for many plants to assume their full potential. Many of these plants will do fine with a little less sunlight, although they may not flower as heavily or their foliage as vibrant. Areas on the southern and western sides of buildings usually are the sunniest. The only exception is when houses or buildings are so close together, shadows are cast from neighboring properties. Full sun usually means 6 or more hours of direct unobstructed sunlight on a sunny day. Partial sun receives less than 6 hours of sun, but more than 3 hours. Plants able to take full sun in some climates may only be able to tolerate part sun in other climates. Know the culture of the plant before you buy and plant it!
Conditions : Light and Plant Selection
For best plant performance, it is desirable to match the correct plant with the available light conditions. Right plant, right place! Plants which do not receive sufficient light may become pale in color, have fewer leaves and a "leggy" stretched-out appearance. Also expect plants to grow slower and have fewer blooms when light is less than desirable. It is possible to provide supplemental lighting for indoor plants with lamps. Plants can also receive too much light. If a shade loving plant is exposed to direct sun, it may wilt and/or cause leaves to be sunburned or otherwise damaged.
Conditions : Full Sun
Full Sun is defined as exposure to more than 6 hours of continuous, direct sun per day.
WateringConditions : Dry
Dry is defined as an area that regularly receives water, but is fast draining. This results in a soil that is often dry to a depth of 18 inches.
Conditions : Dry Plants
Dry plants do not tolerate water logged soils and require very little water. Many cacti and succulents fall into this group. Water only when soil becomes completely dry. When watering, do so slowly for a long period of time so that topsoil does not wash away and so that soil has ample time to become moist enough to accept water. It is much better to water for a long time and less frequently allowing soil to dry out completely between waterings.
Conditions : Regular Moisture for Outdoor Plants
Water when normal rainfall does not provide the preferred 1 inch of moisture most plants prefer. Average water is needed during the growing season, but take care not to overwater. The first two years after a plant is installed, regular watering is important. The first year is critical. It is better to water once a week and water deeply, than to water frequently for a few minutes.
PlantingHow-to : Preparing Garden Beds
Use a soil testing kit to determine the acidity or alkalinity of the soil before beginning any garden bed preparation. This will help you determine which plants are best suited for your site. Check soil drainage and correct drainage where standing water remains. Clear weeds and debris from planting areas and continue to remove weeds as soon as they come up.
A week to 10 days before planting, add 2 to 4 inches of aged manure or compost and work into the planting site to improve fertility and increase water retention and drainage. If soil composition is weak, a layer of topsoil should be considered as well. No matter if your soil is sand or clay, it can be improved by adding the same thing: organic matter. The more, the better; work deep into the soil. Prepare beds to an 18 inch deep for perennials. This will seem like a tremendous amount of work now, but will greatly pay off later. Besides, this is not something that is easily done later, once plants have been established.
How-to : Preparing Containers
Containers are excellent when used as an ornamental feature, a planting option when there is little or no soil to plant in, or for plants that require a soil type not found in the garden or when soil drainage in the garden is inferior. If growing more than one plant in a container, make sure that all have similar cultural requirements. Choose a container that is deep and large enough to allow root development and growth as well as proportional balance between the fully developed plant and the container. Plant large containers in the place you intend them to stay. All containers should have drainage holes. A mesh screen, broken clay pot pieces(crock) or a paper coffee filter placed over the hole will keep soil from washing out. The potting soil you select should be an appropriate mix for the plants you have chosen. Quality soils (or soil-less medias) absorb moisture readily and evenly when wet. If water runs off soil upon initial wetting, this is an indicator that your soil may not be as good as you think.
Prior to filling a container with soil, wet potting soil in the bag or place in a tub or wheelbarrow so that it is evenly moist. Fill container about halfway full or to a level that will allow plants, when planted, to be just below the rim of the pot. Rootballs should be level with soil line when project is complete. Water well.
How-to : Planting Perennials
Determine appropriate perennials for your garden by considering sun and shade through the day, exposure, water requirements, climate, soil makeup, seasonal color desired, and position of other garden plants and trees.
The best times to plant are spring and fall, when soil is workable and out of danger of frost. Fall plantings have the advantage that roots can develop and not have to compete with developing top growth as in the spring. Spring is more desirable for perennials that dislike wet conditions or for colder areas, allowing full establishment before first winter. Planting in summer or winter is not advisable for most plants, unless planting a more established sized plant.
To plant container-grown plants: Prepare planting holes with appropriate depth and space between. Water the plant thoroughly and let the excess water drain before carefully removing from the container. Carefully loosen the root ball and place the plant in the hole, working soil around the roots as you fill. If the plant is extremely root bound, separate roots with fingers. A few slits made with a pocket knife are okay, but should be kept to a minimum. Continue filling in soil and water thoroughly, protecting from direct sun until stable.
