A widely-regarded problem facing many Australian investors is an overconcentration of their portfolios in a limited number of “blue-chip” stocks.

This “concentration risk” includes the four major banks and the two major miners BHP Billiton Limited (ASX: BHP) and Rio Tinto Limited (ASX: RIO).

There are of course a few other stocks which are widely held and that provide some diversification, including Telstra Corporation Ltd (ASX: TLS), Wesfarmers Ltd (ASX: WES), Woolworths Limited (ASX: WES) and AMP Limited (ASX: AMP).

Unfortunately, even for portfolios that include these, the heavy concentration and exposure to the banking sector has led to massive portfolio underperformance in the past few years.

While significant losses have already been sustained by investors with a portfolio weighting described above, it’s not too late to improve your portfolio positioning for the future.

Arguably one way to do this is by including a basket of smaller growth stocks in your portfolio. Here are three companies that could be worth considering…

Estia Health Ltd (ASX: EHE) is one of a recent wave of aged care accommodation providers to list on the ASX. Estia’s share price has pulled back from a high of $7.84 late last year to around $5.90 today.

Estia can grow through a combination of factors including redevelopment of existing sites, acquiring new “greenfield” sites as well as acquisitions which can create synergies and further economies of scale. The group is also benefiting from the structural tailwind of an aging population.

Select Harvests Limited (ASX: SHV) offers investors exposure to almond production and value added food processing. The share price has tanked from a high of $13.64 to just around $5.20 on account of a sharp fall in the almond price.

Like the oil market, the agricultural sector is also inherently cyclical. Generally, the best time to buy cyclical stocks is after the cycle has bottomed. Given the long-term positive tailwind for increased global food demand, particularly from Asia, now is arguably the right time to consider the investment merits of Select Harvests.

Burson Group Ltd (ASX: BAP) is a leading provider of aftermarket automotive parts and accessories. Unlike Estia and Select Harvests, Burson’s recent share price performance has been exceptional with the stock currently trading near an all-time high.

Burson operates from over 600 locations across Australia which gives the group significant scale and allows it to efficiently service its trade, retail and independent client base. The recent acquisition of the Metcash Limited (ASX: MTS) owned Autobarn, Autopro and Midas businesses has opened up significant new growth avenues for the group.

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Motley Fool contributor Tim McArthur has no position in any stocks mentioned. The Motley Fool Australia owns shares of Burson. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.