11 Perennials to Feed in March for Better Blooms

The real difference is often beneath the soil surface.

As daylight hours increase and the soil begins to warm, perennial roots start another season of growth. March offers a short opportunity: give a select group of plants the right feed now and an ordinary border can become a long-running display of colour. Miss that chance, and you could spend the year asking why nearby gardens appear so much more impressive.

Why March feeding can transform perennial displays

By March, soil is generally thawed, oxygen is moving through it again and roots quickly become active. They are ready to take up nutrients remarkably effectively.

Feeding perennials in March gives them fuel precisely when they restart growth, shaping both the strength of stems and the abundance of flowers.

Plants are now restoring what winter has depleted, including their root networks, energy reserves and fresh shoots. A gradual, consistent nutrient supply helps with each task without causing the soft, lush growth that collapses on the first blustery day.

Organic fertilisers and slow-release feeds are particularly useful for this reason. Spread in late February, March or very early April, they release nutrients over three to six months. Rather than delivering a rapid nitrogen surge, they provide a balanced supply for roots, leaves and developing flowers.

March soil conditions also help. Ground is commonly damp without being saturated, allowing fertiliser granules and pellets to break down slowly. Applying the same feed in a June heatwave is more likely to lose nutrients through evaporation, run-off or uptake by only shallow roots.

The 11 perennials you should feed in March

Perennials do not all react alike to spring fertiliser. While some cope perfectly well with little attention, others reward extra care with a far fuller flowering performance. These 11 benefit most from a March feed.

1. Roses: heavier flowering and stronger stems

Although they grow more like shrubs, roses are often regarded by gardeners as honorary perennials. They are hungry plants that respond very well to feeding in March.

• Choose a balanced fertiliser of around 10-10-10 or 12-12-12.
• Feed after pruning, distributing it in a circle around the drip line instead of placing it at the stem base.
• Gently fork it into the surface soil, then water thoroughly.

This encourages robust new canes and developing buds rather than spindly shoots carrying just a few flowers.

2. Peonies: a feed for this year and the next

Herbaceous peonies dislike disturbance, which makes feeding one of the limited ways to affect how they perform. A March application supports flower buds for both the current season and the following one.

Select an organic or slow-release fertiliser with worthwhile phosphorus and potassium levels. Apply it over a broad area around the clump because established peonies frequently have wide-reaching roots. Do not mound fertiliser against the crown, from which the new red shoots appear.

3. Dahlias: sturdy stems and healthy tubers

Whether dahlias are started under cover or grown in containers, the first feed supplied in March or early April makes a difference. They do not tolerate too much nitrogen, as it produces plentiful foliage but limited blooms.

For dahlias, choose a low-nitrogen feed such as 5-10-10 to prioritise flowers and strong tubers over leafy growth.

Incorporate fertiliser into the planting site before adding tubers or before new shoots emerge. Later in the season, vigorous plants can draw on this stored, balanced nutrition.

4. Delphiniums: early nutrition for tall flower spires

Delphiniums are spectacular plants, but they have demanding needs. Feeding them in March promotes strong, vertical stems capable of supporting packed flower spikes.

Provide a balanced fertiliser alongside plenty of organic matter. Rich soil suits these plants, but abrupt nutrient boosts do not, so slow-release pellets or well-rotted compost combined with fertiliser work best.

5. Phlox paniculata: nutrition to help resist mildew

Border phlox are prized for their colour and fragrance, but powdery mildew is also a common problem. Strong, properly nourished plants cope with stress more effectively.

A balanced feed of approximately 10-10-10 in March promotes compact, dense clumps and abundant flowers. Pair this with adequate spacing and watering at soil level to reduce the risk of fungal issues later in summer.

6. Coreopsis: unassuming plants with prolific blooms

Coreopsis are not among the most demanding perennials, but a small spring feed can keep them blooming for many months. Give clumps a light application of balanced fertiliser in March and follow it with a thin compost mulch. Avoid overfeeding with nitrogen, which can leave them floppy, so it is better to apply too little than too much.

7. Bearded iris: encourage flowers rather than leaves

Bearded irises thrive in sunny, free-draining, relatively poor soil. Heavy feeding, particularly with nitrogen-rich fertiliser, promotes foliage instead of blooms.

Use a low-nitrogen fertiliser such as 5-10-10 in March, keeping granules away from the rhizomes to avoid rot.

Spread the feed in the gaps between leaf fans, never across the exposed rhizomes. Moderate feeding and reliable drainage result in the finest flower stems.

8. Hostas: feed early, before slug season

Hostas emerge in early spring as tender shoots which soon open into striking foliage. A mild March feed supports this rapid growth phase.

