Lobelia, Cardinal Flower
Grows anywhere, adored by hummingbirds and butterflies.
Zone This refers to the USDA hardiness zone assigned to each part of the country, based on the minimum winter temperature that a region typically experiences. Hardiness zone ranges are provided for all perennial plants and you should always choose plants that fall within your range.
Sun The amount of sunlight this product needs daily in order to perform well in the garden. Full sun means 6 hours of direct sun per day; partial sun means 2-4 hours of direct sun per day; shade means little or no direct sun.
Full Sun, Part Sun
Height The typical height of this product at maturity.
Spread The width of the plant at maturity.
Bloom Season The time of the year when this product normally blooms.
Resistant To Adverse garden conditions, such as heat or frost, deer or rabbits, that this product can tolerate well.
Deer, Rabbit, Wet Soil
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Lobelia: Indoor Sow or Potted Perennial Plant
How to Sow and Plant Lobelia Perennials
Sowing Lobelia Seed Indoors:
- Sow indoors seeds 8-12 weeks before the last frost
- Sow thinly and just press into seed-starting formula
- Keep the soil moist at 65-75 degrees F
- Seedlings emerge in about 20 days
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- If you are growing lobelia in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of true leaves before transplanting to the garden so they have enough room to develop strong roots
- Before planting lobelia in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Planting Lobelia in the Garden:
- Select a location with well-drained, rich, moist soil in partial shade to full sun. If in full sun, make sure plants get plenty of water.
- Prepare the bed by turning the soil under to a depth of 6-12 inches removing any debris, and lightly raking as level as possible.
- The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
- Plant on a cloudy day or in late afternoon to reduce transplant shock.
- Dig a hole for each plant, approximately 6-8 inches apart large enough to amply accommodate the root ball.
- Unpot the plant and gently loosen the root ball with your hands to encourage good root growth.
- Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
- Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.
How to Grow Lobelia Plants
- Keep weeds under control during the lobelia growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their germination.
- Mulches can also be used to help retain soil moisture and maintain even soil temperatures. For perennials, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
- Careful watering is essential in getting lobelia perennials off to a good start. Water thoroughly at least once a week to help new roots grow down deeply. Soil should be damp at about 1 inch below the soil surface. You can check this by sticking your finger in the soil. Water early in the morning to give all leaves enough time to dry. One inch of rain or watering per week is recommended for most perennial plants. You can check to see if you need to add water by using a rain gauge.
- Until the plants become established, some protection from extreme winds and direct, hot sunlight may be necessary. Good air movement is also important.
- After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
- Deadhead to encourage repeat blooming.
- Pinch plants if you prefer bushier growth.
- Do not cut back in fall, cut back in spring.
- Divide every 2-3 years.
Lobelia Varieties Available at Burpee Seeds
Lobelia Growing Tips
- Perennial lobelias are useful for difficult, wet locations. They are attractive in the middle or back of the border, and naturalize well in woodlands and along stream banks. They are very effective massed in the landscape.
- Lobelias make great cutting flowers as well. Cut when flowers are 1/3 open.