To plant bare-root plants: Plant as soon as possible after purchase. Prepare suitable planting holes, spread roots and work soil among roots as you fill in. Water well and protect from direct sun until stable.
To plant seedlings: A number of perennials produce self-sown seedlings that can be transplanted. You may also start your own seedling bed for transplanting. Prepare suitable planting holes, spacing appropriately for plant development. Gently lift the seedling and as much surrounding soil as possible with your garden trowel, and replant it immediately, firming soil with fingertips and water well. Shade from direct sun and water regularly until stable.
ProblemsPest : Slugs and Snails
Slugs and snails favor moist climates and are mollusks, not insects. They can be voracious feeders, eating just about anything that is not woody or highly scented. They may eat holes in leaves, strip entire stems, or completely devour seedlings and tender transplants, leaving behind tell-tale silvery, slimy trails.
Prevention and control: Keep your garden as clean as possible, eliminating hiding places such as leaf debris, over-turned pots, and tarps. Groundcover in shady places and heavy mulches provide protection from the elements and can be favorite hiding places. In the spring, patrol for and destroy eggs (clusters of small translucent spheres) and adults during dusk and dawn. Set out beer traps from late spring through fall.
Many chemical controls are available on the market, but can be poisonous and deadly for children and pets; take care when using them - always read the label first!
Fungi : Powdery Mildew
Powdery Mildew is usually found on plants that do not have enough air circulation or adequate light. Problems are worse where nights are cool and days are warm and humid. The powdery white or gray fungus is usually found on the upper surface of leaves or fruit. Leaves will often turn yellow or brown, curl up, and drop off. New foliage emerges crinkled and distorted. Fruit will be dwarfed and often drops early.
Prevention and Control: Plant resistant varieties and space plants properly so they receive adequate light and air circulation. Always water from below, keeping water off the foliage. This is paramount for roses. Go easy on the nitrogen fertilizer. Apply fungicides according to label directions before problem becomes severe and follow directions exactly, not missing any required treatments. Sanitation is a must - clean up and remove all leaves, flowers, or debris in the fall and destroy.
Diseases : Pythium and Phytophtora Root Rot
Rot Rot, Pythium or Phytophthora occurs when soil moisture levels are excessively high and fungal spores present in the soil, come in contact with the susceptible plant. The base of stems discolor and shrink, and leaves further up the stalk wilt and die. Leaves near base are affected first. The roots will turn black and rot or break. This fungi can be introduced by using unsterilized soil mix or contaminated water.
Prevention and Control Remove affected plants and their roots, and discard surrounding soil. Replace with plants that are not susceptible, and only use fresh, sterilized soil mix. Hold back on fertilizing too. Try not to over water plants and make sure that soil is well drained prior to planting. This fungus is not treatable by chemicals.
Rhizoctonia Root and Stem Rot symptoms look similar to Pythium Root Rot, but the Rhizoctonia fungus seems to thrive in well drained soils.
MiscellaneousConditions : Deer Tolerant
There are no plants that are 100% deer resistant, but many that are deer tolerant. There are plants that deer prefer over others. You will find that what deer will or will not eat varies in different parts of the country. A lot of it has to do with how hungry they are. Most deer will sample everything at least once, decide if they like it or not and return if favorable. A fence is the good deer barrier. You may go for a really tall one (7 to 8 feet), or try 2 parallel fences, (4 to 5 feet apart). Use a wire mesh fence rather than board, since deer are capable of wiggling through a 12 inch space.
Conditions : Pollution Tolerant
Air pollution is becoming a bigger problem each day. Pollutants in our air damage plants. The plants are damaged by absorbing sulfur dioxide, ozone, peroxyacetyl nitrate, ethylene, and nitrogen dioxide through their pores. Cell membrane damage may result in leaf drop, blotched or burnt looking leaves, or off-colored tissue between veins. Vehicles and industrial processes are the key culprits and conditions worsen on hot summer days. Though planting only pollution tolerant plants is not the solution to this problem, it is a visual band aid. Your Cooperative Extension Service may have a list of plants that are more pollution tolerant in your area.
Conditions : Rabbit Tolerant
As cute as they are, rabbits can really damage a vegetable garden. Young, tender lettuce plants seem to be their favorite. If a free-roaming dog is not a possibility for you, consider installing raised vegetable beds and covering tender shoots with netting. If you have ample room, you can opt to plant enough for you and the bunnies. Scents don't always repel animals, as they get used to them and are often washed off in the rain.
Conditions : Slope Tolerant
Slope tolerant plants are those that have a fibrous root system and are often plants that prefer good soil drainage. These plants assist in erosion control by stabilizing/holding the soil on slopes intact.
