when to divide black eyed susan

When to Divide Black Eyed Susan: The Complete Guide
As an avid gardener, I’m always looking for ways to expand my garden and get more plants without spending a fortune. One easy way to do this is by dividing perennials like the cheery black eyed susan. Black eyed susans (Rudbeckia hirta) are popular perennials that provide a burst of golden yellow color in gardens from mid summer into fall. But over time, black eyed susan clumps can get overcrowded which leads to reduced flowering. Luckily, dividing black eyed susan is an easy gardening task that will rejuvenate your plants and give you more flowers. In this complete guide, I’ll cover when to divide black eyed susan, how to do it properly, and what care is needed after dividing.

When is the Best Time to Divide Black Eyed Susan?

Timing is crucial when it comes to successfully dividing perennials. For black eyed susans, the optimal time to divide is either early spring or late fall. Specifically the best months are April/May in spring and September/October in fall.

Spring

Dividing in early spring allows the new sections to establish roots before summer heat arrives. In spring, temperatures are cool providing ideal conditions for new root growth. The plants are just starting to emerge from winter dormancy so transplant shock will be minimal.

Fall:

Late fall division gives plants time to settle their roots before winter dormancy. Soil retains warmth better in fall, again encouraging root development before cold weather hits. Plants have also completed flowering so you won’t disrupt buds.

Avoid Summer Division

It’s best to avoid dividing black eyed susan in the hot summer months during active growth and flowering. Summer division can stunt growth and lead to fewer blooms that season. The heat and dryness of summer also make it hard for newly divided roots to establish.

Avoid Mid-Winter Division

Mid-winter division when plants are fully dormant should also be avoided. Trying to stimulate root growth in frozen soil will be futile and may damage plants. Wait for the soil to thaw in early spring instead.

How Often to Divide Black Eyed Susan

In general, divide mature, established clumps every 3-4 years. This spacing gives the vigorous black eyed susans time to reach their full size but prevents overcrowding that hampers flowering. Signs it’s time to divide include centers of clumps dying out, smaller/fewer flowers, and excessive self-seeding.

Newly divided plants may take 1-2 years to recover before dividing again. Avoid dividing black eyed susans annually as this is too frequent for them to reach their full potential.

How to Divide Black Eyed Susan Step-By-Step

Dividing black eyed susan is a straightforward process. Follow these simple steps for success:

1. Prepare New Site

If transplanting divided sections elsewhere, prepare new planting holes at least a day in advance. Amend soil with compost to improve drainage. Black eyed susans need full sun.

1. Water Plant

Water clump thoroughly 1-2 days before dividing if soil is dry. This makes removing the roots easier.

1. Dig Out Entire Clump

Use a shovel or garden fork to dig around the clump in a circle near the foliage drip line. Carefully lift the entire clump out of the ground.

1. Remove Excess Soil

Gently shake off any loose soil so you can clearly see the root structure. Remove dead roots or stems.

1. Divide Root Clump

Using a sharp knife or pruners, cut through the root mass into 2-3 pieces. Each should have plenty of healthy roots.

1. Transplant Divided Sections

Plant each root section in prepared holes, backfilling with native soil. Water new transplants well.

Caring for Newly Divided Plants

After dividing black eyed susans, give them extra attention:

• Water frequently for 2-3 weeks until established.

• Fertilize with a balanced fertilizer to encourage new growth.

• Remove spent flowers to promote more blooming.

• Watch for pests/disease and treat promptly.

• Apply mulch to help retain moisture.

By properly timing division and providing good aftercare, you can easily propagate more black eyed susans from a mature plant. Your efforts will be rewarded with vigorous, long-blooming flowers for years to come.

Tips for Successful Black Eyed Susan Division

Here are some additional useful tips to ensure your black eyed susan division goes smoothly:

• Use clean, sharp tools to minimize damage to roots. Disinfect tools between plants.

• On dry soil, water a day before lifting plants to make digging easier.

• Shake off excess soil but don’t wash roots. Keep some soil attached to roots.

• Prune stems to 6″ before dividing for easier handling.

• Divide in cloudy, cool weather to reduce transplant stress.

• Plant crown at same depth as before, don’t bury too deeply.

• Space divided plants 18-24″ apart to allow for growth.

• Water transplants daily the first week, 2-3x/week after.

• Add organic compost to planting holes for nutrients.

• Stake tall varieties if needed until established.

• Deadhead spent blooms to encourage more flowers.

Follow Proper Division Techniques

By dividing black eyed susans properly and at the right time of year, you can invigorate your plants and create more flowers in your garden for free. Avoid dividing in summer or mid-winter when plants are stressed. In fall or early spring, carefully dig up mature clumps and cut them into smaller sections, making sure each division has plenty of healthy roots. Transplant each new plant and water well. With a little time and attention, your divided black eyed susans will soon be thriving. Proper division techniques lead to vigorous, long-blooming perennial flowers.