They benefit from slow-release fertiliser combined with compost. Provide gentle, ongoing nutrition instead of powerful doses. This helps leaves bounce back from slug damage and retain their size throughout summer, particularly when plants are grown in pots.

9. Daylilies (hemerocallis): reserves for prolonged flowering

Daylilies may bloom for several weeks, or even months, producing new flowers each day. Such a display places considerable demand on stored energy.

In March, use a fertiliser containing slightly more phosphorus and potassium. In particularly productive borders, give another light application in midsummer. This strengthens roots and supports repeat blooms without encouraging an excess of leaves.

10. Hydrangeas: flower colour and form begin now

Hydrangeas, especially blue forms, are highly responsive to soil conditions. March is the moment to feed them and alter the balance before flower buds start to enlarge.

• In acidic soil, use a low-phosphorus fertiliser such as 12-4-8 for blue hydrangeas.
• In neutral or alkaline ground, feeding generally encourages pinker shades.
• Applying a light mulch after feeding helps keep moisture levels even.

Regular feeding creates larger, more consistent flower heads and stronger stems that are less likely to flop in wet weather.

11. Astilbes: hungry plants for moist ground

Astilbes enjoy rich, damp soil and have a noticeably greater appetite than many other shade-loving plants. Underfed clumps develop thin plumes and leaves that yellow.

Give astilbes a balanced fertiliser in March, then again in autumn, paired with generous organic mulch to lock in moisture.

In shaded borders where tree roots compete for resources, this approach can turn sparse, uneven groups into dense masses of feathery growth.

How to apply fertiliser without damaging plants

A handful of straightforward practices makes fertiliser a targeted gardening aid rather than a blunt tool.

Action	Good practice in March	What to avoid
Soil condition	Slightly moist soil, neither waterlogged nor bone dry	Frozen, cracked or dust-dry soil
Placement	Spread in a ring around the plant and lightly work it in	Putting it directly against the crown, collar or rhizome
Type of fertiliser	Organic or slow-release fertiliser suited to the plant	Fast-acting, high-nitrogen lawn feeds
Watering	Water after application to begin the breakdown process	Allowing granules to remain dry on the soil for days

Before feeding, lightly rake the surface with a hand fork to improve fertiliser contact and limit run-off. Water afterwards so nutrients can move into the root area and granules do not scorch young shoots.

Do not fertilise frozen or very dry soil, and never pile feed around stem bases. This can burn plant tissue, force weak foliage and still do little to produce strong flowering wood.

Weeding and recycling: a March task that improves flowering

When feeding in March, deal with weeds as well. At this point, annual weeds have shallow root systems and are easy to pull out by hand. Removing them early cuts competition for light and nutrients, giving perennials a valuable early advantage.

Those weeds can also become a free, mild liquid fertiliser. Pack a bucket with chopped young weeds, cover them with water and leave the mixture to steep for a few weeks. The liquid produced, often known as plant “tea”, contains dissolved nutrients.

Strain the mixture and dilute it at roughly one part liquid to ten parts water. Apply it around hungry perennials every couple of weeks. It can smell quite strong, so gardeners often position the bucket in a rear corner away from sitting areas.

Essential terms gardeners rely on

Fertiliser labels may seem confusing, yet understanding a few terms makes choosing the right product much easier:

• N-P-K: The three figures on a packet represent the percentages of nitrogen (N), phosphorus (P) and potassium (K). A higher first figure encourages leaves, a higher middle one supports roots and flowers, and a higher final figure aids overall resilience.
• Slow-release: Organic products or coated granules that decompose over several weeks, releasing nutrients gradually rather than creating a sudden peak.
• Balanced feed: Fertilisers with similar N, P and K values, such as 10-10-10, which suit many flowering perennials.

Once those numbers make sense, it becomes much easier to meet the needs of each perennial instead of using the same all-purpose feed every year.

Realistic results: what if you miss March feeding?

For many gardeners, the main issue is not which fertiliser to choose but whether a March feed makes a genuine difference. Initially, its effects can be subtle, but by early summer they are often clear.

Without feeding, plants may still flower, though stems can be shorter and the display may not last as long. Delphiniums and astilbes are more likely to lean or snap. Hydrangea flower heads can stay smaller, while coreopsis and phlox may fade earlier in the season.

Feed carefully in March and do not expect an instant transformation. Instead, stems become thicker, leaves grow deeper in colour and flower spikes carry more well-shaped blooms. The advantage is most apparent during difficult periods, such as a dry June or an early heatwave. Well-fed perennials tolerate these conditions more successfully and recover more quickly when rain arrives.

For gardeners seeking dependable, lengthy flowering rather than a display lasting only one week, a quiet March job with fertiliser and a hand fork may be the year's most important task.