How-to : Cut Flowers
Flowers suitable for cutting maintain their form for several days when properly conditioned and placed in water or soaked oasis. A cut flower should have a fairly strong, long stem, making it easy to work with in arrangements. There are many short stem flowers that make good cut flowers too, but they look best when floated in a bowl or clustered and placed in a juice glass size vase.
For best results, always cut flowers early in the morning, preferably before dew has had a chance to dry. Always make cuts with a sharp knife or pruners and plunge flowers or foliage into a bucket of water. Store in a cool place until you are ready to work with them, this will keep flowers from opening. Always re-cut stems and change water frequently. Washing vases or containers to rid of existing bacteria helps increase their life, as well.
How-to : Dried Flowers
Some cut flowers make excellent dried flowers. Good dried flower candidates hold their color, form, and often fragrance once dried. Large, fleshy-petaled flowers do not dry well. Air drying is the easiest. Make sure that flowers are not damp. Tie them in a small bunch and hang upside down in a dark, well-ventilated room. Silicone drying is another popular method and crystals can be bought in craft stores.
Glossary : Border Plant
A border plant is one which looks especially nice when used next to other plants in a border. Borders are different from hedges in that they are not clipped. Borders are loose and billowy, often dotted with deciduous flowering shrubs. For best effect, mass smaller plants in groups of 3, 5, 7, or 9. Larger plants may stand alone, or if room permits, group several layers of plants for a dramatic impact. Borders are nice because they define property lines and can screen out bad views and offer seasonal color. Many gardeners use the border to add year round color and interest to the garden.
Glossary : Container Plant
A plant that is considered to be a good container plant is one that does not have a tap root, but rather a more confined, fibrous root system. Plants that usually thrive in containers are slow- growing or relatively small in size. Plants are more adaptable than people give them credit for. Even large growing plants can be used in containers when they are very young, transplanted to the ground when older. Many woody ornamentals make wonderful container plants as well as annuals, perennials, vegetables, herbs, and bulbs.
Conditions : Erosion Control
Plants that help to control erosion have fibrous root systems that help to keep soil intact. Leaves and the overall form of a plant can prevent erosion by breaking up water droplets before they hit the ground, lessening splashing and runoff.
Glossary : Low Maintenance
Low maintenance does not mean no maintenance. It does mean that once a plant is established, very little needs to be done in the way of water, fertilizing, pruning, or treatment in order for the plant to remain healthy and attractive. A well-designed garden, which takes your lifestyle into consideration, can greatly reduce maintenance.
Glossary : Mass Planting
Mass is one of the elements of design and relates directly to balance. Mass planting is defined as the grouping of three or more of the same type of plants in one area. When massing plants, keep in mind what visual effect they will have. Small properties require smaller masses where larger properties can handle larger masses or sweeps of plants.
Glossary : Naturalizing
Naturalizing refers to planting in a random pattern, much as itwould occur in nature. If you spend any time in the woods, you've probably noticed that plants often grow in groups. The center of the group is dense and towards the edges, plants are located farther apart. Narcissus bulbs are easy to naturalize if you use this method: fill a bucket with bulbs and toss them out. Plant them where they fall. You will notice a portion of the bulbs are close together while the others have scattered farther away.
Glossary : Rock Garden
A rock garden is a garden that mimics an alpine area, having dwarf conifers, low-growing sub-shrubs, perennials and ground cover. Often, the soil itself tends to be gravelly or rocky.
Glossary : Some Sand
Some Sand refers to a soil that drains fast, but has lower water holding capacity due to the presence of a little organic matter. A good workable soil that needs added fertilizer due to lower fertility levels and adequate water. Usually gray in color. Forms a loose, crumbly ball that easily falls apart when squeezed in the hand.
Glossary : Sandy Loam
Sandy Loam refers to a soil that drains well, with excellent air space, and evenly crumbled texture when squeezed in the hand. A good workable garden soil that benefits from added fertilizer and proper watering. Dark gray to gray-brown in color.
Glossary : Some Clay
Some Clay refers to a soil that is loam-like, but heavier. Drainage is not bad, prolonged periods of rain cause bog-like conditions. Rich in nutrients, but needs the addition of organic matter to improve texture. Easily forms a ball when squeezed and requires a firm tap with finger to crumble. Light brown to slightly orange color.
Glossary : Evergreen
Evergreen refers to plants that hold onto their leaves or needles for more than one growing season, shedding them over time. Some plants such as live oaks are evergreen, but commonly shed the majority of their older leaves around the end of January.
Glossary : Perennial
Perennial: traditionally a non-woody plant that lives for two or more growing seasons.
Glossary : Seed Start
Seed Start: easily propagated from seed.
Conditions : Site Conditions
When setting criteria for site conditions, check boxes that apply to your planting area. This will narrow the search for appropriate plants. Naturally, you'll need to select a USDA Hardiness Zone. Selecting a specific soil type and pH are just as important as light and water conditions because they enable a search that will find plants best suited to your site.
Glossary : pH
pH, means the potential of Hydrogen, is the measure of alkalinity or acidity. In horticulture, pH refers to the pH of soil. The scale measures from 0, most acid, to 14, most alkaline. Seven is neutral. Most plants prefer a range between 5.5 and about 6.7, an acid range, but there are plenty of other plants that like soil more alkaline, or above 7. A pH of 7 is where the plant can most easily absorb the most nutrients in the soil. Some plants prefer more or less of certain nutrients, and therefore do better at a certain pH.
Glossary : Plant Characteristics
Plant characteristics define the plant, enabling a search that finds specific types of plants such as bulbs, trees, shrubs, grass, perennials, etc.
Glossary : Flower Characteristics
Flower characteristics can vary greatly and may help you decide on a ""look or feel"" for your garden. If you're looking for fragrance or large, showy flowers, click these boxes and possibilities that fit your cultural conditions will be shown. If you have no preference, leave boxes unchecked to return a greater number of possibilities.
Glossary : Foliage Characteristics
By searching foliage characteristics, you will have the opportunity to look for foliage with distinguishable features such as variegated leaves, aromatic foliage, or unusual texture, color or shape. This field will be most helpful to you if you are looking for accent plants. If you have no preference, leave this field blank to return a larger selection of plants.
Glossary : Soil Types
A soil type is defined by granule size, drainage, and amount of organic material in the soil. The three main soil types are sand, loam and clay. Sand has the largest particle size, no organic matter, little to no fertility, and drains rapidly. Clay, at the opposite end of the spectrum, has the smallest particle size, can be rich in organic matter, fertility and moisture, but is often unworkable because particles are held together too tightly, resulting in poor drainage when wet, or is brick-like when dry. The optimum soil type is loam, which is the happy median between sand and clay: It is high in organic matter, nutrient-rich, and has the perfect water holding capacity.
You will often hear loam referred to as a sandy loam (having more sand, yet still plenty of organic matter) or a clay loam (heavier on the clay, yet workable with good drainage.) The addition of organic matter to either sand or clay will result in a loamy soil. Still not sure if your soil is a sand, clay, or loam? Try this simple test. Squeeze a handfull of slightly moist, not wet, soil in your hand. If it forms a tight ball and does not fall apart when gently tapped with a finger, your soil is more than likely clay. If soil does not form a ball or crumbles before it is tapped, it is sand to very sandy loam. If soil forms a ball, then crumbles readily when lightly tapped, it's a loam. Several quick, light taps could mean a clay loam.
How-to : Getting the Most Out of Cut Flowers
Cut flowers bring the garden into your home. While some cut flowers have a long vase life, most are highly perishable. How cut flowers are treated when you first bring them home can significantly increase how long they last.
The most important thing to consider is getting sufficient water taken up into the cut stem. Insufficient water can result in wilting and short-lived flowers. Bent neck of roses, where the flower head droops, is the result of poor water uptake. To maximize water uptake, first re-cut the stems at an angle so that the vascular system (the ""plumbing"" of the stem) is clear. Next immerse the cut stems in warm water.
Remember when the flower is cut, it is cut off from its food supply. Once water is taken care of, food is the resource that will run out next. The plants stems naturally feed the flowers with sugars. If you add a bit of sugar (1 tsp.) to the vase water, this will help feed the flower stems and extend their vase life.
Bacteria will build up in vase water and eventually clog up the stem so the flower cannot take up water. To prevent this, change the vase water frequently and make a new cut in the stems every few days.
Floral preservatives, available from florists, contain sugars, acids and bacteriacides that can extend cut flower life. These come in small packets and are generally available where cut flowers are sold. If used properly, these can extend the vase life of some cut flowers 2 to 3 times when compared with just plain water in the vase.
Glossary : Tolerant
Tolerant refers to a plant's ability to tolerate exposure to an external condition(s). It does not mean that the plant thrives or prefers this situation, but is able to adapt and continue its life cycle.
Glossary : Drought Tolerant
Very few plants, except for those naturally found in desert situations, can tolerate arid soils, but there are plants that seem to be more drought tolerant than others. Plants that are drought tolerant still require moisture, so don't think that they can go for extended period without any water. Drought tolerant plants are often deep rooted, have waxy or thick leaves that conserve water, or leaf structures that close to minimize transpiration. All plants in droughty situations benefit from an occasional deep watering and a 2-3 inch thick layer of mulch. Drought tolerant plants are the backbone of xeriphytic landscaping.